Date: 2022-03-04T17:38:52+00:00

Actual source code: redundant.c

      2: /*
      3:   This file defines a "solve the problem redundantly on each subgroup of processor" preconditioner.
      4: */
      5: #include <petsc/private/pcimpl.h>
      6: #include <petscksp.h>

      8: typedef struct {
      9:   KSP                ksp;
     10:   PC                 pc;                   /* actual preconditioner used on each processor */
     11:   Vec                xsub,ysub;            /* vectors of a subcommunicator to hold parallel vectors of PetscObjectComm((PetscObject)pc) */
     12:   Vec                xdup,ydup;            /* parallel vector that congregates xsub or ysub facilitating vector scattering */
     13:   Mat                pmats;                /* matrix and optional preconditioner matrix belong to a subcommunicator */
     14:   VecScatter         scatterin,scatterout; /* scatter used to move all values to each processor group (subcommunicator) */
     15:   PetscBool          useparallelmat;
     16:   PetscSubcomm       psubcomm;
     17:   PetscInt           nsubcomm;             /* num of data structure PetscSubcomm */
     18:   PetscBool          shifttypeset;
     19:   MatFactorShiftType shifttype;
     20: } PC_Redundant;

     22: PetscErrorCode  PCFactorSetShiftType_Redundant(PC pc,MatFactorShiftType shifttype)
     23: {
     24:   PC_Redundant   *red = (PC_Redundant*)pc->data;

     28:   if (red->ksp) {
     29:     PC pc;
     30:     KSPGetPC(red->ksp,&pc);
     31:     PCFactorSetShiftType(pc,shifttype);
     32:   } else {
     33:     red->shifttypeset = PETSC_TRUE;
     34:     red->shifttype    = shifttype;
     35:   }
     36:   return(0);
     37: }

     39: static PetscErrorCode PCView_Redundant(PC pc,PetscViewer viewer)
     40: {
     41:   PC_Redundant   *red = (PC_Redundant*)pc->data;
     43:   PetscBool      iascii,isstring;
     44:   PetscViewer    subviewer;

     47:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
     48:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
     49:   if (iascii) {
     50:     if (!red->psubcomm) {
     51:       PetscViewerASCIIPrintf(viewer,"  Not yet setup\n");
     52:     } else {
     53:       PetscViewerASCIIPrintf(viewer,"  First (color=0) of %D PCs follows\n",red->nsubcomm);
     54:       PetscViewerGetSubViewer(viewer,((PetscObject)red->pc)->comm,&subviewer);
     55:       if (!red->psubcomm->color) { /* only view first redundant pc */
     56:         PetscViewerASCIIPushTab(subviewer);
     57:         KSPView(red->ksp,subviewer);
     58:         PetscViewerASCIIPopTab(subviewer);
     59:       }
     60:       PetscViewerRestoreSubViewer(viewer,((PetscObject)red->pc)->comm,&subviewer);
     61:     }
     62:   } else if (isstring) {
     63:     PetscViewerStringSPrintf(viewer," Redundant solver preconditioner");
     64:   }
     65:   return(0);
     66: }

     68: #include <../src/mat/impls/aij/mpi/mpiaij.h>
     69: static PetscErrorCode PCSetUp_Redundant(PC pc)
     70: {
     71:   PC_Redundant   *red = (PC_Redundant*)pc->data;
     73:   PetscInt       mstart,mend,mlocal,M;
     74:   PetscMPIInt    size;
     75:   MPI_Comm       comm,subcomm;
     76:   Vec            x;

     79:   PetscObjectGetComm((PetscObject)pc,&comm);

     81:   /* if pmatrix set by user is sequential then we do not need to gather the parallel matrix */
     82:   MPI_Comm_size(comm,&size);
     83:   if (size == 1) red->useparallelmat = PETSC_FALSE;

     85:   if (!pc->setupcalled) {
     86:     PetscInt mloc_sub;
     87:     if (!red->psubcomm) { /* create red->psubcomm, new ksp and pc over subcomm */
     88:       KSP ksp;
     89:       PCRedundantGetKSP(pc,&ksp);
     90:     }
     91:     subcomm = PetscSubcommChild(red->psubcomm);

     93:     if (red->useparallelmat) {
     94:       /* grab the parallel matrix and put it into processors of a subcomminicator */
     95:       MatCreateRedundantMatrix(pc->pmat,red->psubcomm->n,subcomm,MAT_INITIAL_MATRIX,&red->pmats);

     97:       MPI_Comm_size(subcomm,&size);
     98:       if (size > 1) {
     99:         PetscBool foundpack,issbaij;
    100:         PetscObjectTypeCompare((PetscObject)red->pmats,MATMPISBAIJ,&issbaij);
    101:         if (!issbaij) {
    102:           MatGetFactorAvailable(red->pmats,NULL,MAT_FACTOR_LU,&foundpack);
    103:         } else {
    104:           MatGetFactorAvailable(red->pmats,NULL,MAT_FACTOR_CHOLESKY,&foundpack);
    105:         }
    106:         if (!foundpack) { /* reset default ksp and pc */
    107:           KSPSetType(red->ksp,KSPGMRES);
    108:           PCSetType(red->pc,PCBJACOBI);
    109:         } else {
    110:           PCFactorSetMatSolverType(red->pc,NULL);
    111:         }
    112:       }

    114:       KSPSetOperators(red->ksp,red->pmats,red->pmats);

    116:       /* get working vectors xsub and ysub */
    117:       MatCreateVecs(red->pmats,&red->xsub,&red->ysub);

    119:       /* create working vectors xdup and ydup.
    120:        xdup concatenates all xsub's contigously to form a mpi vector over dupcomm  (see PetscSubcommCreate_interlaced())
    121:        ydup concatenates all ysub and has empty local arrays because ysub's arrays will be place into it.
    122:        Note: we use communicator dupcomm, not PetscObjectComm((PetscObject)pc)! */
    123:       MatGetLocalSize(red->pmats,&mloc_sub,NULL);
    124:       VecCreateMPI(PetscSubcommContiguousParent(red->psubcomm),mloc_sub,PETSC_DECIDE,&red->xdup);
    125:       VecCreateMPIWithArray(PetscSubcommContiguousParent(red->psubcomm),1,mloc_sub,PETSC_DECIDE,NULL,&red->ydup);

    127:       /* create vecscatters */
    128:       if (!red->scatterin) { /* efficiency of scatterin is independent from psubcomm_type! */
    129:         IS       is1,is2;
    130:         PetscInt *idx1,*idx2,i,j,k;

    132:         MatCreateVecs(pc->pmat,&x,NULL);
    133:         VecGetSize(x,&M);
    134:         VecGetOwnershipRange(x,&mstart,&mend);
    135:         mlocal = mend - mstart;
    136:         PetscMalloc2(red->psubcomm->n*mlocal,&idx1,red->psubcomm->n*mlocal,&idx2);
    137:         j    = 0;
    138:         for (k=0; k<red->psubcomm->n; k++) {
    139:           for (i=mstart; i<mend; i++) {
    140:             idx1[j]   = i;
    141:             idx2[j++] = i + M*k;
    142:           }
    143:         }
    144:         ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx1,PETSC_COPY_VALUES,&is1);
    145:         ISCreateGeneral(comm,red->psubcomm->n*mlocal,idx2,PETSC_COPY_VALUES,&is2);
    146:         VecScatterCreate(x,is1,red->xdup,is2,&red->scatterin);
    147:         ISDestroy(&is1);
    148:         ISDestroy(&is2);

    150:         /* Impl below is good for PETSC_SUBCOMM_INTERLACED (no inter-process communication) and PETSC_SUBCOMM_CONTIGUOUS (communication within subcomm) */
    151:         ISCreateStride(comm,mlocal,mstart+ red->psubcomm->color*M,1,&is1);
    152:         ISCreateStride(comm,mlocal,mstart,1,&is2);
    153:         VecScatterCreate(red->xdup,is1,x,is2,&red->scatterout);
    154:         ISDestroy(&is1);
    155:         ISDestroy(&is2);
    156:         PetscFree2(idx1,idx2);
    157:         VecDestroy(&x);
    158:       }
    159:     } else { /* !red->useparallelmat */
    160:       KSPSetOperators(red->ksp,pc->mat,pc->pmat);
    161:     }
    162:   } else { /* pc->setupcalled */
    163:     if (red->useparallelmat) {
    164:       MatReuse       reuse;
    165:       /* grab the parallel matrix and put it into processors of a subcomminicator */
    166:       /*--------------------------------------------------------------------------*/
    167:       if (pc->flag == DIFFERENT_NONZERO_PATTERN) {
    168:         /* destroy old matrices */
    169:         MatDestroy(&red->pmats);
    170:         reuse = MAT_INITIAL_MATRIX;
    171:       } else {
    172:         reuse = MAT_REUSE_MATRIX;
    173:       }
    174:       MatCreateRedundantMatrix(pc->pmat,red->psubcomm->n,PetscSubcommChild(red->psubcomm),reuse,&red->pmats);
    175:       KSPSetOperators(red->ksp,red->pmats,red->pmats);
    176:     } else { /* !red->useparallelmat */
    177:       KSPSetOperators(red->ksp,pc->mat,pc->pmat);
    178:     }
    179:   }

    181:   if (pc->setfromoptionscalled) {
    182:     KSPSetFromOptions(red->ksp);
    183:   }
    184:   KSPSetUp(red->ksp);
    185:   return(0);
    186: }

    188: static PetscErrorCode PCApply_Redundant(PC pc,Vec x,Vec y)
    189: {
    190:   PC_Redundant   *red = (PC_Redundant*)pc->data;
    192:   PetscScalar    *array;

    195:   if (!red->useparallelmat) {
    196:     KSPSolve(red->ksp,x,y);
    197:     KSPCheckSolve(red->ksp,pc,y);
    198:     return(0);
    199:   }

    201:   /* scatter x to xdup */
    202:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
    203:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

    205:   /* place xdup's local array into xsub */
    206:   VecGetArray(red->xdup,&array);
    207:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

    209:   /* apply preconditioner on each processor */
    210:   KSPSolve(red->ksp,red->xsub,red->ysub);
    211:   KSPCheckSolve(red->ksp,pc,red->ysub);
    212:   VecResetArray(red->xsub);
    213:   VecRestoreArray(red->xdup,&array);

    215:   /* place ysub's local array into ydup */
    216:   VecGetArray(red->ysub,&array);
    217:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

    219:   /* scatter ydup to y */
    220:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
    221:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
    222:   VecResetArray(red->ydup);
    223:   VecRestoreArray(red->ysub,&array);
    224:   return(0);
    225: }

    227: static PetscErrorCode PCApplyTranspose_Redundant(PC pc,Vec x,Vec y)
    228: {
    229:   PC_Redundant   *red = (PC_Redundant*)pc->data;
    231:   PetscScalar    *array;

    234:   if (!red->useparallelmat) {
    235:     KSPSolveTranspose(red->ksp,x,y);
    236:     KSPCheckSolve(red->ksp,pc,y);
    237:     return(0);
    238:   }

    240:   /* scatter x to xdup */
    241:   VecScatterBegin(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);
    242:   VecScatterEnd(red->scatterin,x,red->xdup,INSERT_VALUES,SCATTER_FORWARD);

    244:   /* place xdup's local array into xsub */
    245:   VecGetArray(red->xdup,&array);
    246:   VecPlaceArray(red->xsub,(const PetscScalar*)array);

    248:   /* apply preconditioner on each processor */
    249:   KSPSolveTranspose(red->ksp,red->xsub,red->ysub);
    250:   KSPCheckSolve(red->ksp,pc,red->ysub);
    251:   VecResetArray(red->xsub);
    252:   VecRestoreArray(red->xdup,&array);

    254:   /* place ysub's local array into ydup */
    255:   VecGetArray(red->ysub,&array);
    256:   VecPlaceArray(red->ydup,(const PetscScalar*)array);

    258:   /* scatter ydup to y */
    259:   VecScatterBegin(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
    260:   VecScatterEnd(red->scatterout,red->ydup,y,INSERT_VALUES,SCATTER_FORWARD);
    261:   VecResetArray(red->ydup);
    262:   VecRestoreArray(red->ysub,&array);
    263:   return(0);
    264: }

    266: static PetscErrorCode PCReset_Redundant(PC pc)
    267: {
    268:   PC_Redundant   *red = (PC_Redundant*)pc->data;

    272:   if (red->useparallelmat) {
    273:     VecScatterDestroy(&red->scatterin);
    274:     VecScatterDestroy(&red->scatterout);
    275:     VecDestroy(&red->ysub);
    276:     VecDestroy(&red->xsub);
    277:     VecDestroy(&red->xdup);
    278:     VecDestroy(&red->ydup);
    279:   }
    280:   MatDestroy(&red->pmats);
    281:   KSPReset(red->ksp);
    282:   return(0);
    283: }

    285: static PetscErrorCode PCDestroy_Redundant(PC pc)
    286: {
    287:   PC_Redundant   *red = (PC_Redundant*)pc->data;

    291:   PCReset_Redundant(pc);
    292:   KSPDestroy(&red->ksp);
    293:   PetscSubcommDestroy(&red->psubcomm);
    294:   PetscFree(pc->data);
    295:   return(0);
    296: }

    298: static PetscErrorCode PCSetFromOptions_Redundant(PetscOptionItems *PetscOptionsObject,PC pc)
    299: {
    301:   PC_Redundant   *red = (PC_Redundant*)pc->data;

    304:   PetscOptionsHead(PetscOptionsObject,"Redundant options");
    305:   PetscOptionsInt("-pc_redundant_number","Number of redundant pc","PCRedundantSetNumber",red->nsubcomm,&red->nsubcomm,NULL);
    306:   PetscOptionsTail();
    307:   return(0);
    308: }

    310: static PetscErrorCode PCRedundantSetNumber_Redundant(PC pc,PetscInt nreds)
    311: {
    312:   PC_Redundant *red = (PC_Redundant*)pc->data;

    315:   red->nsubcomm = nreds;
    316:   return(0);
    317: }

    319: /*@
    320:    PCRedundantSetNumber - Sets the number of redundant preconditioner contexts.

    322:    Logically Collective on PC

    324:    Input Parameters:
    325: +  pc - the preconditioner context
    326: -  nredundant - number of redundant preconditioner contexts; for example if you are using 64 MPI processes and
    327:                               use an nredundant of 4 there will be 4 parallel solves each on 16 = 64/4 processes.

    329:    Level: advanced

    331: @*/
    332: PetscErrorCode PCRedundantSetNumber(PC pc,PetscInt nredundant)
    333: {

    338:   if (nredundant <= 0) SETERRQ1(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONG, "num of redundant pc %D must be positive",nredundant);
    339:   PetscTryMethod(pc,"PCRedundantSetNumber_C",(PC,PetscInt),(pc,nredundant));
    340:   return(0);
    341: }

    343: static PetscErrorCode PCRedundantSetScatter_Redundant(PC pc,VecScatter in,VecScatter out)
    344: {
    345:   PC_Redundant   *red = (PC_Redundant*)pc->data;

    349:   PetscObjectReference((PetscObject)in);
    350:   VecScatterDestroy(&red->scatterin);

    352:   red->scatterin  = in;

    354:   PetscObjectReference((PetscObject)out);
    355:   VecScatterDestroy(&red->scatterout);
    356:   red->scatterout = out;
    357:   return(0);
    358: }

    360: /*@
    361:    PCRedundantSetScatter - Sets the scatter used to copy values into the
    362:      redundant local solve and the scatter to move them back into the global
    363:      vector.

    365:    Logically Collective on PC

    367:    Input Parameters:
    368: +  pc - the preconditioner context
    369: .  in - the scatter to move the values in
    370: -  out - the scatter to move them out

    372:    Level: advanced

    374: @*/
    375: PetscErrorCode PCRedundantSetScatter(PC pc,VecScatter in,VecScatter out)
    376: {

    383:   PetscTryMethod(pc,"PCRedundantSetScatter_C",(PC,VecScatter,VecScatter),(pc,in,out));
    384:   return(0);
    385: }

    387: static PetscErrorCode PCRedundantGetKSP_Redundant(PC pc,KSP *innerksp)
    388: {
    390:   PC_Redundant   *red = (PC_Redundant*)pc->data;
    391:   MPI_Comm       comm,subcomm;
    392:   const char     *prefix;
    393:   PetscBool      issbaij;

    396:   if (!red->psubcomm) {
    397:     PCGetOptionsPrefix(pc,&prefix);

    399:     PetscObjectGetComm((PetscObject)pc,&comm);
    400:     PetscSubcommCreate(comm,&red->psubcomm);
    401:     PetscSubcommSetNumber(red->psubcomm,red->nsubcomm);
    402:     PetscSubcommSetType(red->psubcomm,PETSC_SUBCOMM_CONTIGUOUS);

    404:     PetscSubcommSetOptionsPrefix(red->psubcomm,prefix);
    405:     PetscSubcommSetFromOptions(red->psubcomm);
    406:     PetscLogObjectMemory((PetscObject)pc,sizeof(PetscSubcomm));

    408:     /* create a new PC that processors in each subcomm have copy of */
    409:     subcomm = PetscSubcommChild(red->psubcomm);

    411:     KSPCreate(subcomm,&red->ksp);
    412:     KSPSetErrorIfNotConverged(red->ksp,pc->erroriffailure);
    413:     PetscObjectIncrementTabLevel((PetscObject)red->ksp,(PetscObject)pc,1);
    414:     PetscLogObjectParent((PetscObject)pc,(PetscObject)red->ksp);
    415:     KSPSetType(red->ksp,KSPPREONLY);
    416:     KSPGetPC(red->ksp,&red->pc);
    417:     PetscObjectTypeCompare((PetscObject)pc->pmat,MATSEQSBAIJ,&issbaij);
    418:     if (!issbaij) {
    419:       PetscObjectTypeCompare((PetscObject)pc->pmat,MATMPISBAIJ,&issbaij);
    420:     }
    421:     if (!issbaij) {
    422:       PCSetType(red->pc,PCLU);
    423:     } else {
    424:       PCSetType(red->pc,PCCHOLESKY);
    425:     }
    426:     if (red->shifttypeset) {
    427:       PCFactorSetShiftType(red->pc,red->shifttype);
    428:       red->shifttypeset = PETSC_FALSE;
    429:     }
    430:     KSPSetOptionsPrefix(red->ksp,prefix);
    431:     KSPAppendOptionsPrefix(red->ksp,"redundant_");
    432:   }
    433:   *innerksp = red->ksp;
    434:   return(0);
    435: }

    437: /*@
    438:    PCRedundantGetKSP - Gets the less parallel KSP created by the redundant PC.

    440:    Not Collective

    442:    Input Parameter:
    443: .  pc - the preconditioner context

    445:    Output Parameter:
    446: .  innerksp - the KSP on the smaller set of processes

    448:    Level: advanced

    450: @*/
    451: PetscErrorCode PCRedundantGetKSP(PC pc,KSP *innerksp)
    452: {

    458:   PetscUseMethod(pc,"PCRedundantGetKSP_C",(PC,KSP*),(pc,innerksp));
    459:   return(0);
    460: }

    462: static PetscErrorCode PCRedundantGetOperators_Redundant(PC pc,Mat *mat,Mat *pmat)
    463: {
    464:   PC_Redundant *red = (PC_Redundant*)pc->data;

    467:   if (mat)  *mat  = red->pmats;
    468:   if (pmat) *pmat = red->pmats;
    469:   return(0);
    470: }

    472: /*@
    473:    PCRedundantGetOperators - gets the sequential matrix and preconditioner matrix

    475:    Not Collective

    477:    Input Parameter:
    478: .  pc - the preconditioner context

    480:    Output Parameters:
    481: +  mat - the matrix
    482: -  pmat - the (possibly different) preconditioner matrix

    484:    Level: advanced

    486: @*/
    487: PetscErrorCode PCRedundantGetOperators(PC pc,Mat *mat,Mat *pmat)
    488: {

    495:   PetscUseMethod(pc,"PCRedundantGetOperators_C",(PC,Mat*,Mat*),(pc,mat,pmat));
    496:   return(0);
    497: }

    499: /* -------------------------------------------------------------------------------------*/
    500: /*MC
    501:      PCREDUNDANT - Runs a KSP solver with preconditioner for the entire problem on subgroups of processors

    503:      Options for the redundant preconditioners can be set with -redundant_pc_xxx for the redundant KSP with -redundant_ksp_xxx

    505:   Options Database:
    506: .  -pc_redundant_number <n> - number of redundant solves, for example if you are using 64 MPI processes and
    507:                               use an n of 4 there will be 4 parallel solves each on 16 = 64/4 processes.

    509:    Level: intermediate

    511:    Notes:
    512:     The default KSP is preonly and the default PC is LU or CHOLESKY if Pmat is of type MATSBAIJ.

    514:    PCFactorSetShiftType() applied to this PC will convey they shift type into the inner PC if it is factorization based.

    516:    Developer Notes:
    517:     Note that PCSetInitialGuessNonzero()  is not used by this class but likely should be.

    519: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PCRedundantSetScatter(),
    520:            PCRedundantGetKSP(), PCRedundantGetOperators(), PCRedundantSetNumber()
    521: M*/

    523: PETSC_EXTERN PetscErrorCode PCCreate_Redundant(PC pc)
    524: {
    526:   PC_Redundant   *red;
    527:   PetscMPIInt    size;

    530:   PetscNewLog(pc,&red);
    531:   MPI_Comm_size(PetscObjectComm((PetscObject)pc),&size);

    533:   red->nsubcomm       = size;
    534:   red->useparallelmat = PETSC_TRUE;
    535:   pc->data            = (void*)red;

    537:   pc->ops->apply          = PCApply_Redundant;
    538:   pc->ops->applytranspose = PCApplyTranspose_Redundant;
    539:   pc->ops->setup          = PCSetUp_Redundant;
    540:   pc->ops->destroy        = PCDestroy_Redundant;
    541:   pc->ops->reset          = PCReset_Redundant;
    542:   pc->ops->setfromoptions = PCSetFromOptions_Redundant;
    543:   pc->ops->view           = PCView_Redundant;

    545:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetScatter_C",PCRedundantSetScatter_Redundant);
    546:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantSetNumber_C",PCRedundantSetNumber_Redundant);
    547:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetKSP_C",PCRedundantGetKSP_Redundant);
    548:   PetscObjectComposeFunction((PetscObject)pc,"PCRedundantGetOperators_C",PCRedundantGetOperators_Redundant);
    549:   PetscObjectComposeFunction((PetscObject)pc,"PCFactorSetShiftType_C",PCFactorSetShiftType_Redundant);
    550:   return(0);
    551: }