Actual source code: shift.c
slepc-3.21.1 2024-04-26
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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: static PetscErrorCode STBackTransform_Shift(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     18: {
     19:   PetscInt j;

     21:   PetscFunctionBegin;
     22:   for (j=0;j<n;j++) {
     23:     eigr[j] += st->sigma;
     24:   }
     25:   PetscFunctionReturn(PETSC_SUCCESS);
     26: }

     28: static PetscErrorCode STPostSolve_Shift(ST st)
     29: {
     30:   PetscFunctionBegin;
     31:   if (st->matmode == ST_MATMODE_INPLACE) {
     32:     if (st->nmat>1) PetscCall(MatAXPY(st->A[0],st->sigma,st->A[1],st->str));
     33:     else PetscCall(MatShift(st->A[0],st->sigma));
     34:     st->Astate[0] = ((PetscObject)st->A[0])->state;
     35:     st->state   = ST_STATE_INITIAL;
     36:     st->opready = PETSC_FALSE;
     37:   }
     38:   PetscFunctionReturn(PETSC_SUCCESS);
     39: }

     41: /*
     42:    Operator (shift):
     43:                Op               P         M
     44:    if nmat=1:  A-sI             NULL      A-sI
     45:    if nmat=2:  B^-1 (A-sB)      B         A-sB
     46: */
     47: static PetscErrorCode STComputeOperator_Shift(ST st)
     48: {
     49:   PetscFunctionBegin;
     50:   st->usesksp = (st->nmat>1)? PETSC_TRUE: PETSC_FALSE;
     51:   PetscCall(PetscObjectReference((PetscObject)st->A[1]));
     52:   PetscCall(MatDestroy(&st->T[1]));
     53:   st->T[1] = st->A[1];
     54:   PetscCall(STMatMAXPY_Private(st,-st->sigma,0.0,0,NULL,PetscNot(st->state==ST_STATE_UPDATED),PETSC_FALSE,&st->T[0]));
     55:   if (st->nmat>1) PetscCall(PetscObjectReference((PetscObject)st->T[1]));
     56:   PetscCall(MatDestroy(&st->P));
     57:   st->P = (st->nmat>1)? st->T[1]: NULL;
     58:   st->M = st->T[0];
     59:   if (st->nmat>1 && st->Psplit) {  /* build custom preconditioner from the split matrices */
     60:     PetscCall(MatDestroy(&st->Pmat));
     61:     PetscCall(PetscObjectReference((PetscObject)st->Psplit[1]));
     62:     st->Pmat = st->Psplit[1];
     63:   }
     64:   PetscFunctionReturn(PETSC_SUCCESS);
     65: }

     67: static PetscErrorCode STSetUp_Shift(ST st)
     68: {
     69:   PetscInt       k,nc,nmat=st->nmat;
     70:   PetscScalar    *coeffs=NULL;

     72:   PetscFunctionBegin;
     73:   if (nmat>1) PetscCall(STSetWorkVecs(st,1));
     74:   if (nmat>2) {  /* set-up matrices for polynomial eigenproblems */
     75:     if (st->transform) {
     76:       nc = (nmat*(nmat+1))/2;
     77:       PetscCall(PetscMalloc1(nc,&coeffs));
     78:       /* Compute coeffs */
     79:       PetscCall(STCoeffs_Monomial(st,coeffs));
     80:       /* T[n] = A_n */
     81:       k = nmat-1;
     82:       PetscCall(PetscObjectReference((PetscObject)st->A[k]));
     83:       PetscCall(MatDestroy(&st->T[k]));
     84:       st->T[k] = st->A[k];
     85:       for (k=0;k<nmat-1;k++) PetscCall(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]));
     86:       PetscCall(PetscFree(coeffs));
     87:       PetscCall(PetscObjectReference((PetscObject)st->T[nmat-1]));
     88:       PetscCall(MatDestroy(&st->P));
     89:       st->P = st->T[nmat-1];
     90:       if (st->Psplit) {  /* build custom preconditioner from the split matrices */
     91:         PetscCall(STMatMAXPY_Private(st,st->sigma,0.0,nmat-1,coeffs?coeffs:NULL,PETSC_TRUE,PETSC_TRUE,&st->Pmat));
     92:       }
     93:       PetscCall(ST_KSPSetOperators(st,st->P,st->Pmat?st->Pmat:st->P));
     94:     } else {
     95:       for (k=0;k<nmat;k++) {
     96:         PetscCall(PetscObjectReference((PetscObject)st->A[k]));
     97:         PetscCall(MatDestroy(&st->T[k]));
     98:         st->T[k] = st->A[k];
     99:       }
    100:     }
    101:   }
    102:   if (st->P) PetscCall(KSPSetUp(st->ksp));
    103:   PetscFunctionReturn(PETSC_SUCCESS);
    104: }

    106: static PetscErrorCode STSetShift_Shift(ST st,PetscScalar newshift)
    107: {
    108:   PetscInt       k,nc,nmat=PetscMax(st->nmat,2);
    109:   PetscScalar    *coeffs=NULL;

    111:   PetscFunctionBegin;
    112:   if (st->transform) {
    113:     if (st->matmode == ST_MATMODE_COPY && nmat>2) {
    114:       nc = (nmat*(nmat+1))/2;
    115:       PetscCall(PetscMalloc1(nc,&coeffs));
    116:       /* Compute coeffs */
    117:       PetscCall(STCoeffs_Monomial(st,coeffs));
    118:     }
    119:     for (k=0;k<nmat-1;k++) PetscCall(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]));
    120:     if (st->matmode == ST_MATMODE_COPY && nmat>2) PetscCall(PetscFree(coeffs));
    121:     if (st->nmat<=2) st->M = st->T[0];
    122:   }
    123:   PetscFunctionReturn(PETSC_SUCCESS);
    124: }

    126: SLEPC_EXTERN PetscErrorCode STCreate_Shift(ST st)
    127: {
    128:   PetscFunctionBegin;
    129:   st->usesksp = PETSC_TRUE;

    131:   st->ops->apply           = STApply_Generic;
    132:   st->ops->applytrans      = STApplyTranspose_Generic;
    133:   st->ops->applyhermtrans  = STApplyHermitianTranspose_Generic;
    134:   st->ops->backtransform   = STBackTransform_Shift;
    135:   st->ops->setshift        = STSetShift_Shift;
    136:   st->ops->getbilinearform = STGetBilinearForm_Default;
    137:   st->ops->setup           = STSetUp_Shift;
    138:   st->ops->computeoperator = STComputeOperator_Shift;
    139:   st->ops->postsolve       = STPostSolve_Shift;
    140:   st->ops->setdefaultksp   = STSetDefaultKSP_Default;
    141:   PetscFunctionReturn(PETSC_SUCCESS);
    142: }