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: PetscMalloc1((VEC_OFFSET+2+max_k),&fgmres->prevecs);
46: PetscMalloc1((VEC_OFFSET+2+max_k),&fgmres->prevecs_user_work);
47: PetscLogObjectMemory((PetscObject)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;
69: PCGetOperators(ksp->pc,&Amat,&Pmat);
71: /* put A*x into VEC_TEMP */
72: MatMult(Amat,ksp->vec_sol,VEC_TEMP);
73: /* now put residual (-A*x + f) into vec_vv(0) */
74: VecWAXPY(VEC_VV(0),-1.0,VEC_TEMP,ksp->vec_rhs);
75: return(0);
76: }
78: /*
80: KSPFGMRESCycle - Run fgmres, possibly with restart. Return residual
81: history if requested.
83: input parameters:
84: . fgmres - structure containing parameters and work areas
86: output parameters:
87: . itcount - number of iterations used. If null, ignored.
88: . converged - 0 if not converged
91: Notes:
92: On entry, the value in vector VEC_VV(0) should be
93: the initial residual.
96: */
99: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount,KSP ksp)100: {
102: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
103: PetscReal res_norm;
104: PetscReal hapbnd,tt;
105: PetscBool hapend = PETSC_FALSE; /* indicates happy breakdown ending */
107: PetscInt loc_it; /* local count of # of dir. in Krylov space */
108: PetscInt max_k = fgmres->max_k; /* max # of directions Krylov space */
109: Mat Amat,Pmat;
112: /* Number of pseudo iterations since last restart is the number
113: of prestart directions */
114: loc_it = 0;
116: /* note: (fgmres->it) is always set one less than (loc_it) It is used in
117: KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
118: Note that when KSPFGMRESBuildSoln is called from this function,
119: (loc_it -1) is passed, so the two are equivalent */
120: fgmres->it = (loc_it - 1);
122: /* initial residual is in VEC_VV(0) - compute its norm*/
123: VecNorm(VEC_VV(0),NORM_2,&res_norm);
125: /* first entry in right-hand-side of hessenberg system is just
126: the initial residual norm */
127: *RS(0) = res_norm;
129: ksp->rnorm = res_norm;
130: KSPLogResidualHistory(ksp,res_norm);
131: KSPMonitor(ksp,ksp->its,res_norm);
133: /* check for the convergence - maybe the current guess is good enough */
134: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
135: if (ksp->reason) {
136: if (itcount) *itcount = 0;
137: return(0);
138: }
140: /* scale VEC_VV (the initial residual) */
141: VecScale(VEC_VV(0),1.0/res_norm);
143: /* MAIN ITERATION LOOP BEGINNING*/
144: /* keep iterating until we have converged OR generated the max number
145: of directions OR reached the max number of iterations for the method */
146: while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
147: if (loc_it) {
148: KSPLogResidualHistory(ksp,res_norm);
149: KSPMonitor(ksp,ksp->its,res_norm);
150: }
151: fgmres->it = (loc_it - 1);
153: /* see if more space is needed for work vectors */
154: if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
155: KSPFGMRESGetNewVectors(ksp,loc_it+1);
156: /* (loc_it+1) is passed in as number of the first vector that should
157: be allocated */
158: }
160: /* CHANGE THE PRECONDITIONER? */
161: /* ModifyPC is the callback function that can be used to
162: change the PC or its attributes before its applied */
163: (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);
166: /* apply PRECONDITIONER to direction vector and store with
167: preconditioned vectors in prevec */
168: KSP_PCApply(ksp,VEC_VV(loc_it),PREVEC(loc_it));
170: PCGetOperators(ksp->pc,&Amat,&Pmat);
171: /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
172: MatMult(Amat,PREVEC(loc_it),VEC_VV(1+loc_it));
175: /* update hessenberg matrix and do Gram-Schmidt - new direction is in
176: VEC_VV(1+loc_it)*/
177: (*fgmres->orthog)(ksp,loc_it);
179: /* new entry in hessenburg is the 2-norm of our new direction */
180: VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);
182: *HH(loc_it+1,loc_it) = tt;
183: *HES(loc_it+1,loc_it) = tt;
185: /* Happy Breakdown Check */
186: hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
187: /* RS(loc_it) contains the res_norm from the last iteration */
188: hapbnd = PetscMin(fgmres->haptol,hapbnd);
189: if (tt > hapbnd) {
190: /* scale new direction by its norm */
191: VecScale(VEC_VV(loc_it+1),1.0/tt);
192: } else {
193: /* This happens when the solution is exactly reached. */
194: /* So there is no new direction... */
195: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP to 0 */
196: hapend = PETSC_TRUE;
197: }
198: /* note that for FGMRES we could get HES(loc_it+1, loc_it) = 0 and the
199: current solution would not be exact if HES was singular. Note that
200: HH non-singular implies that HES is no singular, and HES is guaranteed
201: to be nonsingular when PREVECS are linearly independent and A is
202: nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
203: of HES). So we should really add a check to verify that HES is nonsingular.*/
206: /* Now apply rotations to new col of hessenberg (and right side of system),
207: calculate new rotation, and get new residual norm at the same time*/
208: KSPFGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
209: if (ksp->reason) break;
211: loc_it++;
212: fgmres->it = (loc_it-1); /* Add this here in case it has converged */
214: PetscObjectSAWsTakeAccess((PetscObject)ksp);
215: ksp->its++;
216: ksp->rnorm = res_norm;
217: PetscObjectSAWsGrantAccess((PetscObject)ksp);
219: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
221: /* Catch error in happy breakdown and signal convergence and break from loop */
222: if (hapend) {
223: if (!ksp->reason) {
224: if (ksp->errorifnotconverged) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"You reached the happy break down, but convergence was not indicated. Residual norm = %g",(double)res_norm);
225: else {
226: ksp->reason = KSP_DIVERGED_BREAKDOWN;
227: break;
228: }
229: }
230: }
231: }
232: /* END OF ITERATION LOOP */
233: KSPLogResidualHistory(ksp,res_norm);
235: /*
236: Monitor if we know that we will not return for a restart */
237: if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) {
238: KSPMonitor(ksp,ksp->its,res_norm);
239: }
241: if (itcount) *itcount = loc_it;
243: /*
244: Down here we have to solve for the "best" coefficients of the Krylov
245: columns, add the solution values together, and possibly unwind the
246: preconditioning from the solution
247: */
249: /* Form the solution (or the solution so far) */
250: /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
251: properly navigates */
253: KSPFGMRESBuildSoln(RS(0),ksp->vec_sol,ksp->vec_sol,ksp,loc_it-1);
254: return(0);
255: }
257: /*
258: KSPSolve_FGMRES - This routine applies the FGMRES method.
261: Input Parameter:
262: . ksp - the Krylov space object that was set to use fgmres
264: Output Parameter:
265: . outits - number of iterations used
267: */
271: PetscErrorCode KSPSolve_FGMRES(KSP ksp)272: {
274: PetscInt cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
275: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
276: PetscBool diagonalscale;
279: PCGetDiagonalScale(ksp->pc,&diagonalscale);
280: if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);
282: PetscObjectSAWsTakeAccess((PetscObject)ksp);
283: ksp->its = 0;
284: PetscObjectSAWsGrantAccess((PetscObject)ksp);
286: /* Compute the initial (NOT preconditioned) residual */
287: if (!ksp->guess_zero) {
288: KSPFGMRESResidual(ksp);
289: } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
290: VecCopy(ksp->vec_rhs,VEC_VV(0));
291: }
292: /* now the residual is in VEC_VV(0) - which is what
293: KSPFGMRESCycle expects... */
295: KSPFGMRESCycle(&cycle_its,ksp);
296: while (!ksp->reason) {
297: KSPFGMRESResidual(ksp);
298: if (ksp->its >= ksp->max_it) break;
299: KSPFGMRESCycle(&cycle_its,ksp);
300: }
301: /* mark lack of convergence */
302: if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
303: return(0);
304: }
306: extern PetscErrorCode KSPReset_FGMRES(KSP);
307: /*
309: KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.
311: */
314: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)315: {
319: KSPReset_FGMRES(ksp);
320: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",NULL);
321: KSPDestroy_GMRES(ksp);
322: return(0);
323: }
325: /*
326: KSPFGMRESBuildSoln - create the solution from the starting vector and the
327: current iterates.
329: Input parameters:
330: nrs - work area of size it + 1.
331: vguess - index of initial guess
332: vdest - index of result. Note that vguess may == vdest (replace
333: guess with the solution).
334: it - HH upper triangular part is a block of size (it+1) x (it+1)
336: This is an internal routine that knows about the FGMRES internals.
337: */
340: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs,Vec vguess,Vec vdest,KSP ksp,PetscInt it)341: {
342: PetscScalar tt;
344: PetscInt ii,k,j;
345: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
348: /* Solve for solution vector that minimizes the residual */
350: /* If it is < 0, no fgmres steps have been performed */
351: if (it < 0) {
352: VecCopy(vguess,vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
353: return(0);
354: }
356: /* so fgmres steps HAVE been performed */
358: /* solve the upper triangular system - RS is the right side and HH is
359: the upper triangular matrix - put soln in nrs */
360: if (*HH(it,it) != 0.0) {
361: nrs[it] = *RS(it) / *HH(it,it);
362: } else {
363: nrs[it] = 0.0;
364: }
365: for (ii=1; ii<=it; ii++) {
366: k = it - ii;
367: tt = *RS(k);
368: for (j=k+1; j<=it; j++) tt = tt - *HH(k,j) * nrs[j];
369: nrs[k] = tt / *HH(k,k);
370: }
372: /* Accumulate the correction to the soln of the preconditioned prob. in
373: VEC_TEMP - note that we use the preconditioned vectors */
374: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP components to 0 */
375: VecMAXPY(VEC_TEMP,it+1,nrs,&PREVEC(0));
377: /* put updated solution into vdest.*/
378: if (vdest != vguess) {
379: VecCopy(VEC_TEMP,vdest);
380: VecAXPY(vdest,1.0,vguess);
381: } else { /* replace guess with solution */
382: VecAXPY(vdest,1.0,VEC_TEMP);
383: }
384: return(0);
385: }
387: /*
389: KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
390: Return new residual.
392: input parameters:
394: . ksp - Krylov space object
395: . it - plane rotations are applied to the (it+1)th column of the
396: modified hessenberg (i.e. HH(:,it))
397: . hapend - PETSC_FALSE not happy breakdown ending.
399: output parameters:
400: . res - the new residual
402: */
405: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp,PetscInt it,PetscBool hapend,PetscReal *res)406: {
407: PetscScalar *hh,*cc,*ss,tt;
408: PetscInt j;
409: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
412: hh = HH(0,it); /* pointer to beginning of column to update - so
413: incrementing hh "steps down" the (it+1)th col of HH*/
414: cc = CC(0); /* beginning of cosine rotations */
415: ss = SS(0); /* beginning of sine rotations */
417: /* Apply all the previously computed plane rotations to the new column
418: of the Hessenberg matrix */
419: /* Note: this uses the rotation [conj(c) s ; -s c], c= cos(theta), s= sin(theta),
420: and some refs have [c s ; -conj(s) c] (don't be confused!) */
422: for (j=1; j<=it; j++) {
423: tt = *hh;
424: *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
425: hh++;
426: *hh = *cc++ * *hh - (*ss++ * tt);
427: /* hh, cc, and ss have all been incremented one by end of loop */
428: }
430: /*
431: compute the new plane rotation, and apply it to:
432: 1) the right-hand-side of the Hessenberg system (RS)
433: note: it affects RS(it) and RS(it+1)
434: 2) the new column of the Hessenberg matrix
435: note: it affects HH(it,it) which is currently pointed to
436: by hh and HH(it+1, it) (*(hh+1))
437: thus obtaining the updated value of the residual...
438: */
440: /* compute new plane rotation */
442: if (!hapend) {
443: tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
444: if (tt == 0.0) {
445: ksp->reason = KSP_DIVERGED_NULL;
446: return(0);
447: }
449: *cc = *hh / tt; /* new cosine value */
450: *ss = *(hh+1) / tt; /* new sine value */
452: /* apply to 1) and 2) */
453: *RS(it+1) = -(*ss * *RS(it));
454: *RS(it) = PetscConj(*cc) * *RS(it);
455: *hh = PetscConj(*cc) * *hh + *ss * *(hh+1);
457: /* residual is the last element (it+1) of right-hand side! */
458: *res = PetscAbsScalar(*RS(it+1));
460: } else { /* happy breakdown: HH(it+1, it) = 0, therfore we don't need to apply
461: another rotation matrix (so RH doesn't change). The new residual is
462: always the new sine term times the residual from last time (RS(it)),
463: but now the new sine rotation would be zero...so the residual should
464: be zero...so we will multiply "zero" by the last residual. This might
465: not be exactly what we want to do here -could just return "zero". */
467: *res = 0.0;
468: }
469: return(0);
470: }
472: /*
474: KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
475: VEC_VV(it), and more preconditioned work vectors, starting
476: from PREVEC(i).
478: */
481: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp,PetscInt it)482: {
483: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
484: PetscInt nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
485: PetscInt nalloc; /* number to allocate */
487: PetscInt k;
490: nalloc = fgmres->delta_allocate; /* number of vectors to allocate
491: in a single chunk */
493: /* Adjust the number to allocate to make sure that we don't exceed the
494: number of available slots (fgmres->vecs_allocated)*/
495: if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) {
496: nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
497: }
498: if (!nalloc) return(0);
500: fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */
502: /* work vectors */
503: KSPGetVecs(ksp,nalloc,&fgmres->user_work[nwork],0,NULL);
504: PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
505: for (k=0; k < nalloc; k++) {
506: fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
507: }
508: /* specify size of chunk allocated */
509: fgmres->mwork_alloc[nwork] = nalloc;
511: /* preconditioned vectors */
512: KSPGetVecs(ksp,nalloc,&fgmres->prevecs_user_work[nwork],0,NULL);
513: PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
514: for (k=0; k < nalloc; k++) {
515: fgmres->prevecs[it+VEC_OFFSET+k] = fgmres->prevecs_user_work[nwork][k];
516: }
518: /* increment the number of work vector chunks */
519: fgmres->nwork_alloc++;
520: return(0);
521: }
523: /*
525: KSPBuildSolution_FGMRES
527: Input Parameter:
528: . ksp - the Krylov space object
529: . ptr-
531: Output Parameter:
532: . result - the solution
534: Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
535: calls directly.
537: */
540: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)541: {
542: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
546: if (!ptr) {
547: if (!fgmres->sol_temp) {
548: VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
549: PetscLogObjectParent((PetscObject)ksp,(PetscObject)fgmres->sol_temp);
550: }
551: ptr = fgmres->sol_temp;
552: }
553: if (!fgmres->nrs) {
554: /* allocate the work area */
555: PetscMalloc1(fgmres->max_k,&fgmres->nrs);
556: PetscLogObjectMemory((PetscObject)ksp,fgmres->max_k*sizeof(PetscScalar));
557: }
559: KSPFGMRESBuildSoln(fgmres->nrs,ksp->vec_sol,ptr,ksp,fgmres->it);
560: if (result) *result = ptr;
561: return(0);
562: }
566: PetscErrorCode KSPSetFromOptions_FGMRES(KSP ksp)567: {
569: PetscBool flg;
572: KSPSetFromOptions_GMRES(ksp);
573: PetscOptionsHead("KSP flexible GMRES Options");
574: PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
575: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,0,0);}
576: PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp","vary the KSP based preconditioner","KSPFGMRESSetModifyPC",&flg);
577: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCKSP,0,0);}
578: PetscOptionsTail();
579: return(0);
580: }
582: typedef PetscErrorCode (*FCN1)(KSP,PetscInt,PetscInt,PetscReal,void*); /* force argument to next function to not be extern C*/
583: typedef PetscErrorCode (*FCN2)(void*);
587: static PetscErrorCode KSPFGMRESSetModifyPC_FGMRES(KSP ksp,FCN1 fcn,void *ctx,FCN2 d)588: {
591: ((KSP_FGMRES*)ksp->data)->modifypc = fcn;
592: ((KSP_FGMRES*)ksp->data)->modifydestroy = d;
593: ((KSP_FGMRES*)ksp->data)->modifyctx = ctx;
594: return(0);
595: }
600: PetscErrorCode KSPReset_FGMRES(KSP ksp)601: {
602: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
604: PetscInt i;
607: PetscFree (fgmres->prevecs);
608: for (i=0; i<fgmres->nwork_alloc; i++) {
609: VecDestroyVecs(fgmres->mwork_alloc[i],&fgmres->prevecs_user_work[i]);
610: }
611: PetscFree(fgmres->prevecs_user_work);
612: if (fgmres->modifydestroy) {
613: (*fgmres->modifydestroy)(fgmres->modifyctx);
614: }
615: KSPReset_GMRES(ksp);
616: return(0);
617: }
621: PetscErrorCode KSPGMRESSetRestart_FGMRES(KSP ksp,PetscInt max_k)622: {
623: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
627: if (max_k < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
628: if (!ksp->setupstage) {
629: gmres->max_k = max_k;
630: } else if (gmres->max_k != max_k) {
631: gmres->max_k = max_k;
632: ksp->setupstage = KSP_SETUP_NEW;
633: /* free the data structures, then create them again */
634: KSPReset_FGMRES(ksp);
635: }
636: return(0);
637: }
641: PetscErrorCode KSPGMRESGetRestart_FGMRES(KSP ksp,PetscInt *max_k)642: {
643: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
646: *max_k = gmres->max_k;
647: return(0);
648: }
650: /*MC
651: KSPFGMRES - Implements the Flexible Generalized Minimal Residual method.
652: developed by Saad with restart
655: Options Database Keys:
656: + -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
657: . -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
658: . -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
659: vectors are allocated as needed)
660: . -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
661: . -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
662: . -ksp_gmres_cgs_refinement_type <never,ifneeded,always> - determine if iterative refinement is used to increase the
663: stability of the classical Gram-Schmidt orthogonalization.
664: . -ksp_gmres_krylov_monitor - plot the Krylov space generated
665: . -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
666: - -ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()
668: Level: beginner
670: Notes: See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations
671: Only right preconditioning is supported.
673: 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)
674: be bi-CG-stab with a preconditioner of Jacobi.
676: Developer Notes: This object is subclassed off of KSPGMRES678: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
679: KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(),
680: KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(),
681: KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(), KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(),
682: KSPFGMRESModifyPCKSP()
684: M*/
688: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)689: {
690: KSP_FGMRES *fgmres;
694: PetscNewLog(ksp,&fgmres);
696: ksp->data = (void*)fgmres;
697: ksp->ops->buildsolution = KSPBuildSolution_FGMRES;
698: ksp->ops->setup = KSPSetUp_FGMRES;
699: ksp->ops->solve = KSPSolve_FGMRES;
700: ksp->ops->reset = KSPReset_FGMRES;
701: ksp->ops->destroy = KSPDestroy_FGMRES;
702: ksp->ops->view = KSPView_GMRES;
703: ksp->ops->setfromoptions = KSPSetFromOptions_FGMRES;
704: ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
705: ksp->ops->computeeigenvalues = KSPComputeEigenvalues_GMRES;
707: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,3);
708: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,0);
710: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",KSPGMRESSetPreAllocateVectors_GMRES);
711: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",KSPGMRESSetOrthogonalization_GMRES);
712: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetOrthogonalization_C",KSPGMRESGetOrthogonalization_GMRES);
713: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetRestart_C",KSPGMRESSetRestart_FGMRES);
714: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetRestart_C",KSPGMRESGetRestart_FGMRES);
715: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",KSPFGMRESSetModifyPC_FGMRES);
716: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetCGSRefinementType_C",KSPGMRESSetCGSRefinementType_GMRES);
717: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetCGSRefinementType_C",KSPGMRESGetCGSRefinementType_GMRES);
720: fgmres->haptol = 1.0e-30;
721: fgmres->q_preallocate = 0;
722: fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
723: fgmres->orthog = KSPGMRESClassicalGramSchmidtOrthogonalization;
724: fgmres->nrs = 0;
725: fgmres->sol_temp = 0;
726: fgmres->max_k = FGMRES_DEFAULT_MAXK;
727: fgmres->Rsvd = 0;
728: fgmres->orthogwork = 0;
729: fgmres->modifypc = KSPFGMRESModifyPCNoChange;
730: fgmres->modifyctx = NULL;
731: fgmres->modifydestroy = NULL;
732: fgmres->cgstype = KSP_GMRES_CGS_REFINE_NEVER;
733: return(0);
734: }