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: PetscFunctionBegin;
35: max_k = fgmres->max_k;
37: PetscCall(KSPSetUp_GMRES(ksp));
39: PetscCall(PetscMalloc1(max_k + 2, &fgmres->prevecs));
40: PetscCall(PetscMalloc1(max_k + 2, &fgmres->prevecs_user_work));
42: /* fgmres->vv_allocated includes extra work vectors, which are not used in the additional
43: block of vectors used to store the preconditioned directions, hence the -VEC_OFFSET
44: term for this first allocation of vectors holding preconditioned directions */
45: PetscCall(KSPCreateVecs(ksp, fgmres->vv_allocated - VEC_OFFSET, &fgmres->prevecs_user_work[0], 0, NULL));
46: for (k = 0; k < fgmres->vv_allocated - VEC_OFFSET; k++) fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
47: PetscFunctionReturn(PETSC_SUCCESS);
48: }
50: /*
51: KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
52: */
53: static PetscErrorCode KSPFGMRESResidual(KSP ksp)
54: {
55: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
56: Mat Amat, Pmat;
58: PetscFunctionBegin;
59: PetscCall(PCGetOperators(ksp->pc, &Amat, &Pmat));
61: /* put A*x into VEC_TEMP */
62: PetscCall(KSP_MatMult(ksp, Amat, ksp->vec_sol, VEC_TEMP));
63: /* now put residual (-A*x + f) into vec_vv(0) */
64: PetscCall(VecWAXPY(VEC_VV(0), -1.0, VEC_TEMP, ksp->vec_rhs));
65: PetscFunctionReturn(PETSC_SUCCESS);
66: }
68: /*
70: KSPFGMRESCycle - Run fgmres, possibly with restart. Return residual
71: history if requested.
73: input parameters:
74: . fgmres - structure containing parameters and work areas
76: output parameters:
77: . itcount - number of iterations used. If null, ignored.
78: . converged - 0 if not converged
80: Notes:
81: On entry, the value in vector VEC_VV(0) should be
82: the initial residual.
84: */
85: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount, KSP ksp)
86: {
87: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
88: PetscReal res_norm;
89: PetscReal hapbnd, tt;
90: PetscBool hapend = PETSC_FALSE; /* indicates happy breakdown ending */
91: PetscInt loc_it; /* local count of # of dir. in Krylov space */
92: PetscInt max_k = fgmres->max_k; /* max # of directions Krylov space */
93: Mat Amat, Pmat;
95: PetscFunctionBegin;
96: /* Number of pseudo iterations since last restart is the number
97: of prestart directions */
98: loc_it = 0;
100: /* note: (fgmres->it) is always set one less than (loc_it) It is used in
101: KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
102: Note that when KSPFGMRESBuildSoln is called from this function,
103: (loc_it -1) is passed, so the two are equivalent */
104: fgmres->it = (loc_it - 1);
106: /* initial residual is in VEC_VV(0) - compute its norm*/
107: PetscCall(VecNorm(VEC_VV(0), NORM_2, &res_norm));
108: KSPCheckNorm(ksp, res_norm);
110: /* first entry in right-hand-side of hessenberg system is just
111: the initial residual norm */
112: *RS(0) = res_norm;
114: ksp->rnorm = res_norm;
115: PetscCall(KSPLogResidualHistory(ksp, res_norm));
116: PetscCall(KSPMonitor(ksp, ksp->its, res_norm));
118: /* check for the convergence - maybe the current guess is good enough */
119: PetscCall((*ksp->converged)(ksp, ksp->its, res_norm, &ksp->reason, ksp->cnvP));
120: if (ksp->reason) {
121: if (itcount) *itcount = 0;
122: PetscFunctionReturn(PETSC_SUCCESS);
123: }
125: /* scale VEC_VV (the initial residual) */
126: PetscCall(VecScale(VEC_VV(0), 1.0 / res_norm));
128: /* MAIN ITERATION LOOP BEGINNING*/
129: /* keep iterating until we have converged OR generated the max number
130: of directions OR reached the max number of iterations for the method */
131: while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
132: if (loc_it) {
133: PetscCall(KSPLogResidualHistory(ksp, res_norm));
134: PetscCall(KSPMonitor(ksp, ksp->its, res_norm));
135: }
136: fgmres->it = (loc_it - 1);
138: /* see if more space is needed for work vectors */
139: if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
140: PetscCall(KSPFGMRESGetNewVectors(ksp, loc_it + 1));
141: /* (loc_it+1) is passed in as number of the first vector that should
142: be allocated */
143: }
145: /* CHANGE THE PRECONDITIONER? */
146: /* ModifyPC is the callback function that can be used to
147: change the PC or its attributes before its applied */
148: PetscCall((*fgmres->modifypc)(ksp, ksp->its, loc_it, res_norm, fgmres->modifyctx));
150: /* apply PRECONDITIONER to direction vector and store with
151: preconditioned vectors in prevec */
152: PetscCall(KSP_PCApply(ksp, VEC_VV(loc_it), PREVEC(loc_it)));
154: PetscCall(PCGetOperators(ksp->pc, &Amat, &Pmat));
155: /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
156: PetscCall(KSP_MatMult(ksp, Amat, PREVEC(loc_it), VEC_VV(1 + loc_it)));
158: /* update hessenberg matrix and do Gram-Schmidt - new direction is in
159: VEC_VV(1+loc_it)*/
160: PetscCall((*fgmres->orthog)(ksp, loc_it));
162: /* new entry in hessenburg is the 2-norm of our new direction */
163: PetscCall(VecNorm(VEC_VV(loc_it + 1), NORM_2, &tt));
164: KSPCheckNorm(ksp, tt);
166: *HH(loc_it + 1, loc_it) = tt;
167: *HES(loc_it + 1, loc_it) = tt;
169: /* Happy Breakdown Check */
170: hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
171: /* RS(loc_it) contains the res_norm from the last iteration */
172: hapbnd = PetscMin(fgmres->haptol, hapbnd);
173: if (tt > hapbnd) {
174: /* scale new direction by its norm */
175: PetscCall(VecScale(VEC_VV(loc_it + 1), 1.0 / tt));
176: } else {
177: /* This happens when the solution is exactly reached. */
178: /* So there is no new direction... */
179: PetscCall(VecSet(VEC_TEMP, 0.0)); /* set VEC_TEMP to 0 */
180: hapend = PETSC_TRUE;
181: }
182: /* note that for FGMRES we could get HES(loc_it+1, loc_it) = 0 and the
183: current solution would not be exact if HES was singular. Note that
184: HH non-singular implies that HES is no singular, and HES is guaranteed
185: to be nonsingular when PREVECS are linearly independent and A is
186: nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
187: of HES). So we should really add a check to verify that HES is nonsingular.*/
189: /* Now apply rotations to new col of hessenberg (and right side of system),
190: calculate new rotation, and get new residual norm at the same time*/
191: PetscCall(KSPFGMRESUpdateHessenberg(ksp, loc_it, hapend, &res_norm));
192: if (ksp->reason) break;
194: loc_it++;
195: fgmres->it = (loc_it - 1); /* Add this here in case it has converged */
197: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)ksp));
198: ksp->its++;
199: ksp->rnorm = res_norm;
200: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)ksp));
202: PetscCall((*ksp->converged)(ksp, ksp->its, res_norm, &ksp->reason, ksp->cnvP));
204: /* Catch error in happy breakdown and signal convergence and break from loop */
205: if (hapend) {
206: if (!ksp->reason) {
207: PetscCheck(!ksp->errorifnotconverged, PetscObjectComm((PetscObject)ksp), PETSC_ERR_NOT_CONVERGED, "You reached the happy break down, but convergence was not indicated. Residual norm = %g", (double)res_norm);
208: ksp->reason = KSP_DIVERGED_BREAKDOWN;
209: break;
210: }
211: }
212: }
213: /* END OF ITERATION LOOP */
214: PetscCall(KSPLogResidualHistory(ksp, res_norm));
216: /*
217: Monitor if we know that we will not return for a restart */
218: if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) PetscCall(KSPMonitor(ksp, ksp->its, res_norm));
220: if (itcount) *itcount = loc_it;
222: /*
223: Down here we have to solve for the "best" coefficients of the Krylov
224: columns, add the solution values together, and possibly unwind the
225: preconditioning from the solution
226: */
228: /* Form the solution (or the solution so far) */
229: /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
230: properly navigates */
232: PetscCall(KSPFGMRESBuildSoln(RS(0), ksp->vec_sol, ksp->vec_sol, ksp, loc_it - 1));
233: PetscFunctionReturn(PETSC_SUCCESS);
234: }
236: /*
237: KSPSolve_FGMRES - This routine applies the FGMRES method.
239: Input Parameter:
240: . ksp - the Krylov space object that was set to use fgmres
242: Output Parameter:
243: . outits - number of iterations used
245: */
247: PetscErrorCode KSPSolve_FGMRES(KSP ksp)
248: {
249: PetscInt cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
250: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
251: PetscBool diagonalscale;
253: PetscFunctionBegin;
254: PetscCall(PCGetDiagonalScale(ksp->pc, &diagonalscale));
255: PetscCheck(!diagonalscale, PetscObjectComm((PetscObject)ksp), PETSC_ERR_SUP, "Krylov method %s does not support diagonal scaling", ((PetscObject)ksp)->type_name);
257: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)ksp));
258: ksp->its = 0;
259: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)ksp));
261: /* Compute the initial (NOT preconditioned) residual */
262: if (!ksp->guess_zero) {
263: PetscCall(KSPFGMRESResidual(ksp));
264: } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
265: PetscCall(VecCopy(ksp->vec_rhs, VEC_VV(0)));
266: }
267: /* 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 */
268: if (ksp->reason == KSP_DIVERGED_PC_FAILED) PetscCall(VecSetInf(VEC_VV(0)));
270: /* now the residual is in VEC_VV(0) - which is what
271: KSPFGMRESCycle expects... */
273: PetscCall(KSPFGMRESCycle(&cycle_its, ksp));
274: while (!ksp->reason) {
275: PetscCall(KSPFGMRESResidual(ksp));
276: if (ksp->its >= ksp->max_it) break;
277: PetscCall(KSPFGMRESCycle(&cycle_its, ksp));
278: }
279: /* mark lack of convergence */
280: if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
281: PetscFunctionReturn(PETSC_SUCCESS);
282: }
284: extern PetscErrorCode KSPReset_FGMRES(KSP);
285: /*
287: KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.
289: */
290: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)
291: {
292: PetscFunctionBegin;
293: PetscCall(KSPReset_FGMRES(ksp));
294: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPFGMRESSetModifyPC_C", NULL));
295: PetscCall(KSPDestroy_GMRES(ksp));
296: PetscFunctionReturn(PETSC_SUCCESS);
297: }
299: /*
300: KSPFGMRESBuildSoln - create the solution from the starting vector and the
301: current iterates.
303: Input parameters:
304: nrs - work area of size it + 1.
305: vguess - index of initial guess
306: vdest - index of result. Note that vguess may == vdest (replace
307: guess with the solution).
308: it - HH upper triangular part is a block of size (it+1) x (it+1)
310: This is an internal routine that knows about the FGMRES internals.
311: */
312: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs, Vec vguess, Vec vdest, KSP ksp, PetscInt it)
313: {
314: PetscScalar tt;
315: PetscInt ii, k, j;
316: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
318: PetscFunctionBegin;
319: /* Solve for solution vector that minimizes the residual */
321: /* If it is < 0, no fgmres steps have been performed */
322: if (it < 0) {
323: PetscCall(VecCopy(vguess, vdest)); /* VecCopy() is smart, exists immediately if vguess == vdest */
324: PetscFunctionReturn(PETSC_SUCCESS);
325: }
327: /* so fgmres steps HAVE been performed */
329: /* solve the upper triangular system - RS is the right side and HH is
330: the upper triangular matrix - put soln in nrs */
331: if (*HH(it, it) != 0.0) {
332: nrs[it] = *RS(it) / *HH(it, it);
333: } else {
334: nrs[it] = 0.0;
335: }
336: for (ii = 1; ii <= it; ii++) {
337: k = it - ii;
338: tt = *RS(k);
339: for (j = k + 1; j <= it; j++) tt = tt - *HH(k, j) * nrs[j];
340: nrs[k] = tt / *HH(k, k);
341: }
343: /* Accumulate the correction to the soln of the preconditioned prob. in
344: VEC_TEMP - note that we use the preconditioned vectors */
345: PetscCall(VecSet(VEC_TEMP, 0.0)); /* set VEC_TEMP components to 0 */
346: PetscCall(VecMAXPY(VEC_TEMP, it + 1, nrs, &PREVEC(0)));
348: /* put updated solution into vdest.*/
349: if (vdest != vguess) {
350: PetscCall(VecCopy(VEC_TEMP, vdest));
351: PetscCall(VecAXPY(vdest, 1.0, vguess));
352: } else { /* replace guess with solution */
353: PetscCall(VecAXPY(vdest, 1.0, VEC_TEMP));
354: }
355: PetscFunctionReturn(PETSC_SUCCESS);
356: }
358: /*
360: KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
361: Return new residual.
363: input parameters:
365: . ksp - Krylov space object
366: . it - plane rotations are applied to the (it+1)th column of the
367: modified hessenberg (i.e. HH(:,it))
368: . hapend - PETSC_FALSE not happy breakdown ending.
370: output parameters:
371: . res - the new residual
373: */
374: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp, PetscInt it, PetscBool hapend, PetscReal *res)
375: {
376: PetscScalar *hh, *cc, *ss, tt;
377: PetscInt j;
378: KSP_FGMRES *fgmres = (KSP_FGMRES *)(ksp->data);
380: PetscFunctionBegin;
381: hh = HH(0, it); /* pointer to beginning of column to update - so
382: incrementing hh "steps down" the (it+1)th col of HH*/
383: cc = CC(0); /* beginning of cosine rotations */
384: ss = SS(0); /* beginning of sine rotations */
386: /* Apply all the previously computed plane rotations to the new column
387: of the Hessenberg matrix */
388: /* Note: this uses the rotation [conj(c) s ; -s c], c= cos(theta), s= sin(theta),
389: and some refs have [c s ; -conj(s) c] (don't be confused!) */
391: for (j = 1; j <= it; j++) {
392: tt = *hh;
393: *hh = PetscConj(*cc) * tt + *ss * *(hh + 1);
394: hh++;
395: *hh = *cc++ * *hh - (*ss++ * tt);
396: /* hh, cc, and ss have all been incremented one by end of loop */
397: }
399: /*
400: compute the new plane rotation, and apply it to:
401: 1) the right-hand-side of the Hessenberg system (RS)
402: note: it affects RS(it) and RS(it+1)
403: 2) the new column of the Hessenberg matrix
404: note: it affects HH(it,it) which is currently pointed to
405: by hh and HH(it+1, it) (*(hh+1))
406: thus obtaining the updated value of the residual...
407: */
409: /* compute new plane rotation */
411: if (!hapend) {
412: tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh + 1)) * *(hh + 1));
413: if (tt == 0.0) {
414: ksp->reason = KSP_DIVERGED_NULL;
415: PetscFunctionReturn(PETSC_SUCCESS);
416: }
418: *cc = *hh / tt; /* new cosine value */
419: *ss = *(hh + 1) / tt; /* new sine value */
421: /* apply to 1) and 2) */
422: *RS(it + 1) = -(*ss * *RS(it));
423: *RS(it) = PetscConj(*cc) * *RS(it);
424: *hh = PetscConj(*cc) * *hh + *ss * *(hh + 1);
426: /* residual is the last element (it+1) of right-hand side! */
427: *res = PetscAbsScalar(*RS(it + 1));
429: } else { /* happy breakdown: HH(it+1, it) = 0, therefore we don't need to apply
430: another rotation matrix (so RH doesn't change). The new residual is
431: always the new sine term times the residual from last time (RS(it)),
432: but now the new sine rotation would be zero...so the residual should
433: be zero...so we will multiply "zero" by the last residual. This might
434: not be exactly what we want to do here -could just return "zero". */
436: *res = 0.0;
437: }
438: PetscFunctionReturn(PETSC_SUCCESS);
439: }
441: /*
443: KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
444: VEC_VV(it), and more preconditioned work vectors, starting
445: from PREVEC(i).
447: */
448: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp, PetscInt it)
449: {
450: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
451: PetscInt nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
452: PetscInt nalloc; /* number to allocate */
453: PetscInt k;
455: PetscFunctionBegin;
456: nalloc = fgmres->delta_allocate; /* number of vectors to allocate
457: in a single chunk */
459: /* Adjust the number to allocate to make sure that we don't exceed the
460: number of available slots (fgmres->vecs_allocated)*/
461: if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
462: if (!nalloc) PetscFunctionReturn(PETSC_SUCCESS);
464: fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */
466: /* work vectors */
467: PetscCall(KSPCreateVecs(ksp, nalloc, &fgmres->user_work[nwork], 0, NULL));
468: for (k = 0; k < nalloc; k++) fgmres->vecs[it + VEC_OFFSET + k] = fgmres->user_work[nwork][k];
469: /* specify size of chunk allocated */
470: fgmres->mwork_alloc[nwork] = nalloc;
472: /* preconditioned vectors */
473: PetscCall(KSPCreateVecs(ksp, nalloc, &fgmres->prevecs_user_work[nwork], 0, NULL));
474: for (k = 0; k < nalloc; k++) fgmres->prevecs[it + k] = fgmres->prevecs_user_work[nwork][k];
476: /* increment the number of work vector chunks */
477: fgmres->nwork_alloc++;
478: PetscFunctionReturn(PETSC_SUCCESS);
479: }
481: /*
483: KSPBuildSolution_FGMRES
485: Input Parameter:
486: . ksp - the Krylov space object
487: . ptr-
489: Output Parameter:
490: . result - the solution
492: Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
493: calls directly.
495: */
496: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp, Vec ptr, Vec *result)
497: {
498: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
500: PetscFunctionBegin;
501: if (!ptr) {
502: if (!fgmres->sol_temp) PetscCall(VecDuplicate(ksp->vec_sol, &fgmres->sol_temp));
503: ptr = fgmres->sol_temp;
504: }
505: if (!fgmres->nrs) {
506: /* allocate the work area */
507: PetscCall(PetscMalloc1(fgmres->max_k, &fgmres->nrs));
508: }
510: PetscCall(KSPFGMRESBuildSoln(fgmres->nrs, ksp->vec_sol, ptr, ksp, fgmres->it));
511: if (result) *result = ptr;
512: PetscFunctionReturn(PETSC_SUCCESS);
513: }
515: PetscErrorCode KSPSetFromOptions_FGMRES(KSP ksp, PetscOptionItems *PetscOptionsObject)
516: {
517: PetscBool flg;
519: PetscFunctionBegin;
520: PetscCall(KSPSetFromOptions_GMRES(ksp, PetscOptionsObject));
521: PetscOptionsHeadBegin(PetscOptionsObject, "KSP flexible GMRES Options");
522: PetscCall(PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange", "do not vary the preconditioner", "KSPFGMRESSetModifyPC", &flg));
523: if (flg) PetscCall(KSPFGMRESSetModifyPC(ksp, KSPFGMRESModifyPCNoChange, NULL, NULL));
524: PetscCall(PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp", "vary the KSP based preconditioner", "KSPFGMRESSetModifyPC", &flg));
525: if (flg) PetscCall(KSPFGMRESSetModifyPC(ksp, KSPFGMRESModifyPCKSP, NULL, NULL));
526: PetscOptionsHeadEnd();
527: PetscFunctionReturn(PETSC_SUCCESS);
528: }
530: typedef PetscErrorCode (*FCN1)(KSP, PetscInt, PetscInt, PetscReal, void *); /* force argument to next function to not be extern C*/
531: typedef PetscErrorCode (*FCN2)(void *);
533: static PetscErrorCode KSPFGMRESSetModifyPC_FGMRES(KSP ksp, FCN1 fcn, void *ctx, FCN2 d)
534: {
535: PetscFunctionBegin;
537: ((KSP_FGMRES *)ksp->data)->modifypc = fcn;
538: ((KSP_FGMRES *)ksp->data)->modifydestroy = d;
539: ((KSP_FGMRES *)ksp->data)->modifyctx = ctx;
540: PetscFunctionReturn(PETSC_SUCCESS);
541: }
543: PetscErrorCode KSPReset_FGMRES(KSP ksp)
544: {
545: KSP_FGMRES *fgmres = (KSP_FGMRES *)ksp->data;
546: PetscInt i;
548: PetscFunctionBegin;
549: PetscCall(PetscFree(fgmres->prevecs));
550: if (fgmres->nwork_alloc > 0) {
551: i = 0;
552: /* In the first allocation we allocated VEC_OFFSET fewer vectors in prevecs */
553: PetscCall(VecDestroyVecs(fgmres->mwork_alloc[i] - VEC_OFFSET, &fgmres->prevecs_user_work[i]));
554: for (i = 1; i < fgmres->nwork_alloc; i++) PetscCall(VecDestroyVecs(fgmres->mwork_alloc[i], &fgmres->prevecs_user_work[i]));
555: }
556: PetscCall(PetscFree(fgmres->prevecs_user_work));
557: if (fgmres->modifydestroy) PetscCall((*fgmres->modifydestroy)(fgmres->modifyctx));
558: PetscCall(KSPReset_GMRES(ksp));
559: PetscFunctionReturn(PETSC_SUCCESS);
560: }
562: PetscErrorCode KSPGMRESSetRestart_FGMRES(KSP ksp, PetscInt max_k)
563: {
564: KSP_FGMRES *gmres = (KSP_FGMRES *)ksp->data;
566: PetscFunctionBegin;
567: PetscCheck(max_k >= 1, PetscObjectComm((PetscObject)ksp), PETSC_ERR_ARG_OUTOFRANGE, "Restart must be positive");
568: if (!ksp->setupstage) {
569: gmres->max_k = max_k;
570: } else if (gmres->max_k != max_k) {
571: gmres->max_k = max_k;
572: ksp->setupstage = KSP_SETUP_NEW;
573: /* free the data structures, then create them again */
574: PetscCall(KSPReset_FGMRES(ksp));
575: }
576: PetscFunctionReturn(PETSC_SUCCESS);
577: }
579: PetscErrorCode KSPGMRESGetRestart_FGMRES(KSP ksp, PetscInt *max_k)
580: {
581: KSP_FGMRES *gmres = (KSP_FGMRES *)ksp->data;
583: PetscFunctionBegin;
584: *max_k = gmres->max_k;
585: PetscFunctionReturn(PETSC_SUCCESS);
586: }
588: /*MC
589: KSPFGMRES - Implements the Flexible Generalized Minimal Residual method. [](sec_flexibleksp)
591: Options Database Keys:
592: + -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
593: . -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
594: . -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
595: vectors are allocated as needed)
596: . -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
597: . -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
598: . -ksp_gmres_cgs_refinement_type <refine_never,refine_ifneeded,refine_always> - determine if iterative refinement is used to increase the
599: stability of the classical Gram-Schmidt orthogonalization.
600: . -ksp_gmres_krylov_monitor - plot the Krylov space generated
601: . -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
602: - -ksp_fgmres_modifypcksp - modify the preconditioner using `KSPFGMRESModifyPCKSP()`
604: Level: beginner
606: Notes:
607: See `KSPFGMRESSetModifyPC()` for how to vary the preconditioner between iterations
609: Only right preconditioning is supported.
611: 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)
612: be bi-CG-stab with a preconditioner of Jacobi.
614: Developer Note:
615: This object is subclassed off of `KSPGMRES`
617: Contributed by:
618: Allison Baker
620: .seealso: [](ch_ksp), [](sec_flexibleksp), `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSP`, `KSPGMRES`, `KSPLGMRES`,
621: `KSPGMRESSetRestart()`, `KSPGMRESSetHapTol()`, `KSPGMRESSetPreAllocateVectors()`, `KSPGMRESSetOrthogonalization()`, `KSPGMRESGetOrthogonalization()`,
622: `KSPGMRESClassicalGramSchmidtOrthogonalization()`, `KSPGMRESModifiedGramSchmidtOrthogonalization()`,
623: `KSPGMRESCGSRefinementType`, `KSPGMRESSetCGSRefinementType()`, `KSPGMRESGetCGSRefinementType()`, `KSPGMRESMonitorKrylov()`, `KSPFGMRESSetModifyPC()`,
624: `KSPFGMRESModifyPCKSP()`
625: M*/
627: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)
628: {
629: KSP_FGMRES *fgmres;
631: PetscFunctionBegin;
632: PetscCall(PetscNew(&fgmres));
634: ksp->data = (void *)fgmres;
635: ksp->ops->buildsolution = KSPBuildSolution_FGMRES;
636: ksp->ops->setup = KSPSetUp_FGMRES;
637: ksp->ops->solve = KSPSolve_FGMRES;
638: ksp->ops->reset = KSPReset_FGMRES;
639: ksp->ops->destroy = KSPDestroy_FGMRES;
640: ksp->ops->view = KSPView_GMRES;
641: ksp->ops->setfromoptions = KSPSetFromOptions_FGMRES;
642: ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
643: ksp->ops->computeeigenvalues = KSPComputeEigenvalues_GMRES;
645: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_RIGHT, 3));
646: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_RIGHT, 1));
648: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetPreAllocateVectors_C", KSPGMRESSetPreAllocateVectors_GMRES));
649: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetOrthogonalization_C", KSPGMRESSetOrthogonalization_GMRES));
650: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESGetOrthogonalization_C", KSPGMRESGetOrthogonalization_GMRES));
651: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetRestart_C", KSPGMRESSetRestart_FGMRES));
652: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESGetRestart_C", KSPGMRESGetRestart_FGMRES));
653: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPFGMRESSetModifyPC_C", KSPFGMRESSetModifyPC_FGMRES));
654: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESSetCGSRefinementType_C", KSPGMRESSetCGSRefinementType_GMRES));
655: PetscCall(PetscObjectComposeFunction((PetscObject)ksp, "KSPGMRESGetCGSRefinementType_C", KSPGMRESGetCGSRefinementType_GMRES));
657: fgmres->haptol = 1.0e-30;
658: fgmres->q_preallocate = 0;
659: fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
660: fgmres->orthog = KSPGMRESClassicalGramSchmidtOrthogonalization;
661: fgmres->nrs = NULL;
662: fgmres->sol_temp = NULL;
663: fgmres->max_k = FGMRES_DEFAULT_MAXK;
664: fgmres->Rsvd = NULL;
665: fgmres->orthogwork = NULL;
666: fgmres->modifypc = KSPFGMRESModifyPCNoChange;
667: fgmres->modifyctx = NULL;
668: fgmres->modifydestroy = NULL;
669: fgmres->cgstype = KSP_GMRES_CGS_REFINE_NEVER;
670: PetscFunctionReturn(PETSC_SUCCESS);
671: }