Actual source code: lcd.c
petsc-3.7.1 2016-05-15
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      2: #include <../src/ksp/ksp/impls/lcd/lcdimpl.h>

      6: PetscErrorCode KSPSetUp_LCD(KSP ksp)
      7: {
      8:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;
     10:   PetscInt       restart = lcd->restart;

     13:   /* get work vectors needed by LCD */
     14:   KSPSetWorkVecs(ksp,2);

     16:   VecDuplicateVecs(ksp->work[0],restart+1,&lcd->P);
     17:   VecDuplicateVecs(ksp->work[0], restart + 1, &lcd->Q);
     18:   PetscLogObjectMemory((PetscObject)ksp,2*(restart+2)*sizeof(Vec));
     19:   return(0);
     20: }

     22: /*     KSPSolve_LCD - This routine actually applies the left conjugate
     23:     direction method

     25:    Input Parameter:
     26: .     ksp - the Krylov space object that was set to use LCD, by, for
     27:             example, KSPCreate(MPI_Comm,KSP *ksp); KSPSetType(ksp,KSPLCD);

     29:    Output Parameter:
     30: .     its - number of iterations used

     32: */
     35: PetscErrorCode  KSPSolve_LCD(KSP ksp)
     36: {
     38:   PetscInt       it,j,max_k;
     39:   PetscScalar    alfa, beta, num, den, mone;
     40:   PetscReal      rnorm;
     41:   Vec            X,B,R,Z;
     42:   KSP_LCD        *lcd;
     43:   Mat            Amat,Pmat;
     44:   PetscBool      diagonalscale;

     47:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
     48:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);

     50:   lcd   = (KSP_LCD*)ksp->data;
     51:   X     = ksp->vec_sol;
     52:   B     = ksp->vec_rhs;
     53:   R     = ksp->work[0];
     54:   Z     = ksp->work[1];
     55:   max_k = lcd->restart;
     56:   mone  = -1;

     58:   PCGetOperators(ksp->pc,&Amat,&Pmat);

     60:   ksp->its = 0;
     61:   if (!ksp->guess_zero) {
     62:     KSP_MatMult(ksp,Amat,X,Z);             /*   z <- b - Ax       */
     63:     VecAYPX(Z,mone,B);
     64:   } else {
     65:     VecCopy(B,Z);                         /*     z <- b (x is 0) */
     66:   }

     68:   KSP_PCApply(ksp,Z,R);                   /*     r <- M^-1z         */
     69:   VecNorm(R,NORM_2,&rnorm);
     70:   KSPLogResidualHistory(ksp,rnorm);
     71:   KSPMonitor(ksp,0,rnorm);
     72:   ksp->rnorm = rnorm;

     74:   /* test for convergence */
     75:   (*ksp->converged)(ksp,0,rnorm,&ksp->reason,ksp->cnvP);
     76:   if (ksp->reason) return(0);

     78:   VecCopy(R,lcd->P[0]);

     80:   while (!ksp->reason && ksp->its < ksp->max_it) {
     81:     it   = 0;
     82:     KSP_MatMult(ksp,Amat,lcd->P[it],Z);
     83:     KSP_PCApply(ksp,Z,lcd->Q[it]);

     85:     while (!ksp->reason && it < max_k && ksp->its < ksp->max_it) {
     86:       ksp->its++;
     87:       VecDot(lcd->P[it],R,&num);
     88:       VecDot(lcd->P[it],lcd->Q[it], &den);
     89:       alfa = num/den;
     90:       VecAXPY(X,alfa,lcd->P[it]);
     91:       VecAXPY(R,-alfa,lcd->Q[it]);
     92:       VecNorm(R,NORM_2,&rnorm);

     94:       ksp->rnorm = rnorm;
     95:       KSPLogResidualHistory(ksp,rnorm);
     96:       KSPMonitor(ksp,ksp->its,rnorm);
     97:       (*ksp->converged)(ksp,ksp->its,rnorm,&ksp->reason,ksp->cnvP);

     99:       if (ksp->reason) break;

    101:       VecCopy(R,lcd->P[it+1]);
    102:       KSP_MatMult(ksp,Amat,lcd->P[it+1],Z);
    103:       KSP_PCApply(ksp,Z,lcd->Q[it+1]);

    105:       for (j = 0; j <= it; j++) {
    106:         VecDot(lcd->P[j],lcd->Q[it+1],&num);
    107:         VecDot(lcd->P[j],lcd->Q[j],&den);
    108:         beta = -num/den;
    109:         VecAXPY(lcd->P[it+1],beta,lcd->P[j]);
    110:         VecAXPY(lcd->Q[it+1],beta,lcd->Q[j]);
    111:       }
    112:       it++;
    113:     }
    114:     VecCopy(lcd->P[it],lcd->P[0]);
    115:   }
    116:   if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
    117:   VecCopy(X,ksp->vec_sol);
    118:   return(0);
    119: }
    120: /*
    121:        KSPDestroy_LCD - Frees all memory space used by the Krylov method

    123: */
    126: PetscErrorCode KSPReset_LCD(KSP ksp)
    127: {
    128:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;

    132:   if (lcd->P) { VecDestroyVecs(lcd->restart+1,&lcd->P);}
    133:   if (lcd->Q) { VecDestroyVecs(lcd->restart+1,&lcd->Q);}
    134:   return(0);
    135: }

    140: PetscErrorCode KSPDestroy_LCD(KSP ksp)
    141: {

    145:   KSPReset_LCD(ksp);
    146:   PetscFree(ksp->data);
    147:   return(0);
    148: }

    150: /*
    151:      KSPView_LCD - Prints information about the current Krylov method being used

    153:       Currently this only prints information to a file (or stdout) about the
    154:       symmetry of the problem. If your Krylov method has special options or
    155:       flags that information should be printed here.

    157: */
    160: PetscErrorCode KSPView_LCD(KSP ksp,PetscViewer viewer)
    161: {

    163:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;
    165:   PetscBool      iascii;

    168:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    169:   if (iascii) {
    170:     PetscViewerASCIIPrintf(viewer,"  LCD: restart=%d\n",lcd->restart);
    171:     PetscViewerASCIIPrintf(viewer,"  LCD: happy breakdown tolerance %g\n",lcd->haptol);
    172:   }
    173:   return(0);
    174: }

    176: /*
    177:     KSPSetFromOptions_LCD - Checks the options database for options related to the
    178:                             LCD method.
    179: */
    182: PetscErrorCode KSPSetFromOptions_LCD(PetscOptionItems *PetscOptionsObject,KSP ksp)
    183: {
    185:   PetscBool      flg;
    186:   KSP_LCD        *lcd = (KSP_LCD*)ksp->data;

    189:   PetscOptionsHead(PetscOptionsObject,"KSP LCD options");
    190:   PetscOptionsInt("-ksp_lcd_restart","Number of vectors conjugate","KSPLCDSetRestart",lcd->restart,&lcd->restart,&flg);
    191:   if (flg && lcd->restart < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
    192:   PetscOptionsReal("-ksp_lcd_haptol","Tolerance for exact convergence (happy ending)","KSPLCDSetHapTol",lcd->haptol,&lcd->haptol,&flg);
    193:   if (flg && lcd->haptol < 0.0) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Tolerance must be non-negative");
    194:   return(0);
    195: }

    197: /*MC
    198:      KSPLCD -  Implements the LCD (left conjugate direction) method in PETSc.

    200:    Options Database Keys:
    201: +   -ksp_lcd_restart - number of vectors conjudate
    202: -   -ksp_lcd_haptol - tolerance for exact convergence (happing ending)

    204:    Level: beginner

    206:     Notes: Support only for left preconditioning

    208:     References:
    209: +    1. - J.Y. Yuan, G.H.Golub, R.J. Plemmons, and W.A.G. Cecilio. Semiconjugate
    210:      direction methods for real positive definite system. BIT Numerical
    211:      Mathematics, 44(1),2004.
    212: .    2. - Y. Dai and J.Y. Yuan. Study on semiconjugate direction methods for
    213:      nonsymmetric systems. International Journal for Numerical Methods in
    214:      Engineering, 60, 2004.
    215: .    3. - L. Catabriga, A.L.G.A. Coutinho, and L.P.Franca. Evaluating the LCD
    216:      algorithm for solving linear systems of equations arising from implicit
    217:      SUPG formulation of compressible flows. International Journal for
    218:      Numerical Methods in Engineering, 60, 2004
    219: -    4. - L. Catabriga, A. M. P. Valli, B. Z. Melotti, L. M. Pessoa,
    220:      A. L. G. A. Coutinho, Performance of LCD iterative method in the finite
    221:      element and finite difference solution of convection diffusion
    222:      equations,  Communications in Numerical Methods in Engineering, (Early
    223:      View).

    225:   Contributed by: Lucia Catabriga <luciac@ices.utexas.edu>

    228: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP,
    229:            KSPCGSetType(), KSPLCDSetRestart(), KSPLCDSetHapTol()

    231: M*/

    235: PETSC_EXTERN PetscErrorCode KSPCreate_LCD(KSP ksp)
    236: {
    238:   KSP_LCD        *lcd;

    241:   PetscNewLog(ksp,&lcd);
    242:   ksp->data    = (void*)lcd;
    243:   KSPSetSupportedNorm(ksp,KSP_NORM_PRECONDITIONED,PC_LEFT,3);
    244:   lcd->restart = 30;
    245:   lcd->haptol  = 1.0e-30;

    247:   /*
    248:        Sets the functions that are associated with this data structure
    249:        (in C++ this is the same as defining virtual functions)
    250:   */
    251:   ksp->ops->setup          = KSPSetUp_LCD;
    252:   ksp->ops->solve          = KSPSolve_LCD;
    253:   ksp->ops->reset          = KSPReset_LCD;
    254:   ksp->ops->destroy        = KSPDestroy_LCD;
    255:   ksp->ops->view           = KSPView_LCD;
    256:   ksp->ops->setfromoptions = KSPSetFromOptions_LCD;
    257:   ksp->ops->buildsolution  = KSPBuildSolutionDefault;
    258:   ksp->ops->buildresidual  = KSPBuildResidualDefault;
    259:   return(0);
    260: }