Date: 2023-01-26T12:18:21+00:00

Actual source code: shift.c
slepc-3.18.2 2023-01-26
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.
      7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: */
     10: /*
     11:    Shift spectral transformation, applies (A + sigma I) as operator, or
     12:    inv(B)(A + sigma B) for generalized problems
     13: */

     15: #include <slepc/private/stimpl.h>

     17: PetscErrorCode STBackTransform_Shift(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     18: {
     19:   PetscInt j;

     21:   for (j=0;j<n;j++) {
     22:     eigr[j] += st->sigma;
     23:   }
     24:   return 0;
     25: }

     27: PetscErrorCode STPostSolve_Shift(ST st)
     28: {
     29:   if (st->matmode == ST_MATMODE_INPLACE) {
     30:     if (st->nmat>1) MatAXPY(st->A[0],st->sigma,st->A[1],st->str);
     31:     else MatShift(st->A[0],st->sigma);
     32:     st->Astate[0] = ((PetscObject)st->A[0])->state;
     33:     st->state   = ST_STATE_INITIAL;
     34:     st->opready = PETSC_FALSE;
     35:   }
     36:   return 0;
     37: }

     39: /*
     40:    Operator (shift):
     41:                Op               P         M
     42:    if nmat=1:  A-sI             NULL      A-sI
     43:    if nmat=2:  B^-1 (A-sB)      B         A-sB
     44: */
     45: PetscErrorCode STComputeOperator_Shift(ST st)
     46: {
     47:   st->usesksp = (st->nmat>1)? PETSC_TRUE: PETSC_FALSE;
     48:   PetscObjectReference((PetscObject)st->A[1]);
     49:   MatDestroy(&st->T[1]);
     50:   st->T[1] = st->A[1];
     51:   STMatMAXPY_Private(st,-st->sigma,0.0,0,NULL,PetscNot(st->state==ST_STATE_UPDATED),PETSC_FALSE,&st->T[0]);
     52:   if (st->nmat>1) PetscObjectReference((PetscObject)st->T[1]);
     53:   MatDestroy(&st->P);
     54:   st->P = (st->nmat>1)? st->T[1]: NULL;
     55:   st->M = st->T[0];
     56:   if (st->nmat>1 && st->Psplit) {  /* build custom preconditioner from the split matrices */
     57:     MatDestroy(&st->Pmat);
     58:     PetscObjectReference((PetscObject)st->Psplit[1]);
     59:     st->Pmat = st->Psplit[1];
     60:   }
     61:   return 0;
     62: }

     64: PetscErrorCode STSetUp_Shift(ST st)
     65: {
     66:   PetscInt       k,nc,nmat=st->nmat;
     67:   PetscScalar    *coeffs=NULL;

     69:   if (nmat>1) STSetWorkVecs(st,1);
     70:   if (nmat>2) {  /* set-up matrices for polynomial eigenproblems */
     71:     if (st->transform) {
     72:       nc = (nmat*(nmat+1))/2;
     73:       PetscMalloc1(nc,&coeffs);
     74:       /* Compute coeffs */
     75:       STCoeffs_Monomial(st,coeffs);
     76:       /* T[n] = A_n */
     77:       k = nmat-1;
     78:       PetscObjectReference((PetscObject)st->A[k]);
     79:       MatDestroy(&st->T[k]);
     80:       st->T[k] = st->A[k];
     81:       for (k=0;k<nmat-1;k++) STMatMAXPY_Private(st,nmat>2?st->sigma:-st->sigma,0.0,k,coeffs?coeffs+((nmat-k)*(nmat-k-1))/2:NULL,PetscNot(st->state==ST_STATE_UPDATED),PETSC_FALSE,&st->T[k]);
     82:       PetscFree(coeffs);
     83:       PetscObjectReference((PetscObject)st->T[nmat-1]);
     84:       MatDestroy(&st->P);
     85:       st->P = st->T[nmat-1];
     86:       if (st->Psplit) {  /* build custom preconditioner from the split matrices */
     87:         STMatMAXPY_Private(st,st->sigma,0.0,nmat-1,coeffs?coeffs:NULL,PETSC_TRUE,PETSC_TRUE,&st->Pmat);
     88:       }
     89:       ST_KSPSetOperators(st,st->P,st->Pmat?st->Pmat:st->P);
     90:     } else {
     91:       for (k=0;k<nmat;k++) {
     92:         PetscObjectReference((PetscObject)st->A[k]);
     93:         MatDestroy(&st->T[k]);
     94:         st->T[k] = st->A[k];
     95:       }
     96:     }
     97:   }
     98:   if (st->P) KSPSetUp(st->ksp);
     99:   return 0;
    100: }

    102: PetscErrorCode STSetShift_Shift(ST st,PetscScalar newshift)
    103: {
    104:   PetscInt       k,nc,nmat=PetscMax(st->nmat,2);
    105:   PetscScalar    *coeffs=NULL;

    107:   if (st->transform) {
    108:     if (st->matmode == ST_MATMODE_COPY && nmat>2) {
    109:       nc = (nmat*(nmat+1))/2;
    110:       PetscMalloc1(nc,&coeffs);
    111:       /* Compute coeffs */
    112:       STCoeffs_Monomial(st,coeffs);
    113:     }
    114:     for (k=0;k<nmat-1;k++) STMatMAXPY_Private(st,nmat>2?newshift:-newshift,nmat>2?st->sigma:-st->sigma,k,coeffs?coeffs+((nmat-k)*(nmat-k-1))/2:NULL,PETSC_FALSE,PETSC_FALSE,&st->T[k]);
    115:     if (st->matmode == ST_MATMODE_COPY && nmat>2) PetscFree(coeffs);
    116:     if (st->nmat<=2) st->M = st->T[0];
    117:   }
    118:   return 0;
    119: }

    121: SLEPC_EXTERN PetscErrorCode STCreate_Shift(ST st)
    122: {
    123:   st->usesksp = PETSC_TRUE;

    125:   st->ops->apply           = STApply_Generic;
    126:   st->ops->applytrans      = STApplyTranspose_Generic;
    127:   st->ops->backtransform   = STBackTransform_Shift;
    128:   st->ops->setshift        = STSetShift_Shift;
    129:   st->ops->getbilinearform = STGetBilinearForm_Default;
    130:   st->ops->setup           = STSetUp_Shift;
    131:   st->ops->computeoperator = STComputeOperator_Shift;
    132:   st->ops->postsolve       = STPostSolve_Shift;
    133:   st->ops->setdefaultksp   = STSetDefaultKSP_Default;
    134:   return 0;
    135: }