Actual source code: cgs.c

  1: #define PETSCKSP_DLL

  3: /*                       

  5:     Note that for the complex numbers version, the VecDot() arguments
  6:     within the code MUST remain in the order given for correct computation
  7:     of inner products.
  8: */
 9:  #include src/ksp/ksp/kspimpl.h

 13: static PetscErrorCode KSPSetUp_CGS(KSP ksp)
 14: {

 18:   if (ksp->pc_side == PC_SYMMETRIC) SETERRQ(PETSC_ERR_SUP,"no symmetric preconditioning for KSPCGS");
 19:   KSPDefaultGetWork(ksp,7);
 20:   return(0);
 21: }

 25: static PetscErrorCode  KSPSolve_CGS(KSP ksp)
 26: {
 28:   PetscInt       i;
 29:   PetscScalar    rho,rhoold,a,s,b;
 30:   Vec            X,B,V,P,R,RP,T,Q,U,AUQ;
 31:   PetscReal      dp = 0.0;
 32:   PetscTruth     diagonalscale;

 35:   PCDiagonalScale(ksp->pc,&diagonalscale);
 36:   if (diagonalscale) SETERRQ1(PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",ksp->type_name);

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

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

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

 66:   /* Make the initial Rp == R */
 67:   VecCopy(R,RP);
 68:   /*  added for Fidap */
 69:   /* Penalize Startup - Isaac Hasbani Trick for CGS 
 70:      Since most initial conditions result in a mostly 0 residual,
 71:      we change all the 0 values in the vector RP to the maximum.
 72:   */
 73:   if (ksp->normtype == KSP_NATURAL_NORM) {
 74:      PetscReal   vr0max;
 75:      PetscScalar *tmp_RP=0;
 76:      PetscInt    numnp=0, *max_pos=0;
 77:      VecMax(RP, max_pos, &vr0max);
 78:      VecGetArray(RP, &tmp_RP);
 79:      VecGetLocalSize(RP, &numnp);
 80:      for (i=0; i<numnp; i++) {
 81:        if (tmp_RP[i] == 0.0) tmp_RP[i] = vr0max;
 82:      }
 83:      VecRestoreArray(RP, &tmp_RP);
 84:   }
 85:   /*  end of addition for Fidap */

 87:   /* Set the initial conditions */
 88:   VecDot(R,RP,&rhoold);        /* rhoold = (r,rp)      */
 89:   VecCopy(R,U);
 90:   VecCopy(R,P);
 91:   KSP_PCApplyBAorAB(ksp,P,V,T);

 93:   i = 0;
 94:   do {

 96:     VecDot(V,RP,&s);           /* s <- (v,rp)          */
 97:     a = rhoold / s;                                  /* a <- rho / s         */
 98:     VecWAXPY(Q,-a,V,U);      /* q <- u - a v         */
 99:     VecWAXPY(T,1.0,U,Q);      /* t <- u + q           */
100:     VecAXPY(X,a,T);           /* x <- x + a (u + q)   */
101:     KSP_PCApplyBAorAB(ksp,T,AUQ,U);
102:     VecAXPY(R,-a,AUQ);       /* r <- r - a K (u + q) */
103:     VecDot(R,RP,&rho);         /* rho <- (r,rp)        */
104:     if (ksp->normtype == KSP_PRECONDITIONED_NORM) {
105:       VecNorm(R,NORM_2,&dp);
106:     } else if (ksp->normtype == KSP_NATURAL_NORM) {
107:       dp = PetscAbsScalar(rho);
108:     }

110:     PetscObjectTakeAccess(ksp);
111:     ksp->its++;
112:     ksp->rnorm = dp;
113:     PetscObjectGrantAccess(ksp);
114:     KSPLogResidualHistory(ksp,dp);
115:     KSPMonitor(ksp,i+1,dp);
116:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
117:     if (ksp->reason) break;

119:     b    = rho / rhoold;                             /* b <- rho / rhoold    */
120:     VecWAXPY(U,b,Q,R);         /* u <- r + b q         */
121:     VecAXPY(Q,b,P);
122:     VecWAXPY(P,b,Q,U);         /* p <- u + b(q + b p)  */
123:     KSP_PCApplyBAorAB(ksp,P,V,Q);      /* v <- K p    */
124:     rhoold = rho;
125:     i++;
126:   } while (i<ksp->max_it);
127:   if (i >= ksp->max_it) {
128:     ksp->reason = KSP_DIVERGED_ITS;
129:   }

131:   KSPUnwindPreconditioner(ksp,X,T);
132:   return(0);
133: }

135: /*MC
136:      KSPCGS - This code implements the CGS (Conjugate Gradient Squared) method. 

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

141:    Level: beginner

143:    Notes: Reference: Sonneveld, 1989.

145: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS
146: M*/
150: PetscErrorCode  KSPCreate_CGS(KSP ksp)
151: {
153:   ksp->data                      = (void*)0;
154:   ksp->pc_side                   = PC_LEFT;
155:   ksp->ops->setup                = KSPSetUp_CGS;
156:   ksp->ops->solve                = KSPSolve_CGS;
157:   ksp->ops->destroy              = KSPDefaultDestroy;
158:   ksp->ops->buildsolution        = KSPDefaultBuildSolution;
159:   ksp->ops->buildresidual        = KSPDefaultBuildResidual;
160:   ksp->ops->setfromoptions       = 0;
161:   ksp->ops->view                 = 0;
162:   return(0);
163: }