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(max_k+2,&fgmres->prevecs);
46: PetscMalloc1(max_k+2,&fgmres->prevecs_user_work);
47: PetscLogObjectMemory((PetscObject)ksp,(max_k+2)*(2*sizeof(void*)));
49: /* fgmres->vv_allocated includes extra work vectors, which are not used in the additional
50: block of vectors used to store the preconditioned directions, hence the -VEC_OFFSET
51: term for this first allocation of vectors holding preconditioned directions */
52: KSPCreateVecs(ksp,fgmres->vv_allocated-VEC_OFFSET,&fgmres->prevecs_user_work[0],0,NULL);
53: PetscLogObjectParents(ksp,fgmres->vv_allocated-VEC_OFFSET,fgmres->prevecs_user_work[0]);
54: for (k=0; k < fgmres->vv_allocated - VEC_OFFSET ; k++) {
55: fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
56: }
57: return(0);
58: }
60: /*
61: KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
62: */
65: static PetscErrorCode KSPFGMRESResidual(KSP ksp) 66: {
67: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
68: Mat Amat,Pmat;
72: PCGetOperators(ksp->pc,&Amat,&Pmat);
74: /* put A*x into VEC_TEMP */
75: KSP_MatMult(ksp,Amat,ksp->vec_sol,VEC_TEMP);
76: /* now put residual (-A*x + f) into vec_vv(0) */
77: VecWAXPY(VEC_VV(0),-1.0,VEC_TEMP,ksp->vec_rhs);
78: return(0);
79: }
81: /*
83: KSPFGMRESCycle - Run fgmres, possibly with restart. Return residual
84: history if requested.
86: input parameters:
87: . fgmres - structure containing parameters and work areas
89: output parameters:
90: . itcount - number of iterations used. If null, ignored.
91: . converged - 0 if not converged
94: Notes:
95: On entry, the value in vector VEC_VV(0) should be
96: the initial residual.
99: */
102: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount,KSP ksp)103: {
105: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
106: PetscReal res_norm;
107: PetscReal hapbnd,tt;
108: PetscBool hapend = PETSC_FALSE; /* indicates happy breakdown ending */
110: PetscInt loc_it; /* local count of # of dir. in Krylov space */
111: PetscInt max_k = fgmres->max_k; /* max # of directions Krylov space */
112: Mat Amat,Pmat;
115: /* Number of pseudo iterations since last restart is the number
116: of prestart directions */
117: loc_it = 0;
119: /* note: (fgmres->it) is always set one less than (loc_it) It is used in
120: KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
121: Note that when KSPFGMRESBuildSoln is called from this function,
122: (loc_it -1) is passed, so the two are equivalent */
123: fgmres->it = (loc_it - 1);
125: /* initial residual is in VEC_VV(0) - compute its norm*/
126: VecNorm(VEC_VV(0),NORM_2,&res_norm);
127: KSPCheckNorm(ksp,res_norm);
129: /* first entry in right-hand-side of hessenberg system is just
130: the initial residual norm */
131: *RS(0) = res_norm;
133: ksp->rnorm = res_norm;
134: KSPLogResidualHistory(ksp,res_norm);
135: KSPMonitor(ksp,ksp->its,res_norm);
137: /* check for the convergence - maybe the current guess is good enough */
138: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
139: if (ksp->reason) {
140: if (itcount) *itcount = 0;
141: return(0);
142: }
144: /* scale VEC_VV (the initial residual) */
145: VecScale(VEC_VV(0),1.0/res_norm);
147: /* MAIN ITERATION LOOP BEGINNING*/
148: /* keep iterating until we have converged OR generated the max number
149: of directions OR reached the max number of iterations for the method */
150: while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
151: if (loc_it) {
152: KSPLogResidualHistory(ksp,res_norm);
153: KSPMonitor(ksp,ksp->its,res_norm);
154: }
155: fgmres->it = (loc_it - 1);
157: /* see if more space is needed for work vectors */
158: if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
159: KSPFGMRESGetNewVectors(ksp,loc_it+1);
160: /* (loc_it+1) is passed in as number of the first vector that should
161: be allocated */
162: }
164: /* CHANGE THE PRECONDITIONER? */
165: /* ModifyPC is the callback function that can be used to
166: change the PC or its attributes before its applied */
167: (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);
170: /* apply PRECONDITIONER to direction vector and store with
171: preconditioned vectors in prevec */
172: KSP_PCApply(ksp,VEC_VV(loc_it),PREVEC(loc_it));
174: PCGetOperators(ksp->pc,&Amat,&Pmat);
175: /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
176: KSP_MatMult(ksp,Amat,PREVEC(loc_it),VEC_VV(1+loc_it));
179: /* update hessenberg matrix and do Gram-Schmidt - new direction is in
180: VEC_VV(1+loc_it)*/
181: (*fgmres->orthog)(ksp,loc_it);
183: /* new entry in hessenburg is the 2-norm of our new direction */
184: VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);
186: *HH(loc_it+1,loc_it) = tt;
187: *HES(loc_it+1,loc_it) = tt;
189: /* Happy Breakdown Check */
190: hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
191: /* RS(loc_it) contains the res_norm from the last iteration */
192: hapbnd = PetscMin(fgmres->haptol,hapbnd);
193: if (tt > hapbnd) {
194: /* scale new direction by its norm */
195: VecScale(VEC_VV(loc_it+1),1.0/tt);
196: } else {
197: /* This happens when the solution is exactly reached. */
198: /* So there is no new direction... */
199: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP to 0 */
200: hapend = PETSC_TRUE;
201: }
202: /* note that for FGMRES we could get HES(loc_it+1, loc_it) = 0 and the
203: current solution would not be exact if HES was singular. Note that
204: HH non-singular implies that HES is no singular, and HES is guaranteed
205: to be nonsingular when PREVECS are linearly independent and A is
206: nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
207: of HES). So we should really add a check to verify that HES is nonsingular.*/
210: /* Now apply rotations to new col of hessenberg (and right side of system),
211: calculate new rotation, and get new residual norm at the same time*/
212: KSPFGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
213: if (ksp->reason) break;
215: loc_it++;
216: fgmres->it = (loc_it-1); /* Add this here in case it has converged */
218: PetscObjectSAWsTakeAccess((PetscObject)ksp);
219: ksp->its++;
220: ksp->rnorm = res_norm;
221: PetscObjectSAWsGrantAccess((PetscObject)ksp);
223: (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
225: /* Catch error in happy breakdown and signal convergence and break from loop */
226: if (hapend) {
227: if (!ksp->reason) {
228: 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);
229: else {
230: ksp->reason = KSP_DIVERGED_BREAKDOWN;
231: break;
232: }
233: }
234: }
235: }
236: /* END OF ITERATION LOOP */
237: KSPLogResidualHistory(ksp,res_norm);
239: /*
240: Monitor if we know that we will not return for a restart */
241: if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) {
242: KSPMonitor(ksp,ksp->its,res_norm);
243: }
245: if (itcount) *itcount = loc_it;
247: /*
248: Down here we have to solve for the "best" coefficients of the Krylov
249: columns, add the solution values together, and possibly unwind the
250: preconditioning from the solution
251: */
253: /* Form the solution (or the solution so far) */
254: /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
255: properly navigates */
257: KSPFGMRESBuildSoln(RS(0),ksp->vec_sol,ksp->vec_sol,ksp,loc_it-1);
258: return(0);
259: }
261: /*
262: KSPSolve_FGMRES - This routine applies the FGMRES method.
265: Input Parameter:
266: . ksp - the Krylov space object that was set to use fgmres
268: Output Parameter:
269: . outits - number of iterations used
271: */
275: PetscErrorCode KSPSolve_FGMRES(KSP ksp)276: {
278: PetscInt cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
279: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
280: PetscBool diagonalscale;
283: PCGetDiagonalScale(ksp->pc,&diagonalscale);
284: if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);
286: PetscObjectSAWsTakeAccess((PetscObject)ksp);
287: ksp->its = 0;
288: PetscObjectSAWsGrantAccess((PetscObject)ksp);
290: /* Compute the initial (NOT preconditioned) residual */
291: if (!ksp->guess_zero) {
292: KSPFGMRESResidual(ksp);
293: } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
294: VecCopy(ksp->vec_rhs,VEC_VV(0));
295: }
296: /* now the residual is in VEC_VV(0) - which is what
297: KSPFGMRESCycle expects... */
299: KSPFGMRESCycle(&cycle_its,ksp);
300: while (!ksp->reason) {
301: KSPFGMRESResidual(ksp);
302: if (ksp->its >= ksp->max_it) break;
303: KSPFGMRESCycle(&cycle_its,ksp);
304: }
305: /* mark lack of convergence */
306: if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
307: return(0);
308: }
310: extern PetscErrorCode KSPReset_FGMRES(KSP);
311: /*
313: KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.
315: */
318: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)319: {
323: KSPReset_FGMRES(ksp);
324: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",NULL);
325: KSPDestroy_GMRES(ksp);
326: return(0);
327: }
329: /*
330: KSPFGMRESBuildSoln - create the solution from the starting vector and the
331: current iterates.
333: Input parameters:
334: nrs - work area of size it + 1.
335: vguess - index of initial guess
336: vdest - index of result. Note that vguess may == vdest (replace
337: guess with the solution).
338: it - HH upper triangular part is a block of size (it+1) x (it+1)
340: This is an internal routine that knows about the FGMRES internals.
341: */
344: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs,Vec vguess,Vec vdest,KSP ksp,PetscInt it)345: {
346: PetscScalar tt;
348: PetscInt ii,k,j;
349: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
352: /* Solve for solution vector that minimizes the residual */
354: /* If it is < 0, no fgmres steps have been performed */
355: if (it < 0) {
356: VecCopy(vguess,vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
357: return(0);
358: }
360: /* so fgmres steps HAVE been performed */
362: /* solve the upper triangular system - RS is the right side and HH is
363: the upper triangular matrix - put soln in nrs */
364: if (*HH(it,it) != 0.0) {
365: nrs[it] = *RS(it) / *HH(it,it);
366: } else {
367: nrs[it] = 0.0;
368: }
369: for (ii=1; ii<=it; ii++) {
370: k = it - ii;
371: tt = *RS(k);
372: for (j=k+1; j<=it; j++) tt = tt - *HH(k,j) * nrs[j];
373: nrs[k] = tt / *HH(k,k);
374: }
376: /* Accumulate the correction to the soln of the preconditioned prob. in
377: VEC_TEMP - note that we use the preconditioned vectors */
378: VecSet(VEC_TEMP,0.0); /* set VEC_TEMP components to 0 */
379: VecMAXPY(VEC_TEMP,it+1,nrs,&PREVEC(0));
381: /* put updated solution into vdest.*/
382: if (vdest != vguess) {
383: VecCopy(VEC_TEMP,vdest);
384: VecAXPY(vdest,1.0,vguess);
385: } else { /* replace guess with solution */
386: VecAXPY(vdest,1.0,VEC_TEMP);
387: }
388: return(0);
389: }
391: /*
393: KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
394: Return new residual.
396: input parameters:
398: . ksp - Krylov space object
399: . it - plane rotations are applied to the (it+1)th column of the
400: modified hessenberg (i.e. HH(:,it))
401: . hapend - PETSC_FALSE not happy breakdown ending.
403: output parameters:
404: . res - the new residual
406: */
409: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp,PetscInt it,PetscBool hapend,PetscReal *res)410: {
411: PetscScalar *hh,*cc,*ss,tt;
412: PetscInt j;
413: KSP_FGMRES *fgmres = (KSP_FGMRES*)(ksp->data);
416: hh = HH(0,it); /* pointer to beginning of column to update - so
417: incrementing hh "steps down" the (it+1)th col of HH*/
418: cc = CC(0); /* beginning of cosine rotations */
419: ss = SS(0); /* beginning of sine rotations */
421: /* Apply all the previously computed plane rotations to the new column
422: of the Hessenberg matrix */
423: /* Note: this uses the rotation [conj(c) s ; -s c], c= cos(theta), s= sin(theta),
424: and some refs have [c s ; -conj(s) c] (don't be confused!) */
426: for (j=1; j<=it; j++) {
427: tt = *hh;
428: *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
429: hh++;
430: *hh = *cc++ * *hh - (*ss++ * tt);
431: /* hh, cc, and ss have all been incremented one by end of loop */
432: }
434: /*
435: compute the new plane rotation, and apply it to:
436: 1) the right-hand-side of the Hessenberg system (RS)
437: note: it affects RS(it) and RS(it+1)
438: 2) the new column of the Hessenberg matrix
439: note: it affects HH(it,it) which is currently pointed to
440: by hh and HH(it+1, it) (*(hh+1))
441: thus obtaining the updated value of the residual...
442: */
444: /* compute new plane rotation */
446: if (!hapend) {
447: tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
448: if (tt == 0.0) {
449: ksp->reason = KSP_DIVERGED_NULL;
450: return(0);
451: }
453: *cc = *hh / tt; /* new cosine value */
454: *ss = *(hh+1) / tt; /* new sine value */
456: /* apply to 1) and 2) */
457: *RS(it+1) = -(*ss * *RS(it));
458: *RS(it) = PetscConj(*cc) * *RS(it);
459: *hh = PetscConj(*cc) * *hh + *ss * *(hh+1);
461: /* residual is the last element (it+1) of right-hand side! */
462: *res = PetscAbsScalar(*RS(it+1));
464: } else { /* happy breakdown: HH(it+1, it) = 0, therfore we don't need to apply
465: another rotation matrix (so RH doesn't change). The new residual is
466: always the new sine term times the residual from last time (RS(it)),
467: but now the new sine rotation would be zero...so the residual should
468: be zero...so we will multiply "zero" by the last residual. This might
469: not be exactly what we want to do here -could just return "zero". */
471: *res = 0.0;
472: }
473: return(0);
474: }
476: /*
478: KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
479: VEC_VV(it), and more preconditioned work vectors, starting
480: from PREVEC(i).
482: */
485: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp,PetscInt it)486: {
487: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
488: PetscInt nwork = fgmres->nwork_alloc; /* number of work vector chunks allocated */
489: PetscInt nalloc; /* number to allocate */
491: PetscInt k;
494: nalloc = fgmres->delta_allocate; /* number of vectors to allocate
495: in a single chunk */
497: /* Adjust the number to allocate to make sure that we don't exceed the
498: number of available slots (fgmres->vecs_allocated)*/
499: if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) {
500: nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
501: }
502: if (!nalloc) return(0);
504: fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */
506: /* work vectors */
507: KSPCreateVecs(ksp,nalloc,&fgmres->user_work[nwork],0,NULL);
508: PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
509: for (k=0; k < nalloc; k++) {
510: fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
511: }
512: /* specify size of chunk allocated */
513: fgmres->mwork_alloc[nwork] = nalloc;
515: /* preconditioned vectors */
516: KSPCreateVecs(ksp,nalloc,&fgmres->prevecs_user_work[nwork],0,NULL);
517: PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
518: for (k=0; k < nalloc; k++) {
519: fgmres->prevecs[it+k] = fgmres->prevecs_user_work[nwork][k];
520: }
522: /* increment the number of work vector chunks */
523: fgmres->nwork_alloc++;
524: return(0);
525: }
527: /*
529: KSPBuildSolution_FGMRES
531: Input Parameter:
532: . ksp - the Krylov space object
533: . ptr-
535: Output Parameter:
536: . result - the solution
538: Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
539: calls directly.
541: */
544: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)545: {
546: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
550: if (!ptr) {
551: if (!fgmres->sol_temp) {
552: VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
553: PetscLogObjectParent((PetscObject)ksp,(PetscObject)fgmres->sol_temp);
554: }
555: ptr = fgmres->sol_temp;
556: }
557: if (!fgmres->nrs) {
558: /* allocate the work area */
559: PetscMalloc1(fgmres->max_k,&fgmres->nrs);
560: PetscLogObjectMemory((PetscObject)ksp,fgmres->max_k*sizeof(PetscScalar));
561: }
563: KSPFGMRESBuildSoln(fgmres->nrs,ksp->vec_sol,ptr,ksp,fgmres->it);
564: if (result) *result = ptr;
565: return(0);
566: }
570: PetscErrorCode KSPSetFromOptions_FGMRES(PetscOptionItems *PetscOptionsObject,KSP ksp)571: {
573: PetscBool flg;
576: KSPSetFromOptions_GMRES(PetscOptionsObject,ksp);
577: PetscOptionsHead(PetscOptionsObject,"KSP flexible GMRES Options");
578: PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
579: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,0,0);}
580: PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp","vary the KSP based preconditioner","KSPFGMRESSetModifyPC",&flg);
581: if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCKSP,0,0);}
582: PetscOptionsTail();
583: return(0);
584: }
586: typedef PetscErrorCode (*FCN1)(KSP,PetscInt,PetscInt,PetscReal,void*); /* force argument to next function to not be extern C*/
587: typedef PetscErrorCode (*FCN2)(void*);
591: static PetscErrorCode KSPFGMRESSetModifyPC_FGMRES(KSP ksp,FCN1 fcn,void *ctx,FCN2 d)592: {
595: ((KSP_FGMRES*)ksp->data)->modifypc = fcn;
596: ((KSP_FGMRES*)ksp->data)->modifydestroy = d;
597: ((KSP_FGMRES*)ksp->data)->modifyctx = ctx;
598: return(0);
599: }
604: PetscErrorCode KSPReset_FGMRES(KSP ksp)605: {
606: KSP_FGMRES *fgmres = (KSP_FGMRES*)ksp->data;
608: PetscInt i;
611: PetscFree (fgmres->prevecs);
612: if(fgmres->nwork_alloc>0){
613: i=0;
614: /* In the first allocation we allocated VEC_OFFSET fewer vectors in prevecs */
615: VecDestroyVecs(fgmres->mwork_alloc[i]-VEC_OFFSET,&fgmres->prevecs_user_work[i]);
616: for (i=1; i<fgmres->nwork_alloc; i++) {
617: VecDestroyVecs(fgmres->mwork_alloc[i],&fgmres->prevecs_user_work[i]);
618: }
619: }
620: PetscFree(fgmres->prevecs_user_work);
621: if (fgmres->modifydestroy) {
622: (*fgmres->modifydestroy)(fgmres->modifyctx);
623: }
624: KSPReset_GMRES(ksp);
625: return(0);
626: }
630: PetscErrorCode KSPGMRESSetRestart_FGMRES(KSP ksp,PetscInt max_k)631: {
632: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
636: if (max_k < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
637: if (!ksp->setupstage) {
638: gmres->max_k = max_k;
639: } else if (gmres->max_k != max_k) {
640: gmres->max_k = max_k;
641: ksp->setupstage = KSP_SETUP_NEW;
642: /* free the data structures, then create them again */
643: KSPReset_FGMRES(ksp);
644: }
645: return(0);
646: }
650: PetscErrorCode KSPGMRESGetRestart_FGMRES(KSP ksp,PetscInt *max_k)651: {
652: KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;
655: *max_k = gmres->max_k;
656: return(0);
657: }
659: /*MC
660: KSPFGMRES - Implements the Flexible Generalized Minimal Residual method.
661: developed by Saad with restart
664: Options Database Keys:
665: + -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
666: . -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
667: . -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
668: vectors are allocated as needed)
669: . -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
670: . -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
671: . -ksp_gmres_cgs_refinement_type <never,ifneeded,always> - determine if iterative refinement is used to increase the
672: stability of the classical Gram-Schmidt orthogonalization.
673: . -ksp_gmres_krylov_monitor - plot the Krylov space generated
674: . -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
675: - -ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()
677: Level: beginner
679: Notes: See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations
680: Only right preconditioning is supported.
682: 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)
683: be bi-CG-stab with a preconditioner of Jacobi.
685: Developer Notes: This object is subclassed off of KSPGMRES687: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
688: KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(),
689: KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(),
690: KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(), KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(),
691: KSPFGMRESModifyPCKSP()
693: M*/
697: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)698: {
699: KSP_FGMRES *fgmres;
703: PetscNewLog(ksp,&fgmres);
705: ksp->data = (void*)fgmres;
706: ksp->ops->buildsolution = KSPBuildSolution_FGMRES;
707: ksp->ops->setup = KSPSetUp_FGMRES;
708: ksp->ops->solve = KSPSolve_FGMRES;
709: ksp->ops->reset = KSPReset_FGMRES;
710: ksp->ops->destroy = KSPDestroy_FGMRES;
711: ksp->ops->view = KSPView_GMRES;
712: ksp->ops->setfromoptions = KSPSetFromOptions_FGMRES;
713: ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
714: ksp->ops->computeeigenvalues = KSPComputeEigenvalues_GMRES;
716: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,3);
717: KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,0);
719: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",KSPGMRESSetPreAllocateVectors_GMRES);
720: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",KSPGMRESSetOrthogonalization_GMRES);
721: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetOrthogonalization_C",KSPGMRESGetOrthogonalization_GMRES);
722: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetRestart_C",KSPGMRESSetRestart_FGMRES);
723: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetRestart_C",KSPGMRESGetRestart_FGMRES);
724: PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",KSPFGMRESSetModifyPC_FGMRES);
725: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetCGSRefinementType_C",KSPGMRESSetCGSRefinementType_GMRES);
726: PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetCGSRefinementType_C",KSPGMRESGetCGSRefinementType_GMRES);
729: fgmres->haptol = 1.0e-30;
730: fgmres->q_preallocate = 0;
731: fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
732: fgmres->orthog = KSPGMRESClassicalGramSchmidtOrthogonalization;
733: fgmres->nrs = 0;
734: fgmres->sol_temp = 0;
735: fgmres->max_k = FGMRES_DEFAULT_MAXK;
736: fgmres->Rsvd = 0;
737: fgmres->orthogwork = 0;
738: fgmres->modifypc = KSPFGMRESModifyPCNoChange;
739: fgmres->modifyctx = NULL;
740: fgmres->modifydestroy = NULL;
741: fgmres->cgstype = KSP_GMRES_CGS_REFINE_NEVER;
742: return(0);
743: }