Actual source code: ks-symm.c

slepc-3.7.0 2016-05-16
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  1: /*

  3:    SLEPc eigensolver: "krylovschur"

  5:    Method: Krylov-Schur for symmetric eigenproblems

  7:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  8:    SLEPc - Scalable Library for Eigenvalue Problem Computations
  9:    Copyright (c) 2002-2016, 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>
 28:  #include krylovschur.h

 32: PetscErrorCode EPSSolve_KrylovSchur_Symm(EPS eps)
 33: {
 34:   PetscErrorCode  ierr;
 35:   EPS_KRYLOVSCHUR *ctx = (EPS_KRYLOVSCHUR*)eps->data;
 36:   PetscInt        k,l,ld,nv,nconv;
 37:   Mat             U;
 38:   PetscReal       *a,*b,beta;
 39:   PetscBool       breakdown;

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

 44:   /* Get the starting Lanczos vector */
 45:   EPSGetStartVector(eps,0,NULL);
 46:   l = 0;

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

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

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

 73:     /* Check convergence */
 74:     EPSKrylovConvergence(eps,PETSC_FALSE,eps->nconv,nv-eps->nconv,beta,1.0,&k);
 75:     (*eps->stopping)(eps,eps->its,eps->max_it,k,eps->nev,&eps->reason,eps->stoppingctx);
 76:     nconv = k;

 78:     /* Update l */
 79:     if (eps->reason != EPS_CONVERGED_ITERATING || breakdown) l = 0;
 80:     else l = PetscMax(1,(PetscInt)((nv-k)*ctx->keep));
 81:     if (!ctx->lock && l>0) { l += k; k = 0; } /* non-locking variant: reset no. of converged pairs */

 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,(double)beta);
 87:         if (k<eps->nev) {
 88:           EPSGetStartVector(eps,k,&breakdown);
 89:           if (breakdown) {
 90:             eps->reason = EPS_DIVERGED_BREAKDOWN;
 91:             PetscInfo(eps,"Unable to generate more start vectors\n");
 92:           }
 93:         }
 94:       } else {
 95:         /* Prepare the Rayleigh quotient for restart */
 96:         DSTruncate(eps->ds,k+l);
 97:       }
 98:     }
 99:     /* Update the corresponding vectors V(:,idx) = V*Q(:,idx) */
100:     DSGetMat(eps->ds,DS_MAT_Q,&U);
101:     BVMultInPlace(eps->V,U,eps->nconv,k+l);
102:     MatDestroy(&U);

104:     /* Normalize u and append it to V */
105:     if (eps->reason == EPS_CONVERGED_ITERATING && !breakdown) {
106:       BVCopyColumn(eps->V,nv,k+l);
107:     }

109:     eps->nconv = k;
110:     EPSMonitor(eps,eps->its,nconv,eps->eigr,eps->eigi,eps->errest,nv);
111:   }
112:   return(0);
113: }