Actual source code: epssolve.c
slepc-3.10.1 2018-10-23
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2018, 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:    EPS routines related to the solution process
     12: */

     14: #include <slepc/private/epsimpl.h>   /*I "slepceps.h" I*/
     15: #include <petscdraw.h>

     17: PetscErrorCode EPSComputeVectors(EPS eps)
     18: {

     22:   EPSCheckSolved(eps,1);
     23:   if (eps->state==EPS_STATE_SOLVED && eps->ops->computevectors) {
     24:     (*eps->ops->computevectors)(eps);
     25:   }
     26:   eps->state = EPS_STATE_EIGENVECTORS;
     27:   return(0);
     28: }

     30: #define SWAP(a,b,t) {t=a;a=b;b=t;}

     32: static PetscErrorCode EPSComputeValues(EPS eps)
     33: {
     35:   PetscBool      injective,iscomp,isfilter;
     36:   PetscInt       i,n,aux,nconv0;
     37:   Mat            A,B=NULL,G,Z;

     40:   switch (eps->categ) {
     41:     case EPS_CATEGORY_KRYLOV:
     42:     case EPS_CATEGORY_OTHER:
     43:       STIsInjective(eps->st,&injective);
     44:       if (injective) {
     45:         /* one-to-one mapping: backtransform eigenvalues */
     46:         if (eps->ops->backtransform) {
     47:           (*eps->ops->backtransform)(eps);
     48:         } else SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Internal error, spectral transform should have a backtransform operation");
     49:       } else {
     50:         /* compute eigenvalues from Rayleigh quotient */
     51:         DSGetDimensions(eps->ds,&n,NULL,NULL,NULL,NULL);
     52:         if (!n) break;
     53:         EPSGetOperators(eps,&A,&B);
     54:         BVSetActiveColumns(eps->V,0,n);
     55:         DSGetCompact(eps->ds,&iscomp);
     56:         DSSetCompact(eps->ds,PETSC_FALSE);
     57:         DSGetMat(eps->ds,DS_MAT_A,&G);
     58:         BVMatProject(eps->V,A,eps->V,G);
     59:         DSRestoreMat(eps->ds,DS_MAT_A,&G);
     60:         if (B) {
     61:           DSGetMat(eps->ds,DS_MAT_B,&G);
     62:           BVMatProject(eps->V,B,eps->V,G);
     63:           DSRestoreMat(eps->ds,DS_MAT_A,&G);
     64:         }
     65:         DSSolve(eps->ds,eps->eigr,eps->eigi);
     66:         DSSort(eps->ds,eps->eigr,eps->eigi,NULL,NULL,NULL);
     67:         DSSynchronize(eps->ds,eps->eigr,eps->eigi);
     68:         DSSetCompact(eps->ds,iscomp);
     69:         if (eps->ishermitian && (!eps->isgeneralized || eps->ispositive)) { /* V = V * Z */
     70:           DSVectors(eps->ds,DS_MAT_X,NULL,NULL);
     71:           DSGetMat(eps->ds,DS_MAT_X,&Z);
     72:           BVMultInPlace(eps->V,Z,0,n);
     73:           MatDestroy(&Z);
     74:         }
     75:         /* in case of STFILTER discard computed eigenvalues that lie outside the wanted interval */
     76:         PetscObjectTypeCompare((PetscObject)eps->st,STFILTER,&isfilter);
     77:         if (isfilter) {
     78:           nconv0 = eps->nconv;
     79:           for (i=0;i<eps->nconv;i++) {
     80:             if (PetscRealPart(eps->eigr[eps->perm[i]])<eps->inta || PetscRealPart(eps->eigr[eps->perm[i]])>eps->intb) {
     81:               eps->nconv--;
     82:               if (i<eps->nconv) { SWAP(eps->perm[i],eps->perm[eps->nconv],aux); i--; }
     83:             }
     84:           }
     85:           if (nconv0>eps->nconv) {
     86:             PetscInfo1(eps,"Discarded %D computed eigenvalues lying outside the interval\n",nconv0-eps->nconv);
     87:           }
     88:         }
     89:       }
     90:       break;
     91:     case EPS_CATEGORY_PRECOND:
     92:     case EPS_CATEGORY_CONTOUR:
     93:       /* eigenvalues already available as an output of the solver */
     94:       break;
     95:   }
     96:   return(0);
     97: }

     99: /*@
    100:    EPSSolve - Solves the eigensystem.

    102:    Collective on EPS

    104:    Input Parameter:
    105: .  eps - eigensolver context obtained from EPSCreate()

    107:    Options Database Keys:
    108: +  -eps_view - print information about the solver used
    109: .  -eps_view_mat0 binary - save the first matrix (A) to the default binary viewer
    110: .  -eps_view_mat1 binary - save the second matrix (B) to the default binary viewer
    111: .  -eps_view_vectors binary - save the computed eigenvectors to the default binary viewer
    112: .  -eps_view_values - print computed eigenvalues
    113: .  -eps_converged_reason - print reason for convergence, and number of iterations
    114: .  -eps_error_absolute - print absolute errors of each eigenpair
    115: .  -eps_error_relative - print relative errors of each eigenpair
    116: -  -eps_error_backward - print backward errors of each eigenpair

    118:    Level: beginner

    120: .seealso: EPSCreate(), EPSSetUp(), EPSDestroy(), EPSSetTolerances()
    121: @*/
    122: PetscErrorCode EPSSolve(EPS eps)
    123: {
    125:   PetscInt       i;
    126:   STMatMode      matmode;
    127:   Mat            A,B;

    131:   if (eps->state>=EPS_STATE_SOLVED) return(0);
    132:   PetscLogEventBegin(EPS_Solve,eps,0,0,0);

    134:   /* call setup */
    135:   EPSSetUp(eps);
    136:   eps->nconv = 0;
    137:   eps->its   = 0;
    138:   for (i=0;i<eps->ncv;i++) {
    139:     eps->eigr[i]   = 0.0;
    140:     eps->eigi[i]   = 0.0;
    141:     eps->errest[i] = 0.0;
    142:     eps->perm[i]   = i;
    143:   }
    144:   EPSViewFromOptions(eps,NULL,"-eps_view_pre");
    145:   RGViewFromOptions(eps->rg,NULL,"-rg_view");

    147:   /* call solver */
    148:   (*eps->ops->solve)(eps);
    149:   eps->state = EPS_STATE_SOLVED;

    151:   STGetMatMode(eps->st,&matmode);
    152:   if (matmode == ST_MATMODE_INPLACE && eps->ispositive) {
    153:     /* Purify eigenvectors before reverting operator */
    154:     EPSComputeVectors(eps);
    155:   }
    156:   STPostSolve(eps->st);

    158:   if (!eps->reason) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");

    160:   /* Map eigenvalues back to the original problem if appropriate */
    161:   EPSComputeValues(eps);

    163: #if !defined(PETSC_USE_COMPLEX)
    164:   /* reorder conjugate eigenvalues (positive imaginary first) */
    165:   for (i=0;i<eps->nconv-1;i++) {
    166:     if (eps->eigi[i] != 0) {
    167:       if (eps->eigi[i] < 0) {
    168:         eps->eigi[i] = -eps->eigi[i];
    169:         eps->eigi[i+1] = -eps->eigi[i+1];
    170:         /* the next correction only works with eigenvectors */
    171:         EPSComputeVectors(eps);
    172:         BVScaleColumn(eps->V,i+1,-1.0);
    173:       }
    174:       i++;
    175:     }
    176:   }
    177: #endif

    179:   /* sort eigenvalues according to eps->which parameter */
    180:   SlepcSortEigenvalues(eps->sc,eps->nconv,eps->eigr,eps->eigi,eps->perm);
    181:   PetscLogEventEnd(EPS_Solve,eps,0,0,0);

    183:   /* various viewers */
    184:   EPSViewFromOptions(eps,NULL,"-eps_view");
    185:   EPSReasonViewFromOptions(eps);
    186:   EPSErrorViewFromOptions(eps);
    187:   EPSValuesViewFromOptions(eps);
    188:   EPSVectorsViewFromOptions(eps);
    189:   EPSGetOperators(eps,&A,&B);
    190:   MatViewFromOptions(A,(PetscObject)eps,"-eps_view_mat0");
    191:   if (eps->isgeneralized) {
    192:     MatViewFromOptions(B,(PetscObject)eps,"-eps_view_mat1");
    193:   }

    195:   /* Remove deflation and initial subspaces */
    196:   if (eps->nds) {
    197:     BVSetNumConstraints(eps->V,0);
    198:     eps->nds = 0;
    199:   }
    200:   eps->nini = 0;
    201:   return(0);
    202: }

    204: /*@
    205:    EPSGetIterationNumber - Gets the current iteration number. If the
    206:    call to EPSSolve() is complete, then it returns the number of iterations
    207:    carried out by the solution method.

    209:    Not Collective

    211:    Input Parameter:
    212: .  eps - the eigensolver context

    214:    Output Parameter:
    215: .  its - number of iterations

    217:    Note:
    218:    During the i-th iteration this call returns i-1. If EPSSolve() is
    219:    complete, then parameter "its" contains either the iteration number at
    220:    which convergence was successfully reached, or failure was detected.
    221:    Call EPSGetConvergedReason() to determine if the solver converged or
    222:    failed and why.

    224:    Level: intermediate

    226: .seealso: EPSGetConvergedReason(), EPSSetTolerances()
    227: @*/
    228: PetscErrorCode EPSGetIterationNumber(EPS eps,PetscInt *its)
    229: {
    233:   *its = eps->its;
    234:   return(0);
    235: }

    237: /*@
    238:    EPSGetConverged - Gets the number of converged eigenpairs.

    240:    Not Collective

    242:    Input Parameter:
    243: .  eps - the eigensolver context

    245:    Output Parameter:
    246: .  nconv - number of converged eigenpairs

    248:    Note:
    249:    This function should be called after EPSSolve() has finished.

    251:    Level: beginner

    253: .seealso: EPSSetDimensions(), EPSSolve()
    254: @*/
    255: PetscErrorCode EPSGetConverged(EPS eps,PetscInt *nconv)
    256: {
    260:   EPSCheckSolved(eps,1);
    261:   *nconv = eps->nconv;
    262:   return(0);
    263: }

    265: /*@
    266:    EPSGetConvergedReason - Gets the reason why the EPSSolve() iteration was
    267:    stopped.

    269:    Not Collective

    271:    Input Parameter:
    272: .  eps - the eigensolver context

    274:    Output Parameter:
    275: .  reason - negative value indicates diverged, positive value converged

    277:    Notes:
    278:    Possible values for reason are
    279: +  EPS_CONVERGED_TOL - converged up to tolerance
    280: .  EPS_CONVERGED_USER - converged due to a user-defined condition
    281: .  EPS_DIVERGED_ITS - required more than max_it iterations to reach convergence
    282: .  EPS_DIVERGED_BREAKDOWN - generic breakdown in method
    283: -  EPS_DIVERGED_SYMMETRY_LOST - pseudo-Lanczos was not able to keep symmetry

    285:    Can only be called after the call to EPSSolve() is complete.

    287:    Level: intermediate

    289: .seealso: EPSSetTolerances(), EPSSolve(), EPSConvergedReason
    290: @*/
    291: PetscErrorCode EPSGetConvergedReason(EPS eps,EPSConvergedReason *reason)
    292: {
    296:   EPSCheckSolved(eps,1);
    297:   *reason = eps->reason;
    298:   return(0);
    299: }

    301: /*@
    302:    EPSGetInvariantSubspace - Gets an orthonormal basis of the computed invariant
    303:    subspace.

    305:    Not Collective, but vectors are shared by all processors that share the EPS

    307:    Input Parameter:
    308: .  eps - the eigensolver context

    310:    Output Parameter:
    311: .  v - an array of vectors

    313:    Notes:
    314:    This function should be called after EPSSolve() has finished.

    316:    The user should provide in v an array of nconv vectors, where nconv is
    317:    the value returned by EPSGetConverged().

    319:    The first k vectors returned in v span an invariant subspace associated
    320:    with the first k computed eigenvalues (note that this is not true if the
    321:    k-th eigenvalue is complex and matrix A is real; in this case the first
    322:    k+1 vectors should be used). An invariant subspace X of A satisfies Ax
    323:    in X for all x in X (a similar definition applies for generalized
    324:    eigenproblems).

    326:    Level: intermediate

    328: .seealso: EPSGetEigenpair(), EPSGetConverged(), EPSSolve()
    329: @*/
    330: PetscErrorCode EPSGetInvariantSubspace(EPS eps,Vec *v)
    331: {
    333:   PetscInt       i;

    339:   EPSCheckSolved(eps,1);
    340:   if (!eps->ishermitian && eps->state==EPS_STATE_EIGENVECTORS) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONGSTATE,"EPSGetInvariantSubspace must be called before EPSGetEigenpair,EPSGetEigenvector or EPSComputeError");
    341:   for (i=0;i<eps->nconv;i++) {
    342:     BVCopyVec(eps->V,i,v[i]);
    343:     if (eps->balance!=EPS_BALANCE_NONE && eps->D) {
    344:       VecPointwiseDivide(v[i],v[i],eps->D);
    345:       VecNormalize(v[i],NULL);
    346:     }
    347:   }
    348:   return(0);
    349: }

    351: /*@C
    352:    EPSGetEigenpair - Gets the i-th solution of the eigenproblem as computed by
    353:    EPSSolve(). The solution consists in both the eigenvalue and the eigenvector.

    355:    Logically Collective on EPS

    357:    Input Parameters:
    358: +  eps - eigensolver context
    359: -  i   - index of the solution

    361:    Output Parameters:
    362: +  eigr - real part of eigenvalue
    363: .  eigi - imaginary part of eigenvalue
    364: .  Vr   - real part of eigenvector
    365: -  Vi   - imaginary part of eigenvector

    367:    Notes:
    368:    It is allowed to pass NULL for Vr and Vi, if the eigenvector is not
    369:    required. Otherwise, the caller must provide valid Vec objects, i.e.,
    370:    they must be created by the calling program with e.g. MatCreateVecs().

    372:    If the eigenvalue is real, then eigi and Vi are set to zero. If PETSc is
    373:    configured with complex scalars the eigenvalue is stored
    374:    directly in eigr (eigi is set to zero) and the eigenvector in Vr (Vi is
    375:    set to zero). In both cases, the user can pass NULL in eigi and Vi.

    377:    The index i should be a value between 0 and nconv-1 (see EPSGetConverged()).
    378:    Eigenpairs are indexed according to the ordering criterion established
    379:    with EPSSetWhichEigenpairs().

    381:    The 2-norm of the eigenvector is one unless the problem is generalized
    382:    Hermitian. In this case the eigenvector is normalized with respect to the
    383:    norm defined by the B matrix.

    385:    Level: beginner

    387: .seealso: EPSGetEigenvalue(), EPSGetEigenvector(), EPSSolve(),
    388:           EPSGetConverged(), EPSSetWhichEigenpairs(), EPSGetInvariantSubspace()
    389: @*/
    390: PetscErrorCode EPSGetEigenpair(EPS eps,PetscInt i,PetscScalar *eigr,PetscScalar *eigi,Vec Vr,Vec Vi)
    391: {

    397:   EPSCheckSolved(eps,1);
    398:   if (i<0 || i>=eps->nconv) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_OUTOFRANGE,"Argument 2 out of range");
    399:   EPSGetEigenvalue(eps,i,eigr,eigi);
    400:   if (Vr || Vi) { EPSGetEigenvector(eps,i,Vr,Vi); }
    401:   return(0);
    402: }

    404: /*@C
    405:    EPSGetEigenvalue - Gets the i-th eigenvalue as computed by EPSSolve().

    407:    Not Collective

    409:    Input Parameters:
    410: +  eps - eigensolver context
    411: -  i   - index of the solution

    413:    Output Parameters:
    414: +  eigr - real part of eigenvalue
    415: -  eigi - imaginary part of eigenvalue

    417:    Notes:
    418:    If the eigenvalue is real, then eigi is set to zero. If PETSc is
    419:    configured with complex scalars the eigenvalue is stored
    420:    directly in eigr (eigi is set to zero).

    422:    The index i should be a value between 0 and nconv-1 (see EPSGetConverged()).
    423:    Eigenpairs are indexed according to the ordering criterion established
    424:    with EPSSetWhichEigenpairs().

    426:    Level: beginner

    428: .seealso: EPSSolve(), EPSGetConverged(), EPSSetWhichEigenpairs(), EPSGetEigenpair()
    429: @*/
    430: PetscErrorCode EPSGetEigenvalue(EPS eps,PetscInt i,PetscScalar *eigr,PetscScalar *eigi)
    431: {
    432:   PetscInt k;

    436:   EPSCheckSolved(eps,1);
    437:   if (i<0 || i>=eps->nconv) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_OUTOFRANGE,"Argument 2 out of range");
    438:   k = eps->perm[i];
    439: #if defined(PETSC_USE_COMPLEX)
    440:   if (eigr) *eigr = eps->eigr[k];
    441:   if (eigi) *eigi = 0;
    442: #else
    443:   if (eigr) *eigr = eps->eigr[k];
    444:   if (eigi) *eigi = eps->eigi[k];
    445: #endif
    446:   return(0);
    447: }

    449: /*@
    450:    EPSGetEigenvector - Gets the i-th right eigenvector as computed by EPSSolve().

    452:    Logically Collective on EPS

    454:    Input Parameters:
    455: +  eps - eigensolver context
    456: -  i   - index of the solution

    458:    Output Parameters:
    459: +  Vr   - real part of eigenvector
    460: -  Vi   - imaginary part of eigenvector

    462:    Notes:
    463:    The caller must provide valid Vec objects, i.e., they must be created
    464:    by the calling program with e.g. MatCreateVecs().

    466:    If the corresponding eigenvalue is real, then Vi is set to zero. If PETSc is
    467:    configured with complex scalars the eigenvector is stored
    468:    directly in Vr (Vi is set to zero). In both cases, the user can pass NULL in Vi.

    470:    The index i should be a value between 0 and nconv-1 (see EPSGetConverged()).
    471:    Eigenpairs are indexed according to the ordering criterion established
    472:    with EPSSetWhichEigenpairs().

    474:    The 2-norm of the eigenvector is one unless the problem is generalized
    475:    Hermitian. In this case the eigenvector is normalized with respect to the
    476:    norm defined by the B matrix.

    478:    Level: beginner

    480: .seealso: EPSSolve(), EPSGetConverged(), EPSSetWhichEigenpairs(), EPSGetEigenpair()
    481: @*/
    482: PetscErrorCode EPSGetEigenvector(EPS eps,PetscInt i,Vec Vr,Vec Vi)
    483: {
    485:   PetscInt       k;

    493:   EPSCheckSolved(eps,1);
    494:   if (i<0 || i>=eps->nconv) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_OUTOFRANGE,"Argument 2 out of range");
    495:   EPSComputeVectors(eps);
    496:   k = eps->perm[i];
    497: #if defined(PETSC_USE_COMPLEX)
    498:   BVCopyVec(eps->V,k,Vr);
    499:   if (Vi) { VecSet(Vi,0.0); }
    500: #else
    501:   if (eps->eigi[k] > 0) { /* first value of conjugate pair */
    502:     BVCopyVec(eps->V,k,Vr);
    503:     if (Vi) {
    504:       BVCopyVec(eps->V,k+1,Vi);
    505:     }
    506:   } else if (eps->eigi[k] < 0) { /* second value of conjugate pair */
    507:     BVCopyVec(eps->V,k-1,Vr);
    508:     if (Vi) {
    509:       BVCopyVec(eps->V,k,Vi);
    510:       VecScale(Vi,-1.0);
    511:     }
    512:   } else { /* real eigenvalue */
    513:     BVCopyVec(eps->V,k,Vr);
    514:     if (Vi) { VecSet(Vi,0.0); }
    515:   }
    516: #endif
    517:   return(0);
    518: }

    520: /*@
    521:    EPSGetErrorEstimate - Returns the error estimate associated to the i-th
    522:    computed eigenpair.

    524:    Not Collective

    526:    Input Parameter:
    527: +  eps - eigensolver context
    528: -  i   - index of eigenpair

    530:    Output Parameter:
    531: .  errest - the error estimate

    533:    Notes:
    534:    This is the error estimate used internally by the eigensolver. The actual
    535:    error bound can be computed with EPSComputeError(). See also the users
    536:    manual for details.

    538:    Level: advanced

    540: .seealso: EPSComputeError()
    541: @*/
    542: PetscErrorCode EPSGetErrorEstimate(EPS eps,PetscInt i,PetscReal *errest)
    543: {
    547:   EPSCheckSolved(eps,1);
    548:   if (i<0 || i>=eps->nconv) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_OUTOFRANGE,"Argument 2 out of range");
    549:   *errest = eps->errest[eps->perm[i]];
    550:   return(0);
    551: }

    553: /*
    554:    EPSComputeResidualNorm_Private - Computes the norm of the residual vector
    555:    associated with an eigenpair.

    557:    Input Parameters:
    558:      kr,ki - eigenvalue
    559:      xr,xi - eigenvector
    560:      z     - three work vectors (the second one not referenced in complex scalars)
    561: */
    562: PetscErrorCode EPSComputeResidualNorm_Private(EPS eps,PetscScalar kr,PetscScalar ki,Vec xr,Vec xi,Vec *z,PetscReal *norm)
    563: {
    565:   PetscInt       nmat;
    566:   Mat            A,B;
    567:   Vec            u,w;
    568: #if !defined(PETSC_USE_COMPLEX)
    569:   Vec            v;
    570:   PetscReal      ni,nr;
    571: #endif

    574:   u = z[0]; w = z[2];
    575:   STGetNumMatrices(eps->st,&nmat);
    576:   STGetMatrix(eps->st,0,&A);
    577:   if (nmat>1) { STGetMatrix(eps->st,1,&B); }

    579: #if !defined(PETSC_USE_COMPLEX)
    580:   v = z[1];
    581:   if (ki == 0 || PetscAbsScalar(ki) < PetscAbsScalar(kr*PETSC_MACHINE_EPSILON)) {
    582: #endif
    583:     MatMult(A,xr,u);                             /* u=A*x */
    584:     if (PetscAbsScalar(kr) > PETSC_MACHINE_EPSILON) {
    585:       if (nmat>1) { MatMult(B,xr,w); }
    586:       else { VecCopy(xr,w); }                    /* w=B*x */
    587:       VecAXPY(u,-kr,w);                          /* u=A*x-k*B*x */
    588:     }
    589:     VecNorm(u,NORM_2,norm);
    590: #if !defined(PETSC_USE_COMPLEX)
    591:   } else {
    592:     MatMult(A,xr,u);                             /* u=A*xr */
    593:     if (SlepcAbsEigenvalue(kr,ki) > PETSC_MACHINE_EPSILON) {
    594:       if (nmat>1) { MatMult(B,xr,v); }
    595:       else { VecCopy(xr,v); }                    /* v=B*xr */
    596:       VecAXPY(u,-kr,v);                          /* u=A*xr-kr*B*xr */
    597:       if (nmat>1) { MatMult(B,xi,w); }
    598:       else { VecCopy(xi,w); }                    /* w=B*xi */
    599:       VecAXPY(u,ki,w);                           /* u=A*xr-kr*B*xr+ki*B*xi */
    600:     }
    601:     VecNorm(u,NORM_2,&nr);
    602:     MatMult(A,xi,u);                             /* u=A*xi */
    603:     if (SlepcAbsEigenvalue(kr,ki) > PETSC_MACHINE_EPSILON) {
    604:       VecAXPY(u,-kr,w);                          /* u=A*xi-kr*B*xi */
    605:       VecAXPY(u,-ki,v);                          /* u=A*xi-kr*B*xi-ki*B*xr */
    606:     }
    607:     VecNorm(u,NORM_2,&ni);
    608:     *norm = SlepcAbsEigenvalue(nr,ni);
    609:   }
    610: #endif
    611:   return(0);
    612: }

    614: /*@
    615:    EPSComputeError - Computes the error (based on the residual norm) associated
    616:    with the i-th computed eigenpair.

    618:    Collective on EPS

    620:    Input Parameter:
    621: +  eps  - the eigensolver context
    622: .  i    - the solution index
    623: -  type - the type of error to compute

    625:    Output Parameter:
    626: .  error - the error

    628:    Notes:
    629:    The error can be computed in various ways, all of them based on the residual
    630:    norm ||Ax-kBx||_2 where k is the eigenvalue and x is the eigenvector.

    632:    Level: beginner

    634: .seealso: EPSErrorType, EPSSolve(), EPSGetErrorEstimate()
    635: @*/
    636: PetscErrorCode EPSComputeError(EPS eps,PetscInt i,EPSErrorType type,PetscReal *error)
    637: {
    639:   Mat            A,B;
    640:   Vec            xr,xi,w[3];
    641:   PetscReal      t,vecnorm=1.0;
    642:   PetscScalar    kr,ki;
    643:   PetscBool      flg;

    650:   EPSCheckSolved(eps,1);

    652:   /* allocate work vectors */
    653: #if defined(PETSC_USE_COMPLEX)
    654:   EPSSetWorkVecs(eps,3);
    655:   xi   = NULL;
    656:   w[1] = NULL;
    657: #else
    658:   EPSSetWorkVecs(eps,5);
    659:   xi   = eps->work[3];
    660:   w[1] = eps->work[4];
    661: #endif
    662:   xr   = eps->work[0];
    663:   w[0] = eps->work[1];
    664:   w[2] = eps->work[2];

    666:   /* compute residual norms */
    667:   EPSGetEigenpair(eps,i,&kr,&ki,xr,xi);
    668:   EPSComputeResidualNorm_Private(eps,kr,ki,xr,xi,w,error);

    670:   /* compute 2-norm of eigenvector */
    671:   if (eps->problem_type==EPS_GHEP) {
    672:     VecNorm(xr,NORM_2,&vecnorm);
    673:   }

    675:   /* compute error */
    676:   switch (type) {
    677:     case EPS_ERROR_ABSOLUTE:
    678:       break;
    679:     case EPS_ERROR_RELATIVE:
    680:       *error /= SlepcAbsEigenvalue(kr,ki)*vecnorm;
    681:       break;
    682:     case EPS_ERROR_BACKWARD:
    683:       /* initialization of matrix norms */
    684:       if (!eps->nrma) {
    685:         STGetMatrix(eps->st,0,&A);
    686:         MatHasOperation(A,MATOP_NORM,&flg);
    687:         if (!flg) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONG,"The computation of backward errors requires a matrix norm operation");
    688:         MatNorm(A,NORM_INFINITY,&eps->nrma);
    689:       }
    690:       if (eps->isgeneralized) {
    691:         if (!eps->nrmb) {
    692:           STGetMatrix(eps->st,1,&B);
    693:           MatHasOperation(B,MATOP_NORM,&flg);
    694:           if (!flg) SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONG,"The computation of backward errors requires a matrix norm operation");
    695:           MatNorm(B,NORM_INFINITY,&eps->nrmb);
    696:         }
    697:       } else eps->nrmb = 1.0;
    698:       t = SlepcAbsEigenvalue(kr,ki);
    699:       *error /= (eps->nrma+t*eps->nrmb)*vecnorm;
    700:       break;
    701:     default:
    702:       SETERRQ(PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_OUTOFRANGE,"Invalid error type");
    703:   }
    704:   return(0);
    705: }

    707: /*
    708:    EPSGetStartVector - Generate a suitable vector to be used as the starting vector
    709:    for the recurrence that builds the right subspace.

    711:    Collective on EPS and Vec

    713:    Input Parameters:
    714: +  eps - the eigensolver context
    715: -  i   - iteration number

    717:    Output Parameters:
    718: .  breakdown - flag indicating that a breakdown has occurred

    720:    Notes:
    721:    The start vector is computed from another vector: for the first step (i=0),
    722:    the first initial vector is used (see EPSSetInitialSpace()); otherwise a random
    723:    vector is created. Then this vector is forced to be in the range of OP (only
    724:    for generalized definite problems) and orthonormalized with respect to all
    725:    V-vectors up to i-1. The resulting vector is placed in V[i].

    727:    The flag breakdown is set to true if either i=0 and the vector belongs to the
    728:    deflation space, or i>0 and the vector is linearly dependent with respect
    729:    to the V-vectors.
    730: */
    731: PetscErrorCode EPSGetStartVector(EPS eps,PetscInt i,PetscBool *breakdown)
    732: {
    734:   PetscReal      norm;
    735:   PetscBool      lindep;
    736:   Vec            w,z;

    742:   /* For the first step, use the first initial vector, otherwise a random one */
    743:   if (i>0 || eps->nini==0) {
    744:     BVSetRandomColumn(eps->V,i);
    745:   }

    747:   /* Force the vector to be in the range of OP for definite generalized problems */
    748:   if (eps->ispositive || (eps->isgeneralized && eps->ishermitian)) {
    749:     BVCreateVec(eps->V,&w);
    750:     BVCopyVec(eps->V,i,w);
    751:     BVGetColumn(eps->V,i,&z);
    752:     STApply(eps->st,w,z);
    753:     BVRestoreColumn(eps->V,i,&z);
    754:     VecDestroy(&w);
    755:   }

    757:   /* Orthonormalize the vector with respect to previous vectors */
    758:   BVOrthogonalizeColumn(eps->V,i,NULL,&norm,&lindep);
    759:   if (breakdown) *breakdown = lindep;
    760:   else if (lindep || norm == 0.0) {
    761:     if (i==0) SETERRQ(PetscObjectComm((PetscObject)eps),1,"Initial vector is zero or belongs to the deflation space");
    762:     else SETERRQ(PetscObjectComm((PetscObject)eps),1,"Unable to generate more start vectors");
    763:   }
    764:   BVScaleColumn(eps->V,i,1.0/norm);
    765:   return(0);
    766: }