Date: 2015-09-03T15:05:59+00:00

Actual source code: narnoldi.c
slepc-3.6.1 2015-09-03
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      1: /*

      3:    SLEPc nonlinear eigensolver: "narnoldi"

      5:    Method: Nonlinear Arnoldi

      7:    Algorithm:

      9:        Arnoldi for nonlinear eigenproblems.

     11:    References:

     13:        [1] H. Voss, "An Arnoldi method for nonlinear eigenvalue problems",
     14:            BIT 44:387-401, 2004.

     16:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     17:    SLEPc - Scalable Library for Eigenvalue Problem Computations
     18:    Copyright (c) 2002-2015, Universitat Politecnica de Valencia, Spain

     20:    This file is part of SLEPc.

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

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

     31:    You  should have received a copy of the GNU Lesser General  Public  License
     32:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
     33:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     34: */

     36: #include <slepc/private/nepimpl.h>

     40: PetscErrorCode NEPSetUp_NArnoldi(NEP nep)
     41: {
     43:   PetscBool      istrivial;

     46:   if (nep->ncv) { /* ncv set */
     47:     if (nep->ncv<nep->nev) SETERRQ(PetscObjectComm((PetscObject)nep),1,"The value of ncv must be at least nev");
     48:   } else if (nep->mpd) { /* mpd set */
     49:     nep->ncv = PetscMin(nep->n,nep->nev+nep->mpd);
     50:   } else { /* neither set: defaults depend on nev being small or large */
     51:     if (nep->nev<500) nep->ncv = PetscMin(nep->n,PetscMax(2*nep->nev,nep->nev+15));
     52:     else {
     53:       nep->mpd = 500;
     54:       nep->ncv = PetscMin(nep->n,nep->nev+nep->mpd);
     55:     }
     56:   }
     57:   if (!nep->mpd) nep->mpd = nep->ncv;
     58:   if (nep->ncv>nep->nev+nep->mpd) SETERRQ(PetscObjectComm((PetscObject)nep),1,"The value of ncv must not be larger than nev+mpd");
     59:   if (!nep->max_it) nep->max_it = PetscMax(5000,2*nep->n/nep->ncv);
     60:   if (!nep->max_funcs) nep->max_funcs = nep->max_it;
     61:   if (!nep->split) SETERRQ(PetscObjectComm((PetscObject)nep),PETSC_ERR_SUP,"NARNOLDI only available for split operator");

     63:   RGIsTrivial(nep->rg,&istrivial);
     64:   if (!istrivial) SETERRQ(PetscObjectComm((PetscObject)nep),PETSC_ERR_SUP,"This solver does not support region filtering");

     66:   NEPAllocateSolution(nep,0);
     67:   NEPSetWorkVecs(nep,3);

     69:   /* set-up DS and transfer split operator functions */
     70:   DSSetType(nep->ds,DSNEP);
     71:   DSNEPSetFN(nep->ds,nep->nt,nep->f);
     72:   DSAllocate(nep->ds,nep->ncv);
     73:   return(0);
     74: }

     78: PetscErrorCode NEPSolve_NArnoldi(NEP nep)
     79: {
     80:   PetscErrorCode     ierr;
     81:   Mat                T=nep->function,Tsigma;
     82:   Vec                f,r=nep->work[0],x=nep->work[1],w=nep->work[2];
     83:   PetscScalar        *X,lambda;
     84:   PetscReal          beta,resnorm=0.0,nrm;
     85:   PetscInt           n;
     86:   PetscBool          breakdown;
     87:   KSPConvergedReason kspreason;

     90:   /* get initial space and shift */
     91:   NEPGetDefaultShift(nep,&lambda);
     92:   if (!nep->nini) {
     93:     BVSetRandomColumn(nep->V,0,nep->rand);
     94:     BVNormColumn(nep->V,0,NORM_2,&nrm);
     95:     BVScaleColumn(nep->V,0,1.0/nrm);
     96:     n = 1;
     97:   } else n = nep->nini;

     99:   /* build projected matrices for initial space */
    100:   DSSetDimensions(nep->ds,n,0,0,0);
    101:   NEPProjectOperator(nep,0,n);

    103:   /* prepare linear solver */
    104:   NEPComputeFunction(nep,lambda,T,T);
    105:   MatDuplicate(T,MAT_COPY_VALUES,&Tsigma);
    106:   KSPSetOperators(nep->ksp,Tsigma,Tsigma);

    108:   /* Restart loop */
    109:   while (nep->reason == NEP_CONVERGED_ITERATING) {
    110:     nep->its++;

    112:     /* solve projected problem */
    113:     DSSetDimensions(nep->ds,n,0,0,0);
    114:     DSSetState(nep->ds,DS_STATE_RAW);
    115:     DSSolve(nep->ds,nep->eigr,NULL);
    116:     lambda = nep->eigr[0];

    118:     /* compute Ritz vector, x = V*s */
    119:     DSGetArray(nep->ds,DS_MAT_X,&X);
    120:     BVSetActiveColumns(nep->V,0,n);
    121:     BVMultVec(nep->V,1.0,0.0,x,X);
    122:     DSRestoreArray(nep->ds,DS_MAT_X,&X);

    124:     /* compute the residual, r = T(lambda)*x */
    125:     NEPApplyFunction(nep,lambda,x,w,r,NULL,NULL);

    127:     /* convergence test */
    128:     VecNorm(r,NORM_2,&resnorm);
    129:     nep->errest[nep->nconv] = resnorm;
    130:     if (resnorm<=nep->rtol) {
    131:       BVInsertVec(nep->V,nep->nconv,x);
    132:       nep->nconv = nep->nconv + 1;
    133:       nep->reason = NEP_CONVERGED_FNORM_RELATIVE;
    134:     }
    135:     NEPMonitor(nep,nep->its,nep->nconv,nep->eigr,nep->errest,1);

    137:     if (nep->reason == NEP_CONVERGED_ITERATING) {

    139:       /* continuation vector: f = T(sigma)\r */
    140:       BVGetColumn(nep->V,n,&f);
    141:       NEP_KSPSolve(nep,r,f);
    142:       BVRestoreColumn(nep->V,n,&f);
    143:       KSPGetConvergedReason(nep->ksp,&kspreason);
    144:       if (kspreason<0) {
    145:         PetscInfo1(nep,"iter=%D, linear solve failed, stopping solve\n",nep->its);
    146:         nep->reason = NEP_DIVERGED_LINEAR_SOLVE;
    147:         break;
    148:       }

    150:       /* orthonormalize */
    151:       BVOrthogonalizeColumn(nep->V,n,NULL,&beta,&breakdown);
    152:       if (breakdown || beta==0.0) {
    153:         PetscInfo1(nep,"iter=%D, orthogonalization failed, stopping solve\n",nep->its);
    154:         nep->reason = NEP_DIVERGED_BREAKDOWN;
    155:         break;
    156:       }
    157:       BVScaleColumn(nep->V,n,1.0/beta);

    159:       /* update projected matrices */
    160:       DSSetDimensions(nep->ds,n+1,0,0,0);
    161:       NEPProjectOperator(nep,n,n+1);
    162:       n++;
    163:     }
    164:     if (nep->its >= nep->max_it) nep->reason = NEP_DIVERGED_MAX_IT;
    165:   }
    166:   MatDestroy(&Tsigma);
    167:   return(0);
    168: }

    172: PETSC_EXTERN PetscErrorCode NEPCreate_NArnoldi(NEP nep)
    173: {
    175:   nep->ops->solve          = NEPSolve_NArnoldi;
    176:   nep->ops->setup          = NEPSetUp_NArnoldi;
    177:   return(0);
    178: }