Actual source code: tfqmr.c

  1: /*$Id: tfqmr.c,v 1.61 2001/08/07 03:03:54 balay Exp $*/

 3:  #include src/ksp/ksp/kspimpl.h

  7: static int KSPSetUp_TFQMR(KSP ksp)
  8: {

 12:   if (ksp->pc_side == PC_SYMMETRIC){
 13:     SETERRQ(2,"no symmetric preconditioning for KSPTFQMR");
 14:   }
 15:   KSPDefaultGetWork(ksp,9);
 16:   return(0);
 17: }

 21: static int  KSPSolve_TFQMR(KSP ksp)
 22: {
 23:   int         i,m, ierr;
 24:   PetscScalar rho,rhoold,a,s,b,eta,etaold,psiold,cf,tmp,one = 1.0,zero = 0.0;
 25:   PetscReal   dp,dpold,w,dpest,tau,psi,cm;
 26:   Vec         X,B,V,P,R,RP,T,T1,Q,U,D,AUQ;

 29:   X        = ksp->vec_sol;
 30:   B        = ksp->vec_rhs;
 31:   R        = ksp->work[0];
 32:   RP       = ksp->work[1];
 33:   V        = ksp->work[2];
 34:   T        = ksp->work[3];
 35:   Q        = ksp->work[4];
 36:   P        = ksp->work[5];
 37:   U        = ksp->work[6];
 38:   D        = ksp->work[7];
 39:   T1       = ksp->work[8];
 40:   AUQ      = V;

 42:   /* Compute initial preconditioned residual */
 43:   KSPInitialResidual(ksp,X,V,T,R,B);

 45:   /* Test for nothing to do */
 46:   VecNorm(R,NORM_2,&dp);
 47:   PetscObjectTakeAccess(ksp);
 48:   ksp->rnorm  = dp;
 49:   ksp->its    = 0;
 50:   PetscObjectGrantAccess(ksp);
 51:   KSPMonitor(ksp,0,dp);
 52:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
 53:   if (ksp->reason) return(0);

 55:   /* Make the initial Rp == R */
 56:   VecCopy(R,RP);

 58:   /* Set the initial conditions */
 59:   etaold = 0.0;
 60:   psiold = 0.0;
 61:   tau    = dp;
 62:   dpold  = dp;

 64:   VecDot(R,RP,&rhoold);       /* rhoold = (r,rp)     */
 65:   VecCopy(R,U);
 66:   VecCopy(R,P);
 67:   KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,P,V,T);
 68:   VecSet(&zero,D);

 70:   i=0;
 71:   do {
 72:     PetscObjectTakeAccess(ksp);
 73:     ksp->its++;
 74:     PetscObjectGrantAccess(ksp);
 75:     VecDot(V,RP,&s);          /* s <- (v,rp)          */
 76:     a = rhoold / s;                                 /* a <- rho / s         */
 77:     tmp = -a; VecWAXPY(&tmp,V,U,Q);  /* q <- u - a v         */
 78:     VecWAXPY(&one,U,Q,T);     /* t <- u + q           */
 79:     KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,T,AUQ,T1);
 80:     VecAXPY(&tmp,AUQ,R);      /* r <- r - a K (u + q) */
 81:     VecNorm(R,NORM_2,&dp);
 82:     for (m=0; m<2; m++) {
 83:       if (!m) {
 84:         w = sqrt(dp*dpold);
 85:       } else {
 86:         w = dp;
 87:       }
 88:       psi = w / tau;
 89:       cm  = 1.0 / sqrt(1.0 + psi * psi);
 90:       tau = tau * psi * cm;
 91:       eta = cm * cm * a;
 92:       cf  = psiold * psiold * etaold / a;
 93:       if (!m) {
 94:         VecAYPX(&cf,U,D);
 95:       } else {
 96:         VecAYPX(&cf,Q,D);
 97:       }
 98:       VecAXPY(&eta,D,X);

100:       dpest = sqrt(m + 1.0) * tau;
101:       PetscObjectTakeAccess(ksp);
102:       ksp->rnorm                                    = dpest;
103:       PetscObjectGrantAccess(ksp);
104:       KSPLogResidualHistory(ksp,dpest);
105:       KSPMonitor(ksp,i+1,dpest);
106:       (*ksp->converged)(ksp,i+1,dpest,&ksp->reason,ksp->cnvP);
107:       if (ksp->reason) break;

109:       etaold = eta;
110:       psiold = psi;
111:     }
112:     if (ksp->reason) break;

114:     VecDot(R,RP,&rho);        /* rho <- (r,rp)       */
115:     b = rho / rhoold;                               /* b <- rho / rhoold   */
116:     VecWAXPY(&b,Q,R,U);       /* u <- r + b q        */
117:     VecAXPY(&b,P,Q);
118:     VecWAXPY(&b,Q,U,P);       /* p <- u + b(q + b p) */
119:     KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,P,V,Q); /* v <- K p  */

121:     rhoold = rho;
122:     dpold  = dp;

124:     i++;
125:   } while (i<ksp->max_it);
126:   if (i == ksp->max_it) {
127:     ksp->reason = KSP_DIVERGED_ITS;
128:   }

130:   KSPUnwindPreconditioner(ksp,X,T);
131:   return(0);
132: }

134: /*MC
135:      KSPRTFQMR - A transpose free QMR (quasi minimal residual), Freund, 1993

137:    Options Database Keys:
138: .   see KSPSolve()

140:    Level: beginner

142: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPTCQMR

144: M*/

146: EXTERN_C_BEGIN
149: int KSPCreate_TFQMR(KSP ksp)
150: {
152:   ksp->data                      = (void*)0;
153:   ksp->pc_side                   = PC_LEFT;
154:   ksp->ops->setup                = KSPSetUp_TFQMR;
155:   ksp->ops->solve                = KSPSolve_TFQMR;
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: }
163: EXTERN_C_END