Actual source code: rich.c
2: /*
3: This implements Richardson Iteration.
4: */
5: #include <private/kspimpl.h> /*I "petscksp.h" I*/
6: #include <../src/ksp/ksp/impls/rich/richardsonimpl.h>
10: PetscErrorCode KSPSetUp_Richardson(KSP ksp)
11: {
13: KSP_Richardson *richardsonP = (KSP_Richardson*)ksp->data;
16: if (richardsonP->selfscale) {
17: KSPDefaultGetWork(ksp,4);
18: } else {
19: KSPDefaultGetWork(ksp,2);
20: }
21: return(0);
22: }
26: PetscErrorCode KSPSolve_Richardson(KSP ksp)
27: {
29: PetscInt i,maxit;
30: MatStructure pflag;
31: PetscReal rnorm = 0.0;
32: PetscScalar scale,abr,rdot;
33: Vec x,b,r,z,w = PETSC_NULL,y = PETSC_NULL;
34: PetscInt xs, ws;
35: Mat Amat,Pmat;
36: KSP_Richardson *richardsonP = (KSP_Richardson*)ksp->data;
37: PetscBool exists,diagonalscale;
40: PCGetDiagonalScale(ksp->pc,&diagonalscale);
41: if (diagonalscale) SETERRQ1(((PetscObject)ksp)->comm,PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);
43: ksp->its = 0;
45: PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);
46: x = ksp->vec_sol;
47: b = ksp->vec_rhs;
48: VecGetSize(x,&xs);
49: VecGetSize(ksp->work[0],&ws);
50: if (xs != ws) {
51: if (richardsonP->selfscale) {
52: KSPDefaultGetWork(ksp,4);
53: } else {
54: KSPDefaultGetWork(ksp,2);
55: }
56: }
57: r = ksp->work[0];
58: z = ksp->work[1];
59: if (richardsonP->selfscale) {
60: w = ksp->work[2];
61: y = ksp->work[3];
62: }
63: maxit = ksp->max_it;
65: /* if user has provided fast Richardson code use that */
66: PCApplyRichardsonExists(ksp->pc,&exists);
67: if (exists && !ksp->numbermonitors && !ksp->transpose_solve) {
68: PCRichardsonConvergedReason reason;
69: PCApplyRichardson(ksp->pc,b,x,r,ksp->rtol,ksp->abstol,ksp->divtol,maxit,ksp->guess_zero,&ksp->its,&reason);
70: ksp->reason = (KSPConvergedReason)reason;
71: return(0);
72: }
74: scale = richardsonP->scale;
76: if (!ksp->guess_zero) { /* r <- b - A x */
77: KSP_MatMult(ksp,Amat,x,r);
78: VecAYPX(r,-1.0,b);
79: } else {
80: VecCopy(b,r);
81: }
83: ksp->its = 0;
84: if (richardsonP->selfscale) {
85: KSP_PCApply(ksp,r,z); /* z <- B r */
86: for (i=0; i<maxit; i++) {
87:
88: if (ksp->normtype == KSP_NORM_UNPRECONDITIONED) {
89: VecNorm(r,NORM_2,&rnorm); /* rnorm <- r'*r */
90: KSPMonitor(ksp,i,rnorm);
91: ksp->rnorm = rnorm;
92: KSPLogResidualHistory(ksp,rnorm);
93: (*ksp->converged)(ksp,i,rnorm,&ksp->reason,ksp->cnvP);
94: if (ksp->reason) break;
95: } else if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
96: VecNorm(z,NORM_2,&rnorm); /* rnorm <- z'*z */
97: KSPMonitor(ksp,i,rnorm);
98: ksp->rnorm = rnorm;
99: KSPLogResidualHistory(ksp,rnorm);
100: (*ksp->converged)(ksp,i,rnorm,&ksp->reason,ksp->cnvP);
101: if (ksp->reason) break;
102: }
103: KSP_PCApplyBAorAB(ksp,z,y,w); /* y = BAz = BABr */
104: VecDotNorm2(z,y,&rdot,&abr); /* rdot = (Br)^T(BABR); abr = (BABr)^T (BABr) */
105: scale = rdot/abr;
107: VecAXPY(x,scale,z); /* x <- x + scale z */
108: VecAXPY(r,-scale,w); /* r <- r - scale*Az */
109: VecAXPY(z,-scale,y); /* z <- z - scale*y */
110: ksp->its++;
111: }
112: } else {
113: for (i=0; i<maxit; i++) {
115: if (ksp->normtype == KSP_NORM_UNPRECONDITIONED) {
116: VecNorm(r,NORM_2,&rnorm); /* rnorm <- r'*r */
117: KSPMonitor(ksp,i,rnorm);
118: ksp->rnorm = rnorm;
119: KSPLogResidualHistory(ksp,rnorm);
120: (*ksp->converged)(ksp,i,rnorm,&ksp->reason,ksp->cnvP);
121: if (ksp->reason) break;
122: }
124: KSP_PCApply(ksp,r,z); /* z <- B r */
126: if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
127: VecNorm(z,NORM_2,&rnorm); /* rnorm <- z'*z */
128: KSPMonitor(ksp,i,rnorm);
129: ksp->rnorm = rnorm;
130: KSPLogResidualHistory(ksp,rnorm);
131: (*ksp->converged)(ksp,i,rnorm,&ksp->reason,ksp->cnvP);
132: if (ksp->reason) break;
133: }
134:
135: VecAXPY(x,scale,z); /* x <- x + scale z */
136: ksp->its++;
138: KSP_MatMult(ksp,Amat,x,r); /* r <- b - Ax */
139: VecAYPX(r,-1.0,b);
140: }
141: }
142: if (!ksp->reason) {
143: if (ksp->normtype != KSP_NORM_NONE) {
144: if (ksp->normtype == KSP_NORM_UNPRECONDITIONED){
145: VecNorm(r,NORM_2,&rnorm); /* rnorm <- r'*r */
146: } else {
147: KSP_PCApply(ksp,r,z); /* z <- B r */
148: VecNorm(z,NORM_2,&rnorm); /* rnorm <- z'*z */
149: }
150: ksp->rnorm = rnorm;
151: KSPLogResidualHistory(ksp,rnorm);
152: KSPMonitor(ksp,i,rnorm);
153: }
154: if (ksp->its >= ksp->max_it) {
155: if (ksp->normtype != KSP_NORM_NONE) {
156: (*ksp->converged)(ksp,i,rnorm,&ksp->reason,ksp->cnvP);
157: if (!ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
158: } else {
159: ksp->reason = KSP_CONVERGED_ITS;
160: }
161: }
162: }
163: return(0);
164: }
168: PetscErrorCode KSPView_Richardson(KSP ksp,PetscViewer viewer)
169: {
170: KSP_Richardson *richardsonP = (KSP_Richardson*)ksp->data;
172: PetscBool iascii;
175: PetscTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
176: if (iascii) {
177: PetscViewerASCIIPrintf(viewer," Richardson: damping factor=%G\n",richardsonP->scale);
178: } else {
179: SETERRQ1(((PetscObject)ksp)->comm,PETSC_ERR_SUP,"Viewer type %s not supported for KSP Richardson",((PetscObject)viewer)->type_name);
180: }
181: return(0);
182: }
186: PetscErrorCode KSPSetFromOptions_Richardson(KSP ksp)
187: {
188: KSP_Richardson *rich = (KSP_Richardson*)ksp->data;
190: PetscReal tmp;
191: PetscBool flg,flg2;
194: PetscOptionsHead("KSP Richardson Options");
195: PetscOptionsReal("-ksp_richardson_scale","damping factor","KSPRichardsonSetScale",rich->scale,&tmp,&flg);
196: if (flg) { KSPRichardsonSetScale(ksp,tmp); }
197: PetscOptionsBool("-ksp_richardson_self_scale","dynamically determine optimal damping factor","KSPRichardsonSetSelfScale",rich->selfscale,&flg2,&flg);
198: if (flg) { KSPRichardsonSetSelfScale(ksp,flg2); }
199: PetscOptionsTail();
200: return(0);
201: }
205: PetscErrorCode KSPDestroy_Richardson(KSP ksp)
206: {
210: PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPRichardsonSetScale_C","",PETSC_NULL);
211: KSPDefaultDestroy(ksp);
212: return(0);
213: }
218: PetscErrorCode KSPRichardsonSetScale_Richardson(KSP ksp,PetscReal scale)
219: {
220: KSP_Richardson *richardsonP;
223: richardsonP = (KSP_Richardson*)ksp->data;
224: richardsonP->scale = scale;
225: return(0);
226: }
232: PetscErrorCode KSPRichardsonSetSelfScale_Richardson(KSP ksp,PetscBool selfscale)
233: {
234: KSP_Richardson *richardsonP;
237: richardsonP = (KSP_Richardson*)ksp->data;
238: richardsonP->selfscale = selfscale;
239: return(0);
240: }
243: /*MC
244: KSPRICHARDSON - The preconditioned Richardson iterative method
246: Options Database Keys:
247: . -ksp_richardson_scale - damping factor on the correction (defaults to 1.0)
249: Level: beginner
251: Notes: x^{n+1} = x^{n} + scale*B(b - A x^{n})
252:
253: Here B is the application of the preconditioner
255: This method often (usually) will not converge unless scale is very small. It
256: is described in
259: Notes: For some preconditioners, currently SOR, the convergence test is skipped to improve speed,
260: thus it always iterates the maximum number of iterations you've selected. When -ksp_monitor
261: (or any other monitor) is turned on, the norm is computed at each iteration and so the convergence test is run unless
262: you specifically call KSPSetNormType(ksp,KSP_NORM_NONE);
264: For some preconditioners, currently PCMG and PCHYPRE with BoomerAMG if -ksp_monitor (and also
265: any other monitor) is not turned on then the convergence test is done by the preconditioner itself and
266: so the solver may run more or fewer iterations then if -ksp_monitor is selected.
268: Supports only left preconditioning
270: References:
271: "The Approximate Arithmetical Solution by Finite Differences of Physical Problems Involving
272: Differential Equations, with an Application to the Stresses in a Masonry Dam",
273: L. F. Richardson, Philosophical Transactions of the Royal Society of London. Series A,
274: Containing Papers of a Mathematical or Physical Character, Vol. 210, 1911 (1911), pp. 307-357.
276: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP,
277: KSPRichardsonSetScale()
279: M*/
284: PetscErrorCode KSPCreate_Richardson(KSP ksp)
285: {
287: KSP_Richardson *richardsonP;
290: PetscNewLog(ksp,KSP_Richardson,&richardsonP);
291: ksp->data = (void*)richardsonP;
293: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,2);
294: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_LEFT,1);
296: ksp->ops->setup = KSPSetUp_Richardson;
297: ksp->ops->solve = KSPSolve_Richardson;
298: ksp->ops->destroy = KSPDestroy_Richardson;
299: ksp->ops->buildsolution = KSPDefaultBuildSolution;
300: ksp->ops->buildresidual = KSPDefaultBuildResidual;
301: ksp->ops->view = KSPView_Richardson;
302: ksp->ops->setfromoptions = KSPSetFromOptions_Richardson;
304: PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPRichardsonSetScale_C","KSPRichardsonSetScale_Richardson",KSPRichardsonSetScale_Richardson);
305: PetscObjectComposeFunctionDynamic((PetscObject)ksp,"KSPRichardsonSetSelfScale_C","KSPRichardsonSetSelfScale_Richardson",KSPRichardsonSetSelfScale_Richardson);
306: richardsonP->scale = 1.0;
307: return(0);
308: }