Date: 2016-07-24T17:06:31+00:00

Actual source code: cgs.c
petsc-3.7.3 2016-07-24
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      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>

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

     17:   KSPSetWorkVecs(ksp,7);
     18:   return(0);
     19: }

     23: static PetscErrorCode  KSPSolve_CGS(KSP ksp)
     24: {
     26:   PetscInt       i;
     27:   PetscScalar    rho,rhoold,a,s,b;
     28:   Vec            X,B,V,P,R,RP,T,Q,U,AUQ;
     29:   PetscReal      dp = 0.0;
     30:   PetscBool      diagonalscale;

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

     35:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
     36:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)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_NORM_NATURAL) dp *= dp;
     55:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
     56:   ksp->its   = 0;
     57:   ksp->rnorm = dp;
     58:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
     59:   KSPLogResidualHistory(ksp,dp);
     60:   KSPMonitor(ksp,0,dp);
     61:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
     62:   if (ksp->reason) return(0);

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

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

     91:   i = 0;
     92:   do {

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

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

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

    127:   KSPUnwindPreconditioner(ksp,X,T);
    128:   return(0);
    129: }

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

    134:    Options Database Keys:
    135: .   see KSPSolve()

    137:    Level: beginner

    139:    References:
    140: .     1. - Sonneveld, 1989.

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

    145:    Developer Notes: 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*/
    152: PETSC_EXTERN PetscErrorCode KSPCreate_CGS(KSP ksp)
    153: {

    157:   ksp->data = (void*)0;

    159:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
    160:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
    161:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_LEFT,2);
    162:   KSPSetSupportedNorm(ksp,KSP_NORM_NATURAL,PC_RIGHT,2);

    164:   ksp->ops->setup          = KSPSetUp_CGS;
    165:   ksp->ops->solve          = KSPSolve_CGS;
    166:   ksp->ops->destroy        = KSPDestroyDefault;
    167:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
    168:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
    169:   ksp->ops->setfromoptions = 0;
    170:   ksp->ops->view           = 0;
    171:   return(0);
    172: }