Date: 2022-03-31T15:29:08+00:00

Actual source code: ks-indef.c
slepc-3.17.0 2022-03-31
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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:    SLEPc eigensolver: "krylovschur"

     13:    Method: Krylov-Schur for symmetric-indefinite eigenproblems
     14: */
     15: #include <slepc/private/epsimpl.h>
     16: #include "krylovschur.h"

     18: PetscErrorCode EPSSolve_KrylovSchur_Indefinite(EPS eps)
     19: {
     20:   EPS_KRYLOVSCHUR *ctx = (EPS_KRYLOVSCHUR*)eps->data;
     21:   PetscInt        i,k,l,ld,nv,t,nconv=0;
     22:   Mat             U;
     23:   Vec             vomega,w=eps->work[0];
     24:   PetscScalar     *aux;
     25:   PetscReal       *a,*b,beta,beta1=1.0,*omega;
     26:   PetscBool       breakdown=PETSC_FALSE,symmlost=PETSC_FALSE;

     28:   DSGetLeadingDimension(eps->ds,&ld);

     30:   /* Get the starting Lanczos vector */
     31:   EPSGetStartVector(eps,0,NULL);

     33:   /* Extract sigma[0] from BV, computed during normalization */
     34:   BVSetActiveColumns(eps->V,0,1);
     35:   VecCreateSeq(PETSC_COMM_SELF,1,&vomega);
     36:   BVGetSignature(eps->V,vomega);
     37:   VecGetArray(vomega,&aux);
     38:   DSGetArrayReal(eps->ds,DS_MAT_D,&omega);
     39:   omega[0] = PetscRealPart(aux[0]);
     40:   DSRestoreArrayReal(eps->ds,DS_MAT_D,&omega);
     41:   VecRestoreArray(vomega,&aux);
     42:   VecDestroy(&vomega);
     43:   l = 0;

     45:   /* Restart loop */
     46:   while (eps->reason == EPS_CONVERGED_ITERATING) {
     47:     eps->its++;

     49:     /* Compute an nv-step Lanczos factorization */
     50:     nv = PetscMin(eps->nconv+eps->mpd,eps->ncv);
     51:     DSGetArrayReal(eps->ds,DS_MAT_T,&a);
     52:     b = a + ld;
     53:     DSGetArrayReal(eps->ds,DS_MAT_D,&omega);
     54:     EPSPseudoLanczos(eps,a,b,omega,eps->nconv+l,&nv,&breakdown,&symmlost,NULL,w);
     55:     if (symmlost) {
     56:       eps->reason = EPS_DIVERGED_SYMMETRY_LOST;
     57:       if (nv==eps->nconv+l+1) { eps->nconv = nconv; break; }
     58:     }
     59:     beta = b[nv-1];
     60:     DSRestoreArrayReal(eps->ds,DS_MAT_T,&a);
     61:     DSRestoreArrayReal(eps->ds,DS_MAT_D,&omega);
     62:     DSSetDimensions(eps->ds,nv,eps->nconv,eps->nconv+l);
     63:     if (l==0) DSSetState(eps->ds,DS_STATE_INTERMEDIATE);
     64:     else DSSetState(eps->ds,DS_STATE_RAW);
     65:     BVSetActiveColumns(eps->V,eps->nconv,nv);

     67:     /* Solve projected problem */
     68:     DSSolve(eps->ds,eps->eigr,eps->eigi);
     69:     DSSort(eps->ds,eps->eigr,eps->eigi,NULL,NULL,NULL);
     70:     DSUpdateExtraRow(eps->ds);
     71:     DSSynchronize(eps->ds,eps->eigr,eps->eigi);

     73:     /* Check convergence */
     74:     DSGetDimensions(eps->ds,NULL,NULL,NULL,&t);
     75: #if 0
     76:     /* take into account also left residual */
     77:     BVGetColumn(eps->V,nv,&u);
     78:     VecNorm(u,NORM_2,&beta1);
     79:     BVRestoreColumn(eps->V,nv,&u);
     80:     VecNorm(w,NORM_2,&beta2);  /* w contains B*V[nv] */
     81:     beta1 = PetscMax(beta1,beta2);
     82: #endif
     83:     EPSKrylovConvergence(eps,PETSC_FALSE,eps->nconv,t-eps->nconv,beta*beta1,0.0,1.0,&k);
     84:     (*eps->stopping)(eps,eps->its,eps->max_it,k,eps->nev,&eps->reason,eps->stoppingctx);
     85:     nconv = k;

     87:     /* Update l */
     88:     if (eps->reason != EPS_CONVERGED_ITERATING || breakdown) l = 0;
     89:     else {
     90:       l = PetscMax(1,(PetscInt)((nv-k)*ctx->keep));
     91:       l = PetscMin(l,t);
     92:       DSGetTruncateSize(eps->ds,k,t,&l);
     93:     }
     94:     if (!ctx->lock && l>0) { l += k; k = 0; } /* non-locking variant: reset no. of converged pairs */
     95:     if (l) PetscInfo(eps,"Preparing to restart keeping l=%" PetscInt_FMT " vectors\n",l);

     97:     if (eps->reason == EPS_CONVERGED_ITERATING) {
     99:       /* Prepare the Rayleigh quotient for restart */
    100:       DSTruncate(eps->ds,k+l,PETSC_FALSE);
    101:     }
    102:     /* Update the corresponding vectors V(:,idx) = V*Q(:,idx) */
    103:     DSGetMat(eps->ds,DS_MAT_Q,&U);
    104:     BVMultInPlace(eps->V,U,eps->nconv,k+l);
    105:     MatDestroy(&U);

    107:     /* Move restart vector and update signature */
    108:     if (eps->reason == EPS_CONVERGED_ITERATING && !breakdown) {
    109:       BVCopyColumn(eps->V,nv,k+l);
    110:       DSGetArrayReal(eps->ds,DS_MAT_D,&omega);
    111:       VecCreateSeq(PETSC_COMM_SELF,k+l,&vomega);
    112:       VecGetArray(vomega,&aux);
    113:       for (i=0;i<k+l;i++) aux[i] = omega[i];
    114:       VecRestoreArray(vomega,&aux);
    115:       BVSetActiveColumns(eps->V,0,k+l);
    116:       BVSetSignature(eps->V,vomega);
    117:       VecDestroy(&vomega);
    118:       DSRestoreArrayReal(eps->ds,DS_MAT_D,&omega);
    119:     }

    121:     eps->nconv = k;
    122:     EPSMonitor(eps,eps->its,nconv,eps->eigr,eps->eigi,eps->errest,nv);
    123:   }
    124:   DSTruncate(eps->ds,eps->nconv,PETSC_TRUE);
    125:   PetscFunctionReturn(0);
    126: }