Date: 2022-03-04T17:39:03+00:00

Actual source code: fgmres.c

      2: /*
      3:     This file implements FGMRES (a Generalized Minimal Residual) method.
      4:     Reference:  Saad, 1993.

      6:     Preconditioning:  If the preconditioner is constant then this fgmres
      7:     code is equivalent to RIGHT-PRECONDITIONED GMRES.
      8:     FGMRES is a modification of gmres that allows the preconditioner to change
      9:     at each iteration.

     11:     Restarts:  Restarts are basically solves with x0 not equal to zero.

     13:        Contributed by Allison Baker

     15: */

     17: #include <../src/ksp/ksp/impls/gmres/fgmres/fgmresimpl.h>
     18: #define FGMRES_DELTA_DIRECTIONS 10
     19: #define FGMRES_DEFAULT_MAXK     30
     20: static PetscErrorCode KSPFGMRESGetNewVectors(KSP,PetscInt);
     21: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP,PetscInt,PetscBool,PetscReal*);
     22: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar*,Vec,Vec,KSP,PetscInt);

     24: /*

     26:     KSPSetUp_FGMRES - Sets up the workspace needed by fgmres.

     28:     This is called once, usually automatically by KSPSolve() or KSPSetUp(),
     29:     but can be called directly by KSPSetUp().

     31: */
     32: PetscErrorCode    KSPSetUp_FGMRES(KSP ksp)
     33: {
     35:   PetscInt       max_k,k;
     36:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;

     39:   max_k = fgmres->max_k;

     41:   KSPSetUp_GMRES(ksp);

     43:   PetscMalloc1(max_k+2,&fgmres->prevecs);
     44:   PetscMalloc1(max_k+2,&fgmres->prevecs_user_work);
     45:   PetscLogObjectMemory((PetscObject)ksp,(max_k+2)*(2*sizeof(void*)));

     47:   /* fgmres->vv_allocated includes extra work vectors, which are not used in the additional
     48:      block of vectors used to store the preconditioned directions, hence  the -VEC_OFFSET
     49:      term for this first allocation of vectors holding preconditioned directions */
     50:   KSPCreateVecs(ksp,fgmres->vv_allocated-VEC_OFFSET,&fgmres->prevecs_user_work[0],0,NULL);
     51:   PetscLogObjectParents(ksp,fgmres->vv_allocated-VEC_OFFSET,fgmres->prevecs_user_work[0]);
     52:   for (k=0; k < fgmres->vv_allocated - VEC_OFFSET ; k++) {
     53:     fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
     54:   }
     55:   return(0);
     56: }

     58: /*
     59:     KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
     60: */
     61: static PetscErrorCode KSPFGMRESResidual(KSP ksp)
     62: {
     63:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)(ksp->data);
     64:   Mat            Amat,Pmat;

     68:   PCGetOperators(ksp->pc,&Amat,&Pmat);

     70:   /* put A*x into VEC_TEMP */
     71:   KSP_MatMult(ksp,Amat,ksp->vec_sol,VEC_TEMP);
     72:   /* now put residual (-A*x + f) into vec_vv(0) */
     73:   VecWAXPY(VEC_VV(0),-1.0,VEC_TEMP,ksp->vec_rhs);
     74:   return(0);
     75: }

     77: /*

     79:     KSPFGMRESCycle - Run fgmres, possibly with restart.  Return residual
     80:                   history if requested.

     82:     input parameters:
     83: .        fgmres  - structure containing parameters and work areas

     85:     output parameters:
     86: .        itcount - number of iterations used.  If null, ignored.
     87: .        converged - 0 if not converged

     89:     Notes:
     90:     On entry, the value in vector VEC_VV(0) should be
     91:     the initial residual.

     93:  */
     94: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount,KSP ksp)
     95: {

     97:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)(ksp->data);
     98:   PetscReal      res_norm;
     99:   PetscReal      hapbnd,tt;
    100:   PetscBool      hapend = PETSC_FALSE;  /* indicates happy breakdown ending */
    102:   PetscInt       loc_it;                /* local count of # of dir. in Krylov space */
    103:   PetscInt       max_k = fgmres->max_k; /* max # of directions Krylov space */
    104:   Mat            Amat,Pmat;

    107:   /* Number of pseudo iterations since last restart is the number
    108:      of prestart directions */
    109:   loc_it = 0;

    111:   /* note: (fgmres->it) is always set one less than (loc_it) It is used in
    112:      KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
    113:      Note that when KSPFGMRESBuildSoln is called from this function,
    114:      (loc_it -1) is passed, so the two are equivalent */
    115:   fgmres->it = (loc_it - 1);

    117:   /* initial residual is in VEC_VV(0)  - compute its norm*/
    118:   VecNorm(VEC_VV(0),NORM_2,&res_norm);
    119:   KSPCheckNorm(ksp,res_norm);

    121:   /* first entry in right-hand-side of hessenberg system is just
    122:      the initial residual norm */
    123:   *RS(0) = res_norm;

    125:   ksp->rnorm = res_norm;
    126:   KSPLogResidualHistory(ksp,res_norm);
    127:   KSPMonitor(ksp,ksp->its,res_norm);

    129:   /* check for the convergence - maybe the current guess is good enough */
    130:   (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
    131:   if (ksp->reason) {
    132:     if (itcount) *itcount = 0;
    133:     return(0);
    134:   }

    136:   /* scale VEC_VV (the initial residual) */
    137:   VecScale(VEC_VV(0),1.0/res_norm);

    139:   /* MAIN ITERATION LOOP BEGINNING*/
    140:   /* keep iterating until we have converged OR generated the max number
    141:      of directions OR reached the max number of iterations for the method */
    142:   while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
    143:     if (loc_it) {
    144:       KSPLogResidualHistory(ksp,res_norm);
    145:       KSPMonitor(ksp,ksp->its,res_norm);
    146:     }
    147:     fgmres->it = (loc_it - 1);

    149:     /* see if more space is needed for work vectors */
    150:     if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
    151:       KSPFGMRESGetNewVectors(ksp,loc_it+1);
    152:       /* (loc_it+1) is passed in as number of the first vector that should
    153:          be allocated */
    154:     }

    156:     /* CHANGE THE PRECONDITIONER? */
    157:     /* ModifyPC is the callback function that can be used to
    158:        change the PC or its attributes before its applied */
    159:     (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);

    161:     /* apply PRECONDITIONER to direction vector and store with
    162:        preconditioned vectors in prevec */
    163:     KSP_PCApply(ksp,VEC_VV(loc_it),PREVEC(loc_it));

    165:     PCGetOperators(ksp->pc,&Amat,&Pmat);
    166:     /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
    167:     KSP_MatMult(ksp,Amat,PREVEC(loc_it),VEC_VV(1+loc_it));

    169:     /* update hessenberg matrix and do Gram-Schmidt - new direction is in
    170:        VEC_VV(1+loc_it)*/
    171:     (*fgmres->orthog)(ksp,loc_it);

    173:     /* new entry in hessenburg is the 2-norm of our new direction */
    174:     VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);
    175:     KSPCheckNorm(ksp,tt);

    177:     *HH(loc_it+1,loc_it)  = tt;
    178:     *HES(loc_it+1,loc_it) = tt;

    180:     /* Happy Breakdown Check */
    181:     hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
    182:     /* RS(loc_it) contains the res_norm from the last iteration  */
    183:     hapbnd = PetscMin(fgmres->haptol,hapbnd);
    184:     if (tt > hapbnd) {
    185:       /* scale new direction by its norm */
    186:       VecScale(VEC_VV(loc_it+1),1.0/tt);
    187:     } else {
    188:       /* This happens when the solution is exactly reached. */
    189:       /* So there is no new direction... */
    190:       VecSet(VEC_TEMP,0.0);     /* set VEC_TEMP to 0 */
    191:       hapend = PETSC_TRUE;
    192:     }
    193:     /* note that for FGMRES we could get HES(loc_it+1, loc_it)  = 0 and the
    194:        current solution would not be exact if HES was singular.  Note that
    195:        HH non-singular implies that HES is no singular, and HES is guaranteed
    196:        to be nonsingular when PREVECS are linearly independent and A is
    197:        nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
    198:        of HES). So we should really add a check to verify that HES is nonsingular.*/

    200:     /* Now apply rotations to new col of hessenberg (and right side of system),
    201:        calculate new rotation, and get new residual norm at the same time*/
    202:     KSPFGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
    203:     if (ksp->reason) break;

    205:     loc_it++;
    206:     fgmres->it = (loc_it-1);   /* Add this here in case it has converged */

    208:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
    209:     ksp->its++;
    210:     ksp->rnorm = res_norm;
    211:     PetscObjectSAWsGrantAccess((PetscObject)ksp);

    213:     (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);

    215:     /* Catch error in happy breakdown and signal convergence and break from loop */
    216:     if (hapend) {
    217:       if (!ksp->reason) {
    218:         if (ksp->errorifnotconverged) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"You reached the happy break down, but convergence was not indicated. Residual norm = %g",(double)res_norm);
    219:         else {
    220:           ksp->reason = KSP_DIVERGED_BREAKDOWN;
    221:           break;
    222:         }
    223:       }
    224:     }
    225:   }
    226:   /* END OF ITERATION LOOP */
    227:   KSPLogResidualHistory(ksp,res_norm);

    229:   /*
    230:      Monitor if we know that we will not return for a restart */
    231:   if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) {
    232:     KSPMonitor(ksp,ksp->its,res_norm);
    233:   }

    235:   if (itcount) *itcount = loc_it;

    237:   /*
    238:     Down here we have to solve for the "best" coefficients of the Krylov
    239:     columns, add the solution values together, and possibly unwind the
    240:     preconditioning from the solution
    241:    */

    243:   /* Form the solution (or the solution so far) */
    244:   /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
    245:      properly navigates */

    247:   KSPFGMRESBuildSoln(RS(0),ksp->vec_sol,ksp->vec_sol,ksp,loc_it-1);
    248:   return(0);
    249: }

    251: /*
    252:     KSPSolve_FGMRES - This routine applies the FGMRES method.

    254:    Input Parameter:
    255: .     ksp - the Krylov space object that was set to use fgmres

    257:    Output Parameter:
    258: .     outits - number of iterations used

    260: */

    262: PetscErrorCode KSPSolve_FGMRES(KSP ksp)
    263: {
    265:   PetscInt       cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
    266:   KSP_FGMRES     *fgmres   = (KSP_FGMRES*)ksp->data;
    267:   PetscBool      diagonalscale;

    270:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
    271:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);

    273:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
    274:   ksp->its = 0;
    275:   PetscObjectSAWsGrantAccess((PetscObject)ksp);

    277:   /* Compute the initial (NOT preconditioned) residual */
    278:   if (!ksp->guess_zero) {
    279:     KSPFGMRESResidual(ksp);
    280:   } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
    281:     VecCopy(ksp->vec_rhs,VEC_VV(0));
    282:   }
    283:   /* now the residual is in VEC_VV(0) - which is what
    284:      KSPFGMRESCycle expects... */

    286:   KSPFGMRESCycle(&cycle_its,ksp);
    287:   while (!ksp->reason) {
    288:     KSPFGMRESResidual(ksp);
    289:     if (ksp->its >= ksp->max_it) break;
    290:     KSPFGMRESCycle(&cycle_its,ksp);
    291:   }
    292:   /* mark lack of convergence */
    293:   if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
    294:   return(0);
    295: }

    297: extern PetscErrorCode KSPReset_FGMRES(KSP);
    298: /*

    300:    KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.

    302: */
    303: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)
    304: {

    308:   KSPReset_FGMRES(ksp);
    309:   PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",NULL);
    310:   KSPDestroy_GMRES(ksp);
    311:   return(0);
    312: }

    314: /*
    315:     KSPFGMRESBuildSoln - create the solution from the starting vector and the
    316:                       current iterates.

    318:     Input parameters:
    319:         nrs - work area of size it + 1.
    320:         vguess  - index of initial guess
    321:         vdest - index of result.  Note that vguess may == vdest (replace
    322:                 guess with the solution).
    323:         it - HH upper triangular part is a block of size (it+1) x (it+1)

    325:      This is an internal routine that knows about the FGMRES internals.
    326:  */
    327: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs,Vec vguess,Vec vdest,KSP ksp,PetscInt it)
    328: {
    329:   PetscScalar    tt;
    331:   PetscInt       ii,k,j;
    332:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)(ksp->data);

    335:   /* Solve for solution vector that minimizes the residual */

    337:   /* If it is < 0, no fgmres steps have been performed */
    338:   if (it < 0) {
    339:     VecCopy(vguess,vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
    340:     return(0);
    341:   }

    343:   /* so fgmres steps HAVE been performed */

    345:   /* solve the upper triangular system - RS is the right side and HH is
    346:      the upper triangular matrix  - put soln in nrs */
    347:   if (*HH(it,it) != 0.0) {
    348:     nrs[it] = *RS(it) / *HH(it,it);
    349:   } else {
    350:     nrs[it] = 0.0;
    351:   }
    352:   for (ii=1; ii<=it; ii++) {
    353:     k  = it - ii;
    354:     tt = *RS(k);
    355:     for (j=k+1; j<=it; j++) tt = tt - *HH(k,j) * nrs[j];
    356:     nrs[k] = tt / *HH(k,k);
    357:   }

    359:   /* Accumulate the correction to the soln of the preconditioned prob. in
    360:      VEC_TEMP - note that we use the preconditioned vectors  */
    361:   VecSet(VEC_TEMP,0.0); /* set VEC_TEMP components to 0 */
    362:   VecMAXPY(VEC_TEMP,it+1,nrs,&PREVEC(0));

    364:   /* put updated solution into vdest.*/
    365:   if (vdest != vguess) {
    366:     VecCopy(VEC_TEMP,vdest);
    367:     VecAXPY(vdest,1.0,vguess);
    368:   } else { /* replace guess with solution */
    369:     VecAXPY(vdest,1.0,VEC_TEMP);
    370:   }
    371:   return(0);
    372: }

    374: /*

    376:     KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
    377:                             Return new residual.

    379:     input parameters:

    381: .        ksp -    Krylov space object
    382: .        it  -    plane rotations are applied to the (it+1)th column of the
    383:                   modified hessenberg (i.e. HH(:,it))
    384: .        hapend - PETSC_FALSE not happy breakdown ending.

    386:     output parameters:
    387: .        res - the new residual

    389:  */
    390: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp,PetscInt it,PetscBool hapend,PetscReal *res)
    391: {
    392:   PetscScalar *hh,*cc,*ss,tt;
    393:   PetscInt    j;
    394:   KSP_FGMRES  *fgmres = (KSP_FGMRES*)(ksp->data);

    397:   hh = HH(0,it);   /* pointer to beginning of column to update - so
    398:                       incrementing hh "steps down" the (it+1)th col of HH*/
    399:   cc = CC(0);      /* beginning of cosine rotations */
    400:   ss = SS(0);      /* beginning of sine rotations */

    402:   /* Apply all the previously computed plane rotations to the new column
    403:      of the Hessenberg matrix */
    404:   /* Note: this uses the rotation [conj(c)  s ; -s   c], c= cos(theta), s= sin(theta),
    405:      and some refs have [c   s ; -conj(s)  c] (don't be confused!) */

    407:   for (j=1; j<=it; j++) {
    408:     tt  = *hh;
    409:     *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
    410:     hh++;
    411:     *hh = *cc++ * *hh - (*ss++ * tt);
    412:     /* hh, cc, and ss have all been incremented one by end of loop */
    413:   }

    415:   /*
    416:     compute the new plane rotation, and apply it to:
    417:      1) the right-hand-side of the Hessenberg system (RS)
    418:         note: it affects RS(it) and RS(it+1)
    419:      2) the new column of the Hessenberg matrix
    420:         note: it affects HH(it,it) which is currently pointed to
    421:         by hh and HH(it+1, it) (*(hh+1))
    422:     thus obtaining the updated value of the residual...
    423:   */

    425:   /* compute new plane rotation */

    427:   if (!hapend) {
    428:     tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
    429:     if (tt == 0.0) {
    430:       ksp->reason = KSP_DIVERGED_NULL;
    431:       return(0);
    432:     }

    434:     *cc = *hh / tt;         /* new cosine value */
    435:     *ss = *(hh+1) / tt;        /* new sine value */

    437:     /* apply to 1) and 2) */
    438:     *RS(it+1) = -(*ss * *RS(it));
    439:     *RS(it)   = PetscConj(*cc) * *RS(it);
    440:     *hh       = PetscConj(*cc) * *hh + *ss * *(hh+1);

    442:     /* residual is the last element (it+1) of right-hand side! */
    443:     *res = PetscAbsScalar(*RS(it+1));

    445:   } else { /* happy breakdown: HH(it+1, it) = 0, therefore we don't need to apply
    446:             another rotation matrix (so RH doesn't change).  The new residual is
    447:             always the new sine term times the residual from last time (RS(it)),
    448:             but now the new sine rotation would be zero...so the residual should
    449:             be zero...so we will multiply "zero" by the last residual.  This might
    450:             not be exactly what we want to do here -could just return "zero". */

    452:     *res = 0.0;
    453:   }
    454:   return(0);
    455: }

    457: /*

    459:    KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
    460:                          VEC_VV(it), and more preconditioned work vectors, starting
    461:                          from PREVEC(i).

    463: */
    464: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp,PetscInt it)
    465: {
    466:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;
    467:   PetscInt       nwork   = fgmres->nwork_alloc; /* number of work vector chunks allocated */
    468:   PetscInt       nalloc;                      /* number to allocate */
    470:   PetscInt       k;

    473:   nalloc = fgmres->delta_allocate; /* number of vectors to allocate
    474:                                       in a single chunk */

    476:   /* Adjust the number to allocate to make sure that we don't exceed the
    477:      number of available slots (fgmres->vecs_allocated)*/
    478:   if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) {
    479:     nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
    480:   }
    481:   if (!nalloc) return(0);

    483:   fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */

    485:   /* work vectors */
    486:   KSPCreateVecs(ksp,nalloc,&fgmres->user_work[nwork],0,NULL);
    487:   PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
    488:   for (k=0; k < nalloc; k++) {
    489:     fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
    490:   }
    491:   /* specify size of chunk allocated */
    492:   fgmres->mwork_alloc[nwork] = nalloc;

    494:   /* preconditioned vectors */
    495:   KSPCreateVecs(ksp,nalloc,&fgmres->prevecs_user_work[nwork],0,NULL);
    496:   PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
    497:   for (k=0; k < nalloc; k++) {
    498:     fgmres->prevecs[it+k] = fgmres->prevecs_user_work[nwork][k];
    499:   }

    501:   /* increment the number of work vector chunks */
    502:   fgmres->nwork_alloc++;
    503:   return(0);
    504: }

    506: /*

    508:    KSPBuildSolution_FGMRES

    510:      Input Parameter:
    511: .     ksp - the Krylov space object
    512: .     ptr-

    514:    Output Parameter:
    515: .     result - the solution

    517:    Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
    518:    calls directly.

    520: */
    521: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)
    522: {
    523:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;

    527:   if (!ptr) {
    528:     if (!fgmres->sol_temp) {
    529:       VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
    530:       PetscLogObjectParent((PetscObject)ksp,(PetscObject)fgmres->sol_temp);
    531:     }
    532:     ptr = fgmres->sol_temp;
    533:   }
    534:   if (!fgmres->nrs) {
    535:     /* allocate the work area */
    536:     PetscMalloc1(fgmres->max_k,&fgmres->nrs);
    537:     PetscLogObjectMemory((PetscObject)ksp,fgmres->max_k*sizeof(PetscScalar));
    538:   }

    540:   KSPFGMRESBuildSoln(fgmres->nrs,ksp->vec_sol,ptr,ksp,fgmres->it);
    541:   if (result) *result = ptr;
    542:   return(0);
    543: }

    545: PetscErrorCode KSPSetFromOptions_FGMRES(PetscOptionItems *PetscOptionsObject,KSP ksp)
    546: {
    548:   PetscBool      flg;

    551:   KSPSetFromOptions_GMRES(PetscOptionsObject,ksp);
    552:   PetscOptionsHead(PetscOptionsObject,"KSP flexible GMRES Options");
    553:   PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
    554:   if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,NULL,NULL);}
    555:   PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp","vary the KSP based preconditioner","KSPFGMRESSetModifyPC",&flg);
    556:   if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCKSP,NULL,NULL);}
    557:   PetscOptionsTail();
    558:   return(0);
    559: }

    561: typedef PetscErrorCode (*FCN1)(KSP,PetscInt,PetscInt,PetscReal,void*); /* force argument to next function to not be extern C*/
    562: typedef PetscErrorCode (*FCN2)(void*);

    564: static PetscErrorCode  KSPFGMRESSetModifyPC_FGMRES(KSP ksp,FCN1 fcn,void *ctx,FCN2 d)
    565: {
    568:   ((KSP_FGMRES*)ksp->data)->modifypc      = fcn;
    569:   ((KSP_FGMRES*)ksp->data)->modifydestroy = d;
    570:   ((KSP_FGMRES*)ksp->data)->modifyctx     = ctx;
    571:   return(0);
    572: }

    574: PetscErrorCode KSPReset_FGMRES(KSP ksp)
    575: {
    576:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;
    578:   PetscInt       i;

    581:   PetscFree (fgmres->prevecs);
    582:   if (fgmres->nwork_alloc>0) {
    583:     i=0;
    584:     /* In the first allocation we allocated VEC_OFFSET fewer vectors in prevecs */
    585:     VecDestroyVecs(fgmres->mwork_alloc[i]-VEC_OFFSET,&fgmres->prevecs_user_work[i]);
    586:     for (i=1; i<fgmres->nwork_alloc; i++) {
    587:       VecDestroyVecs(fgmres->mwork_alloc[i],&fgmres->prevecs_user_work[i]);
    588:     }
    589:   }
    590:   PetscFree(fgmres->prevecs_user_work);
    591:   if (fgmres->modifydestroy) {
    592:     (*fgmres->modifydestroy)(fgmres->modifyctx);
    593:   }
    594:   KSPReset_GMRES(ksp);
    595:   return(0);
    596: }

    598: PetscErrorCode  KSPGMRESSetRestart_FGMRES(KSP ksp,PetscInt max_k)
    599: {
    600:   KSP_FGMRES     *gmres = (KSP_FGMRES*)ksp->data;

    604:   if (max_k < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
    605:   if (!ksp->setupstage) {
    606:     gmres->max_k = max_k;
    607:   } else if (gmres->max_k != max_k) {
    608:     gmres->max_k    = max_k;
    609:     ksp->setupstage = KSP_SETUP_NEW;
    610:     /* free the data structures, then create them again */
    611:     KSPReset_FGMRES(ksp);
    612:   }
    613:   return(0);
    614: }

    616: PetscErrorCode  KSPGMRESGetRestart_FGMRES(KSP ksp,PetscInt *max_k)
    617: {
    618:   KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;

    621:   *max_k = gmres->max_k;
    622:   return(0);
    623: }

    625: /*MC
    626:      KSPFGMRES - Implements the Flexible Generalized Minimal Residual method.
    627:                 developed by Saad with restart

    629:    Options Database Keys:
    630: +   -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
    631: .   -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
    632: .   -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
    633:                              vectors are allocated as needed)
    634: .   -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
    635: .   -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
    636: .   -ksp_gmres_cgs_refinement_type <refine_never,refine_ifneeded,refine_always> - determine if iterative refinement is used to increase the
    637:                                    stability of the classical Gram-Schmidt  orthogonalization.
    638: .   -ksp_gmres_krylov_monitor - plot the Krylov space generated
    639: .   -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
    640: -   -ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()

    642:    Level: beginner

    644:     Notes:
    645:     See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations
    646:            Only right preconditioning is supported.

    648:     Notes:
    649:     The following options -ksp_type fgmres -pc_type ksp -ksp_ksp_type bcgs -ksp_view -ksp_pc_type jacobi make the preconditioner (or inner solver)
    650:            be bi-CG-stab with a preconditioner of Jacobi.

    652:     Developer Notes:
    653:     This object is subclassed off of KSPGMRES

    655: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
    656:            KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(),
    657:            KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(),
    658:            KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(),  KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(),
    659:            KSPFGMRESModifyPCKSP()

    661: M*/

    663: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)
    664: {
    665:   KSP_FGMRES     *fgmres;

    669:   PetscNewLog(ksp,&fgmres);

    671:   ksp->data                              = (void*)fgmres;
    672:   ksp->ops->buildsolution                = KSPBuildSolution_FGMRES;
    673:   ksp->ops->setup                        = KSPSetUp_FGMRES;
    674:   ksp->ops->solve                        = KSPSolve_FGMRES;
    675:   ksp->ops->reset                        = KSPReset_FGMRES;
    676:   ksp->ops->destroy                      = KSPDestroy_FGMRES;
    677:   ksp->ops->view                         = KSPView_GMRES;
    678:   ksp->ops->setfromoptions               = KSPSetFromOptions_FGMRES;
    679:   ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
    680:   ksp->ops->computeeigenvalues           = KSPComputeEigenvalues_GMRES;

    682:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,3);
    683:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);

    685:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",KSPGMRESSetPreAllocateVectors_GMRES);
    686:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",KSPGMRESSetOrthogonalization_GMRES);
    687:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetOrthogonalization_C",KSPGMRESGetOrthogonalization_GMRES);
    688:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetRestart_C",KSPGMRESSetRestart_FGMRES);
    689:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetRestart_C",KSPGMRESGetRestart_FGMRES);
    690:   PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",KSPFGMRESSetModifyPC_FGMRES);
    691:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetCGSRefinementType_C",KSPGMRESSetCGSRefinementType_GMRES);
    692:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetCGSRefinementType_C",KSPGMRESGetCGSRefinementType_GMRES);

    694:   fgmres->haptol         = 1.0e-30;
    695:   fgmres->q_preallocate  = 0;
    696:   fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
    697:   fgmres->orthog         = KSPGMRESClassicalGramSchmidtOrthogonalization;
    698:   fgmres->nrs            = NULL;
    699:   fgmres->sol_temp       = NULL;
    700:   fgmres->max_k          = FGMRES_DEFAULT_MAXK;
    701:   fgmres->Rsvd           = NULL;
    702:   fgmres->orthogwork     = NULL;
    703:   fgmres->modifypc       = KSPFGMRESModifyPCNoChange;
    704:   fgmres->modifyctx      = NULL;
    705:   fgmres->modifydestroy  = NULL;
    706:   fgmres->cgstype        = KSP_GMRES_CGS_REFINE_NEVER;
    707:   return(0);
    708: }