Actual source code: tfqmr.c
1: /*$Id: tfqmr.c,v 1.60 2001/03/23 23:23:44 balay Exp $*/
3: /*
4: This code implements the TFQMR (Transpose-free variant of Quasi-Minimal
5: Residual) method. Reference: Freund, 1993
7: Note that for the complex numbers version, the VecDot() arguments
8: within the code MUST remain in the order given for correct computation
9: of inner products.
10: */
12: #include "src/sles/ksp/kspimpl.h"
14: static int KSPSetUp_TFQMR(KSP ksp)
15: {
19: if (ksp->pc_side == PC_SYMMETRIC){
20: SETERRQ(2,"no symmetric preconditioning for KSPTFQMR");
21: }
22: KSPDefaultGetWork(ksp,10);
23: return(0);
24: }
26: static int KSPSolve_TFQMR(KSP ksp,int *its)
27: {
28: int i,maxit,m, ierr;
29: Scalar rho,rhoold,a,s,b,eta,etaold,psiold,cf,tmp,one = 1.0,zero = 0.0;
30: PetscReal dp,dpold,w,dpest,tau,psi,cm;
31: Vec X,B,V,P,R,RP,T,T1,Q,U,D,BINVF,AUQ;
34: maxit = ksp->max_it;
35: X = ksp->vec_sol;
36: B = ksp->vec_rhs;
37: R = ksp->work[0];
38: RP = ksp->work[1];
39: V = ksp->work[2];
40: T = ksp->work[3];
41: Q = ksp->work[4];
42: P = ksp->work[5];
43: BINVF = ksp->work[6];
44: U = ksp->work[7];
45: D = ksp->work[8];
46: T1 = ksp->work[9];
47: AUQ = V;
49: /* Compute initial preconditioned residual */
50: KSPInitialResidual(ksp,X,V,T,R,BINVF,B);
52: /* Test for nothing to do */
53: VecNorm(R,NORM_2,&dp);
54: PetscObjectTakeAccess(ksp);
55: ksp->rnorm = dp;
56: ksp->its = 0;
57: PetscObjectGrantAccess(ksp);
58: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
59: if (ksp->reason) {*its = 0; return(0);}
60: KSPMonitor(ksp,0,dp);
62: /* Make the initial Rp == R */
63: VecCopy(R,RP);
65: /* Set the initial conditions */
66: etaold = 0.0;
67: psiold = 0.0;
68: tau = dp;
69: dpold = dp;
71: VecDot(R,RP,&rhoold); /* rhoold = (r,rp) */
72: VecCopy(R,U);
73: VecCopy(R,P);
74: KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,P,V,T);
75: VecSet(&zero,D);
77: for (i=0; i<maxit; i++) {
78: PetscObjectTakeAccess(ksp);
79: ksp->its++;
80: PetscObjectGrantAccess(ksp);
81: VecDot(V,RP,&s); /* s <- (v,rp) */
82: a = rhoold / s; /* a <- rho / s */
83: tmp = -a; VecWAXPY(&tmp,V,U,Q); /* q <- u - a v */
84: VecWAXPY(&one,U,Q,T); /* t <- u + q */
85: KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,T,AUQ,T1);
86: VecAXPY(&tmp,AUQ,R); /* r <- r - a K (u + q) */
87: VecNorm(R,NORM_2,&dp);
88: for (m=0; m<2; m++) {
89: if (!m) {
90: w = sqrt(dp*dpold);
91: } else {
92: w = dp;
93: }
94: psi = w / tau;
95: cm = 1.0 / sqrt(1.0 + psi * psi);
96: tau = tau * psi * cm;
97: eta = cm * cm * a;
98: cf = psiold * psiold * etaold / a;
99: if (!m) {
100: VecAYPX(&cf,U,D);
101: } else {
102: VecAYPX(&cf,Q,D);
103: }
104: VecAXPY(&eta,D,X);
106: dpest = sqrt(m + 1.0) * tau;
107: PetscObjectTakeAccess(ksp);
108: ksp->rnorm = dpest;
109: PetscObjectGrantAccess(ksp);
110: KSPLogResidualHistory(ksp,dpest);
111: KSPMonitor(ksp,i+1,dpest);
112: (*ksp->converged)(ksp,i+1,dpest,&ksp->reason,ksp->cnvP);
113: if (ksp->reason) break;
115: etaold = eta;
116: psiold = psi;
117: }
118: if (ksp->reason) break;
120: VecDot(R,RP,&rho); /* rho <- (r,rp) */
121: b = rho / rhoold; /* b <- rho / rhoold */
122: VecWAXPY(&b,Q,R,U); /* u <- r + b q */
123: VecAXPY(&b,P,Q);
124: VecWAXPY(&b,Q,U,P); /* p <- u + b(q + b p) */
125: KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,P,V,Q); /* v <- K p */
127: rhoold = rho;
128: dpold = dp;
129: }
130: if (i == maxit) {
131: i--;
132: ksp->reason = KSP_DIVERGED_ITS;
133: }
135: KSPUnwindPreconditioner(ksp,X,T);
136: *its = i + 1;
137: return(0);
138: }
140: EXTERN_C_BEGIN
141: int KSPCreate_TFQMR(KSP ksp)
142: {
144: ksp->data = (void*)0;
145: ksp->pc_side = PC_LEFT;
146: ksp->calc_res = PETSC_TRUE;
147: ksp->ops->setup = KSPSetUp_TFQMR;
148: ksp->ops->solve = KSPSolve_TFQMR;
149: ksp->ops->destroy = KSPDefaultDestroy;
150: ksp->ops->buildsolution = KSPDefaultBuildSolution;
151: ksp->ops->buildresidual = KSPDefaultBuildResidual;
152: ksp->ops->setfromoptions = 0;
153: ksp->ops->view = 0;
154: return(0);
155: }
156: EXTERN_C_END