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> /*I "petscksp.h" I*/
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: */
34: PetscErrorCode KSPSetUp_FGMRES(KSP ksp) 35: {
37: PetscInt max_k,k;
38: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
41: max_k = fgmres->max_k;
43: KSPSetUp_GMRES(ksp);
45: PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(void*),&fgmres->prevecs);
46: PetscMalloc((VEC_OFFSET+2+max_k)*sizeof(void*),&fgmres->prevecs_user_work);
47: PetscLogObjectMemory(ksp,(VEC_OFFSET+2+max_k)*(2*sizeof(void*)));
49: KSPGetVecs(ksp,fgmres->vv_allocated,&fgmres->prevecs_user_work[0],0,NULL);
50: PetscLogObjectParents(ksp,fgmres->vv_allocated,fgmres->prevecs_user_work[0]);
51: for (k=0; k < fgmres->vv_allocated; k++) {
52: fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
53: }
54: return(0);
55: }
57: /*
58: KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
59: */
62: static PetscErrorCode KSPFGMRESResidual(KSP ksp) 63: {
64: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
65: Mat Amat,Pmat;
66: MatStructure pflag;
70: PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);
72: /* put A*x into VEC_TEMP */
73: MatMult(Amat,ksp->vec_sol,VEC_TEMP);
74: /* now put residual (-A*x + f) into vec_vv(0) */
75: VecWAXPY(VEC_VV(0),-1.0,VEC_TEMP,ksp->vec_rhs);
76: return(0);
77: }
79: /*
81: KSPFGMRESCycle - Run fgmres, possibly with restart. Return residual
82: history if requested.
84: input parameters:
85: . fgmres - structure containing parameters and work areas
87: output parameters:
88: . itcount - number of iterations used. If null, ignored.
89: . converged - 0 if not converged
92: Notes:
93: On entry, the value in vector VEC_VV(0) should be
94: the initial residual.
97: */
100: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount,KSP ksp)101: {
103: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
104: PetscReal res_norm;
105: PetscReal hapbnd,tt;
106: PetscBool hapend = PETSC_FALSE; /* indicates happy breakdown ending */
108: PetscInt loc_it; /* local count of # of dir. in Krylov space */
109: PetscInt max_k = fgmres->max_k; /* max # of directions Krylov space */
110: Mat Amat,Pmat;
111: MatStructure pflag;
114: /* Number of pseudo iterations since last restart is the number
115: of prestart directions */
116: loc_it = 0;
118: /* note: (fgmres->it) is always set one less than (loc_it) It is used in
119: KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
120: Note that when KSPFGMRESBuildSoln is called from this function,
121: (loc_it -1) is passed, so the two are equivalent */
122: fgmres->it = (loc_it - 1);
124: /* initial residual is in VEC_VV(0) - compute its norm*/
125: VecNorm(VEC_VV(0),NORM_2,&res_norm);
127: /* first entry in right-hand-side of hessenberg system is just
128: the initial residual norm */
129: *RS(0) = res_norm;
131: ksp->rnorm = res_norm;
132: KSPLogResidualHistory(ksp,res_norm);
134: /* check for the convergence - maybe the current guess is good enough */
135: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
136: if (ksp->reason) {
137: if (itcount) *itcount = 0;
138: return(0);
139: }
141: /* scale VEC_VV (the initial residual) */
142: VecScale(VEC_VV(0),1.0/res_norm);
144: /* MAIN ITERATION LOOP BEGINNING*/
145: /* keep iterating until we have converged OR generated the max number
146: of directions OR reached the max number of iterations for the method */
147: while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
148: if (loc_it) {KSPLogResidualHistory(ksp,res_norm);}
149: fgmres->it = (loc_it - 1);
150: KSPMonitor(ksp,ksp->its,res_norm);
152: /* see if more space is needed for work vectors */
153: if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
154: KSPFGMRESGetNewVectors(ksp,loc_it+1);
155: /* (loc_it+1) is passed in as number of the first vector that should
156: be allocated */
157: }
159: /* CHANGE THE PRECONDITIONER? */
160: /* ModifyPC is the callback function that can be used to
161: change the PC or its attributes before its applied */
162: (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);
165: /* apply PRECONDITIONER to direction vector and store with
166: preconditioned vectors in prevec */
167: KSP_PCApply(ksp,VEC_VV(loc_it),PREVEC(loc_it));
169: PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);
170: /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
171: MatMult(Amat,PREVEC(loc_it),VEC_VV(1+loc_it));
174: /* update hessenberg matrix and do Gram-Schmidt - new direction is in
175: VEC_VV(1+loc_it)*/
176: (*fgmres->orthog)(ksp,loc_it);
178: /* new entry in hessenburg is the 2-norm of our new direction */
179: VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);
181: *HH(loc_it+1,loc_it) = tt;
182: *HES(loc_it+1,loc_it) = tt;
184: /* Happy Breakdown Check */
185: hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
186: /* RS(loc_it) contains the res_norm from the last iteration */
187: hapbnd = PetscMin(fgmres->haptol,hapbnd);
188: if (tt > hapbnd) {
189: /* scale new direction by its norm */
190: VecScale(VEC_VV(loc_it+1),1.0/tt);
191: } else {
192: /* This happens when the solution is exactly reached. */
193: /* So there is no new direction... */
194: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP to 0 */
195: hapend = PETSC_TRUE;
196: }
197: /* note that for FGMRES we could get HES(loc_it+1, loc_it) = 0 and the
198: current solution would not be exact if HES was singular. Note that
199: HH non-singular implies that HES is no singular, and HES is guaranteed
200: to be nonsingular when PREVECS are linearly independent and A is
201: nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
202: of HES). So we should really add a check to verify that HES is nonsingular.*/
205: /* Now apply rotations to new col of hessenberg (and right side of system),
206: calculate new rotation, and get new residual norm at the same time*/
207: KSPFGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
208: if (ksp->reason) break;
210: loc_it++;
211: fgmres->it = (loc_it-1); /* Add this here in case it has converged */
213: PetscObjectAMSTakeAccess((PetscObject)ksp);
214: ksp->its++;
215: ksp->rnorm = res_norm;
216: PetscObjectAMSGrantAccess((PetscObject)ksp);
218: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
220: /* Catch error in happy breakdown and signal convergence and break from loop */
221: if (hapend) {
222: if (!ksp->reason) {
223: 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",res_norm);
224: else {
225: ksp->reason = KSP_DIVERGED_BREAKDOWN;
226: break;
227: }
228: }
229: }
230: }
231: /* END OF ITERATION LOOP */
232: KSPLogResidualHistory(ksp,res_norm);
234: /*
235: Monitor if we know that we will not return for a restart */
236: if (ksp->reason || ksp->its >= ksp->max_it) {
237: KSPMonitor(ksp,ksp->its,res_norm);
238: }
240: if (itcount) *itcount = loc_it;
242: /*
243: Down here we have to solve for the "best" coefficients of the Krylov
244: columns, add the solution values together, and possibly unwind the
245: preconditioning from the solution
246: */
248: /* Form the solution (or the solution so far) */
249: /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
250: properly navigates */
252: KSPFGMRESBuildSoln(RS(0),ksp->vec_sol,ksp->vec_sol,ksp,loc_it-1);
253: return(0);
254: }
256: /*
257: KSPSolve_FGMRES - This routine applies the FGMRES method.
260: Input Parameter:
261: . ksp - the Krylov space object that was set to use fgmres
263: Output Parameter:
264: . outits - number of iterations used
266: */
270: PetscErrorCode KSPSolve_FGMRES(KSP ksp)271: {
273: PetscInt cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
274: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
275: PetscBool diagonalscale;
278: PCGetDiagonalScale(ksp->pc,&diagonalscale);
279: if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);
281: PetscObjectAMSTakeAccess((PetscObject)ksp);
282: ksp->its = 0;
283: PetscObjectAMSGrantAccess((PetscObject)ksp);
285: /* Compute the initial (NOT preconditioned) residual */
286: if (!ksp->guess_zero) {
287: KSPFGMRESResidual(ksp);
288: } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
289: VecCopy(ksp->vec_rhs,VEC_VV(0));
290: }
291: /* now the residual is in VEC_VV(0) - which is what
292: KSPFGMRESCycle expects... */
294: KSPFGMRESCycle(&cycle_its,ksp);
295: while (!ksp->reason) {
296: KSPFGMRESResidual(ksp);
297: if (ksp->its >= ksp->max_it) break;
298: KSPFGMRESCycle(&cycle_its,ksp);
299: }
300: /* mark lack of convergence */
301: if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
302: return(0);
303: }
305: extern PetscErrorCode KSPReset_FGMRES(KSP);
306: /*
308: KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.
310: */
313: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)314: {
318: KSPReset_FGMRES(ksp);
319: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",NULL);
320: KSPDestroy_GMRES(ksp);
321: return(0);
322: }
324: /*
325: KSPFGMRESBuildSoln - create the solution from the starting vector and the
326: current iterates.
328: Input parameters:
329: nrs - work area of size it + 1.
330: vguess - index of initial guess
331: vdest - index of result. Note that vguess may == vdest (replace
332: guess with the solution).
333: it - HH upper triangular part is a block of size (it+1) x (it+1)
335: This is an internal routine that knows about the FGMRES internals.
336: */
339: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs,Vec vguess,Vec vdest,KSP ksp,PetscInt it)340: {
341: PetscScalar tt;
343: PetscInt ii,k,j;
344: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
347: /* Solve for solution vector that minimizes the residual */
349: /* If it is < 0, no fgmres steps have been performed */
350: if (it < 0) {
351: VecCopy(vguess,vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
352: return(0);
353: }
355: /* so fgmres steps HAVE been performed */
357: /* solve the upper triangular system - RS is the right side and HH is
358: the upper triangular matrix - put soln in nrs */
359: if (*HH(it,it) != 0.0) {
360: nrs[it] = *RS(it) / *HH(it,it);
361: } else {
362: nrs[it] = 0.0;
363: }
364: for (ii=1; ii<=it; ii++) {
365: k = it - ii;
366: tt = *RS(k);
367: for (j=k+1; j<=it; j++) tt = tt - *HH(k,j) * nrs[j];
368: nrs[k] = tt / *HH(k,k);
369: }
371: /* Accumulate the correction to the soln of the preconditioned prob. in
372: VEC_TEMP - note that we use the preconditioned vectors */
373: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP components to 0 */
374: VecMAXPY(VEC_TEMP,it+1,nrs,&PREVEC(0));
376: /* put updated solution into vdest.*/
377: if (vdest != vguess) {
378: VecCopy(VEC_TEMP,vdest);
379: VecAXPY(vdest,1.0,vguess);
380: } else { /* replace guess with solution */
381: VecAXPY(vdest,1.0,VEC_TEMP);
382: }
383: return(0);
384: }
386: /*
388: KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
389: Return new residual.
391: input parameters:
393: . ksp - Krylov space object
394: . it - plane rotations are applied to the (it+1)th column of the
395: modified hessenberg (i.e. HH(:,it))
396: . hapend - PETSC_FALSE not happy breakdown ending.
398: output parameters:
399: . res - the new residual
401: */
404: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp,PetscInt it,PetscBool hapend,PetscReal *res)405: {
406: PetscScalar *hh,*cc,*ss,tt;
407: PetscInt j;
408: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
411: hh = HH(0,it); /* pointer to beginning of column to update - so
412: incrementing hh "steps down" the (it+1)th col of HH*/
413: cc = CC(0); /* beginning of cosine rotations */
414: ss = SS(0); /* beginning of sine rotations */
416: /* Apply all the previously computed plane rotations to the new column
417: of the Hessenberg matrix */
418: /* Note: this uses the rotation [conj(c) s ; -s c], c= cos(theta), s= sin(theta),
419: and some refs have [c s ; -conj(s) c] (don't be confused!) */
421: for (j=1; j<=it; j++) {
422: tt = *hh;
423: *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
424: hh++;
425: *hh = *cc++ * *hh - (*ss++ * tt);
426: /* hh, cc, and ss have all been incremented one by end of loop */
427: }
429: /*
430: compute the new plane rotation, and apply it to:
431: 1) the right-hand-side of the Hessenberg system (RS)
432: note: it affects RS(it) and RS(it+1)
433: 2) the new column of the Hessenberg matrix
434: note: it affects HH(it,it) which is currently pointed to
435: by hh and HH(it+1, it) (*(hh+1))
436: thus obtaining the updated value of the residual...
437: */
439: /* compute new plane rotation */
441: if (!hapend) {
442: tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
443: if (tt == 0.0) {
444: ksp->reason = KSP_DIVERGED_NULL;
445: return(0);
446: }
448: *cc = *hh / tt; /* new cosine value */
449: *ss = *(hh+1) / tt; /* new sine value */
451: /* apply to 1) and 2) */
452: *RS(it+1) = -(*ss * *RS(it));
453: *RS(it) = PetscConj(*cc) * *RS(it);
454: *hh = PetscConj(*cc) * *hh + *ss * *(hh+1);
456: /* residual is the last element (it+1) of right-hand side! */
457: *res = PetscAbsScalar(*RS(it+1));
459: } else { /* happy breakdown: HH(it+1, it) = 0, therfore we don't need to apply
460: another rotation matrix (so RH doesn't change). The new residual is
461: always the new sine term times the residual from last time (RS(it)),
462: but now the new sine rotation would be zero...so the residual should
463: be zero...so we will multiply "zero" by the last residual. This might
464: not be exactly what we want to do here -could just return "zero". */
466: *res = 0.0;
467: }
468: return(0);
469: }
471: /*
473: KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
474: VEC_VV(it), and more preconditioned work vectors, starting
475: from PREVEC(i).
477: */
480: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp,PetscInt it)481: {
482: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
483: PetscInt nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
484: PetscInt nalloc; /* number to allocate */
486: PetscInt k;
489: nalloc = fgmres->delta_allocate; /* number of vectors to allocate
490: in a single chunk */
492: /* Adjust the number to allocate to make sure that we don't exceed the
493: number of available slots (fgmres->vecs_allocated)*/
494: if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) {
495: nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
496: }
497: if (!nalloc) return(0);
499: fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */
501: /* work vectors */
502: KSPGetVecs(ksp,nalloc,&fgmres->user_work[nwork],0,NULL);
503: PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
504: for (k=0; k < nalloc; k++) {
505: fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
506: }
507: /* specify size of chunk allocated */
508: fgmres->mwork_alloc[nwork] = nalloc;
510: /* preconditioned vectors */
511: KSPGetVecs(ksp,nalloc,&fgmres->prevecs_user_work[nwork],0,NULL);
512: PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
513: for (k=0; k < nalloc; k++) {
514: fgmres->prevecs[it+VEC_OFFSET+k] = fgmres->prevecs_user_work[nwork][k];
515: }
517: /* increment the number of work vector chunks */
518: fgmres->nwork_alloc++;
519: return(0);
520: }
522: /*
524: KSPBuildSolution_FGMRES
526: Input Parameter:
527: . ksp - the Krylov space object
528: . ptr-
530: Output Parameter:
531: . result - the solution
533: Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
534: calls directly.
536: */
539: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)540: {
541: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
545: if (!ptr) {
546: if (!fgmres->sol_temp) {
547: VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
548: PetscLogObjectParent(ksp,fgmres->sol_temp);
549: }
550: ptr = fgmres->sol_temp;
551: }
552: if (!fgmres->nrs) {
553: /* allocate the work area */
554: PetscMalloc(fgmres->max_k*sizeof(PetscScalar),&fgmres->nrs);
555: PetscLogObjectMemory(ksp,fgmres->max_k*sizeof(PetscScalar));
556: }
558: KSPFGMRESBuildSoln(fgmres->nrs,ksp->vec_sol,ptr,ksp,fgmres->it);
559: if (result) *result = ptr;
560: return(0);
561: }
565: PetscErrorCode KSPSetFromOptions_FGMRES(KSP ksp)566: {
568: PetscBool flg;
571: KSPSetFromOptions_GMRES(ksp);
572: PetscOptionsHead("KSP flexible GMRES Options");
573: PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
574: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,0,0);}
575: PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp","vary the KSP based preconditioner","KSPFGMRESSetModifyPC",&flg);
576: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCKSP,0,0);}
577: PetscOptionsTail();
578: return(0);
579: }
581: typedef PetscErrorCode (*FCN1)(KSP,PetscInt,PetscInt,PetscReal,void*); /* force argument to next function to not be extern C*/
582: typedef PetscErrorCode (*FCN2)(void*);
586: static PetscErrorCode KSPFGMRESSetModifyPC_FGMRES(KSP ksp,FCN1 fcn,void *ctx,FCN2 d)587: {
590: ((KSP_FGMRES*)ksp->data)->modifypc = fcn;
591: ((KSP_FGMRES*)ksp->data)->modifydestroy = d;
592: ((KSP_FGMRES*)ksp->data)->modifyctx = ctx;
593: return(0);
594: }
599: PetscErrorCode KSPReset_FGMRES(KSP ksp)600: {
601: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
603: PetscInt i;
606: PetscFree (fgmres->prevecs);
607: for (i=0; i<fgmres->nwork_alloc; i++) {
608: VecDestroyVecs(fgmres->mwork_alloc[i],&fgmres->prevecs_user_work[i]);
609: }
610: PetscFree(fgmres->prevecs_user_work);
611: if (fgmres->modifydestroy) {
612: (*fgmres->modifydestroy)(fgmres->modifyctx);
613: }
614: KSPReset_GMRES(ksp);
615: return(0);
616: }
620: PetscErrorCode KSPGMRESSetRestart_FGMRES(KSP ksp,PetscInt max_k)621: {
622: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
626: if (max_k < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
627: if (!ksp->setupstage) {
628: gmres->max_k = max_k;
629: } else if (gmres->max_k != max_k) {
630: gmres->max_k = max_k;
631: ksp->setupstage = KSP_SETUP_NEW;
632: /* free the data structures, then create them again */
633: KSPReset_FGMRES(ksp);
634: }
635: return(0);
636: }
640: PetscErrorCode KSPGMRESGetRestart_FGMRES(KSP ksp,PetscInt *max_k)641: {
642: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
645: *max_k = gmres->max_k;
646: return(0);
647: }
649: /*MC
650: KSPFGMRES - Implements the Flexible Generalized Minimal Residual method.
651: developed by Saad with restart
654: Options Database Keys:
655: + -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
656: . -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
657: . -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
658: vectors are allocated as needed)
659: . -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
660: . -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
661: . -ksp_gmres_cgs_refinement_type <never,ifneeded,always> - determine if iterative refinement is used to increase the
662: stability of the classical Gram-Schmidt orthogonalization.
663: . -ksp_gmres_krylov_monitor - plot the Krylov space generated
664: . -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
665: - -ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()
667: Level: beginner
669: Notes: See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations
670: Only right preconditioning is supported.
672: Notes: 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)
673: be bi-CG-stab with a preconditioner of Jacobi.
675: Developer Notes: This object is subclassed off of KSPGMRES677: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
678: KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(),
679: KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(),
680: KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(), KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(),
681: KSPFGMRESModifyPCKSP()
683: M*/
687: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)688: {
689: KSP_FGMRES *fgmres;
693: PetscNewLog(ksp,KSP_FGMRES,&fgmres);
695: ksp->data = (void*)fgmres;
696: ksp->ops->buildsolution = KSPBuildSolution_FGMRES;
697: ksp->ops->setup = KSPSetUp_FGMRES;
698: ksp->ops->solve = KSPSolve_FGMRES;
699: ksp->ops->reset = KSPReset_FGMRES;
700: ksp->ops->destroy = KSPDestroy_FGMRES;
701: ksp->ops->view = KSPView_GMRES;
702: ksp->ops->setfromoptions = KSPSetFromOptions_FGMRES;
703: ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
704: ksp->ops->computeeigenvalues = KSPComputeEigenvalues_GMRES;
706: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
707: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,0);
709: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",KSPGMRESSetPreAllocateVectors_GMRES);
710: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",KSPGMRESSetOrthogonalization_GMRES);
711: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetOrthogonalization_C",KSPGMRESGetOrthogonalization_GMRES);
712: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetRestart_C",KSPGMRESSetRestart_FGMRES);
713: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetRestart_C",KSPGMRESGetRestart_FGMRES);
714: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",KSPFGMRESSetModifyPC_FGMRES);
715: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetCGSRefinementType_C",KSPGMRESSetCGSRefinementType_GMRES);
716: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetCGSRefinementType_C",KSPGMRESGetCGSRefinementType_GMRES);
719: fgmres->haptol = 1.0e-30;
720: fgmres->q_preallocate = 0;
721: fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
722: fgmres->orthog = KSPGMRESClassicalGramSchmidtOrthogonalization;
723: fgmres->nrs = 0;
724: fgmres->sol_temp = 0;
725: fgmres->max_k = FGMRES_DEFAULT_MAXK;
726: fgmres->Rsvd = 0;
727: fgmres->orthogwork = 0;
728: fgmres->modifypc = KSPFGMRESModifyPCNoChange;
729: fgmres->modifyctx = NULL;
730: fgmres->modifydestroy = NULL;
731: fgmres->cgstype = KSP_GMRES_CGS_REFINE_NEVER;
732: return(0);
733: }