Actual source code: tfqmr.c
petsc-3.12.2 2019-11-22
2: #include <petsc/private/kspimpl.h>
4: static PetscErrorCode KSPSetUp_TFQMR(KSP ksp)
5: {
9: if (ksp->pc_side == PC_SYMMETRIC) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"no symmetric preconditioning for KSPTFQMR");
10: KSPSetWorkVecs(ksp,9);
11: return(0);
12: }
14: static PetscErrorCode KSPSolve_TFQMR(KSP ksp)
15: {
17: PetscInt i,m;
18: PetscScalar rho,rhoold,a,s,b,eta,etaold,psiold,cf;
19: PetscReal dp,dpold,w,dpest,tau,psi,cm;
20: Vec X,B,V,P,R,RP,T,T1,Q,U,D,AUQ;
23: X = ksp->vec_sol;
24: B = ksp->vec_rhs;
25: R = ksp->work[0];
26: RP = ksp->work[1];
27: V = ksp->work[2];
28: T = ksp->work[3];
29: Q = ksp->work[4];
30: P = ksp->work[5];
31: U = ksp->work[6];
32: D = ksp->work[7];
33: T1 = ksp->work[8];
34: AUQ = V;
36: /* Compute initial preconditioned residual */
37: KSPInitialResidual(ksp,X,V,T,R,B);
39: /* Test for nothing to do */
40: VecNorm(R,NORM_2,&dp);
41: KSPCheckNorm(ksp,dp);
42: PetscObjectSAWsTakeAccess((PetscObject)ksp);
43: ksp->rnorm = dp;
44: ksp->its = 0;
45: PetscObjectSAWsGrantAccess((PetscObject)ksp);
46: KSPMonitor(ksp,0,dp);
47: (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
48: if (ksp->reason) return(0);
50: /* Make the initial Rp == R */
51: VecCopy(R,RP);
53: /* Set the initial conditions */
54: etaold = 0.0;
55: psiold = 0.0;
56: tau = dp;
57: dpold = dp;
59: VecDot(R,RP,&rhoold); /* rhoold = (r,rp) */
60: VecCopy(R,U);
61: VecCopy(R,P);
62: KSP_PCApplyBAorAB(ksp,P,V,T);
63: VecSet(D,0.0);
65: i=0;
66: do {
67: PetscObjectSAWsTakeAccess((PetscObject)ksp);
68: ksp->its++;
69: PetscObjectSAWsGrantAccess((PetscObject)ksp);
70: VecDot(V,RP,&s); /* s <- (v,rp) */
71: KSPCheckDot(ksp,s);
72: a = rhoold / s; /* a <- rho / s */
73: VecWAXPY(Q,-a,V,U); /* q <- u - a v */
74: VecWAXPY(T,1.0,U,Q); /* t <- u + q */
75: KSP_PCApplyBAorAB(ksp,T,AUQ,T1);
76: VecAXPY(R,-a,AUQ); /* r <- r - a K (u + q) */
77: VecNorm(R,NORM_2,&dp);
78: KSPCheckNorm(ksp,dp);
79: for (m=0; m<2; m++) {
80: if (!m) w = PetscSqrtReal(dp*dpold);
81: else w = dp;
82: psi = w / tau;
83: cm = 1.0 / PetscSqrtReal(1.0 + psi * psi);
84: tau = tau * psi * cm;
85: eta = cm * cm * a;
86: cf = psiold * psiold * etaold / a;
87: if (!m) {
88: VecAYPX(D,cf,U);
89: } else {
90: VecAYPX(D,cf,Q);
91: }
92: VecAXPY(X,eta,D);
94: dpest = PetscSqrtReal(m + 1.0) * tau;
95: PetscObjectSAWsTakeAccess((PetscObject)ksp);
96: ksp->rnorm = dpest;
97: PetscObjectSAWsGrantAccess((PetscObject)ksp);
98: KSPLogResidualHistory(ksp,dpest);
99: KSPMonitor(ksp,i+1,dpest);
100: (*ksp->converged)(ksp,i+1,dpest,&ksp->reason,ksp->cnvP);
101: if (ksp->reason) break;
103: etaold = eta;
104: psiold = psi;
105: }
106: if (ksp->reason) break;
108: VecDot(R,RP,&rho); /* rho <- (r,rp) */
109: b = rho / rhoold; /* b <- rho / rhoold */
110: VecWAXPY(U,b,Q,R); /* u <- r + b q */
111: VecAXPY(Q,b,P);
112: VecWAXPY(P,b,Q,U); /* p <- u + b(q + b p) */
113: KSP_PCApplyBAorAB(ksp,P,V,Q); /* v <- K p */
115: rhoold = rho;
116: dpold = dp;
118: i++;
119: } while (i<ksp->max_it);
120: if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;
122: KSPUnwindPreconditioner(ksp,X,T);
123: return(0);
124: }
126: /*MC
127: KSPTFQMR - A transpose free QMR (quasi minimal residual),
129: Options Database Keys:
130: . see KSPSolve()
132: Level: beginner
134: Notes:
135: Supports left and right preconditioning, but not symmetric
137: The "residual norm" computed in this algorithm is actually just an upper bound on the actual residual norm.
138: That is for left preconditioning it is a bound on the preconditioned residual and for right preconditioning
139: it is a bound on the true residual.
141: References:
142: . 1. - Freund, 1993
144: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPTCQMR
145: M*/
146: PETSC_EXTERN PetscErrorCode KSPCreate_TFQMR(KSP ksp)
147: {
151: KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
152: KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
154: ksp->data = (void*)0;
155: ksp->ops->setup = KSPSetUp_TFQMR;
156: ksp->ops->solve = KSPSolve_TFQMR;
157: ksp->ops->destroy = KSPDestroyDefault;
158: ksp->ops->buildsolution = KSPBuildSolutionDefault;
159: ksp->ops->buildresidual = KSPBuildResidualDefault;
160: ksp->ops->setfromoptions = 0;
161: ksp->ops->view = 0;
162: return(0);
163: }