Actual source code: fgmres.c

  1: /* $Id: fgmres.c,v 1.29 2001/08/07 21:30:49 bsmith Exp $ */

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

  7:     Preconditioning:  It the preconditioner is constant then this fgmres
  8:     code is equivalent to RIGHT-PRECONDITIONED GMRES.

 10:     Restarts:  Restarts are basically solves with x0 not equal to zero.
 11:  
 12:        Contributed by Allison Baker

 14: */

 16:  #include src/sles/ksp/impls/fgmres/fgmresp.h
 17: #define FGMRES_DELTA_DIRECTIONS 10
 18: #define FGMRES_DEFAULT_MAXK     30
 19: static int    FGMRESGetNewVectors(KSP,int);
 20: static int    FGMRESUpdateHessenberg(KSP,int,PetscTruth,PetscReal *);
 21: static int    BuildFgmresSoln(PetscScalar*,Vec,Vec,KSP,int);

 23: /*

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

 27:     This is called once, usually automatically by SLESSolve() or SLESSetUp(),
 28:     but can be called directly by KSPSetUp().

 30: */
 31: int    KSPSetUp_FGMRES(KSP ksp)
 32: {
 33:   unsigned  int size,hh,hes,rs,cc;
 34:   int           ierr,max_k,k;
 35:   KSP_FGMRES    *fgmres = (KSP_FGMRES *)ksp->data;

 38:   if (ksp->pc_side == PC_SYMMETRIC) {
 39:     SETERRQ(2,"no symmetric preconditioning for KSPFGMRES");
 40:   }
 41:   max_k         = fgmres->max_k;
 42:   hh            = (max_k + 2) * (max_k + 1);
 43:   hes           = (max_k + 1) * (max_k + 1);
 44:   rs            = (max_k + 2);
 45:   cc            = (max_k + 1);  /* SS and CC are the same size */
 46:   size          = (hh + hes + rs + 2*cc) * sizeof(PetscScalar);

 48:   /* Allocate space and set pointers to beginning */
 49:   PetscMalloc(size,&fgmres->hh_origin);
 50:   PetscLogObjectMemory(ksp,size);                      /* HH - modified (by plane 
 51:                                                       rotations) hessenburg */
 52:   fgmres->hes_origin = fgmres->hh_origin + hh;     /* HES - unmodified hessenburg */
 53:   fgmres->rs_origin  = fgmres->hes_origin + hes;   /* RS - the right-hand-side of the 
 54:                                                       Hessenberg system */
 55:   fgmres->cc_origin  = fgmres->rs_origin + rs;     /* CC - cosines for rotations */
 56:   fgmres->ss_origin  = fgmres->cc_origin + cc;     /* SS - sines for rotations */

 58:   if (ksp->calc_sings) {
 59:     /* Allocate workspace to hold Hessenberg matrix needed by Eispack */
 60:     size = (max_k + 3)*(max_k + 9)*sizeof(PetscScalar);
 61:     PetscMalloc(size,&fgmres->Rsvd);
 62:     PetscMalloc(5*(max_k+2)*sizeof(PetscReal),&fgmres->Dsvd);
 63:     PetscLogObjectMemory(ksp,size+5*(max_k+2)*sizeof(PetscReal));
 64:   }

 66:   /* Allocate array to hold pointers to user vectors.  Note that we need
 67:    4 + max_k + 1 (since we need it+1 vectors, and it <= max_k) */
 68:   PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(void *),&fgmres->vecs);
 69:   fgmres->vecs_allocated = VEC_OFFSET + 2 + max_k;
 70:   PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(void *),&fgmres->user_work);
 71:   PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(int),&fgmres->mwork_alloc);
 72:   PetscLogObjectMemory(ksp,(VEC_OFFSET+2+max_k)*(2*sizeof(void *)+sizeof(int)));

 74:   /* New for FGMRES - Allocate array to hold pointers to preconditioned 
 75:      vectors - same sizes as user vectors above */
 76:   PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(void *),&fgmres->prevecs);
 77:   PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(void *),&fgmres->prevecs_user_work);
 78:   PetscLogObjectMemory(ksp,(VEC_OFFSET+2+max_k)*(2*sizeof(void *)));


 81:   /* if q_preallocate = 0 then only allocate one "chunck" of space (for 
 82:      5 vectors) - additional will then be allocated from FGMREScycle() 
 83:      as needed.  Otherwise, allocate all of the space that could be needed */
 84:   if (fgmres->q_preallocate) {
 85:     fgmres->vv_allocated   = VEC_OFFSET + 2 + max_k;
 86:   } else {
 87:     fgmres->vv_allocated    = 5;
 88:   }

 90:   /* space for work vectors */
 91:   VecDuplicateVecs(VEC_RHS,fgmres->vv_allocated,&fgmres->user_work[0]);
 92:   PetscLogObjectParents(ksp,fgmres->vv_allocated,fgmres->user_work[0]);
 93:   for (k=0; k < fgmres->vv_allocated; k++) {
 94:     fgmres->vecs[k] = fgmres->user_work[0][k];
 95:   }

 97:   /* space for preconditioned vectors */
 98:   VecDuplicateVecs(VEC_RHS,fgmres->vv_allocated,&fgmres->prevecs_user_work[0]);
 99:   PetscLogObjectParents(ksp,fgmres->vv_allocated,fgmres->prevecs_user_work[0]);
100:   for (k=0; k < fgmres->vv_allocated; k++) {
101:     fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
102:   }

104:   /* specify how many work vectors have been allocated in this 
105:      chunck" (the first one) */
106:   fgmres->mwork_alloc[0] = fgmres->vv_allocated;
107:   fgmres->nwork_alloc    = 1;

109:   return(0);
110: }

112: /* 
113:     FGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED) 
114: */
115: static int FGMRESResidual(KSP ksp)
116: {
117:   KSP_FGMRES   *fgmres = (KSP_FGMRES *)(ksp->data);
118:   PetscScalar  mone = -1.0;
119:   Mat          Amat,Pmat;
120:   MatStructure pflag;
121:   int          ierr;

124:   PCGetOperators(ksp->B,&Amat,&Pmat,&pflag);

126:   /* put A*x into VEC_TEMP */
127:   MatMult(Amat,VEC_SOLN,VEC_TEMP);
128:   /* now put residual (-A*x + f) into vec_vv(0) */
129:   VecWAXPY(&mone,VEC_TEMP,VEC_RHS,VEC_VV(0));
130:   return(0);
131: }

133: /*

135:     FGMRESCycle - Run fgmres, possibly with restart.  Return residual 
136:                   history if requested.

138:     input parameters:
139: .         fgmres  - structure containing parameters and work areas

141:     output parameters:
142: .        itcount - number of iterations used.  If null, ignored.
143: .        converged - 0 if not converged

145:                   
146:     Notes:
147:     On entry, the value in vector VEC_VV(0) should be 
148:     the initial residual.


151:  */
152: int FGMREScycle(int *itcount,KSP ksp)
153: {

155:   KSP_FGMRES   *fgmres = (KSP_FGMRES *)(ksp->data);
156:   PetscReal    res_norm;
157:   PetscReal    hapbnd,tt;
158:   PetscScalar  zero = 0.0;
159:   PetscScalar  tmp;
160:   PetscTruth   hapend = PETSC_FALSE;  /* indicates happy breakdown ending */
161:   int          ierr;
162:   int          loc_it;                /* local count of # of dir. in Krylov space */
163:   int          max_k = fgmres->max_k; /* max # of directions Krylov space */
164:   int          max_it = ksp->max_it;  /* max # of overall iterations for the method */
165:   Mat          Amat,Pmat;
166:   MatStructure pflag;


170:   /* Number of pseudo iterations since last restart is the number 
171:      of prestart directions */
172:   loc_it = 0;

174:   /* initial residual is in VEC_VV(0)  - compute its norm*/
175:   ierr   = VecNorm(VEC_VV(0),NORM_2,&res_norm);

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

181:   /* check for the convergence - maybe the current guess is good enough */
182:   (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
183:   if (ksp->reason) {
184:     if (itcount) *itcount = 0;
185:     return(0);
186:   }

188:   /* scale VEC_VV (the initial residual) */
189:   tmp = 1.0/res_norm; VecScale(&tmp,VEC_VV(0));

191:   /* FYI: AMS calls are for memory snooper */
192:   PetscObjectTakeAccess(ksp);
193:   ksp->rnorm = res_norm;
194:   PetscObjectGrantAccess(ksp);


197:   /* note: (fgmres->it) is always set one less than (loc_it) It is used in 
198:      KSPBUILDSolution_FGMRES, where it is passed to BuildFGmresSoln.  
199:      Note that when BuildFGmresSoln is called from this function, 
200:      (loc_it -1) is passed, so the two are equivalent */
201:   fgmres->it = (loc_it - 1);
202: 
203:   /* MAIN ITERATION LOOP BEGINNING*/
204:   /* keep iterating until we have converged OR generated the max number
205:      of directions OR reached the max number of iterations for the method */
206:   (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
207:   while (!ksp->reason && loc_it < max_k && ksp->its < max_it) {
208:     KSPLogResidualHistory(ksp,res_norm);
209:     fgmres->it = (loc_it - 1);
210:     KSPMonitor(ksp,ksp->its,res_norm);

212:     /* see if more space is needed for work vectors */
213:     if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
214:       FGMRESGetNewVectors(ksp,loc_it+1);
215:       /* (loc_it+1) is passed in as number of the first vector that should
216:          be allocated */
217:     }

219:     /* CHANGE THE PRECONDITIONER? */
220:     /* ModifyPC is the callback function that can be used to
221:        change the PC or its attributes before its applied */
222:     (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);
223: 
224: 
225:     /* apply PRECONDITIONER to direction vector and store with 
226:        preconditioned vectors in prevec */
227:     PCApply(ksp->B,VEC_VV(loc_it),PREVEC(loc_it));
228: 
229:     PCGetOperators(ksp->B,&Amat,&Pmat,&pflag);
230:     /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
231:     MatMult(Amat,PREVEC(loc_it),VEC_VV(1+loc_it));

233: 
234:     /* update hessenberg matrix and do Gram-Schmidt - new direction is in
235:        VEC_VV(1+loc_it)*/
236:     (*fgmres->orthog)(ksp,loc_it);

238:     /* new entry in hessenburg is the 2-norm of our new direction */
239:     VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);
240:     *HH(loc_it+1,loc_it)   = tt;
241:     *HES(loc_it+1,loc_it)  = tt;

243:     /* Happy Breakdown Check */
244:     hapbnd  = PetscAbsScalar((tt) / *RS(loc_it));
245:     /* RS(loc_it) contains the res_norm from the last iteration  */
246:     hapbnd = PetscMin(fgmres->haptol,hapbnd);
247:     if (tt > hapbnd) {
248:         tmp = 1.0/tt;
249:         /* scale new direction by its norm */
250:         VecScale(&tmp,VEC_VV(loc_it+1));
251:     } else {
252:         /* This happens when the solution is exactly reached. */
253:         /* So there is no new direction... */
254:           ierr   = VecSet(&zero,VEC_TEMP); /* set VEC_TEMP to 0 */
255:           hapend = PETSC_TRUE;
256:     }
257:     /* note that for FGMRES we could get HES(loc_it+1, loc_it)  = 0 and the
258:        current solution would not be exact if HES was singular.  Note that 
259:        HH non-singular implies that HES is no singular, and HES is guaranteed
260:        to be nonsingular when PREVECS are linearly independent and A is 
261:        nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity 
262:        of HES). So we should really add a check to verify that HES is nonsingular.*/

264: 
265:     /* Now apply rotations to new col of hessenberg (and right side of system), 
266:        calculate new rotation, and get new residual norm at the same time*/
267:     FGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
268:     loc_it++;
269:     fgmres->it  = (loc_it-1);  /* Add this here in case it has converged */
270: 
271:     PetscObjectTakeAccess(ksp);
272:     ksp->its++;
273:     ksp->rnorm = res_norm;
274:     PetscObjectGrantAccess(ksp);

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

278:     /* Catch error in happy breakdown and signal convergence and break from loop */
279:     if (hapend) {
280:       if (!ksp->reason) {
281:         SETERRQ(0,"You reached the happy break down,but convergence was not indicated.");
282:       }
283:       break;
284:     }
285:   }
286:   /* END OF ITERATION LOOP */

288:   KSPLogResidualHistory(ksp,res_norm);

290:   /*
291:      Monitor if we know that we will not return for a restart */
292:   if (ksp->reason || ksp->its >= max_it) {
293:     KSPMonitor(ksp,ksp->its,res_norm);
294:   }

296:   if (itcount) *itcount    = loc_it;

298:   /*
299:     Down here we have to solve for the "best" coefficients of the Krylov
300:     columns, add the solution values together, and possibly unwind the
301:     preconditioning from the solution
302:    */
303: 
304:   /* Form the solution (or the solution so far) */
305:   /* Note: must pass in (loc_it-1) for iteration count so that BuildFgmresSoln
306:      properly navigates */

308:   BuildFgmresSoln(RS(0),VEC_SOLN,VEC_SOLN,ksp,loc_it-1);

310:   return(0);
311: }

313: /*  
314:     KSPSolve_FGMRES - This routine applies the FGMRES method.


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

320:    Output Parameter:
321: .     outits - number of iterations used

323: */

325: int KSPSolve_FGMRES(KSP ksp,int *outits)
326: {
327:   int        ierr;
328:   int        cycle_its; /* iterations done in a call to FGMREScycle */
329:   int        itcount;   /* running total of iterations, incl. those in restarts */
330:   KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
331:   PetscTruth diagonalscale;

334:   ierr    = PCDiagonalScale(ksp->B,&diagonalscale);
335:   if (diagonalscale) SETERRQ1(1,"Krylov method %s does not support diagonal scaling",ksp->type_name);

337:   PetscObjectTakeAccess(ksp);
338:   ksp->its = 0;
339:   PetscObjectGrantAccess(ksp);

341:   /* initialize */
342:   itcount  = 0;

344:   /* Compute the initial (NOT preconditioned) residual */
345:   if (!ksp->guess_zero) {
346:     FGMRESResidual(ksp);
347:   } else { /* guess is 0 so residual is F (which is in VEC_RHS) */
348:     VecCopy(VEC_RHS,VEC_VV(0));
349:   }
350:   /* now the residual is in VEC_VV(0) - which is what 
351:      FGMREScycle expects... */
352: 
353:   ierr    = FGMREScycle(&cycle_its,ksp);
354:   itcount += cycle_its;
355:   while (!ksp->reason) {
356:     ierr     = FGMRESResidual(ksp);
357:     if (itcount >= ksp->max_it) break;
358:     ierr     = FGMREScycle(&cycle_its,ksp);
359:     itcount += cycle_its;
360:   }
361:   /* mark lack of convergence */
362:   if (itcount >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;

364:   *outits = itcount;
365:   return(0);
366: }

368: /*

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

372: */
373: int KSPDestroy_FGMRES(KSP ksp)
374: {
375:   KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
376:   int       i,ierr;

379:   /* Free the Hessenberg matrices */
380:   if (fgmres->hh_origin) {PetscFree(fgmres->hh_origin);}

382:   /* Free pointers to user variables */
383:   if (fgmres->vecs) {PetscFree(fgmres->vecs);}
384:   if (fgmres->prevecs) {PetscFree (fgmres->prevecs);}

386:   /* free work vectors */
387:   for (i=0; i < fgmres->nwork_alloc; i++) {
388:     VecDestroyVecs(fgmres->user_work[i],fgmres->mwork_alloc[i]);
389:   }
390:   if (fgmres->user_work)  {PetscFree(fgmres->user_work);}

392:   for (i=0; i < fgmres->nwork_alloc; i++) {
393:     VecDestroyVecs(fgmres->prevecs_user_work[i],fgmres->mwork_alloc[i]);
394:   }
395:   if (fgmres->prevecs_user_work) {PetscFree(fgmres->prevecs_user_work);}

397:   if (fgmres->mwork_alloc) {PetscFree(fgmres->mwork_alloc);}
398:   if (fgmres->nrs) {PetscFree(fgmres->nrs);}
399:   if (fgmres->sol_temp) {VecDestroy(fgmres->sol_temp);}
400:   if (fgmres->Rsvd) {PetscFree(fgmres->Rsvd);}
401:   if (fgmres->Dsvd) {PetscFree(fgmres->Dsvd);}
402:   if (fgmres->modifydestroy) {
403:     (*fgmres->modifydestroy)(fgmres->modifyctx);
404:   }
405:   PetscFree(fgmres);
406:   return(0);
407: }

409: /*
410:     BuildFgmresSoln - create the solution from the starting vector and the
411:                       current iterates.

413:     Input parameters:
414:         nrs - work area of size it + 1.
415:         vguess  - index of initial guess
416:         vdest - index of result.  Note that vguess may == vdest (replace
417:                 guess with the solution).
418:         it - HH upper triangular part is a block of size (it+1) x (it+1)  

420:      This is an internal routine that knows about the FGMRES internals.
421:  */
422: static int BuildFgmresSoln(PetscScalar* nrs,Vec vguess,Vec vdest,KSP ksp,int it)
423: {
424:   PetscScalar  tt,zero = 0.0,one = 1.0;
425:   int          ierr,ii,k,j;
426:   KSP_FGMRES   *fgmres = (KSP_FGMRES *)(ksp->data);

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

431:   /* If it is < 0, no fgmres steps have been performed */
432:   if (it < 0) {
433:     if (vdest != vguess) {
434:       VecCopy(vguess,vdest);
435:     }
436:     return(0);
437:   }

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

441:   /* solve the upper triangular system - RS is the right side and HH is 
442:      the upper triangular matrix  - put soln in nrs */
443:   nrs[it] = *RS(it) / *HH(it,it);
444:   for (ii=1; ii<=it; ii++) {
445:     k   = it - ii;
446:     tt  = *RS(k);
447:     for (j=k+1; j<=it; j++) tt  = tt - *HH(k,j) * nrs[j];
448:     nrs[k]   = tt / *HH(k,k);
449:   }

451:   /* Accumulate the correction to the soln of the preconditioned prob. in 
452:      VEC_TEMP - note that we use the preconditioned vectors  */
453:   VecSet(&zero,VEC_TEMP); /* set VEC_TEMP components to 0 */
454:   VecMAXPY(it+1,nrs,VEC_TEMP,&PREVEC(0));

456:   /* put updated solution into vdest.*/
457:   if (vdest != vguess) {
458:     VecCopy(VEC_TEMP,vdest);
459:     VecAXPY(&one,vguess,vdest);
460:   } else  {/* replace guess with solution */
461:     VecAXPY(&one,VEC_TEMP,vdest);
462:   }
463:   return(0);
464: }

466: /*

468:     FGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.  
469:                             Return new residual.

471:     input parameters:

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

478:     output parameters:
479: .        res - the new residual
480:         
481:  */
482: static int FGMRESUpdateHessenberg(KSP ksp,int it,PetscTruth hapend,PetscReal *res)
483: {
484:   PetscScalar   *hh,*cc,*ss,tt;
485:   int           j;
486:   KSP_FGMRES    *fgmres = (KSP_FGMRES *)(ksp->data);

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

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

499:   for (j=1; j<=it; j++) {
500:     tt  = *hh;
501: #if defined(PETSC_USE_COMPLEX)
502:     *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
503: #else
504:     *hh = *cc * tt + *ss * *(hh+1);
505: #endif
506:     hh++;
507:     *hh = *cc++ * *hh - (*ss++ * tt);
508:     /* hh, cc, and ss have all been incremented one by end of loop */
509:   }

511:   /*
512:     compute the new plane rotation, and apply it to:
513:      1) the right-hand-side of the Hessenberg system (RS)
514:         note: it affects RS(it) and RS(it+1)
515:      2) the new column of the Hessenberg matrix
516:         note: it affects HH(it,it) which is currently pointed to 
517:         by hh and HH(it+1, it) (*(hh+1))  
518:     thus obtaining the updated value of the residual...
519:   */

521:   /* compute new plane rotation */

523:   if (!hapend) {
524: #if defined(PETSC_USE_COMPLEX)
525:     tt        = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
526: #else
527:     tt        = PetscSqrtScalar(*hh * *hh + *(hh+1) * *(hh+1));
528: #endif
529:     if (tt == 0.0) {SETERRQ(PETSC_ERR_KSP_BRKDWN,"Your matrix or preconditioner is the null operator");}
530:     *cc       = *hh / tt;   /* new cosine value */
531:     *ss       = *(hh+1) / tt;  /* new sine value */

533:     /* apply to 1) and 2) */
534:     *RS(it+1) = - (*ss * *RS(it));
535: #if defined(PETSC_USE_COMPLEX)
536:     *RS(it)   = PetscConj(*cc) * *RS(it);
537:     *hh       = PetscConj(*cc) * *hh + *ss * *(hh+1);
538: #else
539:     *RS(it)   = *cc * *RS(it);
540:     *hh       = *cc * *hh + *ss * *(hh+1);
541: #endif

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

546:   } else { /* happy breakdown: HH(it+1, it) = 0, therfore we don't need to apply 
547:             another rotation matrix (so RH doesn't change).  The new residual is 
548:             always the new sine term times the residual from last time (RS(it)), 
549:             but now the new sine rotation would be zero...so the residual should
550:             be zero...so we will multiply "zero" by the last residual.  This might
551:             not be exactly what we want to do here -could just return "zero". */
552: 
553:     *res = 0.0;
554:   }
555:   return(0);
556: }

558: /*

560:    FGMRESGetNewVectors - This routine allocates more work vectors, starting from 
561:                          VEC_VV(it), and more preconditioned work vectors, starting 
562:                          from PREVEC(i).

564: */
565: static int FGMRESGetNewVectors(KSP ksp,int it)
566: {
567:   KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
568:   int        nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
569:   int        nalloc;                      /* number to allocate */
570:   int        k,ierr;
571: 
573:   nalloc = fgmres->delta_allocate; /* number of vectors to allocate 
574:                                       in a single chunk */

576:   /* Adjust the number to allocate to make sure that we don't exceed the
577:      number of available slots (fgmres->vecs_allocated)*/
578:   if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated){
579:     nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
580:   }
581:   if (!nalloc) return(0);

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

585:   /* work vectors */
586:   VecDuplicateVecs(VEC_RHS,nalloc,&fgmres->user_work[nwork]);
587:   PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
588:   for (k=0; k < nalloc; k++) {
589:     fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
590:   }
591:   /* specify size of chunk allocated */
592:   fgmres->mwork_alloc[nwork] = nalloc;

594:   /* preconditioned vectors */
595:   VecDuplicateVecs(VEC_RHS,nalloc,&fgmres->prevecs_user_work[nwork]);
596:   PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
597:   for (k=0; k < nalloc; k++) {
598:     fgmres->prevecs[it+VEC_OFFSET+k] = fgmres->prevecs_user_work[nwork][k];
599:   }

601:   /* increment the number of work vector chunks */
602:   fgmres->nwork_alloc++;
603:   return(0);
604: }

606: /* 

608:    KSPBuildSolution_FGMRES

610:      Input Parameter:
611: .     ksp - the Krylov space object
612: .     ptr-

614:    Output Parameter:
615: .     result - the solution

617:    Note: this calls BuildFgmresSoln - the same function that FGMREScycle
618:    calls directly.  

620: */
621: int KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)
622: {
623:   KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
624:   int        ierr;

627:   if (!ptr) {
628:     if (!fgmres->sol_temp) {
629:       VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
630:       PetscLogObjectParent(ksp,fgmres->sol_temp);
631:     }
632:     ptr = fgmres->sol_temp;
633:   }
634:   if (!fgmres->nrs) {
635:     /* allocate the work area */
636:     PetscMalloc(fgmres->max_k*sizeof(PetscScalar),&fgmres->nrs);
637:     PetscLogObjectMemory(ksp,fgmres->max_k*sizeof(PetscScalar));
638:   }
639: 
640:   BuildFgmresSoln(fgmres->nrs,VEC_SOLN,ptr,ksp,fgmres->it);
641:   *result = ptr;
642: 
643:   return(0);
644: }

646: /*

648:    KSPView_FGMRES -Prints information about the current Krylov method 
649:                   being used.

651:  */
652: int KSPView_FGMRES(KSP ksp,PetscViewer viewer)
653: {
654:   KSP_FGMRES   *fgmres = (KSP_FGMRES *)ksp->data;
655:   char         *cstr;
656:   int          ierr;
657:   PetscTruth   isascii;

660:   PetscTypeCompare((PetscObject)viewer,PETSC_VIEWER_ASCII,&isascii);
661:   if (isascii) {
662:     if (fgmres->orthog == KSPGMRESUnmodifiedGramSchmidtOrthogonalization) {
663:       cstr = "Unmodified Gram-Schmidt Orthogonalization";
664:     } else if (fgmres->orthog == KSPGMRESModifiedGramSchmidtOrthogonalization) {
665:       cstr = "Modified Gram-Schmidt Orthogonalization";
666:     } else if (fgmres->orthog == KSPGMRESIROrthogonalization) {
667:       cstr = "Unmodified Gram-Schmidt + 1 step Iterative Refinement Orthogonalization";
668:     } else {
669:       cstr = "unknown orthogonalization";
670:     }
671:     PetscViewerASCIIPrintf(viewer,"  FGMRES: restart=%d, using %sn",fgmres->max_k,cstr);
672:   } else {
673:     SETERRQ(1,"Viewer type not supported for this object");
674:   }
675:   return(0);
676: }

678: int KSPSetFromOptions_FGMRES(KSP ksp)
679: {
680:   int         ierr,restart;
681:   PetscReal   haptol;
682:   KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
683:   PetscTruth  flg;

686:   PetscOptionsHead("KSP flexible GMRES Options");
687:     PetscOptionsInt("-ksp_gmres_restart","Number of Krylov search directions","KSPGMRESSetRestart",gmres->max_k,&restart,&flg);
688:     if (flg) { KSPGMRESSetRestart(ksp,restart); }
689:     PetscOptionsReal("-ksp_gmres_haptol","Tolerance for declaring exact convergence (happy ending)","KSPGMRESSetHapTol",gmres->haptol,&haptol,&flg);
690:     if (flg) { KSPGMRESSetHapTol(ksp,haptol); }
691:     PetscOptionsName("-ksp_gmres_preallocate","Preallocate all Krylov vectors","KSPGMRESSetPreAllocateVectors",&flg);
692:     if (flg) {KSPGMRESSetPreAllocateVectors(ksp);}
693:     PetscOptionsLogicalGroupBegin("-ksp_gmres_unmodifiedgramschmidt","Use classical (unmodified) Gram-Schmidt (fast)","KSPGMRESSetOrthogonalization",&flg);
694:     if (flg) {KSPGMRESSetOrthogonalization(ksp,KSPGMRESUnmodifiedGramSchmidtOrthogonalization);}
695:     PetscOptionsLogicalGroup("-ksp_gmres_modifiedgramschmidt","Use modified Gram-Schmidt (slow but more stable)","KSPGMRESSetOrthogonalization",&flg);
696:     if (flg) {KSPGMRESSetOrthogonalization(ksp,KSPGMRESModifiedGramSchmidtOrthogonalization);}
697:     PetscOptionsLogicalGroupEnd("-ksp_gmres_irorthog","Use classical Gram-Schmidt with iterative refinement","KSPGMRESSetOrthogonalization",&flg);
698:     if (flg) {KSPGMRESSetOrthogonalization(ksp,KSPGMRESIROrthogonalization);}
699:     PetscOptionsName("-ksp_gmres_krylov_monitor","Graphically plot the Krylov directions","KSPSetMonitor",&flg);
700:     if (flg) {
701:       PetscViewers viewers;
702:       PetscViewersCreate(ksp->comm,&viewers);
703:       KSPSetMonitor(ksp,KSPGMRESKrylovMonitor,viewers,(int (*)(void*))PetscViewersDestroy);
704:     }
705:     PetscOptionsLogicalGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
706:     if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,0,0);}
707:     PetscOptionsLogicalGroupEnd("-ksp_fgmres_modifypcsles","vary the SLES based preconditioner","KSPFGMRESSetModifyPC",&flg);
708:     if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCSLES,0,0);}
709:   PetscOptionsTail();
710:   return(0);
711: }

713: EXTERN_C_BEGIN
714: int KSPFGMRESSetModifyPC_FGMRES(KSP ksp,int (*fcn)(KSP,int,int,PetscReal,void*),void *ctx,int (*d)(void*))
715: {
718:   ((KSP_FGMRES *)ksp->data)->modifypc      = fcn;
719:   ((KSP_FGMRES *)ksp->data)->modifydestroy = d;
720:   ((KSP_FGMRES *)ksp->data)->modifyctx     = ctx;
721:   return(0);
722: }
723: EXTERN_C_END

725: EXTERN_C_BEGIN
726: EXTERN int KSPGMRESSetPreAllocateVectors_GMRES(KSP);
727: EXTERN int KSPGMRESSetRestart_GMRES(KSP,int);
728: EXTERN int KSPGMRESSetOrthogonalization_GMRES(KSP,int (*)(KSP,int));
729: EXTERN_C_END

731: EXTERN_C_BEGIN
732: int KSPCreate_FGMRES(KSP ksp)
733: {
734:   KSP_FGMRES *fgmres;
735:   int        ierr;

738:   PetscNew(KSP_FGMRES,&fgmres);
739:   PetscMemzero(fgmres,sizeof(KSP_FGMRES));
740:   PetscLogObjectMemory(ksp,sizeof(KSP_FGMRES));
741:   ksp->data                              = (void*)fgmres;
742:   ksp->ops->buildsolution                = KSPBuildSolution_FGMRES;

744:   ksp->ops->setup                        = KSPSetUp_FGMRES;
745:   ksp->ops->solve                        = KSPSolve_FGMRES;
746:   ksp->ops->destroy                      = KSPDestroy_FGMRES;
747:   ksp->ops->view                         = KSPView_FGMRES;
748:   ksp->ops->setfromoptions               = KSPSetFromOptions_FGMRES;
749:   ksp->ops->computeextremesingularvalues = 0;
750:   ksp->ops->computeeigenvalues           = 0;

752:   PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",
753:                                     "KSPGMRESSetPreAllocateVectors_GMRES",
754:                                      KSPGMRESSetPreAllocateVectors_GMRES);
755:   PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",
756:                                     "KSPGMRESSetOrthogonalization_GMRES",
757:                                      KSPGMRESSetOrthogonalization_GMRES);
758:   PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPGMRESSetRestart_C",
759:                                     "KSPGMRESSetRestart_GMRES",
760:                                      KSPGMRESSetRestart_GMRES);
761:   PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",
762:                                     "KSPFGMRESSetModifyPC_FGMRES",
763:                                      KSPFGMRESSetModifyPC_FGMRES);


766:   fgmres->haptol              = 1.0e-30;
767:   fgmres->q_preallocate       = 0;
768:   fgmres->delta_allocate      = FGMRES_DELTA_DIRECTIONS;
769:   fgmres->orthog              = KSPGMRESIROrthogonalization;
770:   fgmres->nrs                 = 0;
771:   fgmres->sol_temp            = 0;
772:   fgmres->max_k               = FGMRES_DEFAULT_MAXK;
773:   fgmres->Rsvd                = 0;
774:   fgmres->modifypc            = KSPFGMRESModifyPCNoChange;
775:   fgmres->modifyctx           = PETSC_NULL;
776:   fgmres->modifydestroy       = PETSC_NULL;

778:   return(0);
779: }
780: EXTERN_C_END