Actual source code: cr.c
1: #define PETSCKSP_DLL
3: #include private/kspimpl.h
7: static PetscErrorCode KSPSetUp_CR(KSP ksp)
8: {
12: if (ksp->pc_side == PC_RIGHT) {SETERRQ(PETSC_ERR_SUP,"no right preconditioning for KSPCR");}
13: else if (ksp->pc_side == PC_SYMMETRIC) {SETERRQ(PETSC_ERR_SUP,"no symmetric preconditioning for KSPCR");}
14: KSPDefaultGetWork(ksp,6);
15: return(0);
16: }
20: static PetscErrorCode KSPSolve_CR(KSP ksp)
21: {
23: PetscInt i = 0;
24: MatStructure pflag;
25: PetscReal dp;
26: PetscScalar ai, bi;
27: PetscScalar apq,btop, bbot;
28: Vec X,B,R,RT,P,AP,ART,Q;
29: Mat Amat, Pmat;
32: X = ksp->vec_sol;
33: B = ksp->vec_rhs;
34: R = ksp->work[0];
35: RT = ksp->work[1];
36: P = ksp->work[2];
37: AP = ksp->work[3];
38: ART = ksp->work[4];
39: Q = ksp->work[5];
41: /* R is the true residual norm, RT is the preconditioned residual norm */
42: PCGetOperators(ksp->pc,&Amat,&Pmat,&pflag);
43: if (!ksp->guess_zero) {
44: KSP_MatMult(ksp,Amat,X,R); /* R <- A*X */
45: VecAYPX(R,-1.0,B); /* R <- B-R == B-A*X */
46: } else {
47: VecCopy(B,R); /* R <- B (X is 0) */
48: }
49: KSP_PCApply(ksp,R,P); /* P <- B*R */
50: KSP_MatMult(ksp,Amat,P,AP); /* AP <- A*P */
51: VecCopy(P,RT); /* RT <- P */
52: VecCopy(AP,ART); /* ART <- AP */
53: VecDotBegin(RT,ART,&btop); /* (RT,ART) */
54:
55: if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
56: VecNormBegin(RT,NORM_2,&dp); /* dp <- RT'*RT */
57: VecDotEnd (RT,ART,&btop) ; /* (RT,ART) */
58: VecNormEnd (RT,NORM_2,&dp); /* dp <- RT'*RT */
59: } else if (ksp->normtype == KSP_NORM_UNPRECONDITIONED) {
60: VecNormBegin(R,NORM_2,&dp); /* dp <- R'*R */
61: VecDotEnd (RT,ART,&btop); /* (RT,ART) */
62: VecNormEnd (R,NORM_2,&dp); /* dp <- RT'*RT */
63: } else if (ksp->normtype == KSP_NORM_NATURAL) {
64: VecDotEnd (RT,ART,&btop) ; /* (RT,ART) */
65: dp = sqrt(PetscAbsScalar(btop)); /* dp = sqrt(R,AR) */
66: }
67: if (PetscAbsScalar(btop) < 0.0) {
68: ksp->reason = KSP_DIVERGED_INDEFINITE_MAT;
69: PetscInfo(ksp,"diverging due to indefinite or negative definite matrix\n");
70: return(0);
71: }
73: ksp->its = 0;
74: KSPMonitor(ksp,0,dp);
75: PetscObjectTakeAccess(ksp);
76: ksp->rnorm = dp;
77: PetscObjectGrantAccess(ksp);
78: KSPLogResidualHistory(ksp,dp);
79: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
80: if (ksp->reason) return(0);
82: i = 0;
83: do {
84: KSP_PCApply(ksp,AP,Q);/* Q <- B* AP */
86: VecDot(AP,Q,&apq);
87: if (PetscAbsScalar(apq) <= 0.0) {
88: ksp->reason = KSP_DIVERGED_INDEFINITE_PC;
89: PetscInfo(ksp,"KSPSolve_CR:diverging due to indefinite or negative definite PC\n");
90: break;
91: }
92: ai = btop/apq; /* ai = (RT,ART)/(AP,Q) */
94: VecAXPY(X,ai,P); /* X <- X + ai*P */
95: VecAXPY(RT,-ai,Q); /* RT <- RT - ai*Q */
96: KSP_MatMult(ksp,Amat,RT,ART);/* ART <- A*RT */
97: bbot = btop;
98: VecDotBegin(RT,ART,&btop);
100: if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
101: VecNormBegin(RT,NORM_2,&dp); /* dp <- || RT || */
102: VecDotEnd (RT,ART,&btop) ;
103: VecNormEnd (RT,NORM_2,&dp); /* dp <- || RT || */
104: } else if (ksp->normtype == KSP_NORM_NATURAL) {
105: VecDotEnd(RT,ART,&btop);
106: dp = sqrt(PetscAbsScalar(btop)); /* dp = sqrt(R,AR) */
107: } else if (ksp->normtype == KSP_NORM_NO) {
108: VecDotEnd(RT,ART,&btop);
109: dp = 0.0;
110: } else if (ksp->normtype == KSP_NORM_UNPRECONDITIONED) {
111: VecAXPY(R,ai,AP); /* R <- R - ai*AP */
112: VecNormBegin(R,NORM_2,&dp); /* dp <- R'*R */
113: VecDotEnd (RT,ART,&btop);
114: VecNormEnd (R,NORM_2,&dp); /* dp <- R'*R */
115: } else {
116: SETERRQ1(PETSC_ERR_SUP,"KSPNormType of %d not supported",(int)ksp->normtype);
117: }
118: if (PetscAbsScalar(btop) < 0.0) {
119: ksp->reason = KSP_DIVERGED_INDEFINITE_MAT;
120: PetscInfo(ksp,"diverging due to indefinite or negative definite PC\n");
121: break;
122: }
124: PetscObjectTakeAccess(ksp);
125: ksp->its++;
126: ksp->rnorm = dp;
127: PetscObjectGrantAccess(ksp);
129: KSPLogResidualHistory(ksp,dp);
130: KSPMonitor(ksp,i+1,dp);
131: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
132: if (ksp->reason) break;
134: bi = btop/bbot;
135: VecAYPX(P,bi,RT); /* P <- RT + Bi P */
136: VecAYPX(AP,bi,ART); /* AP <- ART + Bi AP */
137: i++;
138: } while (i<ksp->max_it);
139: if (i >= ksp->max_it) {
140: ksp->reason = KSP_DIVERGED_ITS;
141: }
142: return(0);
143: }
146: /*MC
147: KSPCR - This code implements the (preconditioned) conjugate residuals method
149: Options Database Keys:
150: . see KSPSolve()
152: Level: beginner
154: Notes: The operator and the preconditioner must be symmetric for this method. The
155: preconditioner must be POSITIVE-DEFINITE and the operator POSITIVE-SEMIDEFINITE
158: References:
159: Methods of Conjugate Gradients for Solving Linear Systems, Magnus R. Hestenes and Eduard Stiefel,
160: Journal of Research of the National Bureau of Standards Vol. 49, No. 6, December 1952 Research Paper 2379
161: pp. 409--436.
164: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPCG
165: M*/
169: PetscErrorCode KSPCreate_CR(KSP ksp)
170: {
172: ksp->pc_side = PC_LEFT;
173: ksp->ops->setup = KSPSetUp_CR;
174: ksp->ops->solve = KSPSolve_CR;
175: ksp->ops->destroy = KSPDefaultDestroy;
176: ksp->ops->buildsolution = KSPDefaultBuildSolution;
177: ksp->ops->buildresidual = KSPDefaultBuildResidual;
178: ksp->ops->setfromoptions = 0;
179: ksp->ops->view = 0;
180: return(0);
181: }