Date: 2021-03-03T22:27:21+00:00

Actual source code: bcgs.c
petsc-3.14.5 2021-03-03
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      2: #include <../src/ksp/ksp/impls/bcgs/bcgsimpl.h>

      4: PetscErrorCode KSPSetFromOptions_BCGS(PetscOptionItems *PetscOptionsObject,KSP ksp)
      5: {

      9:   PetscOptionsHead(PetscOptionsObject,"KSP BCGS Options");
     10:   PetscOptionsTail();
     11:   return(0);
     12: }

     14: PetscErrorCode KSPSetUp_BCGS(KSP ksp)
     15: {

     19:   KSPSetWorkVecs(ksp,6);
     20:   return(0);
     21: }

     24: PetscErrorCode KSPSolve_BCGS(KSP ksp)
     25: {
     27:   PetscInt       i;
     28:   PetscScalar    rho,rhoold,alpha,beta,omega,omegaold,d1;
     29:   Vec            X,B,V,P,R,RP,T,S;
     30:   PetscReal      dp    = 0.0,d2;
     31:   KSP_BCGS       *bcgs = (KSP_BCGS*)ksp->data;

     34:   X  = ksp->vec_sol;
     35:   B  = ksp->vec_rhs;
     36:   R  = ksp->work[0];
     37:   RP = ksp->work[1];
     38:   V  = ksp->work[2];
     39:   T  = ksp->work[3];
     40:   S  = ksp->work[4];
     41:   P  = ksp->work[5];

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

     46:   /* with right preconditioning need to save initial guess to add to final solution */
     47:   if (ksp->pc_side == PC_RIGHT && !ksp->guess_zero) {
     48:     if (!bcgs->guess) {
     49:       VecDuplicate(X,&bcgs->guess);
     50:     }
     51:     VecCopy(X,bcgs->guess);
     52:     VecSet(X,0.0);
     53:   }

     55:   /* Test for nothing to do */
     56:   if (ksp->normtype != KSP_NORM_NONE) {
     57:     VecNorm(R,NORM_2,&dp);
     58:     KSPCheckNorm(ksp,dp);
     59:   }
     60:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
     61:   ksp->its   = 0;
     62:   ksp->rnorm = dp;
     63:   PetscObjectSAWsGrantAccess((PetscObject)ksp);
     64:   KSPLogResidualHistory(ksp,dp);
     65:   KSPMonitor(ksp,0,dp);
     66:   (*ksp->converged)(ksp,0,dp,&ksp->reason,ksp->cnvP);
     67:   if (ksp->reason) {
     68:     if (bcgs->guess) {
     69:       VecAXPY(X,1.0,bcgs->guess);
     70:     }
     71:     return(0);
     72:   }

     74:   /* Make the initial Rp == R */
     75:   VecCopy(R,RP);

     77:   rhoold   = 1.0;
     78:   alpha    = 1.0;
     79:   omegaold = 1.0;
     80:   VecSet(P,0.0);
     81:   VecSet(V,0.0);

     83:   i=0;
     84:   do {
     85:     VecDot(R,RP,&rho);       /*   rho <- (r,rp)      */
     86:     beta = (rho/rhoold) * (alpha/omegaold);
     87:     VecAXPBYPCZ(P,1.0,-omegaold*beta,beta,R,V);  /* p <- r - omega * beta* v + beta * p */
     88:     KSP_PCApplyBAorAB(ksp,P,V,T);  /*   v <- K p           */
     89:     VecDot(V,RP,&d1);
     90:     KSPCheckDot(ksp,d1);
     91:     if (d1 == 0.0) {
     92:       if (ksp->errorifnotconverged) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"KSPSolve has not converged due to Nan or Inf inner product");
     93:       else {
     94:         ksp->reason = KSP_DIVERGED_NANORINF;
     95:         break;
     96:       }
     97:     }
     98:     alpha = rho / d1;                 /*   a <- rho / (v,rp)  */
     99:     VecWAXPY(S,-alpha,V,R);     /*   s <- r - a v       */
    100:     KSP_PCApplyBAorAB(ksp,S,T,R); /*   t <- K s    */
    101:     VecDotNorm2(S,T,&d1,&d2);
    102:     if (d2 == 0.0) {
    103:       /* t is 0.  if s is 0, then alpha v == r, and hence alpha p
    104:          may be our solution.  Give it a try? */
    105:       VecDot(S,S,&d1);
    106:       if (d1 != 0.0) {
    107:         ksp->reason = KSP_DIVERGED_BREAKDOWN;
    108:         break;
    109:       }
    110:       VecAXPY(X,alpha,P);   /*   x <- x + a p       */
    111:       PetscObjectSAWsTakeAccess((PetscObject)ksp);
    112:       ksp->its++;
    113:       ksp->rnorm  = 0.0;
    114:       ksp->reason = KSP_CONVERGED_RTOL;
    115:       PetscObjectSAWsGrantAccess((PetscObject)ksp);
    116:       KSPLogResidualHistory(ksp,dp);
    117:       KSPMonitor(ksp,i+1,0.0);
    118:       break;
    119:     }
    120:     omega = d1 / d2;                               /*   w <- (t's) / (t't) */
    121:     VecAXPBYPCZ(X,alpha,omega,1.0,P,S); /* x <- alpha * p + omega * s + x */
    122:     VecWAXPY(R,-omega,T,S);     /*   r <- s - w t       */
    123:     if (ksp->normtype != KSP_NORM_NONE && ksp->chknorm < i+2) {
    124:       VecNorm(R,NORM_2,&dp);
    125:       KSPCheckNorm(ksp,dp);
    126:     }

    128:     rhoold   = rho;
    129:     omegaold = omega;

    131:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
    132:     ksp->its++;
    133:     ksp->rnorm = dp;
    134:     PetscObjectSAWsGrantAccess((PetscObject)ksp);
    135:     KSPLogResidualHistory(ksp,dp);
    136:     KSPMonitor(ksp,i+1,dp);
    137:     (*ksp->converged)(ksp,i+1,dp,&ksp->reason,ksp->cnvP);
    138:     if (ksp->reason) break;
    139:     if (rho == 0.0) {
    140:       ksp->reason = KSP_DIVERGED_BREAKDOWN;
    141:       break;
    142:     }
    143:     i++;
    144:   } while (i<ksp->max_it);

    146:   if (i >= ksp->max_it) ksp->reason = KSP_DIVERGED_ITS;

    148:   KSPUnwindPreconditioner(ksp,X,T);
    149:   if (bcgs->guess) {
    150:     VecAXPY(X,1.0,bcgs->guess);
    151:   }
    152:   return(0);
    153: }

    155: PetscErrorCode KSPBuildSolution_BCGS(KSP ksp,Vec v,Vec *V)
    156: {
    158:   KSP_BCGS       *bcgs = (KSP_BCGS*)ksp->data;

    161:   if (ksp->pc_side == PC_RIGHT) {
    162:     if (v) {
    163:       KSP_PCApply(ksp,ksp->vec_sol,v);
    164:       if (bcgs->guess) {
    165:         VecAXPY(v,1.0,bcgs->guess);
    166:       }
    167:       *V = v;
    168:     } else SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Not working with right preconditioner");
    169:   } else {
    170:     if (v) {
    171:       VecCopy(ksp->vec_sol,v); *V = v;
    172:     } else *V = ksp->vec_sol;
    173:   }
    174:   return(0);
    175: }

    177: PetscErrorCode KSPReset_BCGS(KSP ksp)
    178: {
    179:   KSP_BCGS       *cg = (KSP_BCGS*)ksp->data;

    183:   VecDestroy(&cg->guess);
    184:   return(0);
    185: }

    187: PetscErrorCode KSPDestroy_BCGS(KSP ksp)
    188: {

    192:   KSPReset_BCGS(ksp);
    193:   KSPDestroyDefault(ksp);
    194:   return(0);
    195: }

    197: /*MC
    198:      KSPBCGS - Implements the BiCGStab (Stabilized version of BiConjugate Gradient) method.

    200:    Options Database Keys:
    201: .   see KSPSolve()

    203:    Level: beginner

    205:    Notes:
    206:     See KSPBCGSL for additional stabilization
    207:           Supports left and right preconditioning but not symmetric

    209:    References:
    210: .    1. -   van der Vorst, SIAM J. Sci. Stat. Comput., 1992.

    212: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPBICG, KSPBCGSL, KSPFBICG, KSPSetPCSide()
    213: M*/
    214: PETSC_EXTERN PetscErrorCode KSPCreate_BCGS(KSP ksp)
    215: {
    217:   KSP_BCGS       *bcgs;

    220:   PetscNewLog(ksp,&bcgs);

    222:   ksp->data                = bcgs;
    223:   ksp->ops->setup          = KSPSetUp_BCGS;
    224:   ksp->ops->solve          = KSPSolve_BCGS;
    225:   ksp->ops->destroy        = KSPDestroy_BCGS;
    226:   ksp->ops->reset          = KSPReset_BCGS;
    227:   ksp->ops->buildsolution  = KSPBuildSolution_BCGS;
    228:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
    229:   ksp->ops->setfromoptions = KSPSetFromOptions_BCGS;

    231:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
    232:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,2);
    233:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_LEFT,1);
    234:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);
    235:   return(0);
    236: }