Actual source code: tfqmr.c

  1: /*$Id: tfqmr.c,v 1.61 2001/08/07 03:03:54 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: #undef __FUNCT__  
 16: static int KSPSetUp_TFQMR(KSP ksp)
 17: {

 21:   if (ksp->pc_side == PC_SYMMETRIC){
 22:     SETERRQ(2,"no symmetric preconditioning for KSPTFQMR");
 23:   }
 24:   KSPDefaultGetWork(ksp,9);
 25:   return(0);
 26: }

 28: #undef __FUNCT__  
 30: static int  KSPSolve_TFQMR(KSP ksp,int *its)
 31: {
 32:   int       i,maxit,m, ierr;
 33:   PetscScalar    rho,rhoold,a,s,b,eta,etaold,psiold,cf,tmp,one = 1.0,zero = 0.0;
 34:   PetscReal dp,dpold,w,dpest,tau,psi,cm;
 35:   Vec       X,B,V,P,R,RP,T,T1,Q,U,D,AUQ;

 38:   maxit    = ksp->max_it;
 39:   X        = ksp->vec_sol;
 40:   B        = ksp->vec_rhs;
 41:   R        = ksp->work[0];
 42:   RP       = ksp->work[1];
 43:   V        = ksp->work[2];
 44:   T        = ksp->work[3];
 45:   Q        = ksp->work[4];
 46:   P        = ksp->work[5];
 47:   U        = ksp->work[6];
 48:   D        = ksp->work[7];
 49:   T1       = ksp->work[8];
 50:   AUQ      = V;

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

 55:   /* Test for nothing to do */
 56:   VecNorm(R,NORM_2,&dp);
 57:   PetscObjectTakeAccess(ksp);
 58:   ksp->rnorm  = dp;
 59:   ksp->its    = 0;
 60:   PetscObjectGrantAccess(ksp);
 61:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
 62:   if (ksp->reason) {*its = 0; return(0);}
 63:   KSPMonitor(ksp,0,dp);

 65:   /* Make the initial Rp == R */
 66:   VecCopy(R,RP);

 68:   /* Set the initial conditions */
 69:   etaold = 0.0;
 70:   psiold = 0.0;
 71:   tau    = dp;
 72:   dpold  = dp;

 74:   VecDot(R,RP,&rhoold);       /* rhoold = (r,rp)     */
 75:   VecCopy(R,U);
 76:   VecCopy(R,P);
 77:   KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,P,V,T);
 78:   VecSet(&zero,D);

 80:   for (i=0; i<maxit; i++) {
 81:     PetscObjectTakeAccess(ksp);
 82:     ksp->its++;
 83:     PetscObjectGrantAccess(ksp);
 84:     VecDot(V,RP,&s);          /* s <- (v,rp)          */
 85:     a = rhoold / s;                                 /* a <- rho / s         */
 86:     tmp = -a; VecWAXPY(&tmp,V,U,Q);  /* q <- u - a v         */
 87:     VecWAXPY(&one,U,Q,T);     /* t <- u + q           */
 88:     KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,T,AUQ,T1);
 89:     VecAXPY(&tmp,AUQ,R);      /* r <- r - a K (u + q) */
 90:     VecNorm(R,NORM_2,&dp);
 91:     for (m=0; m<2; m++) {
 92:       if (!m) {
 93:         w = sqrt(dp*dpold);
 94:       } else {
 95:         w = dp;
 96:       }
 97:       psi = w / tau;
 98:       cm  = 1.0 / sqrt(1.0 + psi * psi);
 99:       tau = tau * psi * cm;
100:       eta = cm * cm * a;
101:       cf  = psiold * psiold * etaold / a;
102:       if (!m) {
103:         VecAYPX(&cf,U,D);
104:       } else {
105:         VecAYPX(&cf,Q,D);
106:       }
107:       VecAXPY(&eta,D,X);

109:       dpest = sqrt(m + 1.0) * tau;
110:       PetscObjectTakeAccess(ksp);
111:       ksp->rnorm                                    = dpest;
112:       PetscObjectGrantAccess(ksp);
113:       KSPLogResidualHistory(ksp,dpest);
114:       KSPMonitor(ksp,i+1,dpest);
115:       (*ksp->converged)(ksp,i+1,dpest,&ksp->reason,ksp->cnvP);
116:       if (ksp->reason) break;

118:       etaold = eta;
119:       psiold = psi;
120:     }
121:     if (ksp->reason) break;

123:     VecDot(R,RP,&rho);        /* rho <- (r,rp)       */
124:     b = rho / rhoold;                               /* b <- rho / rhoold   */
125:     VecWAXPY(&b,Q,R,U);       /* u <- r + b q        */
126:     VecAXPY(&b,P,Q);
127:     VecWAXPY(&b,Q,U,P);       /* p <- u + b(q + b p) */
128:     KSP_PCApplyBAorAB(ksp,ksp->B,ksp->pc_side,P,V,Q); /* v <- K p  */

130:     rhoold = rho;
131:     dpold  = dp;
132:   }
133:   if (i == maxit) {
134:     ksp->reason = KSP_DIVERGED_ITS;
135:   }

137:   KSPUnwindPreconditioner(ksp,X,T);
138:   *its = ksp->its;
139:   return(0);
140: }

142: EXTERN_C_BEGIN
143: #undef __FUNCT__  
145: int KSPCreate_TFQMR(KSP ksp)
146: {
148:   ksp->data                      = (void*)0;
149:   ksp->pc_side                   = PC_LEFT;
150:   ksp->ops->setup                = KSPSetUp_TFQMR;
151:   ksp->ops->solve                = KSPSolve_TFQMR;
152:   ksp->ops->destroy              = KSPDefaultDestroy;
153:   ksp->ops->buildsolution        = KSPDefaultBuildSolution;
154:   ksp->ops->buildresidual        = KSPDefaultBuildResidual;
155:   ksp->ops->setfromoptions       = 0;
156:   ksp->ops->view                 = 0;
157:   return(0);
158: }
159: EXTERN_C_END