Actual source code: cr.c
1: #define PETSCKSP_DLL
3: #include 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: VecDot(RT,ART,&btop); /* (RT,ART) */
54: if (PetscAbsScalar(btop) < 0.0) {
55: ksp->reason = KSP_DIVERGED_INDEFINITE_MAT;
56: PetscInfo(ksp,"diverging due to indefinite or negative definite matrix\n");
57: return(0);
58: }
59:
60: if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
61: VecNorm(RT,NORM_2,&dp); /* dp <- RT'*RT */
62: } else if (ksp->normtype == KSP_NORM_UNPRECONDITIONED) {
63: VecNorm(R,NORM_2,&dp); /* dp <- R'*R */
64: } else if (ksp->normtype == KSP_NORM_NATURAL) {
65: dp = sqrt(PetscAbsScalar(btop)); /* dp = sqrt(R,AR) */
66: }
67: ksp->its = 0;
68: KSPMonitor(ksp,0,dp);
69: PetscObjectTakeAccess(ksp);
70: ksp->rnorm = dp;
71: PetscObjectGrantAccess(ksp);
72: KSPLogResidualHistory(ksp,dp);
73: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
74: if (ksp->reason) return(0);
76: i = 0;
77: do {
78: KSP_PCApply(ksp,AP,Q);/* Q <- B* AP */
80: VecDot(AP,Q,&apq);
81: if (PetscAbsScalar(apq) <= 0.0) {
82: ksp->reason = KSP_DIVERGED_INDEFINITE_PC;
83: PetscInfo(ksp,"diverging due to indefinite or negative definite PC\n");
84: break;
85: }
86: ai = btop/apq; /* ai = (RT,ART)/(AP,Q) */
88: VecAXPY(X,ai,P); /* X <- X + ai*P */
89: VecAXPY(RT,-ai,Q); /* RT <- RT - ai*Q */
90: KSP_MatMult(ksp,Amat,RT,ART);/* ART <- A*RT */
91: bbot = btop;
92: VecDot(RT,ART,&btop);
93: if (PetscAbsScalar(btop) < 0.0) {
94: ksp->reason = KSP_DIVERGED_INDEFINITE_MAT;
95: PetscInfo(ksp,"diverging due to indefinite or negative definite matrix\n");
96: break;
97: }
99: if (ksp->normtype == KSP_NORM_PRECONDITIONED) {
100: VecNorm(RT,NORM_2,&dp); /* dp <- || RT || */
101: } else if (ksp->normtype == KSP_NORM_NATURAL) {
102: dp = sqrt(PetscAbsScalar(btop)); /* dp = sqrt(R,AR) */
103: } else if (ksp->normtype == KSP_NORM_NO) {
104: dp = 0.0;
105: } else if (ksp->normtype == KSP_NORM_UNPRECONDITIONED) {
106: VecAXPY(R,-ai,AP); /* R <- R - ai*AP */
107: VecNorm(R,NORM_2,&dp); /* dp <- R'*R */
108: } else {
109: SETERRQ1(PETSC_ERR_SUP,"KSPNormType of %d not supported",(int)ksp->normtype);
110: }
112: PetscObjectTakeAccess(ksp);
113: ksp->its++;
114: ksp->rnorm = dp;
115: PetscObjectGrantAccess(ksp);
117: KSPLogResidualHistory(ksp,dp);
118: KSPMonitor(ksp,i+1,dp);
119: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
120: if (ksp->reason) break;
122: bi = btop/bbot;
123: VecAYPX(P,bi,RT); /* P <- RT + Bi P */
124: VecAYPX(AP,bi,ART); /* AP <- ART + Bi AP */
125: i++;
126: } while (i<ksp->max_it);
127: if (i >= ksp->max_it) {
128: ksp->reason = KSP_DIVERGED_ITS;
129: }
130: return(0);
131: }
134: /*MC
135: KSPCR - This code implements the (preconditioned) conjugate residuals method
137: Options Database Keys:
138: . see KSPSolve()
140: Level: beginner
142: Notes: The operator and the preconditioner must be symmetric for this method. The
143: preconditioner must be POSITIVE-DEFINITE and the operator POSITIVE-SEMIDEFINITE
145: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPCG
146: M*/
150: PetscErrorCode KSPCreate_CR(KSP ksp)
151: {
153: ksp->pc_side = PC_LEFT;
154: ksp->ops->setup = KSPSetUp_CR;
155: ksp->ops->solve = KSPSolve_CR;
156: ksp->ops->destroy = KSPDefaultDestroy;
157: ksp->ops->buildsolution = KSPDefaultBuildSolution;
158: ksp->ops->buildresidual = KSPDefaultBuildResidual;
159: ksp->ops->setfromoptions = 0;
160: ksp->ops->view = 0;
161: return(0);
162: }