Date: 2013-09-02T10:03:31+00:00

Actual source code: ks-symm.c

      1: /*

      3:    SLEPc eigensolver: "krylovschur"

      5:    Method: Krylov-Schur for symmetric eigenproblems

      7:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      8:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      9:    Copyright (c) 2002-2013, Universitat Politecnica de Valencia, Spain

     11:    This file is part of SLEPc.

     13:    SLEPc is free software: you can redistribute it and/or modify it under  the
     14:    terms of version 3 of the GNU Lesser General Public License as published by
     15:    the Free Software Foundation.

     17:    SLEPc  is  distributed in the hope that it will be useful, but WITHOUT  ANY
     18:    WARRANTY;  without even the implied warranty of MERCHANTABILITY or  FITNESS
     19:    FOR  A  PARTICULAR PURPOSE. See the GNU Lesser General Public  License  for
     20:    more details.

     22:    You  should have received a copy of the GNU Lesser General  Public  License
     23:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
     24:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     25: */

     27: #include <slepc-private/epsimpl.h>                /*I "slepceps.h" I*/
     28: #include <slepcblaslapack.h>
     29:  #include krylovschur.h

     33: PetscErrorCode EPSSolve_KrylovSchur_Symm(EPS eps)
     34: {
     35:   PetscErrorCode  ierr;
     36:   EPS_KRYLOVSCHUR *ctx = (EPS_KRYLOVSCHUR*)eps->data;
     37:   PetscInt        k,l,ld,nv;
     38:   Vec             u=eps->work[0];
     39:   PetscScalar     *Q;
     40:   PetscReal       *a,*b,beta;
     41:   PetscBool       breakdown;

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

     46:   /* Get the starting Lanczos vector */
     47:   EPSGetStartVector(eps,0,eps->V[0],NULL);
     48:   l = 0;

     50:   /* Restart loop */
     51:   while (eps->reason == EPS_CONVERGED_ITERATING) {
     52:     eps->its++;

     54:     /* Compute an nv-step Lanczos factorization */
     55:     nv = PetscMin(eps->nconv+eps->mpd,eps->ncv);
     56:     DSGetArrayReal(eps->ds,DS_MAT_T,&a);
     57:     b = a + ld;
     58:     EPSFullLanczos(eps,a,b,eps->V,eps->nconv+l,&nv,u,&breakdown);
     59:     beta = b[nv-1];
     60:     DSRestoreArrayReal(eps->ds,DS_MAT_T,&a);
     61:     DSSetDimensions(eps->ds,nv,0,eps->nconv,eps->nconv+l);
     62:     if (l==0) {
     63:       DSSetState(eps->ds,DS_STATE_INTERMEDIATE);
     64:     } else {
     65:       DSSetState(eps->ds,DS_STATE_RAW);
     66:     }

     68:     /* Solve projected problem */
     69:     DSSolve(eps->ds,eps->eigr,NULL);
     70:     if (eps->arbitrary) { EPSGetArbitraryValues(eps,eps->rr,eps->ri); }
     71:     DSSort(eps->ds,eps->eigr,NULL,eps->rr,eps->ri,NULL);
     72:     DSUpdateExtraRow(eps->ds);

     74:     /* Check convergence */
     75:     EPSKrylovConvergence(eps,PETSC_FALSE,eps->nconv,nv-eps->nconv,eps->V,nv,beta,1.0,&k);
     76:     if (eps->its >= eps->max_it) eps->reason = EPS_DIVERGED_ITS;
     77:     if (k >= eps->nev) eps->reason = EPS_CONVERGED_TOL;

     79:     /* Update l */
     80:     if (eps->reason != EPS_CONVERGED_ITERATING || breakdown) l = 0;
     81:     else l = PetscMax(1,(PetscInt)((nv-k)*ctx->keep));

     83:     if (eps->reason == EPS_CONVERGED_ITERATING) {
     84:       if (breakdown) {
     85:         /* Start a new Lanczos factorization */
     86:         PetscInfo2(eps,"Breakdown in Krylov-Schur method (it=%D norm=%G)\n",eps->its,beta);
     87:         EPSGetStartVector(eps,k,eps->V[k],&breakdown);
     88:         if (breakdown) {
     89:           eps->reason = EPS_DIVERGED_BREAKDOWN;
     90:           PetscInfo(eps,"Unable to generate more start vectors\n");
     91:         }
     92:       } else {
     93:         /* Prepare the Rayleigh quotient for restart */
     94:         DSTruncate(eps->ds,k+l);
     95:       }
     96:     }
     97:     /* Update the corresponding vectors V(:,idx) = V*Q(:,idx) */
     98:     DSGetArray(eps->ds,DS_MAT_Q,&Q);
     99:     SlepcUpdateVectors(nv,eps->V,eps->nconv,k+l,Q,ld,PETSC_FALSE);
    100:     DSRestoreArray(eps->ds,DS_MAT_Q,&Q);
    101:     /* Normalize u and append it to V */
    102:     if (eps->reason == EPS_CONVERGED_ITERATING && !breakdown) {
    103:       VecAXPBY(eps->V[k+l],1.0/beta,0.0,u);
    104:     }

    106:     EPSMonitor(eps,eps->its,k,eps->eigr,eps->eigi,eps->errest,nv);
    107:     eps->nconv = k;
    108:   }
    109:   return(0);
    110: }