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

Actual source code: sinvert.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:    Implements the shift-and-invert technique for eigenvalue problems
     12: */

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

     16: PetscErrorCode STBackTransform_Sinvert(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     17: {
     18:   PetscInt    j;
     19: #if !defined(PETSC_USE_COMPLEX)
     20:   PetscScalar t;
     21: #endif

     23: #if !defined(PETSC_USE_COMPLEX)
     24:   for (j=0;j<n;j++) {
     25:     if (eigi[j] == 0) eigr[j] = 1.0 / eigr[j] + st->sigma;
     26:     else {
     27:       t = eigr[j] * eigr[j] + eigi[j] * eigi[j];
     28:       eigr[j] = eigr[j] / t + st->sigma;
     29:       eigi[j] = - eigi[j] / t;
     30:     }
     31:   }
     32: #else
     33:   for (j=0;j<n;j++) {
     34:     eigr[j] = 1.0 / eigr[j] + st->sigma;
     35:   }
     36: #endif
     37:   return 0;
     38: }

     40: PetscErrorCode STPostSolve_Sinvert(ST st)
     41: {
     42:   if (st->matmode == ST_MATMODE_INPLACE) {
     43:     if (st->nmat>1) MatAXPY(st->A[0],st->sigma,st->A[1],st->str);
     44:     else MatShift(st->A[0],st->sigma);
     45:     st->Astate[0] = ((PetscObject)st->A[0])->state;
     46:     st->state   = ST_STATE_INITIAL;
     47:     st->opready = PETSC_FALSE;
     48:   }
     49:   return 0;
     50: }

     52: /*
     53:    Operator (sinvert):
     54:                Op               P         M
     55:    if nmat=1:  (A-sI)^-1        A-sI      NULL
     56:    if nmat=2:  (A-sB)^-1 B      A-sB      B
     57: */
     58: PetscErrorCode STComputeOperator_Sinvert(ST st)
     59: {
     60:   /* if the user did not set the shift, use the target value */
     61:   if (!st->sigma_set) st->sigma = st->defsigma;
     62:   PetscObjectReference((PetscObject)st->A[1]);
     63:   MatDestroy(&st->T[0]);
     64:   st->T[0] = st->A[1];
     65:   STMatMAXPY_Private(st,-st->sigma,0.0,0,NULL,PetscNot(st->state==ST_STATE_UPDATED),PETSC_FALSE,&st->T[1]);
     66:   PetscObjectReference((PetscObject)st->T[1]);
     67:   MatDestroy(&st->P);
     68:   st->P = st->T[1];
     69:   st->M = (st->nmat>1)? st->T[0]: NULL;
     70:   if (st->Psplit) {  /* build custom preconditioner from the split matrices */
     71:     STMatMAXPY_Private(st,-st->sigma,0.0,0,NULL,PETSC_TRUE,PETSC_TRUE,&st->Pmat);
     72:   }
     73:   return 0;
     74: }

     76: PetscErrorCode STSetUp_Sinvert(ST st)
     77: {
     78:   PetscInt       k,nc,nmat=st->nmat;
     79:   PetscScalar    *coeffs=NULL;

     81:   if (nmat>1) STSetWorkVecs(st,1);
     82:   /* if the user did not set the shift, use the target value */
     83:   if (!st->sigma_set) st->sigma = st->defsigma;
     84:   if (nmat>2) {  /* set-up matrices for polynomial eigenproblems */
     85:     if (st->transform) {
     86:       nc = (nmat*(nmat+1))/2;
     87:       PetscMalloc1(nc,&coeffs);
     88:       /* Compute coeffs */
     89:       STCoeffs_Monomial(st,coeffs);
     90:       /* T[0] = A_n */
     91:       k = nmat-1;
     92:       PetscObjectReference((PetscObject)st->A[k]);
     93:       MatDestroy(&st->T[0]);
     94:       st->T[0] = st->A[k];
     95:       for (k=1;k<nmat;k++) STMatMAXPY_Private(st,nmat>2?st->sigma:-st->sigma,0.0,nmat-k-1,coeffs?coeffs+(k*(k+1))/2:NULL,PetscNot(st->state==ST_STATE_UPDATED),PETSC_FALSE,&st->T[k]);
     96:       PetscFree(coeffs);
     97:       PetscObjectReference((PetscObject)st->T[nmat-1]);
     98:       MatDestroy(&st->P);
     99:       st->P = st->T[nmat-1];
    100:       if (st->Psplit) {  /* build custom preconditioner from the split matrices */
    101:         STMatMAXPY_Private(st,st->sigma,0.0,0,coeffs?coeffs+((nmat-1)*nmat)/2:NULL,PETSC_TRUE,PETSC_TRUE,&st->Pmat);
    102:       }
    103:       ST_KSPSetOperators(st,st->P,st->Pmat?st->Pmat:st->P);
    104:     } else {
    105:       for (k=0;k<nmat;k++) {
    106:         PetscObjectReference((PetscObject)st->A[k]);
    107:         MatDestroy(&st->T[k]);
    108:         st->T[k] = st->A[k];
    109:       }
    110:     }
    111:   }
    112:   if (st->P) KSPSetUp(st->ksp);
    113:   return 0;
    114: }

    116: PetscErrorCode STSetShift_Sinvert(ST st,PetscScalar newshift)
    117: {
    118:   PetscInt       nmat=PetscMax(st->nmat,2),k,nc;
    119:   PetscScalar    *coeffs=NULL;

    121:   if (st->transform) {
    122:     if (st->matmode == ST_MATMODE_COPY && nmat>2) {
    123:       nc = (nmat*(nmat+1))/2;
    124:       PetscMalloc1(nc,&coeffs);
    125:       /* Compute coeffs */
    126:       STCoeffs_Monomial(st,coeffs);
    127:     }
    128:     for (k=1;k<nmat;k++) STMatMAXPY_Private(st,nmat>2?newshift:-newshift,nmat>2?st->sigma:-st->sigma,nmat-k-1,coeffs?coeffs+(k*(k+1))/2:NULL,PETSC_FALSE,PETSC_FALSE,&st->T[k]);
    129:     if (st->matmode == ST_MATMODE_COPY && nmat>2) PetscFree(coeffs);
    130:     if (st->P!=st->T[nmat-1]) {
    131:       PetscObjectReference((PetscObject)st->T[nmat-1]);
    132:       MatDestroy(&st->P);
    133:       st->P = st->T[nmat-1];
    134:     }
    135:     if (st->Psplit) {  /* build custom preconditioner from the split matrices */
    136:       STMatMAXPY_Private(st,nmat>2?newshift:-newshift,nmat>2?st->sigma:-st->sigma,0,coeffs?coeffs+((nmat-1)*nmat)/2:NULL,PETSC_FALSE,PETSC_TRUE,&st->Pmat);
    137:     }
    138:   }
    139:   if (st->P) {
    140:     ST_KSPSetOperators(st,st->P,st->Pmat?st->Pmat:st->P);
    141:     KSPSetUp(st->ksp);
    142:   }
    143:   return 0;
    144: }

    146: SLEPC_EXTERN PetscErrorCode STCreate_Sinvert(ST st)
    147: {
    148:   st->usesksp = PETSC_TRUE;

    150:   st->ops->apply           = STApply_Generic;
    151:   st->ops->applytrans      = STApplyTranspose_Generic;
    152:   st->ops->backtransform   = STBackTransform_Sinvert;
    153:   st->ops->setshift        = STSetShift_Sinvert;
    154:   st->ops->getbilinearform = STGetBilinearForm_Default;
    155:   st->ops->setup           = STSetUp_Sinvert;
    156:   st->ops->computeoperator = STComputeOperator_Sinvert;
    157:   st->ops->postsolve       = STPostSolve_Sinvert;
    158:   st->ops->checknullspace  = STCheckNullSpace_Default;
    159:   st->ops->setdefaultksp   = STSetDefaultKSP_Default;
    160:   return 0;
    161: }