Actual source code: cr.c
1: /*$Id: cr.c,v 1.64 2001/08/07 03:03:49 balay Exp $*/
3: /*
4: This implements Preconditioned Conjugate Residuals.
5: */
6: #include src/sles/ksp/kspimpl.h
8: static int KSPSetUp_CR(KSP ksp)
9: {
13: if (ksp->pc_side == PC_RIGHT) {SETERRQ(2,"no right preconditioning for KSPCR");}
14: else if (ksp->pc_side == PC_SYMMETRIC) {SETERRQ(2,"no symmetric preconditioning for KSPCR");}
15: KSPDefaultGetWork(ksp,6);
16: return(0);
17: }
19: static int KSPSolve_CR(KSP ksp,int *its)
20: {
21: int i = 0, maxit, ierr;
22: MatStructure pflag;
23: PetscReal dp;
24: PetscScalar ai, bi;
25: PetscScalar apq,btop, bbot, mone = -1.0;
26: Vec X,B,R,RT,P,AP,ART,Q;
27: Mat Amat, Pmat;
31: maxit = ksp->max_it;
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->B,&Amat,&Pmat,&pflag);
43: if (!ksp->guess_zero) {
44: KSP_MatMult(ksp,Amat,X,R); /* R <- A*X */
45: VecAYPX(&mone,B,R); /* R <- B-R == B-A*X */
46: } else {
47: VecCopy(B,R); /* R <- B (X is 0) */
48: }
49: KSP_PCApply(ksp,ksp->B,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: ierr = VecDot(RT,ART,&btop); /* (RT,ART) */
54: if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
55: VecNorm(RT,NORM_2,&dp); /* dp <- RT'*RT */
56: } else if (ksp->normtype == KSP_UNPRECONDITIONED_NORM) {
57: VecNorm(R,NORM_2,&dp); /* dp <- R'*R */
58: } else if (ksp->normtype == KSP_NATURAL_NORM) {
59: dp = sqrt(PetscAbsScalar(btop)); /* dp = sqrt(R,AR) */
60: }
61: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
62: if (ksp->reason) {*its = 0; return(0);}
63: KSPMonitor(ksp,0,dp);
64: PetscObjectTakeAccess(ksp);
65: ksp->its = 0;
66: ksp->rnorm = dp;
67: PetscObjectGrantAccess(ksp);
68: KSPLogResidualHistory(ksp,dp);
70: for ( i=0; i<maxit; i++) {
71: ierr = KSP_PCApply(ksp,ksp->B,AP,Q);/* Q <- B* AP */
72: /* Step 3 */
74: ierr = VecDot(AP,Q,&apq);
75: ai = btop/apq; /* ai = (RT,ART)/(AP,Q) */
77: ierr = VecAXPY(&ai,P,X); /* X <- X + ai*P */
78: ai = -ai;
79: ierr = VecAXPY(&ai,Q,RT); /* RT <- RT - ai*Q */
80: ierr = KSP_MatMult(ksp,Amat,RT,ART);/* ART <- A*RT */
81: bbot = btop;
82: ierr = VecDot(RT,ART,&btop);
84: if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
85: VecNorm(RT,NORM_2,&dp); /* dp <- || RT || */
86: } else if (ksp->normtype == KSP_NATURAL_NORM) {
87: dp = sqrt(PetscAbsScalar(btop)); /* dp = sqrt(R,AR) */
88: } else if (ksp->normtype == KSP_NO_NORM) {
89: dp = 0.0;
90: } else if (ksp->normtype == KSP_UNPRECONDITIONED_NORM) {
91: VecAXPY(&ai,AP,R); /* R <- R - ai*AP */
92: VecNorm(R,NORM_2,&dp); /* dp <- R'*R */
93: } else {
94: SETERRQ1(1,"KSPNormType of %d not supported",(int)ksp->normtype);
95: }
97: PetscObjectTakeAccess(ksp);
98: ksp->its++;
99: ksp->rnorm = dp;
100: PetscObjectGrantAccess(ksp);
102: KSPLogResidualHistory(ksp,dp);
103: KSPMonitor(ksp,i+1,dp);
104: (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
105: if (ksp->reason) break;
107: bi = btop/bbot;
108: VecAYPX(&bi,RT,P); /* P <- RT + Bi P */
109: VecAYPX(&bi,ART,AP); /* AP <- ART + Bi AP */
110: }
111: if (i == maxit) {
112: ksp->reason = KSP_DIVERGED_ITS;
113: i--;
114: }
115: *its = i + 1;
116: return(0);
117: }
120: EXTERN_C_BEGIN
121: int KSPCreate_CR(KSP ksp)
122: {
124: ksp->pc_side = PC_LEFT;
125: ksp->ops->setup = KSPSetUp_CR;
126: ksp->ops->solve = KSPSolve_CR;
127: ksp->ops->destroy = KSPDefaultDestroy;
128: ksp->ops->buildsolution = KSPDefaultBuildSolution;
129: ksp->ops->buildresidual = KSPDefaultBuildResidual;
130: ksp->ops->setfromoptions = 0;
131: ksp->ops->view = 0;
132: return(0);
133: }
134: EXTERN_C_END