Date: 2022-03-31T04:48:28+00:00

Actual source code: snes.c

      1: #include <petsc/private/snesimpl.h>
      2: #include <petscdmshell.h>
      3: #include <petscdraw.h>
      4: #include <petscds.h>
      5: #include <petscdmadaptor.h>
      6: #include <petscconvest.h>

      8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
      9: PetscFunctionList SNESList              = NULL;

     11: /* Logging support */
     12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
     13: PetscLogEvent SNES_Solve, SNES_Setup, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve, SNES_ObjectiveEval;

     15: /*@
     16:    SNESSetErrorIfNotConverged - Causes SNESSolve() to generate an error if the solver has not converged.

     18:    Logically Collective on SNES

     20:    Input Parameters:
     21: +  snes - iterative context obtained from SNESCreate()
     22: -  flg - PETSC_TRUE indicates you want the error generated

     24:    Options database keys:
     25: .  -snes_error_if_not_converged <true,false> - cause an immediate error condition and stop the program if the solver does not converge

     27:    Level: intermediate

     29:    Notes:
     30:     Normally PETSc continues if a linear solver fails to converge, you can call SNESGetConvergedReason() after a SNESSolve()
     31:     to determine if it has converged.

     33: .seealso: SNESGetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIfNotConverged()
     34: @*/
     35: PetscErrorCode  SNESSetErrorIfNotConverged(SNES snes,PetscBool flg)
     36: {
     39:   snes->errorifnotconverged = flg;
     40:   return 0;
     41: }

     43: /*@
     44:    SNESGetErrorIfNotConverged - Will SNESSolve() generate an error if the solver does not converge?

     46:    Not Collective

     48:    Input Parameter:
     49: .  snes - iterative context obtained from SNESCreate()

     51:    Output Parameter:
     52: .  flag - PETSC_TRUE if it will generate an error, else PETSC_FALSE

     54:    Level: intermediate

     56: .seealso:  SNESSetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIfNotConverged()
     57: @*/
     58: PetscErrorCode  SNESGetErrorIfNotConverged(SNES snes,PetscBool  *flag)
     59: {
     62:   *flag = snes->errorifnotconverged;
     63:   return 0;
     64: }

     66: /*@
     67:     SNESSetAlwaysComputesFinalResidual - does the SNES always compute the residual at the final solution?

     69:    Logically Collective on SNES

     71:     Input Parameters:
     72: +   snes - the shell SNES
     73: -   flg - is the residual computed?

     75:    Level: advanced

     77: .seealso: SNESGetAlwaysComputesFinalResidual()
     78: @*/
     79: PetscErrorCode  SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
     80: {
     82:   snes->alwayscomputesfinalresidual = flg;
     83:   return 0;
     84: }

     86: /*@
     87:     SNESGetAlwaysComputesFinalResidual - does the SNES always compute the residual at the final solution?

     89:    Logically Collective on SNES

     91:     Input Parameter:
     92: .   snes - the shell SNES

     94:     Output Parameter:
     95: .   flg - is the residual computed?

     97:    Level: advanced

     99: .seealso: SNESSetAlwaysComputesFinalResidual()
    100: @*/
    101: PetscErrorCode  SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
    102: {
    104:   *flg = snes->alwayscomputesfinalresidual;
    105:   return 0;
    106: }

    108: /*@
    109:    SNESSetFunctionDomainError - tells SNES that the input vector to your SNESFunction is not
    110:      in the functions domain. For example, negative pressure.

    112:    Logically Collective on SNES

    114:    Input Parameters:
    115: .  snes - the SNES context

    117:    Level: advanced

    119: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction
    120: @*/
    121: PetscErrorCode  SNESSetFunctionDomainError(SNES snes)
    122: {
    125:   snes->domainerror = PETSC_TRUE;
    126:   return 0;
    127: }

    129: /*@
    130:    SNESSetJacobianDomainError - tells SNES that computeJacobian does not make sense any more. For example there is a negative element transformation.

    132:    Logically Collective on SNES

    134:    Input Parameters:
    135: .  snes - the SNES context

    137:    Level: advanced

    139: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction(), SNESSetFunctionDomainError()
    140: @*/
    141: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
    142: {
    145:   snes->jacobiandomainerror = PETSC_TRUE;
    146:   return 0;
    147: }

    149: /*@
    150:    SNESSetCheckJacobianDomainError - if or not to check jacobian domain error after each Jacobian evaluation. By default, we check Jacobian domain error
    151:    in the debug mode, and do not check it in the optimized mode.

    153:    Logically Collective on SNES

    155:    Input Parameters:
    156: +  snes - the SNES context
    157: -  flg  - indicates if or not to check jacobian domain error after each Jacobian evaluation

    159:    Level: advanced

    161: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction(), SNESSetFunctionDomainError(), SNESGetCheckJacobianDomainError()
    162: @*/
    163: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
    164: {
    166:   snes->checkjacdomainerror = flg;
    167:   return 0;
    168: }

    170: /*@
    171:    SNESGetCheckJacobianDomainError - Get an indicator whether or not we are checking Jacobian domain errors after each Jacobian evaluation.

    173:    Logically Collective on SNES

    175:    Input Parameters:
    176: .  snes - the SNES context

    178:    Output Parameters:
    179: .  flg  - PETSC_FALSE indicates that we don't check jacobian domain errors after each Jacobian evaluation

    181:    Level: advanced

    183: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction(), SNESSetFunctionDomainError(), SNESSetCheckJacobianDomainError()
    184: @*/
    185: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
    186: {
    189:   *flg = snes->checkjacdomainerror;
    190:   return 0;
    191: }

    193: /*@
    194:    SNESGetFunctionDomainError - Gets the status of the domain error after a call to SNESComputeFunction;

    196:    Logically Collective on SNES

    198:    Input Parameters:
    199: .  snes - the SNES context

    201:    Output Parameters:
    202: .  domainerror - Set to PETSC_TRUE if there's a domain error; PETSC_FALSE otherwise.

    204:    Level: advanced

    206: .seealso: SNESSetFunctionDomainError(), SNESComputeFunction()
    207: @*/
    208: PetscErrorCode  SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
    209: {
    212:   *domainerror = snes->domainerror;
    213:   return 0;
    214: }

    216: /*@
    217:    SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to SNESComputeJacobian;

    219:    Logically Collective on SNES

    221:    Input Parameters:
    222: .  snes - the SNES context

    224:    Output Parameters:
    225: .  domainerror - Set to PETSC_TRUE if there's a jacobian domain error; PETSC_FALSE otherwise.

    227:    Level: advanced

    229: .seealso: SNESSetFunctionDomainError(), SNESComputeFunction(),SNESGetFunctionDomainError()
    230: @*/
    231: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
    232: {
    235:   *domainerror = snes->jacobiandomainerror;
    236:   return 0;
    237: }

    239: /*@C
    240:   SNESLoad - Loads a SNES that has been stored in binary  with SNESView().

    242:   Collective on PetscViewer

    244:   Input Parameters:
    245: + newdm - the newly loaded SNES, this needs to have been created with SNESCreate() or
    246:            some related function before a call to SNESLoad().
    247: - viewer - binary file viewer, obtained from PetscViewerBinaryOpen()

    249:    Level: intermediate

    251:   Notes:
    252:    The type is determined by the data in the file, any type set into the SNES before this call is ignored.

    254:   Notes for advanced users:
    255:   Most users should not need to know the details of the binary storage
    256:   format, since SNESLoad() and TSView() completely hide these details.
    257:   But for anyone who's interested, the standard binary matrix storage
    258:   format is
    259: .vb
    260:      has not yet been determined
    261: .ve

    263: .seealso: PetscViewerBinaryOpen(), SNESView(), MatLoad(), VecLoad()
    264: @*/
    265: PetscErrorCode  SNESLoad(SNES snes, PetscViewer viewer)
    266: {
    267:   PetscBool      isbinary;
    268:   PetscInt       classid;
    269:   char           type[256];
    270:   KSP            ksp;
    271:   DM             dm;
    272:   DMSNES         dmsnes;

    276:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);

    279:   PetscViewerBinaryRead(viewer,&classid,1,NULL,PETSC_INT);
    281:   PetscViewerBinaryRead(viewer,type,256,NULL,PETSC_CHAR);
    282:   SNESSetType(snes, type);
    283:   if (snes->ops->load) {
    284:     (*snes->ops->load)(snes,viewer);
    285:   }
    286:   SNESGetDM(snes,&dm);
    287:   DMGetDMSNES(dm,&dmsnes);
    288:   DMSNESLoad(dmsnes,viewer);
    289:   SNESGetKSP(snes,&ksp);
    290:   KSPLoad(ksp,viewer);
    291:   return 0;
    292: }

    294: #include <petscdraw.h>
    295: #if defined(PETSC_HAVE_SAWS)
    296: #include <petscviewersaws.h>
    297: #endif

    299: /*@C
    300:    SNESViewFromOptions - View from Options

    302:    Collective on SNES

    304:    Input Parameters:
    305: +  A - the application ordering context
    306: .  obj - Optional object
    307: -  name - command line option

    309:    Level: intermediate
    310: .seealso:  SNES, SNESView, PetscObjectViewFromOptions(), SNESCreate()
    311: @*/
    312: PetscErrorCode  SNESViewFromOptions(SNES A,PetscObject obj,const char name[])
    313: {
    315:   PetscObjectViewFromOptions((PetscObject)A,obj,name);
    316:   return 0;
    317: }

    319: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES,Vec,Mat,Mat,void*);

    321: /*@C
    322:    SNESView - Prints the SNES data structure.

    324:    Collective on SNES

    326:    Input Parameters:
    327: +  SNES - the SNES context
    328: -  viewer - visualization context

    330:    Options Database Key:
    331: .  -snes_view - Calls SNESView() at end of SNESSolve()

    333:    Notes:
    334:    The available visualization contexts include
    335: +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
    336: -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
    337:          output where only the first processor opens
    338:          the file.  All other processors send their
    339:          data to the first processor to print.

    341:    The available formats include
    342: +     PETSC_VIEWER_DEFAULT - standard output (default)
    343: -     PETSC_VIEWER_ASCII_INFO_DETAIL - more verbose output for SNESNASM

    345:    The user can open an alternative visualization context with
    346:    PetscViewerASCIIOpen() - output to a specified file.

    348:   In the debugger you can do "call SNESView(snes,0)" to display the SNES solver. (The same holds for any PETSc object viewer).

    350:    Level: beginner

    352: .seealso: PetscViewerASCIIOpen()
    353: @*/
    354: PetscErrorCode  SNESView(SNES snes,PetscViewer viewer)
    355: {
    356:   SNESKSPEW      *kctx;
    357:   KSP            ksp;
    358:   SNESLineSearch linesearch;
    359:   PetscBool      iascii,isstring,isbinary,isdraw;
    360:   DMSNES         dmsnes;
    361: #if defined(PETSC_HAVE_SAWS)
    362:   PetscBool      issaws;
    363: #endif

    366:   if (!viewer) {
    367:     PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&viewer);
    368:   }

    372:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    373:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
    374:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    375:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    376: #if defined(PETSC_HAVE_SAWS)
    377:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSAWS,&issaws);
    378: #endif
    379:   if (iascii) {
    380:     SNESNormSchedule normschedule;
    381:     DM               dm;
    382:     PetscErrorCode   (*cJ)(SNES,Vec,Mat,Mat,void*);
    383:     void             *ctx;
    384:     const char       *pre = "";

    386:     PetscObjectPrintClassNamePrefixType((PetscObject)snes,viewer);
    387:     if (!snes->setupcalled) {
    388:       PetscViewerASCIIPrintf(viewer,"  SNES has not been set up so information may be incomplete\n");
    389:     }
    390:     if (snes->ops->view) {
    391:       PetscViewerASCIIPushTab(viewer);
    392:       (*snes->ops->view)(snes,viewer);
    393:       PetscViewerASCIIPopTab(viewer);
    394:     }
    395:     PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, maximum function evaluations=%D\n",snes->max_its,snes->max_funcs);
    396:     PetscViewerASCIIPrintf(viewer,"  tolerances: relative=%g, absolute=%g, solution=%g\n",(double)snes->rtol,(double)snes->abstol,(double)snes->stol);
    397:     if (snes->usesksp) {
    398:       PetscViewerASCIIPrintf(viewer,"  total number of linear solver iterations=%D\n",snes->linear_its);
    399:     }
    400:     PetscViewerASCIIPrintf(viewer,"  total number of function evaluations=%D\n",snes->nfuncs);
    401:     SNESGetNormSchedule(snes, &normschedule);
    402:     if (normschedule > 0) PetscViewerASCIIPrintf(viewer,"  norm schedule %s\n",SNESNormSchedules[normschedule]);
    403:     if (snes->gridsequence) {
    404:       PetscViewerASCIIPrintf(viewer,"  total number of grid sequence refinements=%D\n",snes->gridsequence);
    405:     }
    406:     if (snes->ksp_ewconv) {
    407:       kctx = (SNESKSPEW*)snes->kspconvctx;
    408:       if (kctx) {
    409:         PetscViewerASCIIPrintf(viewer,"  Eisenstat-Walker computation of KSP relative tolerance (version %D)\n",kctx->version);
    410:         PetscViewerASCIIPrintf(viewer,"    rtol_0=%g, rtol_max=%g, threshold=%g\n",(double)kctx->rtol_0,(double)kctx->rtol_max,(double)kctx->threshold);
    411:         PetscViewerASCIIPrintf(viewer,"    gamma=%g, alpha=%g, alpha2=%g\n",(double)kctx->gamma,(double)kctx->alpha,(double)kctx->alpha2);
    412:       }
    413:     }
    414:     if (snes->lagpreconditioner == -1) {
    415:       PetscViewerASCIIPrintf(viewer,"  Preconditioned is never rebuilt\n");
    416:     } else if (snes->lagpreconditioner > 1) {
    417:       PetscViewerASCIIPrintf(viewer,"  Preconditioned is rebuilt every %D new Jacobians\n",snes->lagpreconditioner);
    418:     }
    419:     if (snes->lagjacobian == -1) {
    420:       PetscViewerASCIIPrintf(viewer,"  Jacobian is never rebuilt\n");
    421:     } else if (snes->lagjacobian > 1) {
    422:       PetscViewerASCIIPrintf(viewer,"  Jacobian is rebuilt every %D SNES iterations\n",snes->lagjacobian);
    423:     }
    424:     SNESGetDM(snes,&dm);
    425:     DMSNESGetJacobian(dm,&cJ,&ctx);
    426:     if (snes->mf_operator) {
    427:       PetscViewerASCIIPrintf(viewer,"  Jacobian is applied matrix-free with differencing\n");
    428:       pre  = "Preconditioning ";
    429:     }
    430:     if (cJ == SNESComputeJacobianDefault) {
    431:       PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using finite differences one column at a time\n",pre);
    432:     } else if (cJ == SNESComputeJacobianDefaultColor) {
    433:       PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using finite differences with coloring\n",pre);
    434:     /* it slightly breaks data encapsulation for access the DMDA information directly */
    435:     } else if (cJ == SNESComputeJacobian_DMDA) {
    436:       MatFDColoring fdcoloring;
    437:       PetscObjectQuery((PetscObject)dm,"DMDASNES_FDCOLORING",(PetscObject*)&fdcoloring);
    438:       if (fdcoloring) {
    439:         PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using colored finite differences on a DMDA\n",pre);
    440:       } else {
    441:         PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using a DMDA local Jacobian\n",pre);
    442:       }
    443:     } else if (snes->mf) {
    444:       PetscViewerASCIIPrintf(viewer,"  Jacobian is applied matrix-free with differencing, no explicit Jacobian\n");
    445:     }
    446:   } else if (isstring) {
    447:     const char *type;
    448:     SNESGetType(snes,&type);
    449:     PetscViewerStringSPrintf(viewer," SNESType: %-7.7s",type);
    450:     if (snes->ops->view) (*snes->ops->view)(snes,viewer);
    451:   } else if (isbinary) {
    452:     PetscInt    classid = SNES_FILE_CLASSID;
    453:     MPI_Comm    comm;
    454:     PetscMPIInt rank;
    455:     char        type[256];

    457:     PetscObjectGetComm((PetscObject)snes,&comm);
    458:     MPI_Comm_rank(comm,&rank);
    459:     if (rank == 0) {
    460:       PetscViewerBinaryWrite(viewer,&classid,1,PETSC_INT);
    461:       PetscStrncpy(type,((PetscObject)snes)->type_name,sizeof(type));
    462:       PetscViewerBinaryWrite(viewer,type,sizeof(type),PETSC_CHAR);
    463:     }
    464:     if (snes->ops->view) {
    465:       (*snes->ops->view)(snes,viewer);
    466:     }
    467:   } else if (isdraw) {
    468:     PetscDraw draw;
    469:     char      str[36];
    470:     PetscReal x,y,bottom,h;

    472:     PetscViewerDrawGetDraw(viewer,0,&draw);
    473:     PetscDrawGetCurrentPoint(draw,&x,&y);
    474:     PetscStrncpy(str,"SNES: ",sizeof(str));
    475:     PetscStrlcat(str,((PetscObject)snes)->type_name,sizeof(str));
    476:     PetscDrawStringBoxed(draw,x,y,PETSC_DRAW_BLUE,PETSC_DRAW_BLACK,str,NULL,&h);
    477:     bottom = y - h;
    478:     PetscDrawPushCurrentPoint(draw,x,bottom);
    479:     if (snes->ops->view) {
    480:       (*snes->ops->view)(snes,viewer);
    481:     }
    482: #if defined(PETSC_HAVE_SAWS)
    483:   } else if (issaws) {
    484:     PetscMPIInt rank;
    485:     const char *name;

    487:     PetscObjectGetName((PetscObject)snes,&name);
    488:     MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
    489:     if (!((PetscObject)snes)->amsmem && rank == 0) {
    490:       char       dir[1024];

    492:       PetscObjectViewSAWs((PetscObject)snes,viewer);
    493:       PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/its",name);
    494:       PetscStackCallSAWs(SAWs_Register,(dir,&snes->iter,1,SAWs_READ,SAWs_INT));
    495:       if (!snes->conv_hist) {
    496:         SNESSetConvergenceHistory(snes,NULL,NULL,PETSC_DECIDE,PETSC_TRUE);
    497:       }
    498:       PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/conv_hist",name);
    499:       PetscStackCallSAWs(SAWs_Register,(dir,snes->conv_hist,10,SAWs_READ,SAWs_DOUBLE));
    500:     }
    501: #endif
    502:   }
    503:   if (snes->linesearch) {
    504:     SNESGetLineSearch(snes, &linesearch);
    505:     PetscViewerASCIIPushTab(viewer);
    506:     SNESLineSearchView(linesearch, viewer);
    507:     PetscViewerASCIIPopTab(viewer);
    508:   }
    509:   if (snes->npc && snes->usesnpc) {
    510:     PetscViewerASCIIPushTab(viewer);
    511:     SNESView(snes->npc, viewer);
    512:     PetscViewerASCIIPopTab(viewer);
    513:   }
    514:   PetscViewerASCIIPushTab(viewer);
    515:   DMGetDMSNES(snes->dm,&dmsnes);
    516:   DMSNESView(dmsnes, viewer);
    517:   PetscViewerASCIIPopTab(viewer);
    518:   if (snes->usesksp) {
    519:     SNESGetKSP(snes,&ksp);
    520:     PetscViewerASCIIPushTab(viewer);
    521:     KSPView(ksp,viewer);
    522:     PetscViewerASCIIPopTab(viewer);
    523:   }
    524:   if (isdraw) {
    525:     PetscDraw draw;
    526:     PetscViewerDrawGetDraw(viewer,0,&draw);
    527:     PetscDrawPopCurrentPoint(draw);
    528:   }
    529:   return 0;
    530: }

    532: /*
    533:   We retain a list of functions that also take SNES command
    534:   line options. These are called at the end SNESSetFromOptions()
    535: */
    536: #define MAXSETFROMOPTIONS 5
    537: static PetscInt numberofsetfromoptions;
    538: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

    540: /*@C
    541:   SNESAddOptionsChecker - Adds an additional function to check for SNES options.

    543:   Not Collective

    545:   Input Parameter:
    546: . snescheck - function that checks for options

    548:   Level: developer

    550: .seealso: SNESSetFromOptions()
    551: @*/
    552: PetscErrorCode  SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
    553: {
    555:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
    556:   return 0;
    557: }

    559: PETSC_INTERN PetscErrorCode SNESDefaultMatrixFreeCreate2(SNES,Vec,Mat*);

    561: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
    562: {
    563:   Mat            J;
    564:   MatNullSpace   nullsp;

    568:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
    569:     Mat A = snes->jacobian, B = snes->jacobian_pre;
    570:     MatCreateVecs(A ? A : B, NULL,&snes->vec_func);
    571:   }

    573:   if (version == 1) {
    574:     MatCreateSNESMF(snes,&J);
    575:     MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);
    576:     MatSetFromOptions(J);
    577:   } else if (version == 2) {
    579: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
    580:     SNESDefaultMatrixFreeCreate2(snes,snes->vec_func,&J);
    581: #else
    582:     SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
    583: #endif
    584:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");

    586:   /* attach any user provided null space that was on Amat to the newly created matrix free matrix */
    587:   if (snes->jacobian) {
    588:     MatGetNullSpace(snes->jacobian,&nullsp);
    589:     if (nullsp) {
    590:       MatSetNullSpace(J,nullsp);
    591:     }
    592:   }

    594:   PetscInfo(snes,"Setting default matrix-free operator routines (version %D)\n", version);
    595:   if (hasOperator) {

    597:     /* This version replaces the user provided Jacobian matrix with a
    598:        matrix-free version but still employs the user-provided preconditioner matrix. */
    599:     SNESSetJacobian(snes,J,NULL,NULL,NULL);
    600:   } else {
    601:     /* This version replaces both the user-provided Jacobian and the user-
    602:      provided preconditioner Jacobian with the default matrix free version. */
    603:     if (snes->npcside == PC_LEFT && snes->npc) {
    604:       if (!snes->jacobian) SNESSetJacobian(snes,J,NULL,NULL,NULL);
    605:     } else {
    606:       KSP       ksp;
    607:       PC        pc;
    608:       PetscBool match;

    610:       SNESSetJacobian(snes,J,J,MatMFFDComputeJacobian,NULL);
    611:       /* Force no preconditioner */
    612:       SNESGetKSP(snes,&ksp);
    613:       KSPGetPC(ksp,&pc);
    614:       PetscObjectTypeCompare((PetscObject)pc,PCSHELL,&match);
    615:       if (!match) {
    616:         PetscInfo(snes,"Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n");
    617:         PCSetType(pc,PCNONE);
    618:       }
    619:     }
    620:   }
    621:   MatDestroy(&J);
    622:   return 0;
    623: }

    625: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine,Mat Restrict,Vec Rscale,Mat Inject,DM dmcoarse,void *ctx)
    626: {
    627:   SNES           snes = (SNES)ctx;
    628:   Vec            Xfine,Xfine_named = NULL,Xcoarse;

    630:   if (PetscLogPrintInfo) {
    631:     PetscInt finelevel,coarselevel,fineclevel,coarseclevel;
    632:     DMGetRefineLevel(dmfine,&finelevel);
    633:     DMGetCoarsenLevel(dmfine,&fineclevel);
    634:     DMGetRefineLevel(dmcoarse,&coarselevel);
    635:     DMGetCoarsenLevel(dmcoarse,&coarseclevel);
    636:     PetscInfo(dmfine,"Restricting SNES solution vector from level %D-%D to level %D-%D\n",finelevel,fineclevel,coarselevel,coarseclevel);
    637:   }
    638:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
    639:   else {
    640:     DMGetNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);
    641:     Xfine = Xfine_named;
    642:   }
    643:   DMGetNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);
    644:   if (Inject) {
    645:     MatRestrict(Inject,Xfine,Xcoarse);
    646:   } else {
    647:     MatRestrict(Restrict,Xfine,Xcoarse);
    648:     VecPointwiseMult(Xcoarse,Xcoarse,Rscale);
    649:   }
    650:   DMRestoreNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);
    651:   if (Xfine_named) DMRestoreNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);
    652:   return 0;
    653: }

    655: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm,DM dmc,void *ctx)
    656: {
    657:   DMCoarsenHookAdd(dmc,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,ctx);
    658:   return 0;
    659: }

    661: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
    662:  * safely call SNESGetDM() in their residual evaluation routine. */
    663: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp,Mat A,Mat B,void *ctx)
    664: {
    665:   SNES           snes = (SNES)ctx;
    666:   Vec            X,Xnamed = NULL;
    667:   DM             dmsave;
    668:   void           *ctxsave;
    669:   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*) = NULL;

    671:   dmsave = snes->dm;
    672:   KSPGetDM(ksp,&snes->dm);
    673:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
    674:   else {                                     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
    675:     DMGetNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);
    676:     X    = Xnamed;
    677:     SNESGetJacobian(snes,NULL,NULL,&jac,&ctxsave);
    678:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
    679:     if (jac == SNESComputeJacobianDefaultColor) {
    680:       SNESSetJacobian(snes,NULL,NULL,SNESComputeJacobianDefaultColor,NULL);
    681:     }
    682:   }
    683:   /* Make sure KSP DM has the Jacobian computation routine */
    684:   {
    685:     DMSNES sdm;

    687:     DMGetDMSNES(snes->dm, &sdm);
    688:     if (!sdm->ops->computejacobian) {
    689:       DMCopyDMSNES(dmsave, snes->dm);
    690:     }
    691:   }
    692:   /* Compute the operators */
    693:   SNESComputeJacobian(snes,X,A,B);
    694:   /* Put the previous context back */
    695:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) {
    696:     SNESSetJacobian(snes,NULL,NULL,jac,ctxsave);
    697:   }

    699:   if (Xnamed) DMRestoreNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);
    700:   snes->dm = dmsave;
    701:   return 0;
    702: }

    704: /*@
    705:    SNESSetUpMatrices - ensures that matrices are available for SNES, to be called by SNESSetUp_XXX()

    707:    Collective

    709:    Input Parameter:
    710: .  snes - snes to configure

    712:    Level: developer

    714: .seealso: SNESSetUp()
    715: @*/
    716: PetscErrorCode SNESSetUpMatrices(SNES snes)
    717: {
    718:   DM             dm;
    719:   DMSNES         sdm;

    721:   SNESGetDM(snes,&dm);
    722:   DMGetDMSNES(dm,&sdm);
    723:   if (!snes->jacobian && snes->mf) {
    724:     Mat  J;
    725:     void *functx;
    726:     MatCreateSNESMF(snes,&J);
    727:     MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);
    728:     MatSetFromOptions(J);
    729:     SNESGetFunction(snes,NULL,NULL,&functx);
    730:     SNESSetJacobian(snes,J,J,NULL,NULL);
    731:     MatDestroy(&J);
    732:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
    733:     Mat J,B;
    734:     MatCreateSNESMF(snes,&J);
    735:     MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);
    736:     MatSetFromOptions(J);
    737:     DMCreateMatrix(snes->dm,&B);
    738:     /* sdm->computejacobian was already set to reach here */
    739:     SNESSetJacobian(snes,J,B,NULL,NULL);
    740:     MatDestroy(&J);
    741:     MatDestroy(&B);
    742:   } else if (!snes->jacobian_pre) {
    743:     PetscDS   prob;
    744:     Mat       J, B;
    745:     PetscBool hasPrec   = PETSC_FALSE;

    747:     J    = snes->jacobian;
    748:     DMGetDS(dm, &prob);
    749:     if (prob) PetscDSHasJacobianPreconditioner(prob, &hasPrec);
    750:     if (J)            PetscObjectReference((PetscObject) J);
    751:     else if (hasPrec) DMCreateMatrix(snes->dm, &J);
    752:     DMCreateMatrix(snes->dm, &B);
    753:     SNESSetJacobian(snes, J ? J : B, B, NULL, NULL);
    754:     MatDestroy(&J);
    755:     MatDestroy(&B);
    756:   }
    757:   {
    758:     KSP ksp;
    759:     SNESGetKSP(snes,&ksp);
    760:     KSPSetComputeOperators(ksp,KSPComputeOperators_SNES,snes);
    761:     DMCoarsenHookAdd(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);
    762:   }
    763:   return 0;
    764: }

    766: static PetscErrorCode SNESMonitorPauseFinal_Internal(SNES snes)
    767: {
    768:   PetscInt       i;

    770:   if (!snes->pauseFinal) return 0;
    771:   for (i = 0; i < snes->numbermonitors; ++i) {
    772:     PetscViewerAndFormat *vf = (PetscViewerAndFormat *) snes->monitorcontext[i];
    773:     PetscDraw             draw;
    774:     PetscReal             lpause;

    776:     if (!vf) continue;
    777:     if (vf->lg) {
    779:       if (((PetscObject) vf->lg)->classid != PETSC_DRAWLG_CLASSID) continue;
    780:       PetscDrawLGGetDraw(vf->lg, &draw);
    781:       PetscDrawGetPause(draw, &lpause);
    782:       PetscDrawSetPause(draw, -1.0);
    783:       PetscDrawPause(draw);
    784:       PetscDrawSetPause(draw, lpause);
    785:     } else {
    786:       PetscBool isdraw;

    789:       if (((PetscObject) vf->viewer)->classid != PETSC_VIEWER_CLASSID) continue;
    790:       PetscObjectTypeCompare((PetscObject) vf->viewer, PETSCVIEWERDRAW, &isdraw);
    791:       if (!isdraw) continue;
    792:       PetscViewerDrawGetDraw(vf->viewer, 0, &draw);
    793:       PetscDrawGetPause(draw, &lpause);
    794:       PetscDrawSetPause(draw, -1.0);
    795:       PetscDrawPause(draw);
    796:       PetscDrawSetPause(draw, lpause);
    797:     }
    798:   }
    799:   return 0;
    800: }

    802: /*@C
    803:    SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

    805:    Collective on SNES

    807:    Input Parameters:
    808: +  snes - SNES object you wish to monitor
    809: .  name - the monitor type one is seeking
    810: .  help - message indicating what monitoring is done
    811: .  manual - manual page for the monitor
    812: .  monitor - the monitor function
    813: -  monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the SNES or PetscViewer objects

    815:    Level: developer

    817: .seealso: PetscOptionsGetViewer(), PetscOptionsGetReal(), PetscOptionsHasName(), PetscOptionsGetString(),
    818:           PetscOptionsGetIntArray(), PetscOptionsGetRealArray(), PetscOptionsBool()
    819:           PetscOptionsInt(), PetscOptionsString(), PetscOptionsReal(), PetscOptionsBool(),
    820:           PetscOptionsName(), PetscOptionsBegin(), PetscOptionsEnd(), PetscOptionsHead(),
    821:           PetscOptionsStringArray(),PetscOptionsRealArray(), PetscOptionsScalar(),
    822:           PetscOptionsBoolGroupBegin(), PetscOptionsBoolGroup(), PetscOptionsBoolGroupEnd(),
    823:           PetscOptionsFList(), PetscOptionsEList()
    824: @*/
    825: PetscErrorCode  SNESMonitorSetFromOptions(SNES snes,const char name[],const char help[], const char manual[],PetscErrorCode (*monitor)(SNES,PetscInt,PetscReal,PetscViewerAndFormat*),PetscErrorCode (*monitorsetup)(SNES,PetscViewerAndFormat*))
    826: {
    827:   PetscViewer       viewer;
    828:   PetscViewerFormat format;
    829:   PetscBool         flg;

    831:   PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,name,&viewer,&format,&flg);
    832:   if (flg) {
    833:     PetscViewerAndFormat *vf;
    834:     PetscViewerAndFormatCreate(viewer,format,&vf);
    835:     PetscObjectDereference((PetscObject)viewer);
    836:     if (monitorsetup) {
    837:       (*monitorsetup)(snes,vf);
    838:     }
    839:     SNESMonitorSet(snes,(PetscErrorCode (*)(SNES,PetscInt,PetscReal,void*))monitor,vf,(PetscErrorCode (*)(void**))PetscViewerAndFormatDestroy);
    840:   }
    841:   return 0;
    842: }

    844: /*@
    845:    SNESSetFromOptions - Sets various SNES and KSP parameters from user options.

    847:    Collective on SNES

    849:    Input Parameter:
    850: .  snes - the SNES context

    852:    Options Database Keys:
    853: +  -snes_type <type> - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, SNESType for complete list
    854: .  -snes_stol - convergence tolerance in terms of the norm
    855:                 of the change in the solution between steps
    856: .  -snes_atol <abstol> - absolute tolerance of residual norm
    857: .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
    858: .  -snes_divergence_tolerance <divtol> - if the residual goes above divtol*rnorm0, exit with divergence
    859: .  -snes_force_iteration <force> - force SNESSolve() to take at least one iteration
    860: .  -snes_max_it <max_it> - maximum number of iterations
    861: .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
    862: .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
    863: .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
    864: .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
    865: .  -snes_lag_preconditioner_persists <true,false> - retains the -snes_lag_preconditioner information across multiple SNESSolve()
    866: .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
    867: .  -snes_lag_jacobian_persists <true,false> - retains the -snes_lag_jacobian information across multiple SNESSolve()
    868: .  -snes_trtol <trtol> - trust region tolerance
    869: .  -snes_no_convergence_test - skip convergence test in nonlinear
    870:                                solver; hence iterations will continue until max_it
    871:                                or some other criterion is reached. Saves expense
    872:                                of convergence test
    873: .  -snes_monitor [ascii][:filename][:viewer format] - prints residual norm at each iteration. if no filename given prints to stdout
    874: .  -snes_monitor_solution [ascii binary draw][:filename][:viewer format] - plots solution at each iteration
    875: .  -snes_monitor_residual [ascii binary draw][:filename][:viewer format] - plots residual (not its norm) at each iteration
    876: .  -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
    877: .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
    878: .  -snes_monitor_lg_range - plots residual norm at each iteration
    879: .  -snes_monitor_pause_final - Pauses all monitor drawing after the solver ends
    880: .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
    881: .  -snes_fd_color - use finite differences with coloring to compute Jacobian
    882: .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
    883: .  -snes_converged_reason - print the reason for convergence/divergence after each solve
    884: .  -npc_snes_type <type> - the SNES type to use as a nonlinear preconditioner
    885: .   -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
    886: -   -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

    888:     Options Database for Eisenstat-Walker method:
    889: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
    890: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
    891: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
    892: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
    893: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
    894: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
    895: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
    896: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

    898:    Notes:
    899:    To see all options, run your program with the -help option or consult the users manual

    901:    Notes:
    902:       SNES supports three approaches for computing (approximate) Jacobians: user provided via SNESSetJacobian(), matrix free, and computing explicitly with
    903:       finite differences and coloring using MatFDColoring. It is also possible to use automatic differentiation and the MatFDColoring object.

    905:    Level: beginner

    907: .seealso: SNESSetOptionsPrefix(), SNESResetFromOptions(), SNES, SNESCreate()
    908: @*/
    909: PetscErrorCode  SNESSetFromOptions(SNES snes)
    910: {
    911:   PetscBool      flg,pcset,persist,set;
    912:   PetscInt       i,indx,lag,grids;
    913:   const char     *deft        = SNESNEWTONLS;
    914:   const char     *convtests[] = {"default","skip","correct_pressure"};
    915:   SNESKSPEW      *kctx        = NULL;
    916:   char           type[256], monfilename[PETSC_MAX_PATH_LEN];
    918:   PCSide         pcside;
    919:   const char     *optionsprefix;

    922:   SNESRegisterAll();
    923:   PetscObjectOptionsBegin((PetscObject)snes);
    924:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
    925:   PetscOptionsFList("-snes_type","Nonlinear solver method","SNESSetType",SNESList,deft,type,256,&flg);
    926:   if (flg) {
    927:     SNESSetType(snes,type);
    928:   } else if (!((PetscObject)snes)->type_name) {
    929:     SNESSetType(snes,deft);
    930:   }
    931:   PetscOptionsReal("-snes_stol","Stop if step length less than","SNESSetTolerances",snes->stol,&snes->stol,NULL);
    932:   PetscOptionsReal("-snes_atol","Stop if function norm less than","SNESSetTolerances",snes->abstol,&snes->abstol,NULL);

    934:   PetscOptionsReal("-snes_rtol","Stop if decrease in function norm less than","SNESSetTolerances",snes->rtol,&snes->rtol,NULL);
    935:   PetscOptionsReal("-snes_divergence_tolerance","Stop if residual norm increases by this factor","SNESSetDivergenceTolerance",snes->divtol,&snes->divtol,NULL);
    936:   PetscOptionsInt("-snes_max_it","Maximum iterations","SNESSetTolerances",snes->max_its,&snes->max_its,NULL);
    937:   PetscOptionsInt("-snes_max_funcs","Maximum function evaluations","SNESSetTolerances",snes->max_funcs,&snes->max_funcs,NULL);
    938:   PetscOptionsInt("-snes_max_fail","Maximum nonlinear step failures","SNESSetMaxNonlinearStepFailures",snes->maxFailures,&snes->maxFailures,NULL);
    939:   PetscOptionsInt("-snes_max_linear_solve_fail","Maximum failures in linear solves allowed","SNESSetMaxLinearSolveFailures",snes->maxLinearSolveFailures,&snes->maxLinearSolveFailures,NULL);
    940:   PetscOptionsBool("-snes_error_if_not_converged","Generate error if solver does not converge","SNESSetErrorIfNotConverged",snes->errorifnotconverged,&snes->errorifnotconverged,NULL);
    941:   PetscOptionsBool("-snes_force_iteration","Force SNESSolve() to take at least one iteration","SNESSetForceIteration",snes->forceiteration,&snes->forceiteration,NULL);
    942:   PetscOptionsBool("-snes_check_jacobian_domain_error","Check Jacobian domain error after Jacobian evaluation","SNESCheckJacobianDomainError",snes->checkjacdomainerror,&snes->checkjacdomainerror,NULL);

    944:   PetscOptionsInt("-snes_lag_preconditioner","How often to rebuild preconditioner","SNESSetLagPreconditioner",snes->lagpreconditioner,&lag,&flg);
    945:   if (flg) {
    947:     SNESSetLagPreconditioner(snes,lag);
    948:   }
    949:   PetscOptionsBool("-snes_lag_preconditioner_persists","Preconditioner lagging through multiple SNES solves","SNESSetLagPreconditionerPersists",snes->lagjac_persist,&persist,&flg);
    950:   if (flg) {
    951:     SNESSetLagPreconditionerPersists(snes,persist);
    952:   }
    953:   PetscOptionsInt("-snes_lag_jacobian","How often to rebuild Jacobian","SNESSetLagJacobian",snes->lagjacobian,&lag,&flg);
    954:   if (flg) {
    956:     SNESSetLagJacobian(snes,lag);
    957:   }
    958:   PetscOptionsBool("-snes_lag_jacobian_persists","Jacobian lagging through multiple SNES solves","SNESSetLagJacobianPersists",snes->lagjac_persist,&persist,&flg);
    959:   if (flg) {
    960:     SNESSetLagJacobianPersists(snes,persist);
    961:   }

    963:   PetscOptionsInt("-snes_grid_sequence","Use grid sequencing to generate initial guess","SNESSetGridSequence",snes->gridsequence,&grids,&flg);
    964:   if (flg) {
    965:     SNESSetGridSequence(snes,grids);
    966:   }

    968:   PetscOptionsEList("-snes_convergence_test","Convergence test","SNESSetConvergenceTest",convtests,sizeof(convtests)/sizeof(char*),"default",&indx,&flg);
    969:   if (flg) {
    970:     switch (indx) {
    971:     case 0: SNESSetConvergenceTest(snes,SNESConvergedDefault,NULL,NULL); break;
    972:     case 1: SNESSetConvergenceTest(snes,SNESConvergedSkip,NULL,NULL); break;
    973:     case 2: SNESSetConvergenceTest(snes,SNESConvergedCorrectPressure,NULL,NULL); break;
    974:     }
    975:   }

    977:   PetscOptionsEList("-snes_norm_schedule","SNES Norm schedule","SNESSetNormSchedule",SNESNormSchedules,5,"function",&indx,&flg);
    978:   if (flg) SNESSetNormSchedule(snes,(SNESNormSchedule)indx);

    980:   PetscOptionsEList("-snes_function_type","SNES Norm schedule","SNESSetFunctionType",SNESFunctionTypes,2,"unpreconditioned",&indx,&flg);
    981:   if (flg) SNESSetFunctionType(snes,(SNESFunctionType)indx);

    983:   kctx = (SNESKSPEW*)snes->kspconvctx;

    985:   PetscOptionsBool("-snes_ksp_ew","Use Eisentat-Walker linear system convergence test","SNESKSPSetUseEW",snes->ksp_ewconv,&snes->ksp_ewconv,NULL);

    987:   PetscOptionsInt("-snes_ksp_ew_version","Version 1, 2 or 3","SNESKSPSetParametersEW",kctx->version,&kctx->version,NULL);
    988:   PetscOptionsReal("-snes_ksp_ew_rtol0","0 <= rtol0 < 1","SNESKSPSetParametersEW",kctx->rtol_0,&kctx->rtol_0,NULL);
    989:   PetscOptionsReal("-snes_ksp_ew_rtolmax","0 <= rtolmax < 1","SNESKSPSetParametersEW",kctx->rtol_max,&kctx->rtol_max,NULL);
    990:   PetscOptionsReal("-snes_ksp_ew_gamma","0 <= gamma <= 1","SNESKSPSetParametersEW",kctx->gamma,&kctx->gamma,NULL);
    991:   PetscOptionsReal("-snes_ksp_ew_alpha","1 < alpha <= 2","SNESKSPSetParametersEW",kctx->alpha,&kctx->alpha,NULL);
    992:   PetscOptionsReal("-snes_ksp_ew_alpha2","alpha2","SNESKSPSetParametersEW",kctx->alpha2,&kctx->alpha2,NULL);
    993:   PetscOptionsReal("-snes_ksp_ew_threshold","0 < threshold < 1","SNESKSPSetParametersEW",kctx->threshold,&kctx->threshold,NULL);

    995:   flg  = PETSC_FALSE;
    996:   PetscOptionsBool("-snes_monitor_cancel","Remove all monitors","SNESMonitorCancel",flg,&flg,&set);
    997:   if (set && flg) SNESMonitorCancel(snes);

    999:   SNESMonitorSetFromOptions(snes,"-snes_monitor","Monitor norm of function","SNESMonitorDefault",SNESMonitorDefault,SNESMonitorDefaultSetUp);
    1000:   SNESMonitorSetFromOptions(snes,"-snes_monitor_short","Monitor norm of function with fewer digits","SNESMonitorDefaultShort",SNESMonitorDefaultShort,NULL);
    1001:   SNESMonitorSetFromOptions(snes,"-snes_monitor_range","Monitor range of elements of function","SNESMonitorRange",SNESMonitorRange,NULL);

    1003:   SNESMonitorSetFromOptions(snes,"-snes_monitor_ratio","Monitor ratios of the norm of function for consecutive steps","SNESMonitorRatio",SNESMonitorRatio,SNESMonitorRatioSetUp);
    1004:   SNESMonitorSetFromOptions(snes,"-snes_monitor_field","Monitor norm of function (split into fields)","SNESMonitorDefaultField",SNESMonitorDefaultField,NULL);
    1005:   SNESMonitorSetFromOptions(snes,"-snes_monitor_solution","View solution at each iteration","SNESMonitorSolution",SNESMonitorSolution,NULL);
    1006:   SNESMonitorSetFromOptions(snes,"-snes_monitor_solution_update","View correction at each iteration","SNESMonitorSolutionUpdate",SNESMonitorSolutionUpdate,NULL);
    1007:   SNESMonitorSetFromOptions(snes,"-snes_monitor_residual","View residual at each iteration","SNESMonitorResidual",SNESMonitorResidual,NULL);
    1008:   SNESMonitorSetFromOptions(snes,"-snes_monitor_jacupdate_spectrum","Print the change in the spectrum of the Jacobian","SNESMonitorJacUpdateSpectrum",SNESMonitorJacUpdateSpectrum,NULL);
    1009:   SNESMonitorSetFromOptions(snes,"-snes_monitor_fields","Monitor norm of function per field","SNESMonitorSet",SNESMonitorFields,NULL);
    1010:   PetscOptionsBool("-snes_monitor_pause_final", "Pauses all draw monitors at the final iterate", "SNESMonitorPauseFinal_Internal", PETSC_FALSE, &snes->pauseFinal, NULL);

    1012:   PetscOptionsString("-snes_monitor_python","Use Python function","SNESMonitorSet",NULL,monfilename,sizeof(monfilename),&flg);
    1013:   if (flg) PetscPythonMonitorSet((PetscObject)snes,monfilename);

    1015:   flg  = PETSC_FALSE;
    1016:   PetscOptionsBool("-snes_monitor_lg_range","Plot function range at each iteration","SNESMonitorLGRange",flg,&flg,NULL);
    1017:   if (flg) {
    1018:     PetscViewer ctx;

    1020:     PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),NULL,NULL,PETSC_DECIDE,PETSC_DECIDE,400,300,&ctx);
    1021:     SNESMonitorSet(snes,SNESMonitorLGRange,ctx,(PetscErrorCode (*)(void**))PetscViewerDestroy);
    1022:   }

    1024:   flg  = PETSC_FALSE;
    1025:   PetscOptionsBool("-snes_converged_reason_view_cancel","Remove all converged reason viewers","SNESConvergedReasonViewCancel",flg,&flg,&set);
    1026:   if (set && flg) SNESConvergedReasonViewCancel(snes);

    1028:   flg  = PETSC_FALSE;
    1029:   PetscOptionsBool("-snes_fd","Use finite differences (slow) to compute Jacobian","SNESComputeJacobianDefault",flg,&flg,NULL);
    1030:   if (flg) {
    1031:     void    *functx;
    1032:     DM      dm;
    1033:     DMSNES  sdm;
    1034:     SNESGetDM(snes,&dm);
    1035:     DMGetDMSNES(dm,&sdm);
    1036:     sdm->jacobianctx = NULL;
    1037:     SNESGetFunction(snes,NULL,NULL,&functx);
    1038:     SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefault,functx);
    1039:     PetscInfo(snes,"Setting default finite difference Jacobian matrix\n");
    1040:   }

    1042:   flg  = PETSC_FALSE;
    1043:   PetscOptionsBool("-snes_fd_function","Use finite differences (slow) to compute function from user objective","SNESObjectiveComputeFunctionDefaultFD",flg,&flg,NULL);
    1044:   if (flg) {
    1045:     SNESSetFunction(snes,NULL,SNESObjectiveComputeFunctionDefaultFD,NULL);
    1046:   }

    1048:   flg  = PETSC_FALSE;
    1049:   PetscOptionsBool("-snes_fd_color","Use finite differences with coloring to compute Jacobian","SNESComputeJacobianDefaultColor",flg,&flg,NULL);
    1050:   if (flg) {
    1051:     DM             dm;
    1052:     DMSNES         sdm;
    1053:     SNESGetDM(snes,&dm);
    1054:     DMGetDMSNES(dm,&sdm);
    1055:     sdm->jacobianctx = NULL;
    1056:     SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefaultColor,NULL);
    1057:     PetscInfo(snes,"Setting default finite difference coloring Jacobian matrix\n");
    1058:   }

    1060:   flg  = PETSC_FALSE;
    1061:   PetscOptionsBool("-snes_mf_operator","Use a Matrix-Free Jacobian with user-provided preconditioner matrix","SNESSetUseMatrixFree",PETSC_FALSE,&snes->mf_operator,&flg);
    1062:   if (flg && snes->mf_operator) {
    1063:     snes->mf_operator = PETSC_TRUE;
    1064:     snes->mf          = PETSC_TRUE;
    1065:   }
    1066:   flg  = PETSC_FALSE;
    1067:   PetscOptionsBool("-snes_mf","Use a Matrix-Free Jacobian with no preconditioner matrix","SNESSetUseMatrixFree",PETSC_FALSE,&snes->mf,&flg);
    1068:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
    1069:   PetscOptionsInt("-snes_mf_version","Matrix-Free routines version 1 or 2","None",snes->mf_version,&snes->mf_version,NULL);

    1071:   flg  = PETSC_FALSE;
    1072:   SNESGetNPCSide(snes,&pcside);
    1073:   PetscOptionsEnum("-snes_npc_side","SNES nonlinear preconditioner side","SNESSetNPCSide",PCSides,(PetscEnum)pcside,(PetscEnum*)&pcside,&flg);
    1074:   if (flg) SNESSetNPCSide(snes,pcside);

    1076: #if defined(PETSC_HAVE_SAWS)
    1077:   /*
    1078:     Publish convergence information using SAWs
    1079:   */
    1080:   flg  = PETSC_FALSE;
    1081:   PetscOptionsBool("-snes_monitor_saws","Publish SNES progress using SAWs","SNESMonitorSet",flg,&flg,NULL);
    1082:   if (flg) {
    1083:     void *ctx;
    1084:     SNESMonitorSAWsCreate(snes,&ctx);
    1085:     SNESMonitorSet(snes,SNESMonitorSAWs,ctx,SNESMonitorSAWsDestroy);
    1086:   }
    1087: #endif
    1088: #if defined(PETSC_HAVE_SAWS)
    1089:   {
    1090:   PetscBool set;
    1091:   flg  = PETSC_FALSE;
    1092:   PetscOptionsBool("-snes_saws_block","Block for SAWs at end of SNESSolve","PetscObjectSAWsBlock",((PetscObject)snes)->amspublishblock,&flg,&set);
    1093:   if (set) {
    1094:     PetscObjectSAWsSetBlock((PetscObject)snes,flg);
    1095:   }
    1096:   }
    1097: #endif

    1099:   for (i = 0; i < numberofsetfromoptions; i++) {
    1100:     (*othersetfromoptions[i])(snes);
    1101:   }

    1103:   if (snes->ops->setfromoptions) {
    1104:     (*snes->ops->setfromoptions)(PetscOptionsObject,snes);
    1105:   }

    1107:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
    1108:   PetscObjectProcessOptionsHandlers(PetscOptionsObject,(PetscObject)snes);
    1109:   PetscOptionsEnd();

    1111:   if (snes->linesearch) {
    1112:     SNESGetLineSearch(snes, &snes->linesearch);
    1113:     SNESLineSearchSetFromOptions(snes->linesearch);
    1114:   }

    1116:   if (snes->usesksp) {
    1117:     if (!snes->ksp) SNESGetKSP(snes,&snes->ksp);
    1118:     KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);
    1119:     KSPSetFromOptions(snes->ksp);
    1120:   }

    1122:   /* if user has set the SNES NPC type via options database, create it. */
    1123:   SNESGetOptionsPrefix(snes, &optionsprefix);
    1124:   PetscOptionsHasName(((PetscObject)snes)->options,optionsprefix, "-npc_snes_type", &pcset);
    1125:   if (pcset && (!snes->npc)) {
    1126:     SNESGetNPC(snes, &snes->npc);
    1127:   }
    1128:   if (snes->npc) {
    1129:     SNESSetFromOptions(snes->npc);
    1130:   }
    1131:   snes->setfromoptionscalled++;
    1132:   return 0;
    1133: }

    1135: /*@
    1136:    SNESResetFromOptions - Sets various SNES and KSP parameters from user options ONLY if the SNES was previously set from options

    1138:    Collective on SNES

    1140:    Input Parameter:
    1141: .  snes - the SNES context

    1143:    Level: beginner

    1145: .seealso: SNESSetFromOptions(), SNESSetOptionsPrefix()
    1146: @*/
    1147: PetscErrorCode SNESResetFromOptions(SNES snes)
    1148: {
    1149:   if (snes->setfromoptionscalled) SNESSetFromOptions(snes);
    1150:   return 0;
    1151: }

    1153: /*@C
    1154:    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
    1155:    the nonlinear solvers.

    1157:    Logically Collective on SNES

    1159:    Input Parameters:
    1160: +  snes - the SNES context
    1161: .  compute - function to compute the context
    1162: -  destroy - function to destroy the context

    1164:    Level: intermediate

    1166:    Notes:
    1167:    This function is currently not available from Fortran.

    1169: .seealso: SNESGetApplicationContext(), SNESSetComputeApplicationContext(), SNESGetApplicationContext()
    1170: @*/
    1171: PetscErrorCode  SNESSetComputeApplicationContext(SNES snes,PetscErrorCode (*compute)(SNES,void**),PetscErrorCode (*destroy)(void**))
    1172: {
    1174:   snes->ops->usercompute = compute;
    1175:   snes->ops->userdestroy = destroy;
    1176:   return 0;
    1177: }

    1179: /*@
    1180:    SNESSetApplicationContext - Sets the optional user-defined context for
    1181:    the nonlinear solvers.

    1183:    Logically Collective on SNES

    1185:    Input Parameters:
    1186: +  snes - the SNES context
    1187: -  usrP - optional user context

    1189:    Level: intermediate

    1191:    Fortran Notes:
    1192:     To use this from Fortran you must write a Fortran interface definition for this
    1193:     function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

    1195: .seealso: SNESGetApplicationContext()
    1196: @*/
    1197: PetscErrorCode  SNESSetApplicationContext(SNES snes,void *usrP)
    1198: {
    1199:   KSP            ksp;

    1202:   SNESGetKSP(snes,&ksp);
    1203:   KSPSetApplicationContext(ksp,usrP);
    1204:   snes->user = usrP;
    1205:   return 0;
    1206: }

    1208: /*@
    1209:    SNESGetApplicationContext - Gets the user-defined context for the
    1210:    nonlinear solvers.

    1212:    Not Collective

    1214:    Input Parameter:
    1215: .  snes - SNES context

    1217:    Output Parameter:
    1218: .  usrP - user context

    1220:    Fortran Notes:
    1221:     To use this from Fortran you must write a Fortran interface definition for this
    1222:     function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

    1224:    Level: intermediate

    1226: .seealso: SNESSetApplicationContext()
    1227: @*/
    1228: PetscErrorCode  SNESGetApplicationContext(SNES snes,void *usrP)
    1229: {
    1231:   *(void**)usrP = snes->user;
    1232:   return 0;
    1233: }

    1235: /*@
    1236:    SNESSetUseMatrixFree - indicates that SNES should use matrix free finite difference matrix vector products internally to apply the Jacobian.

    1238:    Collective on SNES

    1240:    Input Parameters:
    1241: +  snes - SNES context
    1242: .  mf_operator - use matrix-free only for the Amat used by SNESSetJacobian(), this means the user provided Pmat will continue to be used
    1243: -  mf - use matrix-free for both the Amat and Pmat used by SNESSetJacobian(), both the Amat and Pmat set in SNESSetJacobian() will be ignored

    1245:    Options Database:
    1246: + -snes_mf - use matrix free for both the mat and pmat operator
    1247: . -snes_mf_operator - use matrix free only for the mat operator
    1248: . -snes_fd_color - compute the Jacobian via coloring and finite differences.
    1249: - -snes_fd - compute the Jacobian via finite differences (slow)

    1251:    Level: intermediate

    1253:    Notes:
    1254:       SNES supports three approaches for computing (approximate) Jacobians: user provided via SNESSetJacobian(), matrix free, and computing explicitly with
    1255:       finite differences and coloring using MatFDColoring. It is also possible to use automatic differentiation and the MatFDColoring object.

    1257: .seealso:   SNESGetUseMatrixFree(), MatCreateSNESMF(), SNESComputeJacobianDefaultColor()
    1258: @*/
    1259: PetscErrorCode  SNESSetUseMatrixFree(SNES snes,PetscBool mf_operator,PetscBool mf)
    1260: {
    1264:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
    1265:   snes->mf_operator = mf_operator;
    1266:   return 0;
    1267: }

    1269: /*@
    1270:    SNESGetUseMatrixFree - indicates if the SNES uses matrix free finite difference matrix vector products to apply the Jacobian.

    1272:    Collective on SNES

    1274:    Input Parameter:
    1275: .  snes - SNES context

    1277:    Output Parameters:
    1278: +  mf_operator - use matrix-free only for the Amat used by SNESSetJacobian(), this means the user provided Pmat will continue to be used
    1279: -  mf - use matrix-free for both the Amat and Pmat used by SNESSetJacobian(), both the Amat and Pmat set in SNESSetJacobian() will be ignored

    1281:    Options Database:
    1282: + -snes_mf - use matrix free for both the mat and pmat operator
    1283: - -snes_mf_operator - use matrix free only for the mat operator

    1285:    Level: intermediate

    1287: .seealso:   SNESSetUseMatrixFree(), MatCreateSNESMF()
    1288: @*/
    1289: PetscErrorCode  SNESGetUseMatrixFree(SNES snes,PetscBool *mf_operator,PetscBool *mf)
    1290: {
    1292:   if (mf)          *mf          = snes->mf;
    1293:   if (mf_operator) *mf_operator = snes->mf_operator;
    1294:   return 0;
    1295: }

    1297: /*@
    1298:    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
    1299:    at this time.

    1301:    Not Collective

    1303:    Input Parameter:
    1304: .  snes - SNES context

    1306:    Output Parameter:
    1307: .  iter - iteration number

    1309:    Notes:
    1310:    For example, during the computation of iteration 2 this would return 1.

    1312:    This is useful for using lagged Jacobians (where one does not recompute the
    1313:    Jacobian at each SNES iteration). For example, the code
    1314: .vb
    1315:       SNESGetIterationNumber(snes,&it);
    1316:       if (!(it % 2)) {
    1317:         [compute Jacobian here]
    1318:       }
    1319: .ve
    1320:    can be used in your ComputeJacobian() function to cause the Jacobian to be
    1321:    recomputed every second SNES iteration.

    1323:    After the SNES solve is complete this will return the number of nonlinear iterations used.

    1325:    Level: intermediate

    1327: .seealso:   SNESGetLinearSolveIterations()
    1328: @*/
    1329: PetscErrorCode  SNESGetIterationNumber(SNES snes,PetscInt *iter)
    1330: {
    1333:   *iter = snes->iter;
    1334:   return 0;
    1335: }

    1337: /*@
    1338:    SNESSetIterationNumber - Sets the current iteration number.

    1340:    Not Collective

    1342:    Input Parameters:
    1343: +  snes - SNES context
    1344: -  iter - iteration number

    1346:    Level: developer

    1348: .seealso:   SNESGetLinearSolveIterations()
    1349: @*/
    1350: PetscErrorCode  SNESSetIterationNumber(SNES snes,PetscInt iter)
    1351: {
    1353:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    1354:   snes->iter = iter;
    1355:   PetscObjectSAWsGrantAccess((PetscObject)snes);
    1356:   return 0;
    1357: }

    1359: /*@
    1360:    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
    1361:    attempted by the nonlinear solver.

    1363:    Not Collective

    1365:    Input Parameter:
    1366: .  snes - SNES context

    1368:    Output Parameter:
    1369: .  nfails - number of unsuccessful steps attempted

    1371:    Notes:
    1372:    This counter is reset to zero for each successive call to SNESSolve().

    1374:    Level: intermediate

    1376: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
    1377:           SNESSetMaxNonlinearStepFailures(), SNESGetMaxNonlinearStepFailures()
    1378: @*/
    1379: PetscErrorCode  SNESGetNonlinearStepFailures(SNES snes,PetscInt *nfails)
    1380: {
    1383:   *nfails = snes->numFailures;
    1384:   return 0;
    1385: }

    1387: /*@
    1388:    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
    1389:    attempted by the nonlinear solver before it gives up.

    1391:    Not Collective

    1393:    Input Parameters:
    1394: +  snes     - SNES context
    1395: -  maxFails - maximum of unsuccessful steps

    1397:    Level: intermediate

    1399: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
    1400:           SNESGetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
    1401: @*/
    1402: PetscErrorCode  SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
    1403: {
    1405:   snes->maxFailures = maxFails;
    1406:   return 0;
    1407: }

    1409: /*@
    1410:    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
    1411:    attempted by the nonlinear solver before it gives up.

    1413:    Not Collective

    1415:    Input Parameter:
    1416: .  snes     - SNES context

    1418:    Output Parameter:
    1419: .  maxFails - maximum of unsuccessful steps

    1421:    Level: intermediate

    1423: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
    1424:           SNESSetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()

    1426: @*/
    1427: PetscErrorCode  SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
    1428: {
    1431:   *maxFails = snes->maxFailures;
    1432:   return 0;
    1433: }

    1435: /*@
    1436:    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
    1437:      done by SNES.

    1439:    Not Collective

    1441:    Input Parameter:
    1442: .  snes     - SNES context

    1444:    Output Parameter:
    1445: .  nfuncs - number of evaluations

    1447:    Level: intermediate

    1449:    Notes:
    1450:     Reset every time SNESSolve is called unless SNESSetCountersReset() is used.

    1452: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(), SNESSetCountersReset()
    1453: @*/
    1454: PetscErrorCode  SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
    1455: {
    1458:   *nfuncs = snes->nfuncs;
    1459:   return 0;
    1460: }

    1462: /*@
    1463:    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
    1464:    linear solvers.

    1466:    Not Collective

    1468:    Input Parameter:
    1469: .  snes - SNES context

    1471:    Output Parameter:
    1472: .  nfails - number of failed solves

    1474:    Level: intermediate

    1476:    Options Database Keys:
    1477: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

    1479:    Notes:
    1480:    This counter is reset to zero for each successive call to SNESSolve().

    1482: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures()
    1483: @*/
    1484: PetscErrorCode  SNESGetLinearSolveFailures(SNES snes,PetscInt *nfails)
    1485: {
    1488:   *nfails = snes->numLinearSolveFailures;
    1489:   return 0;
    1490: }

    1492: /*@
    1493:    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
    1494:    allowed before SNES returns with a diverged reason of SNES_DIVERGED_LINEAR_SOLVE

    1496:    Logically Collective on SNES

    1498:    Input Parameters:
    1499: +  snes     - SNES context
    1500: -  maxFails - maximum allowed linear solve failures

    1502:    Level: intermediate

    1504:    Options Database Keys:
    1505: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

    1507:    Notes:
    1508:     By default this is 0; that is SNES returns on the first failed linear solve

    1510: .seealso: SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations()
    1511: @*/
    1512: PetscErrorCode  SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
    1513: {
    1516:   snes->maxLinearSolveFailures = maxFails;
    1517:   return 0;
    1518: }

    1520: /*@
    1521:    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
    1522:      are allowed before SNES terminates

    1524:    Not Collective

    1526:    Input Parameter:
    1527: .  snes     - SNES context

    1529:    Output Parameter:
    1530: .  maxFails - maximum of unsuccessful solves allowed

    1532:    Level: intermediate

    1534:    Notes:
    1535:     By default this is 1; that is SNES returns on the first failed linear solve

    1537: .seealso: SNESGetLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(),
    1538: @*/
    1539: PetscErrorCode  SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
    1540: {
    1543:   *maxFails = snes->maxLinearSolveFailures;
    1544:   return 0;
    1545: }

    1547: /*@
    1548:    SNESGetLinearSolveIterations - Gets the total number of linear iterations
    1549:    used by the nonlinear solver.

    1551:    Not Collective

    1553:    Input Parameter:
    1554: .  snes - SNES context

    1556:    Output Parameter:
    1557: .  lits - number of linear iterations

    1559:    Notes:
    1560:    This counter is reset to zero for each successive call to SNESSolve() unless SNESSetCountersReset() is used.

    1562:    If the linear solver fails inside the SNESSolve() the iterations for that call to the linear solver are not included. If you wish to count them
    1563:    then call KSPGetIterationNumber() after the failed solve.

    1565:    Level: intermediate

    1567: .seealso:  SNESGetIterationNumber(), SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESSetCountersReset()
    1568: @*/
    1569: PetscErrorCode  SNESGetLinearSolveIterations(SNES snes,PetscInt *lits)
    1570: {
    1573:   *lits = snes->linear_its;
    1574:   return 0;
    1575: }

    1577: /*@
    1578:    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
    1579:    are reset every time SNESSolve() is called.

    1581:    Logically Collective on SNES

    1583:    Input Parameters:
    1584: +  snes - SNES context
    1585: -  reset - whether to reset the counters or not

    1587:    Notes:
    1588:    This defaults to PETSC_TRUE

    1590:    Level: developer

    1592: .seealso:  SNESGetNumberFunctionEvals(), SNESGetLinearSolveIterations(), SNESGetNPC()
    1593: @*/
    1594: PetscErrorCode  SNESSetCountersReset(SNES snes,PetscBool reset)
    1595: {
    1598:   snes->counters_reset = reset;
    1599:   return 0;
    1600: }

    1602: /*@
    1603:    SNESSetKSP - Sets a KSP context for the SNES object to use

    1605:    Not Collective, but the SNES and KSP objects must live on the same MPI_Comm

    1607:    Input Parameters:
    1608: +  snes - the SNES context
    1609: -  ksp - the KSP context

    1611:    Notes:
    1612:    The SNES object already has its KSP object, you can obtain with SNESGetKSP()
    1613:    so this routine is rarely needed.

    1615:    The KSP object that is already in the SNES object has its reference count
    1616:    decreased by one.

    1618:    Level: developer

    1620: .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
    1621: @*/
    1622: PetscErrorCode  SNESSetKSP(SNES snes,KSP ksp)
    1623: {
    1627:   PetscObjectReference((PetscObject)ksp);
    1628:   if (snes->ksp) PetscObjectDereference((PetscObject)snes->ksp);
    1629:   snes->ksp = ksp;
    1630:   return 0;
    1631: }

    1633: /* -----------------------------------------------------------*/
    1634: /*@
    1635:    SNESCreate - Creates a nonlinear solver context.

    1637:    Collective

    1639:    Input Parameters:
    1640: .  comm - MPI communicator

    1642:    Output Parameter:
    1643: .  outsnes - the new SNES context

    1645:    Options Database Keys:
    1646: +   -snes_mf - Activates default matrix-free Jacobian-vector products,
    1647:                and no preconditioning matrix
    1648: .   -snes_mf_operator - Activates default matrix-free Jacobian-vector
    1649:                products, and a user-provided preconditioning matrix
    1650:                as set by SNESSetJacobian()
    1651: -   -snes_fd - Uses (slow!) finite differences to compute Jacobian

    1653:    Level: beginner

    1655:    Developer Notes:
    1656:     SNES always creates a KSP object even though many SNES methods do not use it. This is
    1657:                     unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
    1658:                     particular method does use KSP and regulates if the information about the KSP is printed
    1659:                     in SNESView(). TSSetFromOptions() does call SNESSetFromOptions() which can lead to users being confused
    1660:                     by help messages about meaningless SNES options.

    1662:                     SNES always creates the snes->kspconvctx even though it is used by only one type. This should
    1663:                     be fixed.

    1665: .seealso: SNESSolve(), SNESDestroy(), SNES, SNESSetLagPreconditioner(), SNESSetLagJacobian()

    1667: @*/
    1668: PetscErrorCode  SNESCreate(MPI_Comm comm,SNES *outsnes)
    1669: {
    1670:   SNES           snes;
    1671:   SNESKSPEW      *kctx;

    1674:   *outsnes = NULL;
    1675:   SNESInitializePackage();

    1677:   PetscHeaderCreate(snes,SNES_CLASSID,"SNES","Nonlinear solver","SNES",comm,SNESDestroy,SNESView);

    1679:   snes->ops->converged    = SNESConvergedDefault;
    1680:   snes->usesksp           = PETSC_TRUE;
    1681:   snes->tolerancesset     = PETSC_FALSE;
    1682:   snes->max_its           = 50;
    1683:   snes->max_funcs         = 10000;
    1684:   snes->norm              = 0.0;
    1685:   snes->xnorm             = 0.0;
    1686:   snes->ynorm             = 0.0;
    1687:   snes->normschedule      = SNES_NORM_ALWAYS;
    1688:   snes->functype          = SNES_FUNCTION_DEFAULT;
    1689: #if defined(PETSC_USE_REAL_SINGLE)
    1690:   snes->rtol              = 1.e-5;
    1691: #else
    1692:   snes->rtol              = 1.e-8;
    1693: #endif
    1694:   snes->ttol              = 0.0;
    1695: #if defined(PETSC_USE_REAL_SINGLE)
    1696:   snes->abstol            = 1.e-25;
    1697: #else
    1698:   snes->abstol            = 1.e-50;
    1699: #endif
    1700: #if defined(PETSC_USE_REAL_SINGLE)
    1701:   snes->stol              = 1.e-5;
    1702: #else
    1703:   snes->stol              = 1.e-8;
    1704: #endif
    1705: #if defined(PETSC_USE_REAL_SINGLE)
    1706:   snes->deltatol          = 1.e-6;
    1707: #else
    1708:   snes->deltatol          = 1.e-12;
    1709: #endif
    1710:   snes->divtol            = 1.e4;
    1711:   snes->rnorm0            = 0;
    1712:   snes->nfuncs            = 0;
    1713:   snes->numFailures       = 0;
    1714:   snes->maxFailures       = 1;
    1715:   snes->linear_its        = 0;
    1716:   snes->lagjacobian       = 1;
    1717:   snes->jac_iter          = 0;
    1718:   snes->lagjac_persist    = PETSC_FALSE;
    1719:   snes->lagpreconditioner = 1;
    1720:   snes->pre_iter          = 0;
    1721:   snes->lagpre_persist    = PETSC_FALSE;
    1722:   snes->numbermonitors    = 0;
    1723:   snes->numberreasonviews = 0;
    1724:   snes->data              = NULL;
    1725:   snes->setupcalled       = PETSC_FALSE;
    1726:   snes->ksp_ewconv        = PETSC_FALSE;
    1727:   snes->nwork             = 0;
    1728:   snes->work              = NULL;
    1729:   snes->nvwork            = 0;
    1730:   snes->vwork             = NULL;
    1731:   snes->conv_hist_len     = 0;
    1732:   snes->conv_hist_max     = 0;
    1733:   snes->conv_hist         = NULL;
    1734:   snes->conv_hist_its     = NULL;
    1735:   snes->conv_hist_reset   = PETSC_TRUE;
    1736:   snes->counters_reset    = PETSC_TRUE;
    1737:   snes->vec_func_init_set = PETSC_FALSE;
    1738:   snes->reason            = SNES_CONVERGED_ITERATING;
    1739:   snes->npcside           = PC_RIGHT;
    1740:   snes->setfromoptionscalled = 0;

    1742:   snes->mf          = PETSC_FALSE;
    1743:   snes->mf_operator = PETSC_FALSE;
    1744:   snes->mf_version  = 1;

    1746:   snes->numLinearSolveFailures = 0;
    1747:   snes->maxLinearSolveFailures = 1;

    1749:   snes->vizerotolerance = 1.e-8;
    1750:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

    1752:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
    1753:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

    1755:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
    1756:   PetscNewLog(snes,&kctx);

    1758:   snes->kspconvctx  = (void*)kctx;
    1759:   kctx->version     = 2;
    1760:   kctx->rtol_0      = .3; /* Eisenstat and Walker suggest rtol_0=.5, but
    1761:                              this was too large for some test cases */
    1762:   kctx->rtol_last   = 0.0;
    1763:   kctx->rtol_max    = .9;
    1764:   kctx->gamma       = 1.0;
    1765:   kctx->alpha       = .5*(1.0 + PetscSqrtReal(5.0));
    1766:   kctx->alpha2      = kctx->alpha;
    1767:   kctx->threshold   = .1;
    1768:   kctx->lresid_last = 0.0;
    1769:   kctx->norm_last   = 0.0;

    1771:   *outsnes = snes;
    1772:   return 0;
    1773: }

    1775: /*MC
    1776:     SNESFunction - Functional form used to convey the nonlinear function to be solved by SNES

    1778:      Synopsis:
    1779:      #include "petscsnes.h"
    1780:      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);

    1782:      Collective on snes

    1784:      Input Parameters:
    1785: +     snes - the SNES context
    1786: .     x    - state at which to evaluate residual
    1787: -     ctx     - optional user-defined function context, passed in with SNESSetFunction()

    1789:      Output Parameter:
    1790: .     f  - vector to put residual (function value)

    1792:    Level: intermediate

    1794: .seealso:   SNESSetFunction(), SNESGetFunction()
    1795: M*/

    1797: /*@C
    1798:    SNESSetFunction - Sets the function evaluation routine and function
    1799:    vector for use by the SNES routines in solving systems of nonlinear
    1800:    equations.

    1802:    Logically Collective on SNES

    1804:    Input Parameters:
    1805: +  snes - the SNES context
    1806: .  r - vector to store function values, may be NULL
    1807: .  f - function evaluation routine; see SNESFunction for calling sequence details
    1808: -  ctx - [optional] user-defined context for private data for the
    1809:          function evaluation routine (may be NULL)

    1811:    Notes:
    1812:    The Newton-like methods typically solve linear systems of the form
    1813: $      f'(x) x = -f(x),
    1814:    where f'(x) denotes the Jacobian matrix and f(x) is the function.

    1816:    Level: beginner

    1818: .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetPicard(), SNESFunction
    1819: @*/
    1820: PetscErrorCode  SNESSetFunction(SNES snes,Vec r,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
    1821: {
    1822:   DM             dm;

    1825:   if (r) {
    1828:     PetscObjectReference((PetscObject)r);
    1829:     VecDestroy(&snes->vec_func);
    1830:     snes->vec_func = r;
    1831:   }
    1832:   SNESGetDM(snes,&dm);
    1833:   DMSNESSetFunction(dm,f,ctx);
    1834:   if (f == SNESPicardComputeFunction) {
    1835:     DMSNESSetMFFunction(dm,SNESPicardComputeMFFunction,ctx);
    1836:   }
    1837:   return 0;
    1838: }

    1840: /*@C
    1841:    SNESSetInitialFunction - Sets the function vector to be used as the
    1842:    function norm at the initialization of the method.  In some
    1843:    instances, the user has precomputed the function before calling
    1844:    SNESSolve.  This function allows one to avoid a redundant call
    1845:    to SNESComputeFunction in that case.

    1847:    Logically Collective on SNES

    1849:    Input Parameters:
    1850: +  snes - the SNES context
    1851: -  f - vector to store function value

    1853:    Notes:
    1854:    This should not be modified during the solution procedure.

    1856:    This is used extensively in the SNESFAS hierarchy and in nonlinear preconditioning.

    1858:    Level: developer

    1860: .seealso: SNESSetFunction(), SNESComputeFunction(), SNESSetInitialFunctionNorm()
    1861: @*/
    1862: PetscErrorCode  SNESSetInitialFunction(SNES snes, Vec f)
    1863: {
    1864:   Vec            vec_func;

    1869:   if (snes->npcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
    1870:     snes->vec_func_init_set = PETSC_FALSE;
    1871:     return 0;
    1872:   }
    1873:   SNESGetFunction(snes,&vec_func,NULL,NULL);
    1874:   VecCopy(f,vec_func);

    1876:   snes->vec_func_init_set = PETSC_TRUE;
    1877:   return 0;
    1878: }

    1880: /*@
    1881:    SNESSetNormSchedule - Sets the SNESNormSchedule used in convergence and monitoring
    1882:    of the SNES method.

    1884:    Logically Collective on SNES

    1886:    Input Parameters:
    1887: +  snes - the SNES context
    1888: -  normschedule - the frequency of norm computation

    1890:    Options Database Key:
    1891: .  -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - set the schedule

    1893:    Notes:
    1894:    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
    1895:    of the nonlinear function and the taking of its norm at every iteration to
    1896:    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
    1897:    (SNESNGS) and the like do not require the norm of the function to be computed, and therefore
    1898:    may either be monitored for convergence or not.  As these are often used as nonlinear
    1899:    preconditioners, monitoring the norm of their error is not a useful enterprise within
    1900:    their solution.

    1902:    Level: developer

    1904: .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1905: @*/
    1906: PetscErrorCode  SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
    1907: {
    1909:   snes->normschedule = normschedule;
    1910:   return 0;
    1911: }

    1913: /*@
    1914:    SNESGetNormSchedule - Gets the SNESNormSchedule used in convergence and monitoring
    1915:    of the SNES method.

    1917:    Logically Collective on SNES

    1919:    Input Parameters:
    1920: +  snes - the SNES context
    1921: -  normschedule - the type of the norm used

    1923:    Level: advanced

    1925: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1926: @*/
    1927: PetscErrorCode  SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
    1928: {
    1930:   *normschedule = snes->normschedule;
    1931:   return 0;
    1932: }

    1934: /*@
    1935:   SNESSetFunctionNorm - Sets the last computed residual norm.

    1937:   Logically Collective on SNES

    1939:   Input Parameters:
    1940: + snes - the SNES context

    1942: - normschedule - the frequency of norm computation

    1944:   Level: developer

    1946: .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1947: @*/
    1948: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
    1949: {
    1951:   snes->norm = norm;
    1952:   return 0;
    1953: }

    1955: /*@
    1956:   SNESGetFunctionNorm - Gets the last computed norm of the residual

    1958:   Not Collective

    1960:   Input Parameter:
    1961: . snes - the SNES context

    1963:   Output Parameter:
    1964: . norm - the last computed residual norm

    1966:   Level: developer

    1968: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1969: @*/
    1970: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
    1971: {
    1974:   *norm = snes->norm;
    1975:   return 0;
    1976: }

    1978: /*@
    1979:   SNESGetUpdateNorm - Gets the last computed norm of the Newton update

    1981:   Not Collective

    1983:   Input Parameter:
    1984: . snes - the SNES context

    1986:   Output Parameter:
    1987: . ynorm - the last computed update norm

    1989:   Level: developer

    1991: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), SNESGetFunctionNorm()
    1992: @*/
    1993: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
    1994: {
    1997:   *ynorm = snes->ynorm;
    1998:   return 0;
    1999: }

    2001: /*@
    2002:   SNESGetSolutionNorm - Gets the last computed norm of the solution

    2004:   Not Collective

    2006:   Input Parameter:
    2007: . snes - the SNES context

    2009:   Output Parameter:
    2010: . xnorm - the last computed solution norm

    2012:   Level: developer

    2014: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), SNESGetFunctionNorm(), SNESGetUpdateNorm()
    2015: @*/
    2016: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
    2017: {
    2020:   *xnorm = snes->xnorm;
    2021:   return 0;
    2022: }

    2024: /*@C
    2025:    SNESSetFunctionType - Sets the SNESNormSchedule used in convergence and monitoring
    2026:    of the SNES method.

    2028:    Logically Collective on SNES

    2030:    Input Parameters:
    2031: +  snes - the SNES context
    2032: -  normschedule - the frequency of norm computation

    2034:    Notes:
    2035:    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
    2036:    of the nonlinear function and the taking of its norm at every iteration to
    2037:    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
    2038:    (SNESNGS) and the like do not require the norm of the function to be computed, and therefore
    2039:    may either be monitored for convergence or not.  As these are often used as nonlinear
    2040:    preconditioners, monitoring the norm of their error is not a useful enterprise within
    2041:    their solution.

    2043:    Level: developer

    2045: .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    2046: @*/
    2047: PetscErrorCode  SNESSetFunctionType(SNES snes, SNESFunctionType type)
    2048: {
    2050:   snes->functype = type;
    2051:   return 0;
    2052: }

    2054: /*@C
    2055:    SNESGetFunctionType - Gets the SNESNormSchedule used in convergence and monitoring
    2056:    of the SNES method.

    2058:    Logically Collective on SNES

    2060:    Input Parameters:
    2061: +  snes - the SNES context
    2062: -  normschedule - the type of the norm used

    2064:    Level: advanced

    2066: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    2067: @*/
    2068: PetscErrorCode  SNESGetFunctionType(SNES snes, SNESFunctionType *type)
    2069: {
    2071:   *type = snes->functype;
    2072:   return 0;
    2073: }

    2075: /*MC
    2076:     SNESNGSFunction - function used to convey a Gauss-Seidel sweep on the nonlinear function

    2078:      Synopsis:
    2079: #include <petscsnes.h>
    2080: $    SNESNGSFunction(SNES snes,Vec x,Vec b,void *ctx);

    2082:      Collective on snes

    2084:      Input Parameters:
    2085: +  X   - solution vector
    2086: .  B   - RHS vector
    2087: -  ctx - optional user-defined Gauss-Seidel context

    2089:      Output Parameter:
    2090: .  X   - solution vector

    2092:    Level: intermediate

    2094: .seealso:   SNESSetNGS(), SNESGetNGS()
    2095: M*/

    2097: /*@C
    2098:    SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
    2099:    use with composed nonlinear solvers.

    2101:    Input Parameters:
    2102: +  snes   - the SNES context
    2103: .  f - function evaluation routine to apply Gauss-Seidel see SNESNGSFunction
    2104: -  ctx    - [optional] user-defined context for private data for the
    2105:             smoother evaluation routine (may be NULL)

    2107:    Notes:
    2108:    The NGS routines are used by the composed nonlinear solver to generate
    2109:     a problem appropriate update to the solution, particularly FAS.

    2111:    Level: intermediate

    2113: .seealso: SNESGetFunction(), SNESComputeNGS()
    2114: @*/
    2115: PetscErrorCode SNESSetNGS(SNES snes,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
    2116: {
    2117:   DM             dm;

    2120:   SNESGetDM(snes,&dm);
    2121:   DMSNESSetNGS(dm,f,ctx);
    2122:   return 0;
    2123: }

    2125: /*
    2126:      This is used for -snes_mf_operator; it uses a duplicate of snes->jacobian_pre because snes->jacobian_pre cannot be
    2127:    changed during the KSPSolve()
    2128: */
    2129: PetscErrorCode SNESPicardComputeMFFunction(SNES snes,Vec x,Vec f,void *ctx)
    2130: {
    2131:   DM             dm;
    2132:   DMSNES         sdm;

    2134:   SNESGetDM(snes,&dm);
    2135:   DMGetDMSNES(dm,&sdm);
    2137:   /*  A(x)*x - b(x) */
    2138:   if (sdm->ops->computepfunction) {
    2139:     PetscStackPush("SNES Picard user function");
    2140:     (*sdm->ops->computepfunction)(snes,x,f,sdm->pctx);
    2141:     PetscStackPop;
    2142:     VecScale(f,-1.0);
    2143:     if (!snes->picard) {
    2144:       /* Cannot share nonzero pattern because of the possible use of SNESComputeJacobianDefault() */
    2145:       MatDuplicate(snes->jacobian_pre,MAT_DO_NOT_COPY_VALUES,&snes->picard);
    2146:     }
    2147:     PetscStackPush("SNES Picard user Jacobian");
    2148:     (*sdm->ops->computepjacobian)(snes,x,snes->picard,snes->picard,sdm->pctx);
    2149:     PetscStackPop;
    2150:     MatMultAdd(snes->picard,x,f,f);
    2151:   } else {
    2152:     PetscStackPush("SNES Picard user Jacobian");
    2153:     (*sdm->ops->computepjacobian)(snes,x,snes->picard,snes->picard,sdm->pctx);
    2154:     PetscStackPop;
    2155:     MatMult(snes->picard,x,f);
    2156:   }
    2157:   return 0;
    2158: }

    2160: PetscErrorCode SNESPicardComputeFunction(SNES snes,Vec x,Vec f,void *ctx)
    2161: {
    2162:   DM             dm;
    2163:   DMSNES         sdm;

    2165:   SNESGetDM(snes,&dm);
    2166:   DMGetDMSNES(dm,&sdm);
    2168:   /*  A(x)*x - b(x) */
    2169:   if (sdm->ops->computepfunction) {
    2170:     PetscStackPush("SNES Picard user function");
    2171:     (*sdm->ops->computepfunction)(snes,x,f,sdm->pctx);
    2172:     PetscStackPop;
    2173:     VecScale(f,-1.0);
    2174:     PetscStackPush("SNES Picard user Jacobian");
    2175:     (*sdm->ops->computepjacobian)(snes,x,snes->jacobian,snes->jacobian_pre,sdm->pctx);
    2176:     PetscStackPop;
    2177:     MatMultAdd(snes->jacobian_pre,x,f,f);
    2178:   } else {
    2179:     PetscStackPush("SNES Picard user Jacobian");
    2180:     (*sdm->ops->computepjacobian)(snes,x,snes->jacobian,snes->jacobian_pre,sdm->pctx);
    2181:     PetscStackPop;
    2182:     MatMult(snes->jacobian_pre,x,f);
    2183:   }
    2184:   return 0;
    2185: }

    2187: PetscErrorCode SNESPicardComputeJacobian(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
    2188: {
    2189:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
    2190:   /* must assembly if matrix-free to get the last SNES solution */
    2191:   MatAssemblyBegin(J,MAT_FINAL_ASSEMBLY);
    2192:   MatAssemblyEnd(J,MAT_FINAL_ASSEMBLY);
    2193:   return 0;
    2194: }

    2196: /*@C
    2197:    SNESSetPicard - Use SNES to solve the system A(x) x = bp(x) + b via a Picard type iteration (Picard linearization)

    2199:    Logically Collective on SNES

    2201:    Input Parameters:
    2202: +  snes - the SNES context
    2203: .  r - vector to store function values, may be NULL
    2204: .  bp - function evaluation routine, may be NULL
    2205: .  Amat - matrix with which A(x) x - bp(x) - b is to be computed
    2206: .  Pmat - matrix from which preconditioner is computed (usually the same as Amat)
    2207: .  J  - function to compute matrix values, see SNESJacobianFunction() for details on its calling sequence
    2208: -  ctx - [optional] user-defined context for private data for the function evaluation routine (may be NULL)

    2210:    Notes:
    2211:     It is often better to provide the nonlinear function F() and some approximation to its Jacobian directly and use
    2212:     an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

    2214:     One can call SNESSetPicard() or SNESSetFunction() (and possibly SNESSetJacobian()) but cannot call both

    2216: $     Solves the equation A(x) x = bp(x) - b via the defect correction algorithm A(x^{n}) (x^{n+1} - x^{n}) = bp(x^{n}) + b - A(x^{n})x^{n}
    2217: $     Note that when an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = bp(x^{n}) + b iteration.

    2219:      Run with -snes_mf_operator to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.

    2221:    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
    2222:    the direct Picard iteration A(x^n) x^{n+1} = bp(x^n) + b

    2224:    There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
    2225:    believe it is the iteration  A(x^{n}) x^{n+1} = b(x^{n}) hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
    2226:    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).

    2228:    When used with -snes_mf_operator this will run matrix-free Newton's method where the matrix-vector product is of the true Jacobian of A(x)x - bp(x) -b.

    2230:    When used with -snes_fd this will compute the true Jacobian (very slowly one column at at time) and thus represent Newton's method.

    2232:    When used with -snes_fd_coloring this will compute the Jacobian via coloring and thus represent a faster implementation of Newton's method. But the
    2233:    the nonzero structure of the Jacobian is, in general larger than that of the Picard matrix A so you must provide in A the needed nonzero structure for the correct
    2234:    coloring. When using DMDA this may mean creating the matrix A with DMCreateMatrix() using a wider stencil than strictly needed for A or with a DMDA_STENCIL_BOX.
    2235:    See the commment in src/snes/tutorials/ex15.c.

    2237:    Level: intermediate

    2239: .seealso: SNESGetFunction(), SNESSetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESGetPicard(), SNESLineSearchPreCheckPicard(), SNESJacobianFunction
    2240: @*/
    2241: PetscErrorCode  SNESSetPicard(SNES snes,Vec r,PetscErrorCode (*bp)(SNES,Vec,Vec,void*),Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
    2242: {
    2243:   DM             dm;

    2246:   SNESGetDM(snes, &dm);
    2247:   DMSNESSetPicard(dm,bp,J,ctx);
    2248:   DMSNESSetMFFunction(dm,SNESPicardComputeMFFunction,ctx);
    2249:   SNESSetFunction(snes,r,SNESPicardComputeFunction,ctx);
    2250:   SNESSetJacobian(snes,Amat,Pmat,SNESPicardComputeJacobian,ctx);
    2251:   return 0;
    2252: }

    2254: /*@C
    2255:    SNESGetPicard - Returns the context for the Picard iteration

    2257:    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.

    2259:    Input Parameter:
    2260: .  snes - the SNES context

    2262:    Output Parameters:
    2263: +  r - the function (or NULL)
    2264: .  f - the function (or NULL); see SNESFunction for calling sequence details
    2265: .  Amat - the matrix used to defined the operation A(x) x - b(x) (or NULL)
    2266: .  Pmat  - the matrix from which the preconditioner will be constructed (or NULL)
    2267: .  J - the function for matrix evaluation (or NULL); see SNESJacobianFunction for calling sequence details
    2268: -  ctx - the function context (or NULL)

    2270:    Level: advanced

    2272: .seealso: SNESSetPicard(), SNESGetFunction(), SNESGetJacobian(), SNESGetDM(), SNESFunction, SNESJacobianFunction
    2273: @*/
    2274: PetscErrorCode  SNESGetPicard(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
    2275: {
    2276:   DM             dm;

    2279:   SNESGetFunction(snes,r,NULL,NULL);
    2280:   SNESGetJacobian(snes,Amat,Pmat,NULL,NULL);
    2281:   SNESGetDM(snes,&dm);
    2282:   DMSNESGetPicard(dm,f,J,ctx);
    2283:   return 0;
    2284: }

    2286: /*@C
    2287:    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the problem

    2289:    Logically Collective on SNES

    2291:    Input Parameters:
    2292: +  snes - the SNES context
    2293: .  func - function evaluation routine
    2294: -  ctx - [optional] user-defined context for private data for the
    2295:          function evaluation routine (may be NULL)

    2297:    Calling sequence of func:
    2298: $    func (SNES snes,Vec x,void *ctx);

    2300: .  f - function vector
    2301: -  ctx - optional user-defined function context

    2303:    Level: intermediate

    2305: .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian()
    2306: @*/
    2307: PetscErrorCode  SNESSetComputeInitialGuess(SNES snes,PetscErrorCode (*func)(SNES,Vec,void*),void *ctx)
    2308: {
    2310:   if (func) snes->ops->computeinitialguess = func;
    2311:   if (ctx)  snes->initialguessP            = ctx;
    2312:   return 0;
    2313: }

    2315: /* --------------------------------------------------------------- */
    2316: /*@C
    2317:    SNESGetRhs - Gets the vector for solving F(x) = rhs. If rhs is not set
    2318:    it assumes a zero right hand side.

    2320:    Logically Collective on SNES

    2322:    Input Parameter:
    2323: .  snes - the SNES context

    2325:    Output Parameter:
    2326: .  rhs - the right hand side vector or NULL if the right hand side vector is null

    2328:    Level: intermediate

    2330: .seealso: SNESGetSolution(), SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
    2331: @*/
    2332: PetscErrorCode  SNESGetRhs(SNES snes,Vec *rhs)
    2333: {
    2336:   *rhs = snes->vec_rhs;
    2337:   return 0;
    2338: }

    2340: /*@
    2341:    SNESComputeFunction - Calls the function that has been set with SNESSetFunction().

    2343:    Collective on SNES

    2345:    Input Parameters:
    2346: +  snes - the SNES context
    2347: -  x - input vector

    2349:    Output Parameter:
    2350: .  y - function vector, as set by SNESSetFunction()

    2352:    Notes:
    2353:    SNESComputeFunction() is typically used within nonlinear solvers
    2354:    implementations, so users would not generally call this routine themselves.

    2356:    Level: developer

    2358: .seealso: SNESSetFunction(), SNESGetFunction(), SNESComputeMFFunction()
    2359: @*/
    2360: PetscErrorCode  SNESComputeFunction(SNES snes,Vec x,Vec y)
    2361: {
    2362:   DM             dm;
    2363:   DMSNES         sdm;

    2370:   VecValidValues(x,2,PETSC_TRUE);

    2372:   SNESGetDM(snes,&dm);
    2373:   DMGetDMSNES(dm,&sdm);
    2374:   if (sdm->ops->computefunction) {
    2375:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) {
    2376:       PetscLogEventBegin(SNES_FunctionEval,snes,x,y,0);
    2377:     }
    2378:     VecLockReadPush(x);
    2379:     PetscStackPush("SNES user function");
    2380:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
    2381:     snes->domainerror = PETSC_FALSE;
    2382:     (*sdm->ops->computefunction)(snes,x,y,sdm->functionctx);
    2383:     PetscStackPop;
    2384:     VecLockReadPop(x);
    2385:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) {
    2386:       PetscLogEventEnd(SNES_FunctionEval,snes,x,y,0);
    2387:     }
    2388:   } else if (snes->vec_rhs) {
    2389:     MatMult(snes->jacobian, x, y);
    2390:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
    2391:   if (snes->vec_rhs) {
    2392:     VecAXPY(y,-1.0,snes->vec_rhs);
    2393:   }
    2394:   snes->nfuncs++;
    2395:   /*
    2396:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
    2397:      propagate the value to all processes
    2398:   */
    2399:   if (snes->domainerror) {
    2400:     VecSetInf(y);
    2401:   }
    2402:   return 0;
    2403: }

    2405: /*@
    2406:    SNESComputeMFFunction - Calls the function that has been set with SNESSetMFFunction().

    2408:    Collective on SNES

    2410:    Input Parameters:
    2411: +  snes - the SNES context
    2412: -  x - input vector

    2414:    Output Parameter:
    2415: .  y - function vector, as set by SNESSetMFFunction()

    2417:    Notes:
    2418:        SNESComputeMFFunction() is used within the matrix vector products called by the matrix created with MatCreateSNESMF()
    2419:    so users would not generally call this routine themselves.

    2421:        Since this function is intended for use with finite differencing it does not subtract the right hand side vector provided with SNESSolve()
    2422:     while SNESComputeFunction() does. As such, this routine cannot be used with  MatMFFDSetBase() with a provided F function value even if it applies the
    2423:     same function as SNESComputeFunction() if a SNESSolve() right hand side vector is use because the two functions difference would include this right hand side function.

    2425:    Level: developer

    2427: .seealso: SNESSetFunction(), SNESGetFunction(), SNESComputeFunction(), MatCreateSNESMF
    2428: @*/
    2429: PetscErrorCode  SNESComputeMFFunction(SNES snes,Vec x,Vec y)
    2430: {
    2431:   DM             dm;
    2432:   DMSNES         sdm;

    2439:   VecValidValues(x,2,PETSC_TRUE);

    2441:   SNESGetDM(snes,&dm);
    2442:   DMGetDMSNES(dm,&sdm);
    2443:   PetscLogEventBegin(SNES_FunctionEval,snes,x,y,0);
    2444:   VecLockReadPush(x);
    2445:   PetscStackPush("SNES user function");
    2446:   /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
    2447:   snes->domainerror = PETSC_FALSE;
    2448:   (*sdm->ops->computemffunction)(snes,x,y,sdm->mffunctionctx);
    2449:   PetscStackPop;
    2450:   VecLockReadPop(x);
    2451:   PetscLogEventEnd(SNES_FunctionEval,snes,x,y,0);
    2452:   snes->nfuncs++;
    2453:   /*
    2454:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
    2455:      propagate the value to all processes
    2456:   */
    2457:   if (snes->domainerror) {
    2458:     VecSetInf(y);
    2459:   }
    2460:   return 0;
    2461: }

    2463: /*@
    2464:    SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  SNESSetNGS().

    2466:    Collective on SNES

    2468:    Input Parameters:
    2469: +  snes - the SNES context
    2470: .  x - input vector
    2471: -  b - rhs vector

    2473:    Output Parameter:
    2474: .  x - new solution vector

    2476:    Notes:
    2477:    SNESComputeNGS() is typically used within composed nonlinear solver
    2478:    implementations, so most users would not generally call this routine
    2479:    themselves.

    2481:    Level: developer

    2483: .seealso: SNESSetNGS(), SNESComputeFunction()
    2484: @*/
    2485: PetscErrorCode  SNESComputeNGS(SNES snes,Vec b,Vec x)
    2486: {
    2487:   DM             dm;
    2488:   DMSNES         sdm;

    2495:   if (b) VecValidValues(b,2,PETSC_TRUE);
    2496:   PetscLogEventBegin(SNES_NGSEval,snes,x,b,0);
    2497:   SNESGetDM(snes,&dm);
    2498:   DMGetDMSNES(dm,&sdm);
    2499:   if (sdm->ops->computegs) {
    2500:     if (b) VecLockReadPush(b);
    2501:     PetscStackPush("SNES user NGS");
    2502:     (*sdm->ops->computegs)(snes,x,b,sdm->gsctx);
    2503:     PetscStackPop;
    2504:     if (b) VecLockReadPop(b);
    2505:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
    2506:   PetscLogEventEnd(SNES_NGSEval,snes,x,b,0);
    2507:   return 0;
    2508: }

    2510: PetscErrorCode SNESTestJacobian(SNES snes)
    2511: {
    2512:   Mat               A,B,C,D,jacobian;
    2513:   Vec               x = snes->vec_sol,f = snes->vec_func;
    2514:   PetscErrorCode    ierr;
    2515:   PetscReal         nrm,gnorm;
    2516:   PetscReal         threshold = 1.e-5;
    2517:   MatType           mattype;
    2518:   PetscInt          m,n,M,N;
    2519:   void              *functx;
    2520:   PetscBool         complete_print = PETSC_FALSE,threshold_print = PETSC_FALSE,test = PETSC_FALSE,flg,istranspose;
    2521:   PetscViewer       viewer,mviewer;
    2522:   MPI_Comm          comm;
    2523:   PetscInt          tabs;
    2524:   static PetscBool  directionsprinted = PETSC_FALSE;
    2525:   PetscViewerFormat format;

    2527:   PetscObjectOptionsBegin((PetscObject)snes);
    2528:   PetscOptionsName("-snes_test_jacobian","Compare hand-coded and finite difference Jacobians","None",&test);
    2529:   PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold,NULL);
    2530:   PetscOptionsViewer("-snes_test_jacobian_view","View difference between hand-coded and finite difference Jacobians element entries","None",&mviewer,&format,&complete_print);
    2531:   if (!complete_print) {
    2532:     PetscOptionsDeprecated("-snes_test_jacobian_display","-snes_test_jacobian_view","3.13",NULL);
    2533:     PetscOptionsViewer("-snes_test_jacobian_display","Display difference between hand-coded and finite difference Jacobians","None",&mviewer,&format,&complete_print);
    2534:   }
    2535:   /* for compatibility with PETSc 3.9 and older. */
    2536:   PetscOptionsDeprecated("-snes_test_jacobian_display_threshold","-snes_test_jacobian","3.13","-snes_test_jacobian accepts an optional threshold (since v3.10)");
    2537:   PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print);
    2538:   PetscOptionsEnd();
    2539:   if (!test) return 0;

    2541:   PetscObjectGetComm((PetscObject)snes,&comm);
    2542:   PetscViewerASCIIGetStdout(comm,&viewer);
    2543:   PetscViewerASCIIGetTab(viewer, &tabs);
    2544:   PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel);
    2545:   PetscViewerASCIIPrintf(viewer,"  ---------- Testing Jacobian -------------\n");
    2546:   if (!complete_print && !directionsprinted) {
    2547:     PetscViewerASCIIPrintf(viewer,"  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n");
    2548:     PetscViewerASCIIPrintf(viewer,"    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n");
    2549:   }
    2550:   if (!directionsprinted) {
    2551:     PetscViewerASCIIPrintf(viewer,"  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n");
    2552:     PetscViewerASCIIPrintf(viewer,"    O(1.e-8), the hand-coded Jacobian is probably correct.\n");
    2553:     directionsprinted = PETSC_TRUE;
    2554:   }
    2555:   if (complete_print) {
    2556:     PetscViewerPushFormat(mviewer,format);
    2557:   }

    2559:   PetscObjectTypeCompare((PetscObject)snes->jacobian,MATMFFD,&flg);
    2560:   if (!flg) jacobian = snes->jacobian;
    2561:   else jacobian = snes->jacobian_pre;

    2563:   if (!x) {
    2564:     MatCreateVecs(jacobian, &x, NULL);
    2565:   } else {
    2566:     PetscObjectReference((PetscObject) x);
    2567:   }
    2568:   if (!f) {
    2569:     VecDuplicate(x, &f);
    2570:   } else {
    2571:     PetscObjectReference((PetscObject) f);
    2572:   }
    2573:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
    2574:   SNESComputeFunction(snes,x,f);
    2575:   VecDestroy(&f);
    2576:   PetscObjectTypeCompare((PetscObject)snes,SNESKSPTRANSPOSEONLY,&istranspose);
    2577:   while (jacobian) {
    2578:     Mat JT = NULL, Jsave = NULL;

    2580:     if (istranspose) {
    2581:       MatCreateTranspose(jacobian,&JT);
    2582:       Jsave = jacobian;
    2583:       jacobian = JT;
    2584:     }
    2585:     PetscObjectBaseTypeCompareAny((PetscObject)jacobian,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPISBAIJ,"");
    2586:     if (flg) {
    2587:       A    = jacobian;
    2588:       PetscObjectReference((PetscObject)A);
    2589:     } else {
    2590:       MatComputeOperator(jacobian,MATAIJ,&A);
    2591:     }

    2593:     MatGetType(A,&mattype);
    2594:     MatGetSize(A,&M,&N);
    2595:     MatGetLocalSize(A,&m,&n);
    2596:     MatCreate(PetscObjectComm((PetscObject)A),&B);
    2597:     MatSetType(B,mattype);
    2598:     MatSetSizes(B,m,n,M,N);
    2599:     MatSetBlockSizesFromMats(B,A,A);
    2600:     MatSetUp(B);
    2601:     MatSetOption(B,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_FALSE);

    2603:     SNESGetFunction(snes,NULL,NULL,&functx);
    2604:     SNESComputeJacobianDefault(snes,x,B,B,functx);

    2606:     MatDuplicate(B,MAT_COPY_VALUES,&D);
    2607:     MatAYPX(D,-1.0,A,DIFFERENT_NONZERO_PATTERN);
    2608:     MatNorm(D,NORM_FROBENIUS,&nrm);
    2609:     MatNorm(A,NORM_FROBENIUS,&gnorm);
    2610:     MatDestroy(&D);
    2611:     if (!gnorm) gnorm = 1; /* just in case */
    2612:     PetscViewerASCIIPrintf(viewer,"  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n",(double)(nrm/gnorm),(double)nrm);

    2614:     if (complete_print) {
    2615:       PetscViewerASCIIPrintf(viewer,"  Hand-coded Jacobian ----------\n");
    2616:       MatView(A,mviewer);
    2617:       PetscViewerASCIIPrintf(viewer,"  Finite difference Jacobian ----------\n");
    2618:       MatView(B,mviewer);
    2619:     }

    2621:     if (threshold_print || complete_print) {
    2622:       PetscInt          Istart, Iend, *ccols, bncols, cncols, j, row;
    2623:       PetscScalar       *cvals;
    2624:       const PetscInt    *bcols;
    2625:       const PetscScalar *bvals;

    2627:       MatCreate(PetscObjectComm((PetscObject)A),&C);
    2628:       MatSetType(C,mattype);
    2629:       MatSetSizes(C,m,n,M,N);
    2630:       MatSetBlockSizesFromMats(C,A,A);
    2631:       MatSetUp(C);
    2632:       MatSetOption(C,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_FALSE);

    2634:       MatAYPX(B,-1.0,A,DIFFERENT_NONZERO_PATTERN);
    2635:       MatGetOwnershipRange(B,&Istart,&Iend);

    2637:       for (row = Istart; row < Iend; row++) {
    2638:         MatGetRow(B,row,&bncols,&bcols,&bvals);
    2639:         PetscMalloc2(bncols,&ccols,bncols,&cvals);
    2640:         for (j = 0, cncols = 0; j < bncols; j++) {
    2641:           if (PetscAbsScalar(bvals[j]) > threshold) {
    2642:             ccols[cncols] = bcols[j];
    2643:             cvals[cncols] = bvals[j];
    2644:             cncols += 1;
    2645:           }
    2646:         }
    2647:         if (cncols) {
    2648:           MatSetValues(C,1,&row,cncols,ccols,cvals,INSERT_VALUES);
    2649:         }
    2650:         MatRestoreRow(B,row,&bncols,&bcols,&bvals);
    2651:         PetscFree2(ccols,cvals);
    2652:       }
    2653:       MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
    2654:       MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
    2655:       PetscViewerASCIIPrintf(viewer,"  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n",(double)threshold);
    2656:       MatView(C,complete_print ? mviewer : viewer);
    2657:       MatDestroy(&C);
    2658:     }
    2659:     MatDestroy(&A);
    2660:     MatDestroy(&B);
    2661:     MatDestroy(&JT);
    2662:     if (Jsave) jacobian = Jsave;
    2663:     if (jacobian != snes->jacobian_pre) {
    2664:       jacobian = snes->jacobian_pre;
    2665:       PetscViewerASCIIPrintf(viewer,"  ---------- Testing Jacobian for preconditioner -------------\n");
    2666:     }
    2667:     else jacobian = NULL;
    2668:   }
    2669:   VecDestroy(&x);
    2670:   if (complete_print) {
    2671:     PetscViewerPopFormat(mviewer);
    2672:   }
    2673:   if (mviewer) PetscViewerDestroy(&mviewer);
    2674:   PetscViewerASCIISetTab(viewer,tabs);
    2675:   return 0;
    2676: }

    2678: /*@
    2679:    SNESComputeJacobian - Computes the Jacobian matrix that has been set with SNESSetJacobian().

    2681:    Collective on SNES

    2683:    Input Parameters:
    2684: +  snes - the SNES context
    2685: -  x - input vector

    2687:    Output Parameters:
    2688: +  A - Jacobian matrix
    2689: -  B - optional preconditioning matrix

    2691:   Options Database Keys:
    2692: +    -snes_lag_preconditioner <lag> - how often to rebuild preconditioner
    2693: .    -snes_lag_jacobian <lag> - how often to rebuild Jacobian
    2694: .    -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
    2695: .    -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
    2696: .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
    2697: .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
    2698: .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
    2699: .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
    2700: .    -snes_compare_coloring - Compute the finite difference Jacobian using coloring and display norms of difference
    2701: .    -snes_compare_coloring_display - Compute the finite difference Jacobian using coloring and display verbose differences
    2702: .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
    2703: .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
    2704: .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
    2705: .    -snes_compare_coloring_draw - Compute the finite difference Jacobian using coloring and draw differences
    2706: -    -snes_compare_coloring_draw_contour - Compute the finite difference Jacobian using coloring and show contours of matrices and differences

    2708:    Notes:
    2709:    Most users should not need to explicitly call this routine, as it
    2710:    is used internally within the nonlinear solvers.

    2712:    Developer Notes:
    2713:     This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine SNESTestJacobian() use to used
    2714:       for with the SNESType of test that has been removed.

    2716:    Level: developer

    2718: .seealso:  SNESSetJacobian(), KSPSetOperators(), MatStructure, SNESSetLagPreconditioner(), SNESSetLagJacobian()
    2719: @*/
    2720: PetscErrorCode  SNESComputeJacobian(SNES snes,Vec X,Mat A,Mat B)
    2721: {
    2722:   PetscBool      flag;
    2723:   DM             dm;
    2724:   DMSNES         sdm;
    2725:   KSP            ksp;

    2730:   VecValidValues(X,2,PETSC_TRUE);
    2731:   SNESGetDM(snes,&dm);
    2732:   DMGetDMSNES(dm,&sdm);

    2736:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */

    2738:   if (snes->lagjacobian == -2) {
    2739:     snes->lagjacobian = -1;

    2741:     PetscInfo(snes,"Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n");
    2742:   } else if (snes->lagjacobian == -1) {
    2743:     PetscInfo(snes,"Reusing Jacobian/preconditioner because lag is -1\n");
    2744:     PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);
    2745:     if (flag) {
    2746:       MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    2747:       MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    2748:     }
    2749:     return 0;
    2750:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
    2751:     PetscInfo(snes,"Reusing Jacobian/preconditioner because lag is %D and SNES iteration is %D\n",snes->lagjacobian,snes->iter);
    2752:     PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);
    2753:     if (flag) {
    2754:       MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    2755:       MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    2756:     }
    2757:     return 0;
    2758:   }
    2759:   if (snes->npc && snes->npcside == PC_LEFT) {
    2760:     MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    2761:     MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    2762:     return 0;
    2763:   }

    2765:   PetscLogEventBegin(SNES_JacobianEval,snes,X,A,B);
    2766:   VecLockReadPush(X);
    2767:   PetscStackPush("SNES user Jacobian function");
    2768:   (*sdm->ops->computejacobian)(snes,X,A,B,sdm->jacobianctx);
    2769:   PetscStackPop;
    2770:   VecLockReadPop(X);
    2771:   PetscLogEventEnd(SNES_JacobianEval,snes,X,A,B);

    2773:   /* attach latest linearization point to the preconditioning matrix */
    2774:   PetscObjectCompose((PetscObject)B,"__SNES_latest_X",(PetscObject)X);

    2776:   /* the next line ensures that snes->ksp exists */
    2777:   SNESGetKSP(snes,&ksp);
    2778:   if (snes->lagpreconditioner == -2) {
    2779:     PetscInfo(snes,"Rebuilding preconditioner exactly once since lag is -2\n");
    2780:     KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);
    2781:     snes->lagpreconditioner = -1;
    2782:   } else if (snes->lagpreconditioner == -1) {
    2783:     PetscInfo(snes,"Reusing preconditioner because lag is -1\n");
    2784:     KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);
    2785:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
    2786:     PetscInfo(snes,"Reusing preconditioner because lag is %D and SNES iteration is %D\n",snes->lagpreconditioner,snes->iter);
    2787:     KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);
    2788:   } else {
    2789:     PetscInfo(snes,"Rebuilding preconditioner\n");
    2790:     KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);
    2791:   }

    2793:   SNESTestJacobian(snes);
    2794:   /* make sure user returned a correct Jacobian and preconditioner */
    2797:   {
    2798:     PetscBool flag = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_operator = PETSC_FALSE;
    2799:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_explicit",NULL,NULL,&flag);
    2800:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_explicit_draw",NULL,NULL,&flag_draw);
    2801:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_explicit_draw_contour",NULL,NULL,&flag_contour);
    2802:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_operator",NULL,NULL,&flag_operator);
    2803:     if (flag || flag_draw || flag_contour) {
    2804:       Mat          Bexp_mine = NULL,Bexp,FDexp;
    2805:       PetscViewer  vdraw,vstdout;
    2806:       PetscBool    flg;
    2807:       if (flag_operator) {
    2808:         MatComputeOperator(A,MATAIJ,&Bexp_mine);
    2809:         Bexp = Bexp_mine;
    2810:       } else {
    2811:         /* See if the preconditioning matrix can be viewed and added directly */
    2812:         PetscObjectBaseTypeCompareAny((PetscObject)B,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPIBAIJ,"");
    2813:         if (flg) Bexp = B;
    2814:         else {
    2815:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
    2816:           MatComputeOperator(B,MATAIJ,&Bexp_mine);
    2817:           Bexp = Bexp_mine;
    2818:         }
    2819:       }
    2820:       MatConvert(Bexp,MATSAME,MAT_INITIAL_MATRIX,&FDexp);
    2821:       SNESComputeJacobianDefault(snes,X,FDexp,FDexp,NULL);
    2822:       PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);
    2823:       if (flag_draw || flag_contour) {
    2824:         PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),NULL,"Explicit Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);
    2825:         if (flag_contour) PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);
    2826:       } else vdraw = NULL;
    2827:       PetscViewerASCIIPrintf(vstdout,"Explicit %s\n",flag_operator ? "Jacobian" : "preconditioning Jacobian");
    2828:       if (flag) MatView(Bexp,vstdout);
    2829:       if (vdraw) MatView(Bexp,vdraw);
    2830:       PetscViewerASCIIPrintf(vstdout,"Finite difference Jacobian\n");
    2831:       if (flag) MatView(FDexp,vstdout);
    2832:       if (vdraw) MatView(FDexp,vdraw);
    2833:       MatAYPX(FDexp,-1.0,Bexp,SAME_NONZERO_PATTERN);
    2834:       PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian\n");
    2835:       if (flag) MatView(FDexp,vstdout);
    2836:       if (vdraw) {              /* Always use contour for the difference */
    2837:         PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);
    2838:         MatView(FDexp,vdraw);
    2839:         PetscViewerPopFormat(vdraw);
    2840:       }
    2841:       if (flag_contour) PetscViewerPopFormat(vdraw);
    2842:       PetscViewerDestroy(&vdraw);
    2843:       MatDestroy(&Bexp_mine);
    2844:       MatDestroy(&FDexp);
    2845:     }
    2846:   }
    2847:   {
    2848:     PetscBool flag = PETSC_FALSE,flag_display = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_threshold = PETSC_FALSE;
    2849:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON,threshold_rtol = 10*PETSC_SQRT_MACHINE_EPSILON;
    2850:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring",NULL,NULL,&flag);
    2851:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_display",NULL,NULL,&flag_display);
    2852:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_draw",NULL,NULL,&flag_draw);
    2853:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_draw_contour",NULL,NULL,&flag_contour);
    2854:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold",NULL,NULL,&flag_threshold);
    2855:     if (flag_threshold) {
    2856:       PetscOptionsGetReal(((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_rtol",&threshold_rtol,NULL);
    2857:       PetscOptionsGetReal(((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_atol",&threshold_atol,NULL);
    2858:     }
    2859:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
    2860:       Mat            Bfd;
    2861:       PetscViewer    vdraw,vstdout;
    2862:       MatColoring    coloring;
    2863:       ISColoring     iscoloring;
    2864:       MatFDColoring  matfdcoloring;
    2865:       PetscErrorCode (*func)(SNES,Vec,Vec,void*);
    2866:       void           *funcctx;
    2867:       PetscReal      norm1,norm2,normmax;

    2869:       MatDuplicate(B,MAT_DO_NOT_COPY_VALUES,&Bfd);
    2870:       MatColoringCreate(Bfd,&coloring);
    2871:       MatColoringSetType(coloring,MATCOLORINGSL);
    2872:       MatColoringSetFromOptions(coloring);
    2873:       MatColoringApply(coloring,&iscoloring);
    2874:       MatColoringDestroy(&coloring);
    2875:       MatFDColoringCreate(Bfd,iscoloring,&matfdcoloring);
    2876:       MatFDColoringSetFromOptions(matfdcoloring);
    2877:       MatFDColoringSetUp(Bfd,iscoloring,matfdcoloring);
    2878:       ISColoringDestroy(&iscoloring);

    2880:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
    2881:       SNESGetFunction(snes,NULL,&func,&funcctx);
    2882:       MatFDColoringSetFunction(matfdcoloring,(PetscErrorCode (*)(void))func,funcctx);
    2883:       PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring,((PetscObject)snes)->prefix);
    2884:       PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring,"coloring_");
    2885:       MatFDColoringSetFromOptions(matfdcoloring);
    2886:       MatFDColoringApply(Bfd,matfdcoloring,X,snes);
    2887:       MatFDColoringDestroy(&matfdcoloring);

    2889:       PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);
    2890:       if (flag_draw || flag_contour) {
    2891:         PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),NULL,"Colored Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);
    2892:         if (flag_contour) PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);
    2893:       } else vdraw = NULL;
    2894:       PetscViewerASCIIPrintf(vstdout,"Explicit preconditioning Jacobian\n");
    2895:       if (flag_display) MatView(B,vstdout);
    2896:       if (vdraw) MatView(B,vdraw);
    2897:       PetscViewerASCIIPrintf(vstdout,"Colored Finite difference Jacobian\n");
    2898:       if (flag_display) MatView(Bfd,vstdout);
    2899:       if (vdraw) MatView(Bfd,vdraw);
    2900:       MatAYPX(Bfd,-1.0,B,SAME_NONZERO_PATTERN);
    2901:       MatNorm(Bfd,NORM_1,&norm1);
    2902:       MatNorm(Bfd,NORM_FROBENIUS,&norm2);
    2903:       MatNorm(Bfd,NORM_MAX,&normmax);
    2904:       PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n",(double)norm1,(double)norm2,(double)normmax);
    2905:       if (flag_display) MatView(Bfd,vstdout);
    2906:       if (vdraw) {              /* Always use contour for the difference */
    2907:         PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);
    2908:         MatView(Bfd,vdraw);
    2909:         PetscViewerPopFormat(vdraw);
    2910:       }
    2911:       if (flag_contour) PetscViewerPopFormat(vdraw);

    2913:       if (flag_threshold) {
    2914:         PetscInt bs,rstart,rend,i;
    2915:         MatGetBlockSize(B,&bs);
    2916:         MatGetOwnershipRange(B,&rstart,&rend);
    2917:         for (i=rstart; i<rend; i++) {
    2918:           const PetscScalar *ba,*ca;
    2919:           const PetscInt    *bj,*cj;
    2920:           PetscInt          bn,cn,j,maxentrycol = -1,maxdiffcol = -1,maxrdiffcol = -1;
    2921:           PetscReal         maxentry = 0,maxdiff = 0,maxrdiff = 0;
    2922:           MatGetRow(B,i,&bn,&bj,&ba);
    2923:           MatGetRow(Bfd,i,&cn,&cj,&ca);
    2925:           for (j=0; j<bn; j++) {
    2926:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
    2927:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
    2928:               maxentrycol = bj[j];
    2929:               maxentry    = PetscRealPart(ba[j]);
    2930:             }
    2931:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
    2932:               maxdiffcol = bj[j];
    2933:               maxdiff    = PetscRealPart(ca[j]);
    2934:             }
    2935:             if (rdiff > maxrdiff) {
    2936:               maxrdiffcol = bj[j];
    2937:               maxrdiff    = rdiff;
    2938:             }
    2939:           }
    2940:           if (maxrdiff > 1) {
    2941:             PetscViewerASCIIPrintf(vstdout,"row %D (maxentry=%g at %D, maxdiff=%g at %D, maxrdiff=%g at %D):",i,(double)maxentry,maxentrycol,(double)maxdiff,maxdiffcol,(double)maxrdiff,maxrdiffcol);
    2942:             for (j=0; j<bn; j++) {
    2943:               PetscReal rdiff;
    2944:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
    2945:               if (rdiff > 1) {
    2946:                 PetscViewerASCIIPrintf(vstdout," (%D,%g:%g)",bj[j],(double)PetscRealPart(ba[j]),(double)PetscRealPart(ca[j]));
    2947:               }
    2948:             }
    2949:             PetscViewerASCIIPrintf(vstdout,"\n",i,maxentry,maxdiff,maxrdiff);
    2950:           }
    2951:           MatRestoreRow(B,i,&bn,&bj,&ba);
    2952:           MatRestoreRow(Bfd,i,&cn,&cj,&ca);
    2953:         }
    2954:       }
    2955:       PetscViewerDestroy(&vdraw);
    2956:       MatDestroy(&Bfd);
    2957:     }
    2958:   }
    2959:   return 0;
    2960: }

    2962: /*MC
    2963:     SNESJacobianFunction - Function used to convey the nonlinear Jacobian of the function to be solved by SNES

    2965:      Synopsis:
    2966:      #include "petscsnes.h"
    2967:      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);

    2969:      Collective on snes

    2971:     Input Parameters:
    2972: +  x - input vector, the Jacobian is to be computed at this value
    2973: -  ctx - [optional] user-defined Jacobian context

    2975:     Output Parameters:
    2976: +  Amat - the matrix that defines the (approximate) Jacobian
    2977: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.

    2979:    Level: intermediate

    2981: .seealso:   SNESSetFunction(), SNESGetFunction(), SNESSetJacobian(), SNESGetJacobian()
    2982: M*/

    2984: /*@C
    2985:    SNESSetJacobian - Sets the function to compute Jacobian as well as the
    2986:    location to store the matrix.

    2988:    Logically Collective on SNES

    2990:    Input Parameters:
    2991: +  snes - the SNES context
    2992: .  Amat - the matrix that defines the (approximate) Jacobian
    2993: .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
    2994: .  J - Jacobian evaluation routine (if NULL then SNES retains any previously set value), see SNESJacobianFunction for details
    2995: -  ctx - [optional] user-defined context for private data for the
    2996:          Jacobian evaluation routine (may be NULL) (if NULL then SNES retains any previously set value)

    2998:    Notes:
    2999:    If the Amat matrix and Pmat matrix are different you must call MatAssemblyBegin/End() on
    3000:    each matrix.

    3002:    If you know the operator Amat has a null space you can use MatSetNullSpace() and MatSetTransposeNullSpace() to supply the null
    3003:    space to Amat and the KSP solvers will automatically use that null space as needed during the solution process.

    3005:    If using SNESComputeJacobianDefaultColor() to assemble a Jacobian, the ctx argument
    3006:    must be a MatFDColoring.

    3008:    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
    3009:    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term.

    3011:    Level: beginner

    3013: .seealso: KSPSetOperators(), SNESSetFunction(), MatMFFDComputeJacobian(), SNESComputeJacobianDefaultColor(), MatStructure, J,
    3014:           SNESSetPicard(), SNESJacobianFunction
    3015: @*/
    3016: PetscErrorCode  SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
    3017: {
    3018:   DM             dm;

    3025:   SNESGetDM(snes,&dm);
    3026:   DMSNESSetJacobian(dm,J,ctx);
    3027:   if (Amat) {
    3028:     PetscObjectReference((PetscObject)Amat);
    3029:     MatDestroy(&snes->jacobian);

    3031:     snes->jacobian = Amat;
    3032:   }
    3033:   if (Pmat) {
    3034:     PetscObjectReference((PetscObject)Pmat);
    3035:     MatDestroy(&snes->jacobian_pre);

    3037:     snes->jacobian_pre = Pmat;
    3038:   }
    3039:   return 0;
    3040: }

    3042: /*@C
    3043:    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
    3044:    provided context for evaluating the Jacobian.

    3046:    Not Collective, but Mat object will be parallel if SNES object is

    3048:    Input Parameter:
    3049: .  snes - the nonlinear solver context

    3051:    Output Parameters:
    3052: +  Amat - location to stash (approximate) Jacobian matrix (or NULL)
    3053: .  Pmat - location to stash matrix used to compute the preconditioner (or NULL)
    3054: .  J - location to put Jacobian function (or NULL), see SNESJacobianFunction for details on its calling sequence
    3055: -  ctx - location to stash Jacobian ctx (or NULL)

    3057:    Level: advanced

    3059: .seealso: SNESSetJacobian(), SNESComputeJacobian(), SNESJacobianFunction, SNESGetFunction()
    3060: @*/
    3061: PetscErrorCode SNESGetJacobian(SNES snes,Mat *Amat,Mat *Pmat,PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
    3062: {
    3063:   DM             dm;
    3064:   DMSNES         sdm;

    3067:   if (Amat) *Amat = snes->jacobian;
    3068:   if (Pmat) *Pmat = snes->jacobian_pre;
    3069:   SNESGetDM(snes,&dm);
    3070:   DMGetDMSNES(dm,&sdm);
    3071:   if (J) *J = sdm->ops->computejacobian;
    3072:   if (ctx) *ctx = sdm->jacobianctx;
    3073:   return 0;
    3074: }

    3076: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
    3077: {
    3078:   DM             dm;
    3079:   DMSNES         sdm;

    3081:   SNESGetDM(snes,&dm);
    3082:   DMGetDMSNES(dm,&sdm);
    3083:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
    3084:     DM        dm;
    3085:     PetscBool isdense,ismf;

    3087:     SNESGetDM(snes,&dm);
    3088:     PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre,&isdense,MATSEQDENSE,MATMPIDENSE,MATDENSE,NULL);
    3089:     PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre,&ismf,MATMFFD,MATSHELL,NULL);
    3090:     if (isdense) {
    3091:       DMSNESSetJacobian(dm,SNESComputeJacobianDefault,NULL);
    3092:     } else if (!ismf) {
    3093:       DMSNESSetJacobian(dm,SNESComputeJacobianDefaultColor,NULL);
    3094:     }
    3095:   }
    3096:   return 0;
    3097: }

    3099: /*@
    3100:    SNESSetUp - Sets up the internal data structures for the later use
    3101:    of a nonlinear solver.

    3103:    Collective on SNES

    3105:    Input Parameters:
    3106: .  snes - the SNES context

    3108:    Notes:
    3109:    For basic use of the SNES solvers the user need not explicitly call
    3110:    SNESSetUp(), since these actions will automatically occur during
    3111:    the call to SNESSolve().  However, if one wishes to control this
    3112:    phase separately, SNESSetUp() should be called after SNESCreate()
    3113:    and optional routines of the form SNESSetXXX(), but before SNESSolve().

    3115:    Level: advanced

    3117: .seealso: SNESCreate(), SNESSolve(), SNESDestroy()
    3118: @*/
    3119: PetscErrorCode  SNESSetUp(SNES snes)
    3120: {
    3121:   DM             dm;
    3122:   DMSNES         sdm;
    3123:   SNESLineSearch linesearch, pclinesearch;
    3124:   void           *lsprectx,*lspostctx;
    3125:   PetscErrorCode (*precheck)(SNESLineSearch,Vec,Vec,PetscBool*,void*);
    3126:   PetscErrorCode (*postcheck)(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
    3127:   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
    3128:   Vec            f,fpc;
    3129:   void           *funcctx;
    3130:   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*);
    3131:   void           *jacctx,*appctx;
    3132:   Mat            j,jpre;

    3135:   if (snes->setupcalled) return 0;
    3136:   PetscLogEventBegin(SNES_Setup,snes,0,0,0);

    3138:   if (!((PetscObject)snes)->type_name) {
    3139:     SNESSetType(snes,SNESNEWTONLS);
    3140:   }

    3142:   SNESGetFunction(snes,&snes->vec_func,NULL,NULL);

    3144:   SNESGetDM(snes,&dm);
    3145:   DMGetDMSNES(dm,&sdm);
    3147:   SNESSetDefaultComputeJacobian(snes);

    3149:   if (!snes->vec_func) {
    3150:     DMCreateGlobalVector(dm,&snes->vec_func);
    3151:   }

    3153:   if (!snes->ksp) {
    3154:     SNESGetKSP(snes, &snes->ksp);
    3155:   }

    3157:   if (snes->linesearch) {
    3158:     SNESGetLineSearch(snes, &snes->linesearch);
    3159:     SNESLineSearchSetFunction(snes->linesearch,SNESComputeFunction);
    3160:   }

    3162:   if (snes->npc && snes->npcside == PC_LEFT) {
    3163:     snes->mf          = PETSC_TRUE;
    3164:     snes->mf_operator = PETSC_FALSE;
    3165:   }

    3167:   if (snes->npc) {
    3168:     /* copy the DM over */
    3169:     SNESGetDM(snes,&dm);
    3170:     SNESSetDM(snes->npc,dm);

    3172:     SNESGetFunction(snes,&f,&func,&funcctx);
    3173:     VecDuplicate(f,&fpc);
    3174:     SNESSetFunction(snes->npc,fpc,func,funcctx);
    3175:     SNESGetJacobian(snes,&j,&jpre,&jac,&jacctx);
    3176:     SNESSetJacobian(snes->npc,j,jpre,jac,jacctx);
    3177:     SNESGetApplicationContext(snes,&appctx);
    3178:     SNESSetApplicationContext(snes->npc,appctx);
    3179:     VecDestroy(&fpc);

    3181:     /* copy the function pointers over */
    3182:     PetscObjectCopyFortranFunctionPointers((PetscObject)snes,(PetscObject)snes->npc);

    3184:     /* default to 1 iteration */
    3185:     SNESSetTolerances(snes->npc,0.0,0.0,0.0,1,snes->npc->max_funcs);
    3186:     if (snes->npcside == PC_RIGHT) {
    3187:       SNESSetNormSchedule(snes->npc,SNES_NORM_FINAL_ONLY);
    3188:     } else {
    3189:       SNESSetNormSchedule(snes->npc,SNES_NORM_NONE);
    3190:     }
    3191:     SNESSetFromOptions(snes->npc);

    3193:     /* copy the line search context over */
    3194:     if (snes->linesearch && snes->npc->linesearch) {
    3195:       SNESGetLineSearch(snes,&linesearch);
    3196:       SNESGetLineSearch(snes->npc,&pclinesearch);
    3197:       SNESLineSearchGetPreCheck(linesearch,&precheck,&lsprectx);
    3198:       SNESLineSearchGetPostCheck(linesearch,&postcheck,&lspostctx);
    3199:       SNESLineSearchSetPreCheck(pclinesearch,precheck,lsprectx);
    3200:       SNESLineSearchSetPostCheck(pclinesearch,postcheck,lspostctx);
    3201:       PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch);
    3202:     }
    3203:   }
    3204:   if (snes->mf) {
    3205:     SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version);
    3206:   }
    3207:   if (snes->ops->usercompute && !snes->user) {
    3208:     (*snes->ops->usercompute)(snes,(void**)&snes->user);
    3209:   }

    3211:   snes->jac_iter = 0;
    3212:   snes->pre_iter = 0;

    3214:   if (snes->ops->setup) {
    3215:     (*snes->ops->setup)(snes);
    3216:   }

    3218:   SNESSetDefaultComputeJacobian(snes);

    3220:   if (snes->npc && snes->npcside == PC_LEFT) {
    3221:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
    3222:       if (snes->linesearch) {
    3223:         SNESGetLineSearch(snes,&linesearch);
    3224:         SNESLineSearchSetFunction(linesearch,SNESComputeFunctionDefaultNPC);
    3225:       }
    3226:     }
    3227:   }
    3228:   PetscLogEventEnd(SNES_Setup,snes,0,0,0);
    3229:   snes->setupcalled = PETSC_TRUE;
    3230:   return 0;
    3231: }

    3233: /*@
    3234:    SNESReset - Resets a SNES context to the snessetupcalled = 0 state and removes any allocated Vecs and Mats

    3236:    Collective on SNES

    3238:    Input Parameter:
    3239: .  snes - iterative context obtained from SNESCreate()

    3241:    Level: intermediate

    3243:    Notes:
    3244:     Also calls the application context destroy routine set with SNESSetComputeApplicationContext()

    3246: .seealso: SNESCreate(), SNESSetUp(), SNESSolve()
    3247: @*/
    3248: PetscErrorCode  SNESReset(SNES snes)
    3249: {
    3251:   if (snes->ops->userdestroy && snes->user) {
    3252:     (*snes->ops->userdestroy)((void**)&snes->user);
    3253:     snes->user = NULL;
    3254:   }
    3255:   if (snes->npc) {
    3256:     SNESReset(snes->npc);
    3257:   }

    3259:   if (snes->ops->reset) {
    3260:     (*snes->ops->reset)(snes);
    3261:   }
    3262:   if (snes->ksp) {
    3263:     KSPReset(snes->ksp);
    3264:   }

    3266:   if (snes->linesearch) {
    3267:     SNESLineSearchReset(snes->linesearch);
    3268:   }

    3270:   VecDestroy(&snes->vec_rhs);
    3271:   VecDestroy(&snes->vec_sol);
    3272:   VecDestroy(&snes->vec_sol_update);
    3273:   VecDestroy(&snes->vec_func);
    3274:   MatDestroy(&snes->jacobian);
    3275:   MatDestroy(&snes->jacobian_pre);
    3276:   MatDestroy(&snes->picard);
    3277:   VecDestroyVecs(snes->nwork,&snes->work);
    3278:   VecDestroyVecs(snes->nvwork,&snes->vwork);

    3280:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

    3282:   snes->nwork       = snes->nvwork = 0;
    3283:   snes->setupcalled = PETSC_FALSE;
    3284:   return 0;
    3285: }

    3287: /*@
    3288:    SNESConvergedReasonViewCancel - Clears all the reasonview functions for a SNES object.

    3290:    Collective on SNES

    3292:    Input Parameter:
    3293: .  snes - iterative context obtained from SNESCreate()

    3295:    Level: intermediate

    3297: .seealso: SNESCreate(), SNESDestroy(), SNESReset()
    3298: @*/
    3299: PetscErrorCode  SNESConvergedReasonViewCancel(SNES snes)
    3300: {
    3301:   PetscInt       i;

    3304:   for (i=0; i<snes->numberreasonviews; i++) {
    3305:     if (snes->reasonviewdestroy[i]) {
    3306:       (*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]);
    3307:     }
    3308:   }
    3309:   snes->numberreasonviews = 0;
    3310:   return 0;
    3311: }

    3313: /*@C
    3314:    SNESDestroy - Destroys the nonlinear solver context that was created
    3315:    with SNESCreate().

    3317:    Collective on SNES

    3319:    Input Parameter:
    3320: .  snes - the SNES context

    3322:    Level: beginner

    3324: .seealso: SNESCreate(), SNESSolve()
    3325: @*/
    3326: PetscErrorCode  SNESDestroy(SNES *snes)
    3327: {
    3328:   if (!*snes) return 0;
    3330:   if (--((PetscObject)(*snes))->refct > 0) {*snes = NULL; return 0;}

    3332:   SNESReset((*snes));
    3333:   SNESDestroy(&(*snes)->npc);

    3335:   /* if memory was published with SAWs then destroy it */
    3336:   PetscObjectSAWsViewOff((PetscObject)*snes);
    3337:   if ((*snes)->ops->destroy) (*((*snes))->ops->destroy)((*snes));

    3339:   if ((*snes)->dm) DMCoarsenHookRemove((*snes)->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,*snes);
    3340:   DMDestroy(&(*snes)->dm);
    3341:   KSPDestroy(&(*snes)->ksp);
    3342:   SNESLineSearchDestroy(&(*snes)->linesearch);

    3344:   PetscFree((*snes)->kspconvctx);
    3345:   if ((*snes)->ops->convergeddestroy) {
    3346:     (*(*snes)->ops->convergeddestroy)((*snes)->cnvP);
    3347:   }
    3348:   if ((*snes)->conv_hist_alloc) {
    3349:     PetscFree2((*snes)->conv_hist,(*snes)->conv_hist_its);
    3350:   }
    3351:   SNESMonitorCancel((*snes));
    3352:   SNESConvergedReasonViewCancel((*snes));
    3353:   PetscHeaderDestroy(snes);
    3354:   return 0;
    3355: }

    3357: /* ----------- Routines to set solver parameters ---------- */

    3359: /*@
    3360:    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.

    3362:    Logically Collective on SNES

    3364:    Input Parameters:
    3365: +  snes - the SNES context
    3366: -  lag - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3367:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

    3369:    Options Database Keys:
    3370: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3371: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3372: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3373: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3375:    Notes:
    3376:    The default is 1
    3377:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or SNESSetLagPreconditionerPersists() was called

    3379:    SNESSetLagPreconditionerPersists() allows using the same uniform lagging (for example every second solve) across multiple solves.

    3381:    Level: intermediate

    3383: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESSetLagPreconditionerPersists(),
    3384:           SNESSetLagJacobianPersists()

    3386: @*/
    3387: PetscErrorCode  SNESSetLagPreconditioner(SNES snes,PetscInt lag)
    3388: {
    3393:   snes->lagpreconditioner = lag;
    3394:   return 0;
    3395: }

    3397: /*@
    3398:    SNESSetGridSequence - sets the number of steps of grid sequencing that SNES does

    3400:    Logically Collective on SNES

    3402:    Input Parameters:
    3403: +  snes - the SNES context
    3404: -  steps - the number of refinements to do, defaults to 0

    3406:    Options Database Keys:
    3407: .    -snes_grid_sequence <steps> - Use grid sequencing to generate initial guess

    3409:    Level: intermediate

    3411:    Notes:
    3412:    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.

    3414: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetGridSequence()

    3416: @*/
    3417: PetscErrorCode  SNESSetGridSequence(SNES snes,PetscInt steps)
    3418: {
    3421:   snes->gridsequence = steps;
    3422:   return 0;
    3423: }

    3425: /*@
    3426:    SNESGetGridSequence - gets the number of steps of grid sequencing that SNES does

    3428:    Logically Collective on SNES

    3430:    Input Parameter:
    3431: .  snes - the SNES context

    3433:    Output Parameter:
    3434: .  steps - the number of refinements to do, defaults to 0

    3436:    Options Database Keys:
    3437: .    -snes_grid_sequence <steps> - set number of refinements

    3439:    Level: intermediate

    3441:    Notes:
    3442:    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.

    3444: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESSetGridSequence()

    3446: @*/
    3447: PetscErrorCode  SNESGetGridSequence(SNES snes,PetscInt *steps)
    3448: {
    3450:   *steps = snes->gridsequence;
    3451:   return 0;
    3452: }

    3454: /*@
    3455:    SNESGetLagPreconditioner - Indicates how often the preconditioner is rebuilt

    3457:    Not Collective

    3459:    Input Parameter:
    3460: .  snes - the SNES context

    3462:    Output Parameter:
    3463: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3464:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

    3466:    Options Database Keys:
    3467: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3468: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3469: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3470: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3472:    Notes:
    3473:    The default is 1
    3474:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

    3476:    Level: intermediate

    3478: .seealso: SNESSetTrustRegionTolerance(), SNESSetLagPreconditioner(), SNESSetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

    3480: @*/
    3481: PetscErrorCode  SNESGetLagPreconditioner(SNES snes,PetscInt *lag)
    3482: {
    3484:   *lag = snes->lagpreconditioner;
    3485:   return 0;
    3486: }

    3488: /*@
    3489:    SNESSetLagJacobian - Determines when the Jacobian is rebuilt in the nonlinear solve. See SNESSetLagPreconditioner() for determining how
    3490:      often the preconditioner is rebuilt.

    3492:    Logically Collective on SNES

    3494:    Input Parameters:
    3495: +  snes - the SNES context
    3496: -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3497:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

    3499:    Options Database Keys:
    3500: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3501: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3502: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3503: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag.

    3505:    Notes:
    3506:    The default is 1
    3507:    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
    3508:    If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
    3509:    at the next Newton step but never again (unless it is reset to another value)

    3511:    Level: intermediate

    3513: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagPreconditioner(), SNESGetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

    3515: @*/
    3516: PetscErrorCode  SNESSetLagJacobian(SNES snes,PetscInt lag)
    3517: {
    3522:   snes->lagjacobian = lag;
    3523:   return 0;
    3524: }

    3526: /*@
    3527:    SNESGetLagJacobian - Indicates how often the Jacobian is rebuilt. See SNESGetLagPreconditioner() to determine when the preconditioner is rebuilt

    3529:    Not Collective

    3531:    Input Parameter:
    3532: .  snes - the SNES context

    3534:    Output Parameter:
    3535: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3536:          the Jacobian is built etc.

    3538:    Notes:
    3539:    The default is 1
    3540:    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or SNESSetLagJacobianPersists() was called.

    3542:    Level: intermediate

    3544: .seealso: SNESSetTrustRegionTolerance(), SNESSetLagJacobian(), SNESSetLagPreconditioner(), SNESGetLagPreconditioner(), SNESSetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

    3546: @*/
    3547: PetscErrorCode  SNESGetLagJacobian(SNES snes,PetscInt *lag)
    3548: {
    3550:   *lag = snes->lagjacobian;
    3551:   return 0;
    3552: }

    3554: /*@
    3555:    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple solves

    3557:    Logically collective on SNES

    3559:    Input Parameters:
    3560: +  snes - the SNES context
    3561: -   flg - jacobian lagging persists if true

    3563:    Options Database Keys:
    3564: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3565: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3566: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3567: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3569:    Notes:
    3570:     This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
    3571:    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
    3572:    timesteps may present huge efficiency gains.

    3574:    Level: developer

    3576: .seealso: SNESSetLagPreconditionerPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC(), SNESSetLagJacobianPersists()

    3578: @*/
    3579: PetscErrorCode  SNESSetLagJacobianPersists(SNES snes,PetscBool flg)
    3580: {
    3583:   snes->lagjac_persist = flg;
    3584:   return 0;
    3585: }

    3587: /*@
    3588:    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

    3590:    Logically Collective on SNES

    3592:    Input Parameters:
    3593: +  snes - the SNES context
    3594: -   flg - preconditioner lagging persists if true

    3596:    Options Database Keys:
    3597: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3598: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3599: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3600: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3602:    Notes:
    3603:     This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
    3604:    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
    3605:    several timesteps may present huge efficiency gains.

    3607:    Level: developer

    3609: .seealso: SNESSetLagJacobianPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC(), SNESSetLagPreconditioner()

    3611: @*/
    3612: PetscErrorCode  SNESSetLagPreconditionerPersists(SNES snes,PetscBool flg)
    3613: {
    3616:   snes->lagpre_persist = flg;
    3617:   return 0;
    3618: }

    3620: /*@
    3621:    SNESSetForceIteration - force SNESSolve() to take at least one iteration regardless of the initial residual norm

    3623:    Logically Collective on SNES

    3625:    Input Parameters:
    3626: +  snes - the SNES context
    3627: -  force - PETSC_TRUE require at least one iteration

    3629:    Options Database Keys:
    3630: .    -snes_force_iteration <force> - Sets forcing an iteration

    3632:    Notes:
    3633:    This is used sometimes with TS to prevent TS from detecting a false steady state solution

    3635:    Level: intermediate

    3637: .seealso: SNESSetTrustRegionTolerance(), SNESSetDivergenceTolerance()
    3638: @*/
    3639: PetscErrorCode  SNESSetForceIteration(SNES snes,PetscBool force)
    3640: {
    3642:   snes->forceiteration = force;
    3643:   return 0;
    3644: }

    3646: /*@
    3647:    SNESGetForceIteration - Whether or not to force SNESSolve() take at least one iteration regardless of the initial residual norm

    3649:    Logically Collective on SNES

    3651:    Input Parameters:
    3652: .  snes - the SNES context

    3654:    Output Parameter:
    3655: .  force - PETSC_TRUE requires at least one iteration.

    3657:    Level: intermediate

    3659: .seealso: SNESSetForceIteration(), SNESSetTrustRegionTolerance(), SNESSetDivergenceTolerance()
    3660: @*/
    3661: PetscErrorCode  SNESGetForceIteration(SNES snes,PetscBool *force)
    3662: {
    3664:   *force = snes->forceiteration;
    3665:   return 0;
    3666: }

    3668: /*@
    3669:    SNESSetTolerances - Sets various parameters used in convergence tests.

    3671:    Logically Collective on SNES

    3673:    Input Parameters:
    3674: +  snes - the SNES context
    3675: .  abstol - absolute convergence tolerance
    3676: .  rtol - relative convergence tolerance
    3677: .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
    3678: .  maxit - maximum number of iterations
    3679: -  maxf - maximum number of function evaluations (-1 indicates no limit)

    3681:    Options Database Keys:
    3682: +    -snes_atol <abstol> - Sets abstol
    3683: .    -snes_rtol <rtol> - Sets rtol
    3684: .    -snes_stol <stol> - Sets stol
    3685: .    -snes_max_it <maxit> - Sets maxit
    3686: -    -snes_max_funcs <maxf> - Sets maxf

    3688:    Notes:
    3689:    The default maximum number of iterations is 50.
    3690:    The default maximum number of function evaluations is 1000.

    3692:    Level: intermediate

    3694: .seealso: SNESSetTrustRegionTolerance(), SNESSetDivergenceTolerance(), SNESSetForceIteration()
    3695: @*/
    3696: PetscErrorCode  SNESSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit,PetscInt maxf)
    3697: {

    3705:   if (abstol != PETSC_DEFAULT) {
    3707:     snes->abstol = abstol;
    3708:   }
    3709:   if (rtol != PETSC_DEFAULT) {
    3711:     snes->rtol = rtol;
    3712:   }
    3713:   if (stol != PETSC_DEFAULT) {
    3715:     snes->stol = stol;
    3716:   }
    3717:   if (maxit != PETSC_DEFAULT) {
    3719:     snes->max_its = maxit;
    3720:   }
    3721:   if (maxf != PETSC_DEFAULT) {
    3723:     snes->max_funcs = maxf;
    3724:   }
    3725:   snes->tolerancesset = PETSC_TRUE;
    3726:   return 0;
    3727: }

    3729: /*@
    3730:    SNESSetDivergenceTolerance - Sets the divergence tolerance used for the SNES divergence test.

    3732:    Logically Collective on SNES

    3734:    Input Parameters:
    3735: +  snes - the SNES context
    3736: -  divtol - the divergence tolerance. Use -1 to deactivate the test.

    3738:    Options Database Keys:
    3739: .    -snes_divergence_tolerance <divtol> - Sets divtol

    3741:    Notes:
    3742:    The default divergence tolerance is 1e4.

    3744:    Level: intermediate

    3746: .seealso: SNESSetTolerances(), SNESGetDivergenceTolerance
    3747: @*/
    3748: PetscErrorCode  SNESSetDivergenceTolerance(SNES snes,PetscReal divtol)
    3749: {

    3753:   if (divtol != PETSC_DEFAULT) {
    3754:     snes->divtol = divtol;
    3755:   }
    3756:   else {
    3757:     snes->divtol = 1.0e4;
    3758:   }
    3759:   return 0;
    3760: }

    3762: /*@
    3763:    SNESGetTolerances - Gets various parameters used in convergence tests.

    3765:    Not Collective

    3767:    Input Parameters:
    3768: +  snes - the SNES context
    3769: .  atol - absolute convergence tolerance
    3770: .  rtol - relative convergence tolerance
    3771: .  stol -  convergence tolerance in terms of the norm
    3772:            of the change in the solution between steps
    3773: .  maxit - maximum number of iterations
    3774: -  maxf - maximum number of function evaluations

    3776:    Notes:
    3777:    The user can specify NULL for any parameter that is not needed.

    3779:    Level: intermediate

    3781: .seealso: SNESSetTolerances()
    3782: @*/
    3783: PetscErrorCode  SNESGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit,PetscInt *maxf)
    3784: {
    3786:   if (atol)  *atol  = snes->abstol;
    3787:   if (rtol)  *rtol  = snes->rtol;
    3788:   if (stol)  *stol  = snes->stol;
    3789:   if (maxit) *maxit = snes->max_its;
    3790:   if (maxf)  *maxf  = snes->max_funcs;
    3791:   return 0;
    3792: }

    3794: /*@
    3795:    SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

    3797:    Not Collective

    3799:    Input Parameters:
    3800: +  snes - the SNES context
    3801: -  divtol - divergence tolerance

    3803:    Level: intermediate

    3805: .seealso: SNESSetDivergenceTolerance()
    3806: @*/
    3807: PetscErrorCode  SNESGetDivergenceTolerance(SNES snes,PetscReal *divtol)
    3808: {
    3810:   if (divtol) *divtol = snes->divtol;
    3811:   return 0;
    3812: }

    3814: /*@
    3815:    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.

    3817:    Logically Collective on SNES

    3819:    Input Parameters:
    3820: +  snes - the SNES context
    3821: -  tol - tolerance

    3823:    Options Database Key:
    3824: .  -snes_trtol <tol> - Sets tol

    3826:    Level: intermediate

    3828: .seealso: SNESSetTolerances()
    3829: @*/
    3830: PetscErrorCode  SNESSetTrustRegionTolerance(SNES snes,PetscReal tol)
    3831: {
    3834:   snes->deltatol = tol;
    3835:   return 0;
    3836: }

    3838: PETSC_INTERN PetscErrorCode  SNESMonitorRange_Private(SNES,PetscInt,PetscReal*);

    3840: PetscErrorCode  SNESMonitorLGRange(SNES snes,PetscInt n,PetscReal rnorm,void *monctx)
    3841: {
    3842:   PetscDrawLG      lg;
    3843:   PetscReal        x,y,per;
    3844:   PetscViewer      v = (PetscViewer)monctx;
    3845:   static PetscReal prev; /* should be in the context */
    3846:   PetscDraw        draw;

    3849:   PetscViewerDrawGetDrawLG(v,0,&lg);
    3850:   if (!n) PetscDrawLGReset(lg);
    3851:   PetscDrawLGGetDraw(lg,&draw);
    3852:   PetscDrawSetTitle(draw,"Residual norm");
    3853:   x    = (PetscReal)n;
    3854:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
    3855:   else y = -15.0;
    3856:   PetscDrawLGAddPoint(lg,&x,&y);
    3857:   if (n < 20 || !(n % 5) || snes->reason) {
    3858:     PetscDrawLGDraw(lg);
    3859:     PetscDrawLGSave(lg);
    3860:   }

    3862:   PetscViewerDrawGetDrawLG(v,1,&lg);
    3863:   if (!n) PetscDrawLGReset(lg);
    3864:   PetscDrawLGGetDraw(lg,&draw);
    3865:   PetscDrawSetTitle(draw,"% elemts > .2*max elemt");
    3866:   SNESMonitorRange_Private(snes,n,&per);
    3867:   x    = (PetscReal)n;
    3868:   y    = 100.0*per;
    3869:   PetscDrawLGAddPoint(lg,&x,&y);
    3870:   if (n < 20 || !(n % 5) || snes->reason) {
    3871:     PetscDrawLGDraw(lg);
    3872:     PetscDrawLGSave(lg);
    3873:   }

    3875:   PetscViewerDrawGetDrawLG(v,2,&lg);
    3876:   if (!n) {prev = rnorm;PetscDrawLGReset(lg);}
    3877:   PetscDrawLGGetDraw(lg,&draw);
    3878:   PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm");
    3879:   x    = (PetscReal)n;
    3880:   y    = (prev - rnorm)/prev;
    3881:   PetscDrawLGAddPoint(lg,&x,&y);
    3882:   if (n < 20 || !(n % 5) || snes->reason) {
    3883:     PetscDrawLGDraw(lg);
    3884:     PetscDrawLGSave(lg);
    3885:   }

    3887:   PetscViewerDrawGetDrawLG(v,3,&lg);
    3888:   if (!n) PetscDrawLGReset(lg);
    3889:   PetscDrawLGGetDraw(lg,&draw);
    3890:   PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm*(% > .2 max)");
    3891:   x    = (PetscReal)n;
    3892:   y    = (prev - rnorm)/(prev*per);
    3893:   if (n > 2) { /*skip initial crazy value */
    3894:     PetscDrawLGAddPoint(lg,&x,&y);
    3895:   }
    3896:   if (n < 20 || !(n % 5) || snes->reason) {
    3897:     PetscDrawLGDraw(lg);
    3898:     PetscDrawLGSave(lg);
    3899:   }
    3900:   prev = rnorm;
    3901:   return 0;
    3902: }

    3904: /*@
    3905:    SNESMonitor - runs the user provided monitor routines, if they exist

    3907:    Collective on SNES

    3909:    Input Parameters:
    3910: +  snes - nonlinear solver context obtained from SNESCreate()
    3911: .  iter - iteration number
    3912: -  rnorm - relative norm of the residual

    3914:    Notes:
    3915:    This routine is called by the SNES implementations.
    3916:    It does not typically need to be called by the user.

    3918:    Level: developer

    3920: .seealso: SNESMonitorSet()
    3921: @*/
    3922: PetscErrorCode  SNESMonitor(SNES snes,PetscInt iter,PetscReal rnorm)
    3923: {
    3924:   PetscInt       i,n = snes->numbermonitors;

    3926:   VecLockReadPush(snes->vec_sol);
    3927:   for (i=0; i<n; i++) {
    3928:     (*snes->monitor[i])(snes,iter,rnorm,snes->monitorcontext[i]);
    3929:   }
    3930:   VecLockReadPop(snes->vec_sol);
    3931:   return 0;
    3932: }

    3934: /* ------------ Routines to set performance monitoring options ----------- */

    3936: /*MC
    3937:     SNESMonitorFunction - functional form passed to SNESMonitorSet() to monitor convergence of nonlinear solver

    3939:      Synopsis:
    3940: #include <petscsnes.h>
    3941: $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)

    3943:      Collective on snes

    3945:     Input Parameters:
    3946: +    snes - the SNES context
    3947: .    its - iteration number
    3948: .    norm - 2-norm function value (may be estimated)
    3949: -    mctx - [optional] monitoring context

    3951:    Level: advanced

    3953: .seealso:   SNESMonitorSet(), SNESMonitorGet()
    3954: M*/

    3956: /*@C
    3957:    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
    3958:    iteration of the nonlinear solver to display the iteration's
    3959:    progress.

    3961:    Logically Collective on SNES

    3963:    Input Parameters:
    3964: +  snes - the SNES context
    3965: .  f - the monitor function, see SNESMonitorFunction for the calling sequence
    3966: .  mctx - [optional] user-defined context for private data for the
    3967:           monitor routine (use NULL if no context is desired)
    3968: -  monitordestroy - [optional] routine that frees monitor context
    3969:           (may be NULL)

    3971:    Options Database Keys:
    3972: +    -snes_monitor        - sets SNESMonitorDefault()
    3973: .    -snes_monitor draw::draw_lg - sets line graph monitor,
    3974: -    -snes_monitor_cancel - cancels all monitors that have
    3975:                             been hardwired into a code by
    3976:                             calls to SNESMonitorSet(), but
    3977:                             does not cancel those set via
    3978:                             the options database.

    3980:    Notes:
    3981:    Several different monitoring routines may be set by calling
    3982:    SNESMonitorSet() multiple times; all will be called in the
    3983:    order in which they were set.

    3985:    Fortran Notes:
    3986:     Only a single monitor function can be set for each SNES object

    3988:    Level: intermediate

    3990: .seealso: SNESMonitorDefault(), SNESMonitorCancel(), SNESMonitorFunction
    3991: @*/
    3992: PetscErrorCode  SNESMonitorSet(SNES snes,PetscErrorCode (*f)(SNES,PetscInt,PetscReal,void*),void *mctx,PetscErrorCode (*monitordestroy)(void**))
    3993: {
    3994:   PetscInt       i;
    3995:   PetscBool      identical;

    3998:   for (i=0; i<snes->numbermonitors;i++) {
    3999:     PetscMonitorCompare((PetscErrorCode (*)(void))f,mctx,monitordestroy,(PetscErrorCode (*)(void))snes->monitor[i],snes->monitorcontext[i],snes->monitordestroy[i],&identical);
    4000:     if (identical) return 0;
    4001:   }
    4003:   snes->monitor[snes->numbermonitors]          = f;
    4004:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
    4005:   snes->monitorcontext[snes->numbermonitors++] = (void*)mctx;
    4006:   return 0;
    4007: }

    4009: /*@
    4010:    SNESMonitorCancel - Clears all the monitor functions for a SNES object.

    4012:    Logically Collective on SNES

    4014:    Input Parameters:
    4015: .  snes - the SNES context

    4017:    Options Database Key:
    4018: .  -snes_monitor_cancel - cancels all monitors that have been hardwired
    4019:     into a code by calls to SNESMonitorSet(), but does not cancel those
    4020:     set via the options database

    4022:    Notes:
    4023:    There is no way to clear one specific monitor from a SNES object.

    4025:    Level: intermediate

    4027: .seealso: SNESMonitorDefault(), SNESMonitorSet()
    4028: @*/
    4029: PetscErrorCode  SNESMonitorCancel(SNES snes)
    4030: {
    4031:   PetscInt       i;

    4034:   for (i=0; i<snes->numbermonitors; i++) {
    4035:     if (snes->monitordestroy[i]) {
    4036:       (*snes->monitordestroy[i])(&snes->monitorcontext[i]);
    4037:     }
    4038:   }
    4039:   snes->numbermonitors = 0;
    4040:   return 0;
    4041: }

    4043: /*MC
    4044:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

    4046:      Synopsis:
    4047: #include <petscsnes.h>
    4048: $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)

    4050:      Collective on snes

    4052:     Input Parameters:
    4053: +    snes - the SNES context
    4054: .    it - current iteration (0 is the first and is before any Newton step)
    4055: .    xnorm - 2-norm of current iterate
    4056: .    gnorm - 2-norm of current step
    4057: .    f - 2-norm of function
    4058: -    cctx - [optional] convergence context

    4060:     Output Parameter:
    4061: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

    4063:    Level: intermediate

    4065: .seealso:   SNESSetConvergenceTest(), SNESGetConvergenceTest()
    4066: M*/

    4068: /*@C
    4069:    SNESSetConvergenceTest - Sets the function that is to be used
    4070:    to test for convergence of the nonlinear iterative solution.

    4072:    Logically Collective on SNES

    4074:    Input Parameters:
    4075: +  snes - the SNES context
    4076: .  SNESConvergenceTestFunction - routine to test for convergence
    4077: .  cctx - [optional] context for private data for the convergence routine  (may be NULL)
    4078: -  destroy - [optional] destructor for the context (may be NULL; PETSC_NULL_FUNCTION in Fortran)

    4080:    Level: advanced

    4082: .seealso: SNESConvergedDefault(), SNESConvergedSkip(), SNESConvergenceTestFunction
    4083: @*/
    4084: PetscErrorCode  SNESSetConvergenceTest(SNES snes,PetscErrorCode (*SNESConvergenceTestFunction)(SNES,PetscInt,PetscReal,PetscReal,PetscReal,SNESConvergedReason*,void*),void *cctx,PetscErrorCode (*destroy)(void*))
    4085: {
    4087:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
    4088:   if (snes->ops->convergeddestroy) {
    4089:     (*snes->ops->convergeddestroy)(snes->cnvP);
    4090:   }
    4091:   snes->ops->converged        = SNESConvergenceTestFunction;
    4092:   snes->ops->convergeddestroy = destroy;
    4093:   snes->cnvP                  = cctx;
    4094:   return 0;
    4095: }

    4097: /*@
    4098:    SNESGetConvergedReason - Gets the reason the SNES iteration was stopped.

    4100:    Not Collective

    4102:    Input Parameter:
    4103: .  snes - the SNES context

    4105:    Output Parameter:
    4106: .  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
    4107:             manual pages for the individual convergence tests for complete lists

    4109:    Options Database:
    4110: .   -snes_converged_reason - prints the reason to standard out

    4112:    Level: intermediate

    4114:    Notes:
    4115:     Should only be called after the call the SNESSolve() is complete, if it is called earlier it returns the value SNES__CONVERGED_ITERATING.

    4117: .seealso: SNESSetConvergenceTest(), SNESSetConvergedReason(), SNESConvergedReason
    4118: @*/
    4119: PetscErrorCode SNESGetConvergedReason(SNES snes,SNESConvergedReason *reason)
    4120: {
    4123:   *reason = snes->reason;
    4124:   return 0;
    4125: }

    4127: /*@C
    4128:    SNESGetConvergedReasonString - Return a human readable string for snes converged reason

    4130:    Not Collective

    4132:    Input Parameter:
    4133: .  snes - the SNES context

    4135:    Output Parameter:
    4136: .  strreason - a human readable string that describes SNES converged reason

    4138:    Level: beginner

    4140: .seealso: SNESGetConvergedReason()
    4141: @*/
    4142: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char** strreason)
    4143: {
    4146:   *strreason = SNESConvergedReasons[snes->reason];
    4147:   return 0;
    4148: }

    4150: /*@
    4151:    SNESSetConvergedReason - Sets the reason the SNES iteration was stopped.

    4153:    Not Collective

    4155:    Input Parameters:
    4156: +  snes - the SNES context
    4157: -  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
    4158:             manual pages for the individual convergence tests for complete lists

    4160:    Level: intermediate

    4162: .seealso: SNESGetConvergedReason(), SNESSetConvergenceTest(), SNESConvergedReason
    4163: @*/
    4164: PetscErrorCode SNESSetConvergedReason(SNES snes,SNESConvergedReason reason)
    4165: {
    4167:   snes->reason = reason;
    4168:   return 0;
    4169: }

    4171: /*@
    4172:    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.

    4174:    Logically Collective on SNES

    4176:    Input Parameters:
    4177: +  snes - iterative context obtained from SNESCreate()
    4178: .  a   - array to hold history, this array will contain the function norms computed at each step
    4179: .  its - integer array holds the number of linear iterations for each solve.
    4180: .  na  - size of a and its
    4181: -  reset - PETSC_TRUE indicates each new nonlinear solve resets the history counter to zero,
    4182:            else it continues storing new values for new nonlinear solves after the old ones

    4184:    Notes:
    4185:    If 'a' and 'its' are NULL then space is allocated for the history. If 'na' PETSC_DECIDE or PETSC_DEFAULT then a
    4186:    default array of length 10000 is allocated.

    4188:    This routine is useful, e.g., when running a code for purposes
    4189:    of accurate performance monitoring, when no I/O should be done
    4190:    during the section of code that is being timed.

    4192:    Level: intermediate

    4194: .seealso: SNESGetConvergenceHistory()

    4196: @*/
    4197: PetscErrorCode  SNESSetConvergenceHistory(SNES snes,PetscReal a[],PetscInt its[],PetscInt na,PetscBool reset)
    4198: {
    4202:   if (!a) {
    4203:     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
    4204:     PetscCalloc2(na,&a,na,&its);
    4205:     snes->conv_hist_alloc = PETSC_TRUE;
    4206:   }
    4207:   snes->conv_hist       = a;
    4208:   snes->conv_hist_its   = its;
    4209:   snes->conv_hist_max   = (size_t)na;
    4210:   snes->conv_hist_len   = 0;
    4211:   snes->conv_hist_reset = reset;
    4212:   return 0;
    4213: }

    4215: #if defined(PETSC_HAVE_MATLAB_ENGINE)
    4216: #include <engine.h>   /* MATLAB include file */
    4217: #include <mex.h>      /* MATLAB include file */

    4219: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
    4220: {
    4221:   mxArray   *mat;
    4222:   PetscInt  i;
    4223:   PetscReal *ar;

    4225:   mat = mxCreateDoubleMatrix(snes->conv_hist_len,1,mxREAL);
    4226:   ar  = (PetscReal*) mxGetData(mat);
    4227:   for (i=0; i<snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
    4228:   return mat;
    4229: }
    4230: #endif

    4232: /*@C
    4233:    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.

    4235:    Not Collective

    4237:    Input Parameter:
    4238: .  snes - iterative context obtained from SNESCreate()

    4240:    Output Parameters:
    4241: +  a   - array to hold history
    4242: .  its - integer array holds the number of linear iterations (or
    4243:          negative if not converged) for each solve.
    4244: -  na  - size of a and its

    4246:    Notes:
    4247:     The calling sequence for this routine in Fortran is
    4248: $   call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)

    4250:    This routine is useful, e.g., when running a code for purposes
    4251:    of accurate performance monitoring, when no I/O should be done
    4252:    during the section of code that is being timed.

    4254:    Level: intermediate

    4256: .seealso: SNESSetConvergenceHistory()

    4258: @*/
    4259: PetscErrorCode  SNESGetConvergenceHistory(SNES snes,PetscReal *a[],PetscInt *its[],PetscInt *na)
    4260: {
    4262:   if (a)   *a   = snes->conv_hist;
    4263:   if (its) *its = snes->conv_hist_its;
    4264:   if (na)  *na  = (PetscInt) snes->conv_hist_len;
    4265:   return 0;
    4266: }

    4268: /*@C
    4269:   SNESSetUpdate - Sets the general-purpose update function called
    4270:   at the beginning of every iteration of the nonlinear solve. Specifically
    4271:   it is called just before the Jacobian is "evaluated".

    4273:   Logically Collective on SNES

    4275:   Input Parameters:
    4276: + snes - The nonlinear solver context
    4277: - func - The function

    4279:   Calling sequence of func:
    4280: $ func (SNES snes, PetscInt step);

    4282: . step - The current step of the iteration

    4284:   Level: advanced

    4286:   Note:
    4287:      This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your FormFunction()
    4288:      This is not used by most users.

    4290:      There are a varity of function hooks one many set that are called at different stages of the nonlinear solution process, see the functions listed below.

    4292: .seealso SNESSetJacobian(), SNESSolve(), SNESLineSearchSetPreCheck(), SNESLineSearchSetPostCheck(), SNESNewtonTRSetPreCheck(), SNESNewtonTRSetPostCheck(),
    4293:          SNESMonitorSet(), SNESSetDivergenceTest()
    4294: @*/
    4295: PetscErrorCode  SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
    4296: {
    4298:   snes->ops->update = func;
    4299:   return 0;
    4300: }

    4302: /*
    4303:    SNESScaleStep_Private - Scales a step so that its length is less than the
    4304:    positive parameter delta.

    4306:     Input Parameters:
    4307: +   snes - the SNES context
    4308: .   y - approximate solution of linear system
    4309: .   fnorm - 2-norm of current function
    4310: -   delta - trust region size

    4312:     Output Parameters:
    4313: +   gpnorm - predicted function norm at the new point, assuming local
    4314:     linearization.  The value is zero if the step lies within the trust
    4315:     region, and exceeds zero otherwise.
    4316: -   ynorm - 2-norm of the step

    4318:     Note:
    4319:     For non-trust region methods such as SNESNEWTONLS, the parameter delta
    4320:     is set to be the maximum allowable step size.

    4322: */
    4323: PetscErrorCode SNESScaleStep_Private(SNES snes,Vec y,PetscReal *fnorm,PetscReal *delta,PetscReal *gpnorm,PetscReal *ynorm)
    4324: {
    4325:   PetscReal      nrm;
    4326:   PetscScalar    cnorm;

    4332:   VecNorm(y,NORM_2,&nrm);
    4333:   if (nrm > *delta) {
    4334:     nrm     = *delta/nrm;
    4335:     *gpnorm = (1.0 - nrm)*(*fnorm);
    4336:     cnorm   = nrm;
    4337:     VecScale(y,cnorm);
    4338:     *ynorm  = *delta;
    4339:   } else {
    4340:     *gpnorm = 0.0;
    4341:     *ynorm  = nrm;
    4342:   }
    4343:   return 0;
    4344: }

    4346: /*@C
    4347:    SNESConvergedReasonView - Displays the reason a SNES solve converged or diverged to a viewer

    4349:    Collective on SNES

    4351:    Parameter:
    4352: +  snes - iterative context obtained from SNESCreate()
    4353: -  viewer - the viewer to display the reason

    4355:    Options Database Keys:
    4356: +  -snes_converged_reason - print reason for converged or diverged, also prints number of iterations
    4357: -  -snes_converged_reason ::failed - only print reason and number of iterations when diverged

    4359:   Notes:
    4360:      To change the format of the output call PetscViewerPushFormat(viewer,format) before this call. Use PETSC_VIEWER_DEFAULT for the default,
    4361:      use PETSC_VIEWER_FAILED to only display a reason if it fails.

    4363:    Level: beginner

    4365: .seealso: SNESCreate(), SNESSetUp(), SNESDestroy(), SNESSetTolerances(), SNESConvergedDefault(), SNESGetConvergedReason(), SNESConvergedReasonViewFromOptions(),
    4366:           PetscViewerPushFormat(), PetscViewerPopFormat()

    4368: @*/
    4369: PetscErrorCode  SNESConvergedReasonView(SNES snes,PetscViewer viewer)
    4370: {
    4371:   PetscViewerFormat format;
    4372:   PetscBool         isAscii;

    4374:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
    4375:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isAscii);
    4376:   if (isAscii) {
    4377:     PetscViewerGetFormat(viewer, &format);
    4378:     PetscViewerASCIIAddTab(viewer,((PetscObject)snes)->tablevel);
    4379:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
    4380:       DM              dm;
    4381:       Vec             u;
    4382:       PetscDS         prob;
    4383:       PetscInt        Nf, f;
    4384:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
    4385:       void            **exactCtx;
    4386:       PetscReal       error;

    4388:       SNESGetDM(snes, &dm);
    4389:       SNESGetSolution(snes, &u);
    4390:       DMGetDS(dm, &prob);
    4391:       PetscDSGetNumFields(prob, &Nf);
    4392:       PetscMalloc2(Nf, &exactSol, Nf, &exactCtx);
    4393:       for (f = 0; f < Nf; ++f) PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]);
    4394:       DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error);
    4395:       PetscFree2(exactSol, exactCtx);
    4396:       if (error < 1.0e-11) PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n");
    4397:       else                 PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", error);
    4398:     }
    4399:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
    4400:       if (((PetscObject) snes)->prefix) {
    4401:         PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve converged due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);
    4402:       } else {
    4403:         PetscViewerASCIIPrintf(viewer,"Nonlinear solve converged due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);
    4404:       }
    4405:     } else if (snes->reason <= 0) {
    4406:       if (((PetscObject) snes)->prefix) {
    4407:         PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve did not converge due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);
    4408:       } else {
    4409:         PetscViewerASCIIPrintf(viewer,"Nonlinear solve did not converge due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);
    4410:       }
    4411:     }
    4412:     PetscViewerASCIISubtractTab(viewer,((PetscObject)snes)->tablevel);
    4413:   }
    4414:   return 0;
    4415: }

    4417: /*@C
    4418:    SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
    4419:     end of the nonlinear solver to display the conver reason of the nonlinear solver.

    4421:    Logically Collective on SNES

    4423:    Input Parameters:
    4424: +  snes - the SNES context
    4425: .  f - the snes converged reason view function
    4426: .  vctx - [optional] user-defined context for private data for the
    4427:           snes converged reason view routine (use NULL if no context is desired)
    4428: -  reasonviewdestroy - [optional] routine that frees reasonview context
    4429:           (may be NULL)

    4431:    Options Database Keys:
    4432: +    -snes_converged_reason        - sets a default SNESConvergedReasonView()
    4433: -    -snes_converged_reason_view_cancel - cancels all converged reason viewers that have
    4434:                             been hardwired into a code by
    4435:                             calls to SNESConvergedReasonViewSet(), but
    4436:                             does not cancel those set via
    4437:                             the options database.

    4439:    Notes:
    4440:    Several different converged reason view routines may be set by calling
    4441:    SNESConvergedReasonViewSet() multiple times; all will be called in the
    4442:    order in which they were set.

    4444:    Level: intermediate

    4446: .seealso: SNESConvergedReasonView(), SNESConvergedReasonViewCancel()
    4447: @*/
    4448: PetscErrorCode  SNESConvergedReasonViewSet(SNES snes,PetscErrorCode (*f)(SNES,void*),void *vctx,PetscErrorCode (*reasonviewdestroy)(void**))
    4449: {
    4450:   PetscInt       i;
    4451:   PetscBool      identical;

    4454:   for (i=0; i<snes->numberreasonviews;i++) {
    4455:     PetscMonitorCompare((PetscErrorCode (*)(void))f,vctx,reasonviewdestroy,(PetscErrorCode (*)(void))snes->reasonview[i],snes->reasonviewcontext[i],snes->reasonviewdestroy[i],&identical);
    4456:     if (identical) return 0;
    4457:   }
    4459:   snes->reasonview[snes->numberreasonviews]          = f;
    4460:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
    4461:   snes->reasonviewcontext[snes->numberreasonviews++] = (void*)vctx;
    4462:   return 0;
    4463: }

    4465: /*@
    4466:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a SNESReason is to be viewed.
    4467:                                        All the user-provided convergedReasonView routines will be involved as well, if they exist.

    4469:   Collective on SNES

    4471:   Input Parameters:
    4472: . snes   - the SNES object

    4474:   Level: intermediate

    4476: .seealso: SNESCreate(), SNESSetUp(), SNESDestroy(), SNESSetTolerances(), SNESConvergedDefault(), SNESGetConvergedReason(), SNESConvergedReasonView()

    4478: @*/
    4479: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
    4480: {
    4481:   PetscViewer       viewer;
    4482:   PetscBool         flg;
    4483:   static PetscBool  incall = PETSC_FALSE;
    4484:   PetscViewerFormat format;
    4485:   PetscInt          i;

    4487:   if (incall) return 0;
    4488:   incall = PETSC_TRUE;

    4490:   /* All user-provided viewers are called first, if they exist. */
    4491:   for (i=0; i<snes->numberreasonviews; i++) {
    4492:     (*snes->reasonview[i])(snes,snes->reasonviewcontext[i]);
    4493:   }

    4495:   /* Call PETSc default routine if users ask for it */
    4496:   PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_converged_reason",&viewer,&format,&flg);
    4497:   if (flg) {
    4498:     PetscViewerPushFormat(viewer,format);
    4499:     SNESConvergedReasonView(snes,viewer);
    4500:     PetscViewerPopFormat(viewer);
    4501:     PetscViewerDestroy(&viewer);
    4502:   }
    4503:   incall = PETSC_FALSE;
    4504:   return 0;
    4505: }

    4507: /*@
    4508:    SNESSolve - Solves a nonlinear system F(x) = b.
    4509:    Call SNESSolve() after calling SNESCreate() and optional routines of the form SNESSetXXX().

    4511:    Collective on SNES

    4513:    Input Parameters:
    4514: +  snes - the SNES context
    4515: .  b - the constant part of the equation F(x) = b, or NULL to use zero.
    4516: -  x - the solution vector.

    4518:    Notes:
    4519:    The user should initialize the vector,x, with the initial guess
    4520:    for the nonlinear solve prior to calling SNESSolve().  In particular,
    4521:    to employ an initial guess of zero, the user should explicitly set
    4522:    this vector to zero by calling VecSet().

    4524:    Level: beginner

    4526: .seealso: SNESCreate(), SNESDestroy(), SNESSetFunction(), SNESSetJacobian(), SNESSetGridSequence(), SNESGetSolution(),
    4527:           SNESNewtonTRSetPreCheck(), SNESNewtonTRGetPreCheck(), SNESNewtonTRSetPostCheck(), SNESNewtonTRGetPostCheck(),
    4528:           SNESLineSearchSetPostCheck(), SNESLineSearchGetPostCheck(), SNESLineSearchSetPreCheck(), SNESLineSearchGetPreCheck()
    4529: @*/
    4530: PetscErrorCode  SNESSolve(SNES snes,Vec b,Vec x)
    4531: {
    4532:   PetscBool         flg;
    4533:   PetscInt          grid;
    4534:   Vec               xcreated = NULL;
    4535:   DM                dm;

    4543:   /* High level operations using the nonlinear solver */
    4544:   {
    4545:     PetscViewer       viewer;
    4546:     PetscViewerFormat format;
    4547:     PetscInt          num;
    4548:     PetscBool         flg;
    4549:     static PetscBool  incall = PETSC_FALSE;

    4551:     if (!incall) {
    4552:       /* Estimate the convergence rate of the discretization */
    4553:       PetscOptionsGetViewer(PetscObjectComm((PetscObject) snes),((PetscObject)snes)->options, ((PetscObject) snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg);
    4554:       if (flg) {
    4555:         PetscConvEst conv;
    4556:         DM           dm;
    4557:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
    4558:         PetscInt     Nf;

    4560:         incall = PETSC_TRUE;
    4561:         SNESGetDM(snes, &dm);
    4562:         DMGetNumFields(dm, &Nf);
    4563:         PetscCalloc1(Nf, &alpha);
    4564:         PetscConvEstCreate(PetscObjectComm((PetscObject) snes), &conv);
    4565:         PetscConvEstSetSolver(conv, (PetscObject) snes);
    4566:         PetscConvEstSetFromOptions(conv);
    4567:         PetscConvEstSetUp(conv);
    4568:         PetscConvEstGetConvRate(conv, alpha);
    4569:         PetscViewerPushFormat(viewer, format);
    4570:         PetscConvEstRateView(conv, alpha, viewer);
    4571:         PetscViewerPopFormat(viewer);
    4572:         PetscViewerDestroy(&viewer);
    4573:         PetscConvEstDestroy(&conv);
    4574:         PetscFree(alpha);
    4575:         incall = PETSC_FALSE;
    4576:       }
    4577:       /* Adaptively refine the initial grid */
    4578:       num  = 1;
    4579:       PetscOptionsGetInt(NULL, ((PetscObject) snes)->prefix, "-snes_adapt_initial", &num, &flg);
    4580:       if (flg) {
    4581:         DMAdaptor adaptor;

    4583:         incall = PETSC_TRUE;
    4584:         DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor);
    4585:         DMAdaptorSetSolver(adaptor, snes);
    4586:         DMAdaptorSetSequenceLength(adaptor, num);
    4587:         DMAdaptorSetFromOptions(adaptor);
    4588:         DMAdaptorSetUp(adaptor);
    4589:         DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x);
    4590:         DMAdaptorDestroy(&adaptor);
    4591:         incall = PETSC_FALSE;
    4592:       }
    4593:       /* Use grid sequencing to adapt */
    4594:       num  = 0;
    4595:       PetscOptionsGetInt(NULL, ((PetscObject) snes)->prefix, "-snes_adapt_sequence", &num, NULL);
    4596:       if (num) {
    4597:         DMAdaptor adaptor;

    4599:         incall = PETSC_TRUE;
    4600:         DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor);
    4601:         DMAdaptorSetSolver(adaptor, snes);
    4602:         DMAdaptorSetSequenceLength(adaptor, num);
    4603:         DMAdaptorSetFromOptions(adaptor);
    4604:         DMAdaptorSetUp(adaptor);
    4605:         DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x);
    4606:         DMAdaptorDestroy(&adaptor);
    4607:         incall = PETSC_FALSE;
    4608:       }
    4609:     }
    4610:   }
    4611:   if (!x) { x = snes->vec_sol; }
    4612:   if (!x) {
    4613:     SNESGetDM(snes,&dm);
    4614:     DMCreateGlobalVector(dm,&xcreated);
    4615:     x    = xcreated;
    4616:   }
    4617:   SNESViewFromOptions(snes,NULL,"-snes_view_pre");

    4619:   for (grid=0; grid<snes->gridsequence; grid++) PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));
    4620:   for (grid=0; grid<snes->gridsequence+1; grid++) {

    4622:     /* set solution vector */
    4623:     if (!grid) PetscObjectReference((PetscObject)x);
    4624:     VecDestroy(&snes->vec_sol);
    4625:     snes->vec_sol = x;
    4626:     SNESGetDM(snes,&dm);

    4628:     /* set affine vector if provided */
    4629:     if (b) PetscObjectReference((PetscObject)b);
    4630:     VecDestroy(&snes->vec_rhs);
    4631:     snes->vec_rhs = b;

    4636:     if (!snes->vec_sol_update /* && snes->vec_sol */) {
    4637:       VecDuplicate(snes->vec_sol,&snes->vec_sol_update);
    4638:       PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->vec_sol_update);
    4639:     }
    4640:     DMShellSetGlobalVector(dm,snes->vec_sol);
    4641:     SNESSetUp(snes);

    4643:     if (!grid) {
    4644:       if (snes->ops->computeinitialguess) {
    4645:         (*snes->ops->computeinitialguess)(snes,snes->vec_sol,snes->initialguessP);
    4646:       }
    4647:     }

    4649:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
    4650:     if (snes->counters_reset) {snes->nfuncs = 0; snes->linear_its = 0; snes->numFailures = 0;}

    4652:     PetscLogEventBegin(SNES_Solve,snes,0,0,0);
    4653:     (*snes->ops->solve)(snes);
    4654:     PetscLogEventEnd(SNES_Solve,snes,0,0,0);
    4656:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

    4658:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
    4659:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

    4661:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_test_local_min",NULL,NULL,&flg);
    4662:     if (flg && !PetscPreLoadingOn) SNESTestLocalMin(snes);
    4663:     /* Call converged reason views. This may involve user-provided viewers as well */
    4664:     SNESConvergedReasonViewFromOptions(snes);

    4667:     if (snes->reason < 0) break;
    4668:     if (grid <  snes->gridsequence) {
    4669:       DM  fine;
    4670:       Vec xnew;
    4671:       Mat interp;

    4673:       DMRefine(snes->dm,PetscObjectComm((PetscObject)snes),&fine);
    4675:       DMCreateInterpolation(snes->dm,fine,&interp,NULL);
    4676:       DMCreateGlobalVector(fine,&xnew);
    4677:       MatInterpolate(interp,x,xnew);
    4678:       DMInterpolate(snes->dm,interp,fine);
    4679:       MatDestroy(&interp);
    4680:       x    = xnew;

    4682:       SNESReset(snes);
    4683:       SNESSetDM(snes,fine);
    4684:       SNESResetFromOptions(snes);
    4685:       DMDestroy(&fine);
    4686:       PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));
    4687:     }
    4688:   }
    4689:   SNESViewFromOptions(snes,NULL,"-snes_view");
    4690:   VecViewFromOptions(snes->vec_sol,(PetscObject)snes,"-snes_view_solution");
    4691:   DMMonitor(snes->dm);
    4692:   SNESMonitorPauseFinal_Internal(snes);

    4694:   VecDestroy(&xcreated);
    4695:   PetscObjectSAWsBlock((PetscObject)snes);
    4696:   return 0;
    4697: }

    4699: /* --------- Internal routines for SNES Package --------- */

    4701: /*@C
    4702:    SNESSetType - Sets the method for the nonlinear solver.

    4704:    Collective on SNES

    4706:    Input Parameters:
    4707: +  snes - the SNES context
    4708: -  type - a known method

    4710:    Options Database Key:
    4711: .  -snes_type <type> - Sets the method; use -help for a list
    4712:    of available methods (for instance, newtonls or newtontr)

    4714:    Notes:
    4715:    See "petsc/include/petscsnes.h" for available methods (for instance)
    4716: +    SNESNEWTONLS - Newton's method with line search
    4717:      (systems of nonlinear equations)
    4718: -    SNESNEWTONTR - Newton's method with trust region
    4719:      (systems of nonlinear equations)

    4721:   Normally, it is best to use the SNESSetFromOptions() command and then
    4722:   set the SNES solver type from the options database rather than by using
    4723:   this routine.  Using the options database provides the user with
    4724:   maximum flexibility in evaluating the many nonlinear solvers.
    4725:   The SNESSetType() routine is provided for those situations where it
    4726:   is necessary to set the nonlinear solver independently of the command
    4727:   line or options database.  This might be the case, for example, when
    4728:   the choice of solver changes during the execution of the program,
    4729:   and the user's application is taking responsibility for choosing the
    4730:   appropriate method.

    4732:     Developer Notes:
    4733:     SNESRegister() adds a constructor for a new SNESType to SNESList, SNESSetType() locates
    4734:     the constructor in that list and calls it to create the spexific object.

    4736:   Level: intermediate

    4738: .seealso: SNESType, SNESCreate(), SNESDestroy(), SNESGetType(), SNESSetFromOptions()

    4740: @*/
    4741: PetscErrorCode  SNESSetType(SNES snes,SNESType type)
    4742: {
    4743:   PetscBool      match;
    4744:   PetscErrorCode (*r)(SNES);

    4749:   PetscObjectTypeCompare((PetscObject)snes,type,&match);
    4750:   if (match) return 0;

    4752:   PetscFunctionListFind(SNESList,type,&r);
    4754:   /* Destroy the previous private SNES context */
    4755:   if (snes->ops->destroy) {
    4756:     (*(snes)->ops->destroy)(snes);
    4757:     snes->ops->destroy = NULL;
    4758:   }
    4759:   /* Reinitialize function pointers in SNESOps structure */
    4760:   snes->ops->setup          = NULL;
    4761:   snes->ops->solve          = NULL;
    4762:   snes->ops->view           = NULL;
    4763:   snes->ops->setfromoptions = NULL;
    4764:   snes->ops->destroy        = NULL;

    4766:   /* It may happen the user has customized the line search before calling SNESSetType */
    4767:   if (((PetscObject)snes)->type_name) SNESLineSearchDestroy(&snes->linesearch);

    4769:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
    4770:   snes->setupcalled = PETSC_FALSE;

    4772:   PetscObjectChangeTypeName((PetscObject)snes,type);
    4773:   (*r)(snes);
    4774:   return 0;
    4775: }

    4777: /*@C
    4778:    SNESGetType - Gets the SNES method type and name (as a string).

    4780:    Not Collective

    4782:    Input Parameter:
    4783: .  snes - nonlinear solver context

    4785:    Output Parameter:
    4786: .  type - SNES method (a character string)

    4788:    Level: intermediate

    4790: @*/
    4791: PetscErrorCode  SNESGetType(SNES snes,SNESType *type)
    4792: {
    4795:   *type = ((PetscObject)snes)->type_name;
    4796:   return 0;
    4797: }

    4799: /*@
    4800:   SNESSetSolution - Sets the solution vector for use by the SNES routines.

    4802:   Logically Collective on SNES

    4804:   Input Parameters:
    4805: + snes - the SNES context obtained from SNESCreate()
    4806: - u    - the solution vector

    4808:   Level: beginner

    4810: @*/
    4811: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
    4812: {
    4813:   DM             dm;

    4817:   PetscObjectReference((PetscObject) u);
    4818:   VecDestroy(&snes->vec_sol);

    4820:   snes->vec_sol = u;

    4822:   SNESGetDM(snes, &dm);
    4823:   DMShellSetGlobalVector(dm, u);
    4824:   return 0;
    4825: }

    4827: /*@
    4828:    SNESGetSolution - Returns the vector where the approximate solution is
    4829:    stored. This is the fine grid solution when using SNESSetGridSequence().

    4831:    Not Collective, but Vec is parallel if SNES is parallel

    4833:    Input Parameter:
    4834: .  snes - the SNES context

    4836:    Output Parameter:
    4837: .  x - the solution

    4839:    Level: intermediate

    4841: .seealso:  SNESGetSolutionUpdate(), SNESGetFunction()
    4842: @*/
    4843: PetscErrorCode  SNESGetSolution(SNES snes,Vec *x)
    4844: {
    4847:   *x = snes->vec_sol;
    4848:   return 0;
    4849: }

    4851: /*@
    4852:    SNESGetSolutionUpdate - Returns the vector where the solution update is
    4853:    stored.

    4855:    Not Collective, but Vec is parallel if SNES is parallel

    4857:    Input Parameter:
    4858: .  snes - the SNES context

    4860:    Output Parameter:
    4861: .  x - the solution update

    4863:    Level: advanced

    4865: .seealso: SNESGetSolution(), SNESGetFunction()
    4866: @*/
    4867: PetscErrorCode  SNESGetSolutionUpdate(SNES snes,Vec *x)
    4868: {
    4871:   *x = snes->vec_sol_update;
    4872:   return 0;
    4873: }

    4875: /*@C
    4876:    SNESGetFunction - Returns the vector where the function is stored.

    4878:    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.

    4880:    Input Parameter:
    4881: .  snes - the SNES context

    4883:    Output Parameters:
    4884: +  r - the vector that is used to store residuals (or NULL if you don't want it)
    4885: .  f - the function (or NULL if you don't want it); see SNESFunction for calling sequence details
    4886: -  ctx - the function context (or NULL if you don't want it)

    4888:    Level: advanced

    4890:     Notes: The vector r DOES NOT, in general contain the current value of the SNES nonlinear function

    4892: .seealso: SNESSetFunction(), SNESGetSolution(), SNESFunction
    4893: @*/
    4894: PetscErrorCode  SNESGetFunction(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),void **ctx)
    4895: {
    4896:   DM             dm;

    4899:   if (r) {
    4900:     if (!snes->vec_func) {
    4901:       if (snes->vec_rhs) {
    4902:         VecDuplicate(snes->vec_rhs,&snes->vec_func);
    4903:       } else if (snes->vec_sol) {
    4904:         VecDuplicate(snes->vec_sol,&snes->vec_func);
    4905:       } else if (snes->dm) {
    4906:         DMCreateGlobalVector(snes->dm,&snes->vec_func);
    4907:       }
    4908:     }
    4909:     *r = snes->vec_func;
    4910:   }
    4911:   SNESGetDM(snes,&dm);
    4912:   DMSNESGetFunction(dm,f,ctx);
    4913:   return 0;
    4914: }

    4916: /*@C
    4917:    SNESGetNGS - Returns the NGS function and context.

    4919:    Input Parameter:
    4920: .  snes - the SNES context

    4922:    Output Parameters:
    4923: +  f - the function (or NULL) see SNESNGSFunction for details
    4924: -  ctx    - the function context (or NULL)

    4926:    Level: advanced

    4928: .seealso: SNESSetNGS(), SNESGetFunction()
    4929: @*/

    4931: PetscErrorCode SNESGetNGS (SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void*), void ** ctx)
    4932: {
    4933:   DM             dm;

    4936:   SNESGetDM(snes,&dm);
    4937:   DMSNESGetNGS(dm,f,ctx);
    4938:   return 0;
    4939: }

    4941: /*@C
    4942:    SNESSetOptionsPrefix - Sets the prefix used for searching for all
    4943:    SNES options in the database.

    4945:    Logically Collective on SNES

    4947:    Input Parameters:
    4948: +  snes - the SNES context
    4949: -  prefix - the prefix to prepend to all option names

    4951:    Notes:
    4952:    A hyphen (-) must NOT be given at the beginning of the prefix name.
    4953:    The first character of all runtime options is AUTOMATICALLY the hyphen.

    4955:    Level: advanced

    4957: .seealso: SNESSetFromOptions()
    4958: @*/
    4959: PetscErrorCode  SNESSetOptionsPrefix(SNES snes,const char prefix[])
    4960: {
    4962:   PetscObjectSetOptionsPrefix((PetscObject)snes,prefix);
    4963:   if (!snes->ksp) SNESGetKSP(snes,&snes->ksp);
    4964:   if (snes->linesearch) {
    4965:     SNESGetLineSearch(snes,&snes->linesearch);
    4966:     PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch,prefix);
    4967:   }
    4968:   KSPSetOptionsPrefix(snes->ksp,prefix);
    4969:   return 0;
    4970: }

    4972: /*@C
    4973:    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
    4974:    SNES options in the database.

    4976:    Logically Collective on SNES

    4978:    Input Parameters:
    4979: +  snes - the SNES context
    4980: -  prefix - the prefix to prepend to all option names

    4982:    Notes:
    4983:    A hyphen (-) must NOT be given at the beginning of the prefix name.
    4984:    The first character of all runtime options is AUTOMATICALLY the hyphen.

    4986:    Level: advanced

    4988: .seealso: SNESGetOptionsPrefix()
    4989: @*/
    4990: PetscErrorCode  SNESAppendOptionsPrefix(SNES snes,const char prefix[])
    4991: {
    4993:   PetscObjectAppendOptionsPrefix((PetscObject)snes,prefix);
    4994:   if (!snes->ksp) SNESGetKSP(snes,&snes->ksp);
    4995:   if (snes->linesearch) {
    4996:     SNESGetLineSearch(snes,&snes->linesearch);
    4997:     PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch,prefix);
    4998:   }
    4999:   KSPAppendOptionsPrefix(snes->ksp,prefix);
    5000:   return 0;
    5001: }

    5003: /*@C
    5004:    SNESGetOptionsPrefix - Sets the prefix used for searching for all
    5005:    SNES options in the database.

    5007:    Not Collective

    5009:    Input Parameter:
    5010: .  snes - the SNES context

    5012:    Output Parameter:
    5013: .  prefix - pointer to the prefix string used

    5015:    Notes:
    5016:     On the fortran side, the user should pass in a string 'prefix' of
    5017:    sufficient length to hold the prefix.

    5019:    Level: advanced

    5021: .seealso: SNESAppendOptionsPrefix()
    5022: @*/
    5023: PetscErrorCode  SNESGetOptionsPrefix(SNES snes,const char *prefix[])
    5024: {
    5026:   PetscObjectGetOptionsPrefix((PetscObject)snes,prefix);
    5027:   return 0;
    5028: }

    5030: /*@C
    5031:   SNESRegister - Adds a method to the nonlinear solver package.

    5033:    Not collective

    5035:    Input Parameters:
    5036: +  name_solver - name of a new user-defined solver
    5037: -  routine_create - routine to create method context

    5039:    Notes:
    5040:    SNESRegister() may be called multiple times to add several user-defined solvers.

    5042:    Sample usage:
    5043: .vb
    5044:    SNESRegister("my_solver",MySolverCreate);
    5045: .ve

    5047:    Then, your solver can be chosen with the procedural interface via
    5048: $     SNESSetType(snes,"my_solver")
    5049:    or at runtime via the option
    5050: $     -snes_type my_solver

    5052:    Level: advanced

    5054:     Note: If your function is not being put into a shared library then use SNESRegister() instead

    5056: .seealso: SNESRegisterAll(), SNESRegisterDestroy()

    5058:   Level: advanced
    5059: @*/
    5060: PetscErrorCode  SNESRegister(const char sname[],PetscErrorCode (*function)(SNES))
    5061: {
    5062:   SNESInitializePackage();
    5063:   PetscFunctionListAdd(&SNESList,sname,function);
    5064:   return 0;
    5065: }

    5067: PetscErrorCode  SNESTestLocalMin(SNES snes)
    5068: {
    5069:   PetscInt       N,i,j;
    5070:   Vec            u,uh,fh;
    5071:   PetscScalar    value;
    5072:   PetscReal      norm;

    5074:   SNESGetSolution(snes,&u);
    5075:   VecDuplicate(u,&uh);
    5076:   VecDuplicate(u,&fh);

    5078:   /* currently only works for sequential */
    5079:   PetscPrintf(PetscObjectComm((PetscObject)snes),"Testing FormFunction() for local min\n");
    5080:   VecGetSize(u,&N);
    5081:   for (i=0; i<N; i++) {
    5082:     VecCopy(u,uh);
    5083:     PetscPrintf(PetscObjectComm((PetscObject)snes),"i = %D\n",i);
    5084:     for (j=-10; j<11; j++) {
    5085:       value = PetscSign(j)*PetscExpReal(PetscAbs(j)-10.0);
    5086:       VecSetValue(uh,i,value,ADD_VALUES);
    5087:       SNESComputeFunction(snes,uh,fh);
    5088:       VecNorm(fh,NORM_2,&norm);
    5089:       PetscPrintf(PetscObjectComm((PetscObject)snes),"       j norm %D %18.16e\n",j,norm);
    5090:       value = -value;
    5091:       VecSetValue(uh,i,value,ADD_VALUES);
    5092:     }
    5093:   }
    5094:   VecDestroy(&uh);
    5095:   VecDestroy(&fh);
    5096:   return 0;
    5097: }

    5099: /*@
    5100:    SNESKSPSetUseEW - Sets SNES use Eisenstat-Walker method for
    5101:    computing relative tolerance for linear solvers within an inexact
    5102:    Newton method.

    5104:    Logically Collective on SNES

    5106:    Input Parameters:
    5107: +  snes - SNES context
    5108: -  flag - PETSC_TRUE or PETSC_FALSE

    5110:     Options Database:
    5111: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
    5112: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
    5113: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
    5114: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
    5115: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
    5116: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
    5117: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
    5118: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

    5120:    Notes:
    5121:    Currently, the default is to use a constant relative tolerance for
    5122:    the inner linear solvers.  Alternatively, one can use the
    5123:    Eisenstat-Walker method, where the relative convergence tolerance
    5124:    is reset at each Newton iteration according progress of the nonlinear
    5125:    solver.

    5127:    Level: advanced

    5129:    Reference:
    5130:    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
    5131:    inexact Newton method", SISC 17 (1), pp.16-32, 1996.

    5133: .seealso: SNESKSPGetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
    5134: @*/
    5135: PetscErrorCode  SNESKSPSetUseEW(SNES snes,PetscBool flag)
    5136: {
    5139:   snes->ksp_ewconv = flag;
    5140:   return 0;
    5141: }

    5143: /*@
    5144:    SNESKSPGetUseEW - Gets if SNES is using Eisenstat-Walker method
    5145:    for computing relative tolerance for linear solvers within an
    5146:    inexact Newton method.

    5148:    Not Collective

    5150:    Input Parameter:
    5151: .  snes - SNES context

    5153:    Output Parameter:
    5154: .  flag - PETSC_TRUE or PETSC_FALSE

    5156:    Notes:
    5157:    Currently, the default is to use a constant relative tolerance for
    5158:    the inner linear solvers.  Alternatively, one can use the
    5159:    Eisenstat-Walker method, where the relative convergence tolerance
    5160:    is reset at each Newton iteration according progress of the nonlinear
    5161:    solver.

    5163:    Level: advanced

    5165:    Reference:
    5166:    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
    5167:    inexact Newton method", SISC 17 (1), pp.16-32, 1996.

    5169: .seealso: SNESKSPSetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
    5170: @*/
    5171: PetscErrorCode  SNESKSPGetUseEW(SNES snes, PetscBool  *flag)
    5172: {
    5175:   *flag = snes->ksp_ewconv;
    5176:   return 0;
    5177: }

    5179: /*@
    5180:    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
    5181:    convergence criteria for the linear solvers within an inexact
    5182:    Newton method.

    5184:    Logically Collective on SNES

    5186:    Input Parameters:
    5187: +    snes - SNES context
    5188: .    version - version 1, 2 (default is 2) or 3
    5189: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
    5190: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
    5191: .    gamma - multiplicative factor for version 2 rtol computation
    5192:              (0 <= gamma2 <= 1)
    5193: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
    5194: .    alpha2 - power for safeguard
    5195: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

    5197:    Note:
    5198:    Version 3 was contributed by Luis Chacon, June 2006.

    5200:    Use PETSC_DEFAULT to retain the default for any of the parameters.

    5202:    Level: advanced

    5204:    Reference:
    5205:    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
    5206:    inexact Newton method", Utah State University Math. Stat. Dept. Res.
    5207:    Report 6/94/75, June, 1994, to appear in SIAM J. Sci. Comput.

    5209: .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPGetParametersEW()
    5210: @*/
    5211: PetscErrorCode  SNESKSPSetParametersEW(SNES snes,PetscInt version,PetscReal rtol_0,PetscReal rtol_max,PetscReal gamma,PetscReal alpha,PetscReal alpha2,PetscReal threshold)
    5212: {
    5213:   SNESKSPEW *kctx;

    5216:   kctx = (SNESKSPEW*)snes->kspconvctx;

    5226:   if (version != PETSC_DEFAULT)   kctx->version   = version;
    5227:   if (rtol_0 != PETSC_DEFAULT)    kctx->rtol_0    = rtol_0;
    5228:   if (rtol_max != PETSC_DEFAULT)  kctx->rtol_max  = rtol_max;
    5229:   if (gamma != PETSC_DEFAULT)     kctx->gamma     = gamma;
    5230:   if (alpha != PETSC_DEFAULT)     kctx->alpha     = alpha;
    5231:   if (alpha2 != PETSC_DEFAULT)    kctx->alpha2    = alpha2;
    5232:   if (threshold != PETSC_DEFAULT) kctx->threshold = threshold;

    5240:   return 0;
    5241: }

    5243: /*@
    5244:    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
    5245:    convergence criteria for the linear solvers within an inexact
    5246:    Newton method.

    5248:    Not Collective

    5250:    Input Parameter:
    5251: .    snes - SNES context

    5253:    Output Parameters:
    5254: +    version - version 1, 2 (default is 2) or 3
    5255: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
    5256: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
    5257: .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
    5258: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
    5259: .    alpha2 - power for safeguard
    5260: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

    5262:    Level: advanced

    5264: .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPSetParametersEW()
    5265: @*/
    5266: PetscErrorCode  SNESKSPGetParametersEW(SNES snes,PetscInt *version,PetscReal *rtol_0,PetscReal *rtol_max,PetscReal *gamma,PetscReal *alpha,PetscReal *alpha2,PetscReal *threshold)
    5267: {
    5268:   SNESKSPEW *kctx;

    5271:   kctx = (SNESKSPEW*)snes->kspconvctx;
    5273:   if (version)   *version   = kctx->version;
    5274:   if (rtol_0)    *rtol_0    = kctx->rtol_0;
    5275:   if (rtol_max)  *rtol_max  = kctx->rtol_max;
    5276:   if (gamma)     *gamma     = kctx->gamma;
    5277:   if (alpha)     *alpha     = kctx->alpha;
    5278:   if (alpha2)    *alpha2    = kctx->alpha2;
    5279:   if (threshold) *threshold = kctx->threshold;
    5280:   return 0;
    5281: }

    5283:  PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
    5284: {
    5285:   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
    5286:   PetscReal      rtol  = PETSC_DEFAULT,stol;

    5288:   if (!snes->ksp_ewconv) return 0;
    5289:   if (!snes->iter) {
    5290:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
    5291:     VecNorm(snes->vec_func,NORM_2,&kctx->norm_first);
    5292:   }
    5293:   else {
    5294:     if (kctx->version == 1) {
    5295:       rtol = (snes->norm - kctx->lresid_last)/kctx->norm_last;
    5296:       if (rtol < 0.0) rtol = -rtol;
    5297:       stol = PetscPowReal(kctx->rtol_last,kctx->alpha2);
    5298:       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
    5299:     } else if (kctx->version == 2) {
    5300:       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
    5301:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last,kctx->alpha);
    5302:       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
    5303:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
    5304:       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
    5305:       /* safeguard: avoid sharp decrease of rtol */
    5306:       stol = kctx->gamma*PetscPowReal(kctx->rtol_last,kctx->alpha);
    5307:       stol = PetscMax(rtol,stol);
    5308:       rtol = PetscMin(kctx->rtol_0,stol);
    5309:       /* safeguard: avoid oversolving */
    5310:       stol = kctx->gamma*(kctx->norm_first*snes->rtol)/snes->norm;
    5311:       stol = PetscMax(rtol,stol);
    5312:       rtol = PetscMin(kctx->rtol_0,stol);
    5313:     } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 or 3 are supported: %D",kctx->version);
    5314:   }
    5315:   /* safeguard: avoid rtol greater than one */
    5316:   rtol = PetscMin(rtol,kctx->rtol_max);
    5317:   KSPSetTolerances(ksp,rtol,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
    5318:   PetscInfo(snes,"iter %D, Eisenstat-Walker (version %D) KSP rtol=%g\n",snes->iter,kctx->version,(double)rtol);
    5319:   return 0;
    5320: }

    5322: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
    5323: {
    5324:   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
    5325:   PCSide         pcside;
    5326:   Vec            lres;

    5328:   if (!snes->ksp_ewconv) return 0;
    5329:   KSPGetTolerances(ksp,&kctx->rtol_last,NULL,NULL,NULL);
    5330:   kctx->norm_last = snes->norm;
    5331:   if (kctx->version == 1) {
    5332:     PC        pc;
    5333:     PetscBool isNone;

    5335:     KSPGetPC(ksp, &pc);
    5336:     PetscObjectTypeCompare((PetscObject) pc, PCNONE, &isNone);
    5337:     KSPGetPCSide(ksp,&pcside);
    5338:      if (pcside == PC_RIGHT || isNone) { /* XXX Should we also test KSP_UNPRECONDITIONED_NORM ? */
    5339:       /* KSP residual is true linear residual */
    5340:       KSPGetResidualNorm(ksp,&kctx->lresid_last);
    5341:     } else {
    5342:       /* KSP residual is preconditioned residual */
    5343:       /* compute true linear residual norm */
    5344:       VecDuplicate(b,&lres);
    5345:       MatMult(snes->jacobian,x,lres);
    5346:       VecAYPX(lres,-1.0,b);
    5347:       VecNorm(lres,NORM_2,&kctx->lresid_last);
    5348:       VecDestroy(&lres);
    5349:     }
    5350:   }
    5351:   return 0;
    5352: }

    5354: /*@
    5355:    SNESGetKSP - Returns the KSP context for a SNES solver.

    5357:    Not Collective, but if SNES object is parallel, then KSP object is parallel

    5359:    Input Parameter:
    5360: .  snes - the SNES context

    5362:    Output Parameter:
    5363: .  ksp - the KSP context

    5365:    Notes:
    5366:    The user can then directly manipulate the KSP context to set various
    5367:    options, etc.  Likewise, the user can then extract and manipulate the
    5368:    PC contexts as well.

    5370:    Level: beginner

    5372: .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
    5373: @*/
    5374: PetscErrorCode  SNESGetKSP(SNES snes,KSP *ksp)
    5375: {

    5379:   if (!snes->ksp) {
    5380:     KSPCreate(PetscObjectComm((PetscObject)snes),&snes->ksp);
    5381:     PetscObjectIncrementTabLevel((PetscObject)snes->ksp,(PetscObject)snes,1);
    5382:     PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->ksp);

    5384:     KSPSetPreSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPreSolve_SNESEW,snes);
    5385:     KSPSetPostSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPostSolve_SNESEW,snes);

    5387:     KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes);
    5388:     PetscObjectSetOptions((PetscObject)snes->ksp,((PetscObject)snes)->options);
    5389:   }
    5390:   *ksp = snes->ksp;
    5391:   return 0;
    5392: }

    5394: #include <petsc/private/dmimpl.h>
    5395: /*@
    5396:    SNESSetDM - Sets the DM that may be used by some nonlinear solvers or their underlying preconditioners

    5398:    Logically Collective on SNES

    5400:    Input Parameters:
    5401: +  snes - the nonlinear solver context
    5402: -  dm - the dm, cannot be NULL

    5404:    Notes:
    5405:    A DM can only be used for solving one problem at a time because information about the problem is stored on the DM,
    5406:    even when not using interfaces like DMSNESSetFunction().  Use DMClone() to get a distinct DM when solving different
    5407:    problems using the same function space.

    5409:    Level: intermediate

    5411: .seealso: SNESGetDM(), KSPSetDM(), KSPGetDM()
    5412: @*/
    5413: PetscErrorCode  SNESSetDM(SNES snes,DM dm)
    5414: {
    5415:   KSP            ksp;
    5416:   DMSNES         sdm;

    5420:   PetscObjectReference((PetscObject)dm);
    5421:   if (snes->dm) {               /* Move the DMSNES context over to the new DM unless the new DM already has one */
    5422:     if (snes->dm->dmsnes && !dm->dmsnes) {
    5423:       DMCopyDMSNES(snes->dm,dm);
    5424:       DMGetDMSNES(snes->dm,&sdm);
    5425:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
    5426:     }
    5427:     DMCoarsenHookRemove(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);
    5428:     DMDestroy(&snes->dm);
    5429:   }
    5430:   snes->dm     = dm;
    5431:   snes->dmAuto = PETSC_FALSE;

    5433:   SNESGetKSP(snes,&ksp);
    5434:   KSPSetDM(ksp,dm);
    5435:   KSPSetDMActive(ksp,PETSC_FALSE);
    5436:   if (snes->npc) {
    5437:     SNESSetDM(snes->npc,snes->dm);
    5438:     SNESSetNPCSide(snes,snes->npcside);
    5439:   }
    5440:   return 0;
    5441: }

    5443: /*@
    5444:    SNESGetDM - Gets the DM that may be used by some preconditioners

    5446:    Not Collective but DM obtained is parallel on SNES

    5448:    Input Parameter:
    5449: . snes - the preconditioner context

    5451:    Output Parameter:
    5452: .  dm - the dm

    5454:    Level: intermediate

    5456: .seealso: SNESSetDM(), KSPSetDM(), KSPGetDM()
    5457: @*/
    5458: PetscErrorCode  SNESGetDM(SNES snes,DM *dm)
    5459: {
    5461:   if (!snes->dm) {
    5462:     DMShellCreate(PetscObjectComm((PetscObject)snes),&snes->dm);
    5463:     snes->dmAuto = PETSC_TRUE;
    5464:   }
    5465:   *dm = snes->dm;
    5466:   return 0;
    5467: }

    5469: /*@
    5470:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

    5472:   Collective on SNES

    5474:   Input Parameters:
    5475: + snes - iterative context obtained from SNESCreate()
    5476: - pc   - the preconditioner object

    5478:   Notes:
    5479:   Use SNESGetNPC() to retrieve the preconditioner context (for example,
    5480:   to configure it using the API).

    5482:   Level: developer

    5484: .seealso: SNESGetNPC(), SNESHasNPC()
    5485: @*/
    5486: PetscErrorCode SNESSetNPC(SNES snes, SNES pc)
    5487: {
    5491:   PetscObjectReference((PetscObject) pc);
    5492:   SNESDestroy(&snes->npc);
    5493:   snes->npc = pc;
    5494:   PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->npc);
    5495:   return 0;
    5496: }

    5498: /*@
    5499:   SNESGetNPC - Creates a nonlinear preconditioning solver (SNES) to be used to precondition the nonlinear solver.

    5501:   Not Collective; but any changes to the obtained SNES object must be applied collectively

    5503:   Input Parameter:
    5504: . snes - iterative context obtained from SNESCreate()

    5506:   Output Parameter:
    5507: . pc - preconditioner context

    5509:   Options Database:
    5510: . -npc_snes_type <type> - set the type of the SNES to use as the nonlinear preconditioner

    5512:   Notes:
    5513:     If a SNES was previously set with SNESSetNPC() then that SNES is returned, otherwise a new SNES object is created.

    5515:     The (preconditioner) SNES returned automatically inherits the same nonlinear function and Jacobian supplied to the original
    5516:     SNES during SNESSetUp()

    5518:   Level: developer

    5520: .seealso: SNESSetNPC(), SNESHasNPC(), SNES, SNESCreate()
    5521: @*/
    5522: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
    5523: {
    5524:   const char     *optionsprefix;

    5528:   if (!snes->npc) {
    5529:     SNESCreate(PetscObjectComm((PetscObject)snes),&snes->npc);
    5530:     PetscObjectIncrementTabLevel((PetscObject)snes->npc,(PetscObject)snes,1);
    5531:     PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->npc);
    5532:     SNESGetOptionsPrefix(snes,&optionsprefix);
    5533:     SNESSetOptionsPrefix(snes->npc,optionsprefix);
    5534:     SNESAppendOptionsPrefix(snes->npc,"npc_");
    5535:     SNESSetCountersReset(snes->npc,PETSC_FALSE);
    5536:   }
    5537:   *pc = snes->npc;
    5538:   return 0;
    5539: }

    5541: /*@
    5542:   SNESHasNPC - Returns whether a nonlinear preconditioner exists

    5544:   Not Collective

    5546:   Input Parameter:
    5547: . snes - iterative context obtained from SNESCreate()

    5549:   Output Parameter:
    5550: . has_npc - whether the SNES has an NPC or not

    5552:   Level: developer

    5554: .seealso: SNESSetNPC(), SNESGetNPC()
    5555: @*/
    5556: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
    5557: {
    5559:   *has_npc = (PetscBool) (snes->npc ? PETSC_TRUE : PETSC_FALSE);
    5560:   return 0;
    5561: }

    5563: /*@
    5564:     SNESSetNPCSide - Sets the preconditioning side.

    5566:     Logically Collective on SNES

    5568:     Input Parameter:
    5569: .   snes - iterative context obtained from SNESCreate()

    5571:     Output Parameter:
    5572: .   side - the preconditioning side, where side is one of
    5573: .vb
    5574:       PC_LEFT - left preconditioning
    5575:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
    5576: .ve

    5578:     Options Database Keys:
    5579: .   -snes_npc_side <right,left> - nonlinear preconditioner side

    5581:     Notes:
    5582:     SNESNRICHARDSON and SNESNCG only support left preconditioning.

    5584:     Level: intermediate

    5586: .seealso: SNESGetNPCSide(), KSPSetPCSide()
    5587: @*/
    5588: PetscErrorCode  SNESSetNPCSide(SNES snes,PCSide side)
    5589: {
    5592:   if (side == PC_SIDE_DEFAULT) side = PC_RIGHT;
    5594:   snes->npcside = side;
    5595:   return 0;
    5596: }

    5598: /*@
    5599:     SNESGetNPCSide - Gets the preconditioning side.

    5601:     Not Collective

    5603:     Input Parameter:
    5604: .   snes - iterative context obtained from SNESCreate()

    5606:     Output Parameter:
    5607: .   side - the preconditioning side, where side is one of
    5608: .vb
    5609:       PC_LEFT - left preconditioning
    5610:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
    5611: .ve

    5613:     Level: intermediate

    5615: .seealso: SNESSetNPCSide(), KSPGetPCSide()
    5616: @*/
    5617: PetscErrorCode  SNESGetNPCSide(SNES snes,PCSide *side)
    5618: {
    5621:   *side = snes->npcside;
    5622:   return 0;
    5623: }

    5625: /*@
    5626:   SNESSetLineSearch - Sets the linesearch on the SNES instance.

    5628:   Collective on SNES

    5630:   Input Parameters:
    5631: + snes - iterative context obtained from SNESCreate()
    5632: - linesearch   - the linesearch object

    5634:   Notes:
    5635:   Use SNESGetLineSearch() to retrieve the preconditioner context (for example,
    5636:   to configure it using the API).

    5638:   Level: developer

    5640: .seealso: SNESGetLineSearch()
    5641: @*/
    5642: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
    5643: {
    5647:   PetscObjectReference((PetscObject) linesearch);
    5648:   SNESLineSearchDestroy(&snes->linesearch);

    5650:   snes->linesearch = linesearch;

    5652:   PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);
    5653:   return 0;
    5654: }

    5656: /*@
    5657:   SNESGetLineSearch - Returns a pointer to the line search context set with SNESSetLineSearch()
    5658:   or creates a default line search instance associated with the SNES and returns it.

    5660:   Not Collective

    5662:   Input Parameter:
    5663: . snes - iterative context obtained from SNESCreate()

    5665:   Output Parameter:
    5666: . linesearch - linesearch context

    5668:   Level: beginner

    5670: .seealso: SNESSetLineSearch(), SNESLineSearchCreate()
    5671: @*/
    5672: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
    5673: {
    5674:   const char     *optionsprefix;

    5678:   if (!snes->linesearch) {
    5679:     SNESGetOptionsPrefix(snes, &optionsprefix);
    5680:     SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch);
    5681:     SNESLineSearchSetSNES(snes->linesearch, snes);
    5682:     SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix);
    5683:     PetscObjectIncrementTabLevel((PetscObject) snes->linesearch, (PetscObject) snes, 1);
    5684:     PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);
    5685:   }
    5686:   *linesearch = snes->linesearch;
    5687:   return 0;
    5688: }