Actual source code: cgs.c


  2: /*

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

 10: static PetscErrorCode KSPSetUp_CGS(KSP ksp)
 11: {
 12:   KSPSetWorkVecs(ksp,7);
 13:   return 0;
 14: }

 16: static PetscErrorCode  KSPSolve_CGS(KSP ksp)
 17: {
 18:   PetscInt       i;
 19:   PetscScalar    rho,rhoold,a,s,b;
 20:   Vec            X,B,V,P,R,RP,T,Q,U,AUQ;
 21:   PetscReal      dp = 0.0;
 22:   PetscBool      diagonalscale;

 24:   /* not sure what residual norm it does use, should use for right preconditioning */

 26:   PCGetDiagonalScale(ksp->pc,&diagonalscale);

 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:   AUQ = V;

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

 43:   /* Test for nothing to do */
 44:   if (ksp->normtype != KSP_NORM_NONE) {
 45:     VecNorm(R,NORM_2,&dp);
 46:     KSPCheckNorm(ksp,dp);
 47:     if (ksp->normtype == KSP_NORM_NATURAL) dp *= dp;
 48:   } else dp = 0.0;

 50:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
 51:   ksp->its   = 0;
 52:   ksp->rnorm = dp;
 53:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
 54:   KSPLogResidualHistory(ksp,dp);
 55:   KSPMonitor(ksp,0,dp);
 56:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
 57:   if (ksp->reason) return 0;

 59:   /* Make the initial Rp == R */
 60:   VecCopy(R,RP);
 61:   /*  added for Fidap */
 62:   /* Penalize Startup - Isaac Hasbani Trick for CGS
 63:      Since most initial conditions result in a mostly 0 residual,
 64:      we change all the 0 values in the vector RP to the maximum.
 65:   */
 66:   if (ksp->normtype == KSP_NORM_NATURAL) {
 67:     PetscReal   vr0max;
 68:     PetscScalar *tmp_RP=NULL;
 69:     PetscInt    numnp  =0, *max_pos=NULL;
 70:     VecMax(RP, max_pos, &vr0max);
 71:     VecGetArray(RP, &tmp_RP);
 72:     VecGetLocalSize(RP, &numnp);
 73:     for (i=0; i<numnp; i++) {
 74:       if (tmp_RP[i] == 0.0) tmp_RP[i] = vr0max;
 75:     }
 76:     VecRestoreArray(RP, &tmp_RP);
 77:   }
 78:   /*  end of addition for Fidap */

 80:   /* Set the initial conditions */
 81:   VecDot(R,RP,&rhoold);        /* rhoold = (r,rp)      */
 82:   VecCopy(R,U);
 83:   VecCopy(R,P);
 84:   KSP_PCApplyBAorAB(ksp,P,V,T);

 86:   i = 0;
 87:   do {

 89:     VecDot(V,RP,&s);           /* s <- (v,rp)          */
 90:     KSPCheckDot(ksp,s);
 91:     a    = rhoold / s;                               /* a <- rho / s         */
 92:     VecWAXPY(Q,-a,V,U);      /* q <- u - a v         */
 93:     VecWAXPY(T,1.0,U,Q);      /* t <- u + q           */
 94:     VecAXPY(X,a,T);           /* x <- x + a (u + q)   */
 95:     KSP_PCApplyBAorAB(ksp,T,AUQ,U);
 96:     VecAXPY(R,-a,AUQ);       /* r <- r - a K (u + q) */
 97:     VecDot(R,RP,&rho);         /* rho <- (r,rp)        */
 98:     KSPCheckDot(ksp,rho);
 99:     if (ksp->normtype == KSP_NORM_NATURAL) {
100:       dp = PetscAbsScalar(rho);
101:     } else if (ksp->normtype != KSP_NORM_NONE) {
102:       VecNorm(R,NORM_2,&dp);
103:       KSPCheckNorm(ksp,dp);
104:     } else dp = 0.0;

106:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
107:     ksp->its++;
108:     ksp->rnorm = dp;
109:     PetscObjectSAWsGrantAccess((PetscObject)ksp);
110:     KSPLogResidualHistory(ksp,dp);
111:     KSPMonitor(ksp,i+1,dp);
112:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
113:     if (ksp->reason) break;

115:     b      = rho / rhoold;                           /* b <- rho / rhoold    */
116:     VecWAXPY(U,b,Q,R);       /* u <- r + b q         */
117:     VecAXPY(Q,b,P);
118:     VecWAXPY(P,b,Q,U);       /* p <- u + b(q + b p)  */
119:     KSP_PCApplyBAorAB(ksp,P,V,Q);    /* v <- K p    */
120:     rhoold = rho;
121:     i++;
122:   } while (i<ksp->max_it);
123:   if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;

125:   KSPUnwindPreconditioner(ksp,X,T);
126:   return 0;
127: }

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

132:    Options Database Keys:
133:     see KSPSolve()

135:    Level: beginner

137:    References:
138: .  * - Sonneveld, 1989.

140:    Notes:
141:     Does not require a symmetric matrix. Does not apply transpose of the matrix.
142:         Supports left and right preconditioning, but not symmetric.

144:    Developer Notes:
145:     Has this weird support for doing the convergence test with the natural norm, I assume this works only with
146:       no preconditioning and symmetric positive definite operator.

148: .seealso: KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBCGS, KSPSetPCSide()
149: M*/
150: PETSC_EXTERN PetscErrorCode KSPCreate_CGS(KSP ksp)
151: {
152:   ksp->data = (void*)0;

154:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
155:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
156:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_LEFT,2);
157:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_RIGHT,2);
158:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,1);
159:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);

161:   ksp->ops->setup          = KSPSetUp_CGS;
162:   ksp->ops->solve          = KSPSolve_CGS;
163:   ksp->ops->destroy        = KSPDestroyDefault;
164:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
165:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
166:   ksp->ops->setfromoptions = NULL;
167:   ksp->ops->view           = NULL;
168:   return 0;
169: }