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.
12: */
14: #include <../src/ksp/ksp/impls/gmres/fgmres/fgmresimpl.h>
15: #define FGMRES_DELTA_DIRECTIONS 10
16: #define FGMRES_DEFAULT_MAXK 30
17: static PetscErrorCode KSPFGMRESGetNewVectors(KSP, PetscInt);
18: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP, PetscInt, PetscBool, PetscReal *);
19: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *, Vec, Vec, KSP, PetscInt);
21: /*
23: KSPSetUp_FGMRES - Sets up the workspace needed by fgmres.
25: This is called once, usually automatically by KSPSolve() or KSPSetUp(),
26: but can be called directly by KSPSetUp().
28: */
29: PetscErrorCode KSPSetUp_FGMRES(KSP ksp)
30: {
31: PetscInt max_k, k;
32: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
34: max_k = fgmres->max_k;
36: KSPSetUp_GMRES(ksp);
38: PetscMalloc1(max_k + 2, &fgmres->prevecs);
39: PetscMalloc1(max_k + 2, &fgmres->prevecs_user_work);
41: /* fgmres->vv_allocated includes extra work vectors, which are not used in the additional
42: block of vectors used to store the preconditioned directions, hence the -VEC_OFFSET
43: term for this first allocation of vectors holding preconditioned directions */
44: KSPCreateVecs(ksp, fgmres->vv_allocated - VEC_OFFSET, &fgmres->prevecs_user_work[0], 0, NULL);
45: for (k = 0; k < fgmres->vv_allocated - VEC_OFFSET; k++) fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
46: return 0;
47: }
49: /*
50: KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
51: */
52: static PetscErrorCode KSPFGMRESResidual(KSP ksp)
53: {
54: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
55: Mat Amat, Pmat;
57: PCGetOperators(ksp->pc, &Amat, &Pmat);
59: /* put A*x into VEC_TEMP */
60: KSP_MatMult(ksp, Amat, ksp->vec_sol, VEC_TEMP);
61: /* now put residual (-A*x + f) into vec_vv(0) */
62: VecWAXPY(VEC_VV(0), -1.0, VEC_TEMP, ksp->vec_rhs);
63: return 0;
64: }
66: /*
68: KSPFGMRESCycle - Run fgmres, possibly with restart. Return residual
69: history if requested.
71: input parameters:
72: . fgmres - structure containing parameters and work areas
74: output parameters:
75: . itcount - number of iterations used. If null, ignored.
76: . converged - 0 if not converged
78: Notes:
79: On entry, the value in vector VEC_VV(0) should be
80: the initial residual.
82: */
83: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount, KSP ksp)
84: {
85: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
86: PetscReal res_norm;
87: PetscReal hapbnd, tt;
88: PetscBool hapend = PETSC_FALSE; /* indicates happy breakdown ending */
89: PetscInt loc_it; /* local count of # of dir. in Krylov space */
90: PetscInt max_k = fgmres->max_k; /* max # of directions Krylov space */
91: Mat Amat, Pmat;
93: /* Number of pseudo iterations since last restart is the number
94: of prestart directions */
95: loc_it = 0;
97: /* note: (fgmres->it) is always set one less than (loc_it) It is used in
98: KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
99: Note that when KSPFGMRESBuildSoln is called from this function,
100: (loc_it -1) is passed, so the two are equivalent */
101: fgmres->it = (loc_it - 1);
103: /* initial residual is in VEC_VV(0) - compute its norm*/
104: VecNorm(VEC_VV(0), NORM_2, &res_norm);
105: KSPCheckNorm(ksp, res_norm);
107: /* first entry in right-hand-side of hessenberg system is just
108: the initial residual norm */
109: *RS(0) = res_norm;
111: ksp->rnorm = res_norm;
112: KSPLogResidualHistory(ksp, res_norm);
113: KSPMonitor(ksp, ksp->its, res_norm);
115: /* check for the convergence - maybe the current guess is good enough */
116: (*ksp->converged)(ksp, ksp->its, res_norm, &ksp->reason, ksp->cnvP);
117: if (ksp->reason) {
118: if (itcount) *itcount = 0;
119: return 0;
120: }
122: /* scale VEC_VV (the initial residual) */
123: VecScale(VEC_VV(0), 1.0 / res_norm);
125: /* MAIN ITERATION LOOP BEGINNING*/
126: /* keep iterating until we have converged OR generated the max number
127: of directions OR reached the max number of iterations for the method */
128: while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
129: if (loc_it) {
130: KSPLogResidualHistory(ksp, res_norm);
131: KSPMonitor(ksp, ksp->its, res_norm);
132: }
133: fgmres->it = (loc_it - 1);
135: /* see if more space is needed for work vectors */
136: if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
137: KSPFGMRESGetNewVectors(ksp, loc_it + 1);
138: /* (loc_it+1) is passed in as number of the first vector that should
139: be allocated */
140: }
142: /* CHANGE THE PRECONDITIONER? */
143: /* ModifyPC is the callback function that can be used to
144: change the PC or its attributes before its applied */
145: (*fgmres->modifypc)(ksp, ksp->its, loc_it, res_norm, fgmres->modifyctx);
147: /* apply PRECONDITIONER to direction vector and store with
148: preconditioned vectors in prevec */
149: KSP_PCApply(ksp, VEC_VV(loc_it), PREVEC(loc_it));
151: PCGetOperators(ksp->pc, &Amat, &Pmat);
152: /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
153: KSP_MatMult(ksp, Amat, PREVEC(loc_it), VEC_VV(1 + loc_it));
155: /* update hessenberg matrix and do Gram-Schmidt - new direction is in
156: VEC_VV(1+loc_it)*/
157: (*fgmres->orthog)(ksp, loc_it);
159: /* new entry in hessenburg is the 2-norm of our new direction */
160: VecNorm(VEC_VV(loc_it + 1), NORM_2, &tt);
161: KSPCheckNorm(ksp, tt);
163: *HH(loc_it + 1, loc_it) = tt;
164: *HES(loc_it + 1, loc_it) = tt;
166: /* Happy Breakdown Check */
167: hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
168: /* RS(loc_it) contains the res_norm from the last iteration */
169: hapbnd = PetscMin(fgmres->haptol, hapbnd);
170: if (tt > hapbnd) {
171: /* scale new direction by its norm */
172: VecScale(VEC_VV(loc_it + 1), 1.0 / tt);
173: } else {
174: /* This happens when the solution is exactly reached. */
175: /* So there is no new direction... */
176: VecSet(VEC_TEMP, 0.0); /* set VEC_TEMP to 0 */
177: hapend = PETSC_TRUE;
178: }
179: /* note that for FGMRES we could get HES(loc_it+1, loc_it) = 0 and the
180: current solution would not be exact if HES was singular. Note that
181: HH non-singular implies that HES is no singular, and HES is guaranteed
182: to be nonsingular when PREVECS are linearly independent and A is
183: nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
184: of HES). So we should really add a check to verify that HES is nonsingular.*/
186: /* Now apply rotations to new col of hessenberg (and right side of system),
187: calculate new rotation, and get new residual norm at the same time*/
188: KSPFGMRESUpdateHessenberg(ksp, loc_it, hapend, &res_norm);
189: if (ksp->reason) break;
191: loc_it++;
192: fgmres->it = (loc_it - 1); /* Add this here in case it has converged */
194: PetscObjectSAWsTakeAccess((PetscObject)ksp);
195: ksp->its++;
196: ksp->rnorm = res_norm;
197: PetscObjectSAWsGrantAccess((PetscObject)ksp);
199: (*ksp->converged)(ksp, ksp->its, res_norm, &ksp->reason, ksp->cnvP);
201: /* Catch error in happy breakdown and signal convergence and break from loop */
202: if (hapend) {
203: if (!ksp->reason) {
205: ksp->reason = KSP_DIVERGED_BREAKDOWN;
206: break;
207: }
208: }
209: }
210: /* END OF ITERATION LOOP */
211: KSPLogResidualHistory(ksp, res_norm);
213: /*
214: Monitor if we know that we will not return for a restart */
215: if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) KSPMonitor(ksp, ksp->its, res_norm);
217: if (itcount) *itcount = loc_it;
219: /*
220: Down here we have to solve for the "best" coefficients of the Krylov
221: columns, add the solution values together, and possibly unwind the
222: preconditioning from the solution
223: */
225: /* Form the solution (or the solution so far) */
226: /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
227: properly navigates */
229: KSPFGMRESBuildSoln(RS(0), ksp->vec_sol, ksp->vec_sol, ksp, loc_it - 1);
230: return 0;
231: }
233: /*
234: KSPSolve_FGMRES - This routine applies the FGMRES method.
236: Input Parameter:
237: . ksp - the Krylov space object that was set to use fgmres
239: Output Parameter:
240: . outits - number of iterations used
242: */
244: PetscErrorCode KSPSolve_FGMRES(KSP ksp)
245: {
246: PetscInt cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
247: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
248: PetscBool diagonalscale;
250: PCGetDiagonalScale(ksp->pc, &diagonalscale);
253: PetscObjectSAWsTakeAccess((PetscObject)ksp);
254: ksp->its = 0;
255: PetscObjectSAWsGrantAccess((PetscObject)ksp);
257: /* Compute the initial (NOT preconditioned) residual */
258: if (!ksp->guess_zero) {
259: KSPFGMRESResidual(ksp);
260: } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
261: VecCopy(ksp->vec_rhs, VEC_VV(0));
262: }
263: /* This may be true only on a subset of MPI ranks; setting it here so it will be detected by the first norm computation in the Krylov method */
264: if (ksp->reason == KSP_DIVERGED_PC_FAILED) VecSetInf(VEC_VV(0));
266: /* now the residual is in VEC_VV(0) - which is what
267: KSPFGMRESCycle expects... */
269: KSPFGMRESCycle(&cycle_its, ksp);
270: while (!ksp->reason) {
271: KSPFGMRESResidual(ksp);
272: if (ksp->its >= ksp->max_it) break;
273: KSPFGMRESCycle(&cycle_its, ksp);
274: }
275: /* mark lack of convergence */
276: if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
277: return 0;
278: }
280: extern PetscErrorCode KSPReset_FGMRES(KSP);
281: /*
283: KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.
285: */
286: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)
287: {
288: KSPReset_FGMRES(ksp);
289: PetscObjectComposeFunction((PetscObject)ksp, "KSPFGMRESSetModifyPC_C", NULL);
290: KSPDestroy_GMRES(ksp);
291: return 0;
292: }
294: /*
295: KSPFGMRESBuildSoln - create the solution from the starting vector and the
296: current iterates.
298: Input parameters:
299: nrs - work area of size it + 1.
300: vguess - index of initial guess
301: vdest - index of result. Note that vguess may == vdest (replace
302: guess with the solution).
303: it - HH upper triangular part is a block of size (it+1) x (it+1)
305: This is an internal routine that knows about the FGMRES internals.
306: */
307: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs, Vec vguess, Vec vdest, KSP ksp, PetscInt it)
308: {
309: PetscScalar tt;
310: PetscInt ii, k, j;
311: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
313: /* Solve for solution vector that minimizes the residual */
315: /* If it is < 0, no fgmres steps have been performed */
316: if (it < 0) {
317: VecCopy(vguess, vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
318: return 0;
319: }
321: /* so fgmres steps HAVE been performed */
323: /* solve the upper triangular system - RS is the right side and HH is
324: the upper triangular matrix - put soln in nrs */
325: if (*HH(it, it) != 0.0) {
326: nrs[it] = *RS(it) / *HH(it, it);
327: } else {
328: nrs[it] = 0.0;
329: }
330: for (ii = 1; ii <= it; ii++) {
331: k = it - ii;
332: tt = *RS(k);
333: for (j = k + 1; j <= it; j++) tt = tt - *HH(k, j) * nrs[j];
334: nrs[k] = tt / *HH(k, k);
335: }
337: /* Accumulate the correction to the soln of the preconditioned prob. in
338: VEC_TEMP - note that we use the preconditioned vectors */
339: VecSet(VEC_TEMP, 0.0); /* set VEC_TEMP components to 0 */
340: VecMAXPY(VEC_TEMP, it + 1, nrs, &PREVEC(0));
342: /* put updated solution into vdest.*/
343: if (vdest != vguess) {
344: VecCopy(VEC_TEMP, vdest);
345: VecAXPY(vdest, 1.0, vguess);
346: } else { /* replace guess with solution */
347: VecAXPY(vdest, 1.0, VEC_TEMP);
348: }
349: return 0;
350: }
352: /*
354: KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
355: Return new residual.
357: input parameters:
359: . ksp - Krylov space object
360: . it - plane rotations are applied to the (it+1)th column of the
361: modified hessenberg (i.e. HH(:,it))
362: . hapend - PETSC_FALSE not happy breakdown ending.
364: output parameters:
365: . res - the new residual
367: */
368: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp, PetscInt it, PetscBool hapend, PetscReal *res)
369: {
370: PetscScalar *hh, *cc, *ss, tt;
371: PetscInt j;
372: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
374: hh = HH(0, it); /* pointer to beginning of column to update - so
375: incrementing hh "steps down" the (it+1)th col of HH*/
376: cc = CC(0); /* beginning of cosine rotations */
377: ss = SS(0); /* beginning of sine rotations */
379: /* Apply all the previously computed plane rotations to the new column
380: of the Hessenberg matrix */
381: /* Note: this uses the rotation [conj(c) s ; -s c], c= cos(theta), s= sin(theta),
382: and some refs have [c s ; -conj(s) c] (don't be confused!) */
384: for (j = 1; j <= it; j++) {
385: tt = *hh;
386: *hh = PetscConj(*cc) * tt + *ss * *(hh + 1);
387: hh++;
388: *hh = *cc++ * *hh - (*ss++ * tt);
389: /* hh, cc, and ss have all been incremented one by end of loop */
390: }
392: /*
393: compute the new plane rotation, and apply it to:
394: 1) the right-hand-side of the Hessenberg system (RS)
395: note: it affects RS(it) and RS(it+1)
396: 2) the new column of the Hessenberg matrix
397: note: it affects HH(it,it) which is currently pointed to
398: by hh and HH(it+1, it) (*(hh+1))
399: thus obtaining the updated value of the residual...
400: */
402: /* compute new plane rotation */
404: if (!hapend) {
405: tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh + 1)) * *(hh + 1));
406: if (tt == 0.0) {
407: ksp->reason = KSP_DIVERGED_NULL;
408: return 0;
409: }
411: *cc = *hh / tt; /* new cosine value */
412: *ss = *(hh + 1) / tt; /* new sine value */
414: /* apply to 1) and 2) */
415: *RS(it + 1) = -(*ss * *RS(it));
416: *RS(it) = PetscConj(*cc) * *RS(it);
417: *hh = PetscConj(*cc) * *hh + *ss * *(hh + 1);
419: /* residual is the last element (it+1) of right-hand side! */
420: *res = PetscAbsScalar(*RS(it + 1));
422: } else { /* happy breakdown: HH(it+1, it) = 0, therefore we don't need to apply
423: another rotation matrix (so RH doesn't change). The new residual is
424: always the new sine term times the residual from last time (RS(it)),
425: but now the new sine rotation would be zero...so the residual should
426: be zero...so we will multiply "zero" by the last residual. This might
427: not be exactly what we want to do here -could just return "zero". */
429: *res = 0.0;
430: }
431: return 0;
432: }
434: /*
436: KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
437: VEC_VV(it), and more preconditioned work vectors, starting
438: from PREVEC(i).
440: */
441: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp, PetscInt it)
442: {
443: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
444: PetscInt nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
445: PetscInt nalloc; /* number to allocate */
446: PetscInt k;
448: nalloc = fgmres->delta_allocate; /* number of vectors to allocate
449: in a single chunk */
451: /* Adjust the number to allocate to make sure that we don't exceed the
452: number of available slots (fgmres->vecs_allocated)*/
453: if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
454: if (!nalloc) return 0;
456: fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */
458: /* work vectors */
459: KSPCreateVecs(ksp, nalloc, &fgmres->user_work[nwork], 0, NULL);
460: for (k = 0; k < nalloc; k++) fgmres->vecs[it + VEC_OFFSET + k] = fgmres->user_work[nwork][k];
461: /* specify size of chunk allocated */
462: fgmres->mwork_alloc[nwork] = nalloc;
464: /* preconditioned vectors */
465: KSPCreateVecs(ksp, nalloc, &fgmres->prevecs_user_work[nwork], 0, NULL);
466: for (k = 0; k < nalloc; k++) fgmres->prevecs[it + k] = fgmres->prevecs_user_work[nwork][k];
468: /* increment the number of work vector chunks */
469: fgmres->nwork_alloc++;
470: return 0;
471: }
473: /*
475: KSPBuildSolution_FGMRES
477: Input Parameter:
478: . ksp - the Krylov space object
479: . ptr-
481: Output Parameter:
482: . result - the solution
484: Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
485: calls directly.
487: */
488: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp, Vec ptr, Vec *result)
489: {
490: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
492: if (!ptr) {
493: if (!fgmres->sol_temp) { VecDuplicate(ksp->vec_sol, &fgmres->sol_temp); }
494: ptr = fgmres->sol_temp;
495: }
496: if (!fgmres->nrs) {
497: /* allocate the work area */
498: PetscMalloc1(fgmres->max_k, &fgmres->nrs);
499: }
501: KSPFGMRESBuildSoln(fgmres->nrs, ksp->vec_sol, ptr, ksp, fgmres->it);
502: if (result) *result = ptr;
503: return 0;
504: }
506: PetscErrorCode KSPSetFromOptions_FGMRES(KSP ksp, PetscOptionItems *PetscOptionsObject)
507: {
508: PetscBool flg;
510: KSPSetFromOptions_GMRES(ksp, PetscOptionsObject);
511: PetscOptionsHeadBegin(PetscOptionsObject, "KSP flexible GMRES Options");
512: PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange", "do not vary the preconditioner", "KSPFGMRESSetModifyPC", &flg);
513: if (flg) KSPFGMRESSetModifyPC(ksp, KSPFGMRESModifyPCNoChange, NULL, NULL);
514: PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp", "vary the KSP based preconditioner", "KSPFGMRESSetModifyPC", &flg);
515: if (flg) KSPFGMRESSetModifyPC(ksp, KSPFGMRESModifyPCKSP, NULL, NULL);
516: PetscOptionsHeadEnd();
517: return 0;
518: }
520: typedef PetscErrorCode (*FCN1)(KSP, PetscInt, PetscInt, PetscReal, void *); /* force argument to next function to not be extern C*/
521: typedef PetscErrorCode (*FCN2)(void *);
523: static PetscErrorCode KSPFGMRESSetModifyPC_FGMRES(KSP ksp, FCN1 fcn, void *ctx, FCN2 d)
524: {
526: ((KSP_FGMRES *)ksp->data)->modifypc = fcn;
527: ((KSP_FGMRES *)ksp->data)->modifydestroy = d;
528: ((KSP_FGMRES *)ksp->data)->modifyctx = ctx;
529: return 0;
530: }
532: PetscErrorCode KSPReset_FGMRES(KSP ksp)
533: {
534: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
535: PetscInt i;
537: PetscFree(fgmres->prevecs);
538: if (fgmres->nwork_alloc > 0) {
539: i = 0;
540: /* In the first allocation we allocated VEC_OFFSET fewer vectors in prevecs */
541: VecDestroyVecs(fgmres->mwork_alloc[i] - VEC_OFFSET, &fgmres->prevecs_user_work[i]);
542: for (i = 1; i < fgmres->nwork_alloc; i++) VecDestroyVecs(fgmres->mwork_alloc[i], &fgmres->prevecs_user_work[i]);
543: }
544: PetscFree(fgmres->prevecs_user_work);
545: if (fgmres->modifydestroy) (*fgmres->modifydestroy)(fgmres->modifyctx);
546: KSPReset_GMRES(ksp);
547: return 0;
548: }
550: PetscErrorCode KSPGMRESSetRestart_FGMRES(KSP ksp, PetscInt max_k)
551: {
552: KSP_FGMRES *gmres = (KSP_FGMRES *)ksp->data;
555: if (!ksp->setupstage) {
556: gmres->max_k = max_k;
557: } else if (gmres->max_k != max_k) {
558: gmres->max_k = max_k;
559: ksp->setupstage = KSP_SETUP_NEW;
560: /* free the data structures, then create them again */
561: KSPReset_FGMRES(ksp);
562: }
563: return 0;
564: }
566: PetscErrorCode KSPGMRESGetRestart_FGMRES(KSP ksp, PetscInt *max_k)
567: {
568: KSP_FGMRES *gmres = (KSP_FGMRES *)ksp->data;
570: *max_k = gmres->max_k;
571: return 0;
572: }
574: /*MC
575: KSPFGMRES - Implements the Flexible Generalized Minimal Residual method. [](sec_flexibleksp)
577: Options Database Keys:
578: + -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
579: . -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
580: . -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
581: vectors are allocated as needed)
582: . -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
583: . -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
584: . -ksp_gmres_cgs_refinement_type <refine_never,refine_ifneeded,refine_always> - determine if iterative refinement is used to increase the
585: stability of the classical Gram-Schmidt orthogonalization.
586: . -ksp_gmres_krylov_monitor - plot the Krylov space generated
587: . -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
588: - -ksp_fgmres_modifypcksp - modify the preconditioner using `KSPFGMRESModifyPCKSP()`
590: Level: beginner
592: Notes:
593: See `KSPFGMRESSetModifyPC()` for how to vary the preconditioner between iterations
595: Only right preconditioning is supported.
597: 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)
598: be bi-CG-stab with a preconditioner of Jacobi.
600: Developer Note:
601: This object is subclassed off of `KSPGMRES`
603: Contributed by:
604: Allison Baker
606: .seealso: [](chapter_ksp), [](sec_flexibleksp), `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSP`, `KSPGMRES`, `KSPLGMRES`,
607: `KSPGMRESSetRestart()`, `KSPGMRESSetHapTol()`, `KSPGMRESSetPreAllocateVectors()`, `KSPGMRESSetOrthogonalization()`, `KSPGMRESGetOrthogonalization()`,
608: `KSPGMRESClassicalGramSchmidtOrthogonalization()`, `KSPGMRESModifiedGramSchmidtOrthogonalization()`,
609: `KSPGMRESCGSRefinementType`, `KSPGMRESSetCGSRefinementType()`, `KSPGMRESGetCGSRefinementType()`, `KSPGMRESMonitorKrylov()`, `KSPFGMRESSetModifyPC()`,
610: `KSPFGMRESModifyPCKSP()`
611: M*/
613: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)
614: {
615: KSP_FGMRES *fgmres;
617: PetscNew(&fgmres);
619: ksp->data = (void *)fgmres;
620: ksp->ops->buildsolution = KSPBuildSolution_FGMRES;
621: ksp->ops->setup = KSPSetUp_FGMRES;
622: ksp->ops->solve = KSPSolve_FGMRES;
623: ksp->ops->reset = KSPReset_FGMRES;
624: ksp->ops->destroy = KSPDestroy_FGMRES;
625: ksp->ops->view = KSPView_GMRES;
626: ksp->ops->setfromoptions = KSPSetFromOptions_FGMRES;
627: ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
628: ksp->ops->computeeigenvalues = KSPComputeEigenvalues_GMRES;
630: KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_RIGHT, 3);
631: KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_RIGHT, 1);
633: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetPreAllocateVectors_C", KSPGMRESSetPreAllocateVectors_GMRES);
634: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetOrthogonalization_C", KSPGMRESSetOrthogonalization_GMRES);
635: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESGetOrthogonalization_C", KSPGMRESGetOrthogonalization_GMRES);
636: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetRestart_C", KSPGMRESSetRestart_FGMRES);
637: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESGetRestart_C", KSPGMRESGetRestart_FGMRES);
638: PetscObjectComposeFunction((PetscObject)ksp, "KSPFGMRESSetModifyPC_C", KSPFGMRESSetModifyPC_FGMRES);
639: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetCGSRefinementType_C", KSPGMRESSetCGSRefinementType_GMRES);
640: PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESGetCGSRefinementType_C", KSPGMRESGetCGSRefinementType_GMRES);
642: fgmres->haptol = 1.0e-30;
643: fgmres->q_preallocate = 0;
644: fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
645: fgmres->orthog = KSPGMRESClassicalGramSchmidtOrthogonalization;
646: fgmres->nrs = NULL;
647: fgmres->sol_temp = NULL;
648: fgmres->max_k = FGMRES_DEFAULT_MAXK;
649: fgmres->Rsvd = NULL;
650: fgmres->orthogwork = NULL;
651: fgmres->modifypc = KSPFGMRESModifyPCNoChange;
652: fgmres->modifyctx = NULL;
653: fgmres->modifydestroy = NULL;
654: fgmres->cgstype = KSP_GMRES_CGS_REFINE_NEVER;
655: return 0;
656: }