Date: 2026-03-09T09:12:28+00:00

Actual source code: ks-slice.c

      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 with spectrum slicing for symmetric eigenproblems

     15:    References:

     17:        [1] R.G. Grimes et al., "A shifted block Lanczos algorithm for
     18:            solving sparse symmetric generalized eigenproblems", SIAM J.
     19:            Matrix Anal. Appl. 15(1):228-272, 1994.

     21:        [2] C. Campos and J.E. Roman, "Spectrum slicing strategies based
     22:            on restarted Lanczos methods", Numer. Algor. 60(2):279-295,
     23:            2012.
     24: */

     26: #include <slepc/private/epsimpl.h>
     27: #include "krylovschur.h"

     29: static PetscBool  cited = PETSC_FALSE;
     30: static const char citation[] =
     31:   "@Article{slepc-slice,\n"
     32:   "   author = \"C. Campos and J. E. Roman\",\n"
     33:   "   title = \"Strategies for spectrum slicing based on restarted {Lanczos} methods\",\n"
     34:   "   journal = \"Numer. Algorithms\",\n"
     35:   "   volume = \"60\",\n"
     36:   "   number = \"2\",\n"
     37:   "   pages = \"279--295\",\n"
     38:   "   year = \"2012,\"\n"
     39:   "   doi = \"https://doi.org/10.1007/s11075-012-9564-z\"\n"
     40:   "}\n";

     42: #define SLICE_PTOL PETSC_SQRT_MACHINE_EPSILON

     44: static PetscErrorCode EPSSliceResetSR(EPS eps)
     45: {
     46:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
     47:   EPS_SR          sr=ctx->sr;
     48:   EPS_shift       s;

     50:   PetscFunctionBegin;
     51:   if (sr) {
     52:     if (ctx->npart>1) {
     53:       PetscCall(BVDestroy(&sr->V));
     54:       PetscCall(PetscFree4(sr->eigr,sr->eigi,sr->errest,sr->perm));
     55:     }
     56:     /* Reviewing list of shifts to free memory */
     57:     s = sr->s0;
     58:     if (s) {
     59:       while (s->neighb[1]) {
     60:         s = s->neighb[1];
     61:         PetscCall(PetscFree(s->neighb[0]));
     62:       }
     63:       PetscCall(PetscFree(s));
     64:     }
     65:     PetscCall(PetscFree(sr));
     66:   }
     67:   ctx->sr = NULL;
     68:   PetscFunctionReturn(PETSC_SUCCESS);
     69: }

     71: PetscErrorCode EPSReset_KrylovSchur_Slice(EPS eps)
     72: {
     73:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;

     75:   PetscFunctionBegin;
     76:   if (!ctx->global) PetscFunctionReturn(PETSC_SUCCESS);
     77:   /* Reset auxiliary EPS */
     78:   PetscCall(EPSSliceResetSR(ctx->eps));
     79:   PetscCall(EPSReset(ctx->eps));
     80:   PetscCall(EPSSliceResetSR(eps));
     81:   PetscCall(PetscFree(ctx->inertias));
     82:   PetscCall(PetscFree(ctx->shifts));
     83:   PetscFunctionReturn(PETSC_SUCCESS);
     84: }

     86: PetscErrorCode EPSDestroy_KrylovSchur_Slice(EPS eps)
     87: {
     88:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;

     90:   PetscFunctionBegin;
     91:   if (!ctx->global) PetscFunctionReturn(PETSC_SUCCESS);
     92:   /* Destroy auxiliary EPS */
     93:   PetscCall(EPSReset_KrylovSchur_Slice(eps));
     94:   PetscCall(EPSDestroy(&ctx->eps));
     95:   if (ctx->npart>1) {
     96:     PetscCall(PetscSubcommDestroy(&ctx->subc));
     97:     if (ctx->commset) {
     98:       PetscCallMPI(MPI_Comm_free(&ctx->commrank));
     99:       ctx->commset = PETSC_FALSE;
    100:     }
    101:     PetscCall(ISDestroy(&ctx->isrow));
    102:     PetscCall(ISDestroy(&ctx->iscol));
    103:     PetscCall(MatDestroyMatrices(1,&ctx->submata));
    104:     PetscCall(MatDestroyMatrices(1,&ctx->submatb));
    105:   }
    106:   PetscCall(PetscFree(ctx->subintervals));
    107:   PetscCall(PetscFree(ctx->nconv_loc));
    108:   PetscFunctionReturn(PETSC_SUCCESS);
    109: }

    111: /*
    112:   EPSSliceAllocateSolution - Allocate memory storage for common variables such
    113:   as eigenvalues and eigenvectors. The argument extra is used for methods
    114:   that require a working basis slightly larger than ncv.
    115: */
    116: static PetscErrorCode EPSSliceAllocateSolution(EPS eps,PetscInt extra)
    117: {
    118:   EPS_KRYLOVSCHUR    *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    119:   PetscReal          eta;
    120:   PetscInt           k;
    121:   BVType             type;
    122:   BVOrthogType       orthog_type;
    123:   BVOrthogRefineType orthog_ref;
    124:   BVOrthogBlockType  ob_type;
    125:   Mat                matrix;
    126:   Vec                t;
    127:   EPS_SR             sr = ctx->sr;

    129:   PetscFunctionBegin;
    130:   /* allocate space for eigenvalues and friends */
    131:   k = PetscMax(1,sr->numEigs);
    132:   PetscCall(PetscFree4(sr->eigr,sr->eigi,sr->errest,sr->perm));
    133:   PetscCall(PetscMalloc4(k,&sr->eigr,k,&sr->eigi,k,&sr->errest,k,&sr->perm));

    135:   /* allocate sr->V and transfer options from eps->V */
    136:   PetscCall(BVDestroy(&sr->V));
    137:   PetscCall(BVCreate(PetscObjectComm((PetscObject)eps),&sr->V));
    138:   if (!eps->V) PetscCall(EPSGetBV(eps,&eps->V));
    139:   if (!((PetscObject)eps->V)->type_name) PetscCall(BVSetType(sr->V,BVMAT));
    140:   else {
    141:     PetscCall(BVGetType(eps->V,&type));
    142:     PetscCall(BVSetType(sr->V,type));
    143:   }
    144:   PetscCall(STMatCreateVecsEmpty(eps->st,&t,NULL));
    145:   PetscCall(BVSetSizesFromVec(sr->V,t,k));
    146:   PetscCall(VecDestroy(&t));
    147:   PetscCall(EPS_SetInnerProduct(eps));
    148:   PetscCall(BVGetMatrix(eps->V,&matrix,NULL));
    149:   PetscCall(BVSetMatrix(sr->V,matrix,PETSC_FALSE));
    150:   PetscCall(BVGetOrthogonalization(eps->V,&orthog_type,&orthog_ref,&eta,&ob_type));
    151:   PetscCall(BVSetOrthogonalization(sr->V,orthog_type,orthog_ref,eta,ob_type));
    152:   PetscFunctionReturn(PETSC_SUCCESS);
    153: }

    155: static PetscErrorCode EPSSliceGetEPS(EPS eps)
    156: {
    157:   EPS_KRYLOVSCHUR    *ctx=(EPS_KRYLOVSCHUR*)eps->data,*ctx_local;
    158:   BV                 V;
    159:   BVType             type;
    160:   PetscReal          eta;
    161:   BVOrthogType       orthog_type;
    162:   BVOrthogRefineType orthog_ref;
    163:   BVOrthogBlockType  ob_type;
    164:   PetscInt           i;
    165:   PetscReal          h,a,b;
    166:   PetscRandom        rand;
    167:   EPS_SR             sr=ctx->sr;

    169:   PetscFunctionBegin;
    170:   if (!ctx->eps) PetscCall(EPSKrylovSchurGetChildEPS(eps,&ctx->eps));

    172:   /* Determine subintervals */
    173:   if (ctx->npart==1) {
    174:     a = eps->inta; b = eps->intb;
    175:   } else {
    176:     if (!ctx->subintset) { /* uniform distribution if no set by user */
    177:       PetscCheck(sr->hasEnd,PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONG,"Global interval must be bounded for splitting it in uniform subintervals");
    178:       h = (eps->intb-eps->inta)/ctx->npart;
    179:       a = eps->inta+ctx->subc->color*h;
    180:       b = (ctx->subc->color==ctx->npart-1)?eps->intb:eps->inta+(ctx->subc->color+1)*h;
    181:       PetscCall(PetscFree(ctx->subintervals));
    182:       PetscCall(PetscMalloc1(ctx->npart+1,&ctx->subintervals));
    183:       for (i=0;i<ctx->npart;i++) ctx->subintervals[i] = eps->inta+h*i;
    184:       ctx->subintervals[ctx->npart] = eps->intb;
    185:     } else {
    186:       a = ctx->subintervals[ctx->subc->color];
    187:       b = ctx->subintervals[ctx->subc->color+1];
    188:     }
    189:   }
    190:   PetscCall(EPSSetInterval(ctx->eps,a,b));
    191:   PetscCall(EPSSetConvergenceTest(ctx->eps,eps->conv));
    192:   PetscCall(EPSSetDimensions(ctx->eps,ctx->nev,ctx->ncv,ctx->mpd));
    193:   PetscCall(EPSKrylovSchurSetLocking(ctx->eps,ctx->lock));

    195:   ctx_local = (EPS_KRYLOVSCHUR*)ctx->eps->data;
    196:   ctx_local->detect = ctx->detect;

    198:   /* transfer options from eps->V */
    199:   PetscCall(EPSGetBV(ctx->eps,&V));
    200:   PetscCall(BVGetRandomContext(V,&rand));  /* make sure the random context is available when duplicating */
    201:   if (!eps->V) PetscCall(EPSGetBV(eps,&eps->V));
    202:   if (!((PetscObject)eps->V)->type_name) PetscCall(BVSetType(V,BVMAT));
    203:   else {
    204:     PetscCall(BVGetType(eps->V,&type));
    205:     PetscCall(BVSetType(V,type));
    206:   }
    207:   PetscCall(BVGetOrthogonalization(eps->V,&orthog_type,&orthog_ref,&eta,&ob_type));
    208:   PetscCall(BVSetOrthogonalization(V,orthog_type,orthog_ref,eta,ob_type));

    210:   ctx->eps->which = eps->which;
    211:   ctx->eps->max_it = eps->max_it;
    212:   ctx->eps->tol = eps->tol;
    213:   ctx->eps->purify = eps->purify;
    214:   if (eps->tol==(PetscReal)PETSC_DETERMINE) eps->tol = SLEPC_DEFAULT_TOL;
    215:   PetscCall(EPSSetProblemType(ctx->eps,eps->problem_type));
    216:   PetscCall(EPSSetUp(ctx->eps));
    217:   ctx->eps->nconv = 0;
    218:   ctx->eps->its   = 0;
    219:   for (i=0;i<ctx->eps->ncv;i++) {
    220:     ctx->eps->eigr[i]   = 0.0;
    221:     ctx->eps->eigi[i]   = 0.0;
    222:     ctx->eps->errest[i] = 0.0;
    223:   }
    224:   PetscFunctionReturn(PETSC_SUCCESS);
    225: }

    227: static PetscErrorCode EPSSliceGetInertia(EPS eps,PetscReal shift,PetscInt *inertia,PetscInt *zeros)
    228: {
    229:   KSP            ksp,kspr;
    230:   PC             pc;
    231:   Mat            F;
    232:   PetscReal      nzshift=shift;
    233:   PetscBool      flg;

    235:   PetscFunctionBegin;
    236:   if (shift >= PETSC_MAX_REAL) { /* Right-open interval */
    237:     if (inertia) *inertia = eps->n;
    238:   } else if (shift <= PETSC_MIN_REAL) {
    239:     if (inertia) *inertia = 0;
    240:     if (zeros) *zeros = 0;
    241:   } else {
    242:     /* If the shift is zero, perturb it to a very small positive value.
    243:        The goal is that the nonzero pattern is the same in all cases and reuse
    244:        the symbolic factorizations */
    245:     nzshift = (shift==0.0)? 10.0/PETSC_MAX_REAL: shift;
    246:     PetscCall(STSetShift(eps->st,nzshift));
    247:     PetscCall(STGetKSP(eps->st,&ksp));
    248:     PetscCall(KSPGetPC(ksp,&pc));
    249:     PetscCall(PetscObjectTypeCompare((PetscObject)pc,PCREDUNDANT,&flg));
    250:     if (flg) {
    251:       PetscCall(PCRedundantGetKSP(pc,&kspr));
    252:       PetscCall(KSPGetPC(kspr,&pc));
    253:     }
    254:     PetscCall(PCFactorGetMatrix(pc,&F));
    255:     PetscCall(MatGetInertia(F,inertia,zeros,NULL));
    256:   }
    257:   if (inertia) PetscCall(PetscInfo(eps,"Computed inertia at shift %g: %" PetscInt_FMT "\n",(double)nzshift,*inertia));
    258:   PetscFunctionReturn(PETSC_SUCCESS);
    259: }

    261: /*
    262:    Dummy backtransform operation
    263:  */
    264: static PetscErrorCode EPSBackTransform_Skip(EPS eps)
    265: {
    266:   PetscFunctionBegin;
    267:   PetscFunctionReturn(PETSC_SUCCESS);
    268: }

    270: PetscErrorCode EPSSetUp_KrylovSchur_Slice(EPS eps)
    271: {
    272:   EPS_KRYLOVSCHUR *ctx = (EPS_KRYLOVSCHUR*)eps->data,*ctx_glob;
    273:   EPS_SR          sr,sr_loc,sr_glob;
    274:   PetscInt        nEigs,dssz=1,i,zeros=0,off=0,method,hiteig=0;
    275:   PetscMPIInt     nproc,rank=0,aux;
    276:   PetscReal       r;
    277:   MPI_Request     req;
    278:   Mat             A,B=NULL;
    279:   DSParallelType  ptype;
    280:   MPI_Comm        child;

    282:   PetscFunctionBegin;
    283:   if (eps->nev==0) eps->nev = 1;
    284:   if (ctx->global) {
    285:     EPSCheckHermitianDefiniteCondition(eps,PETSC_TRUE," with spectrum slicing");
    286:     EPSCheckSinvertCayleyCondition(eps,PETSC_TRUE," with spectrum slicing");
    287:     PetscCheck(eps->inta!=eps->intb,PetscObjectComm((PetscObject)eps),PETSC_ERR_SUP,"This solver does not support computing all eigenvalues unless you provide a computational interval with EPSSetInterval()");
    288:     PetscCheck(eps->intb<PETSC_MAX_REAL || eps->inta>PETSC_MIN_REAL,PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONG,"The defined computational interval should have at least one of their sides bounded");
    289:     PetscCheck(eps->nds==0,PetscObjectComm((PetscObject)eps),PETSC_ERR_SUP,"Spectrum slicing not supported in combination with deflation space");
    290:     EPSCheckUnsupportedCondition(eps,EPS_FEATURE_ARBITRARY | EPS_FEATURE_REGION | EPS_FEATURE_STOPPING,PETSC_TRUE," with spectrum slicing");
    291:     EPSCheckIgnoredCondition(eps,EPS_FEATURE_BALANCE,PETSC_TRUE," with spectrum slicing");
    292:     if (eps->tol==(PetscReal)PETSC_DETERMINE) {
    293: #if defined(PETSC_USE_REAL_SINGLE)
    294:       eps->tol = SLEPC_DEFAULT_TOL;
    295: #else
    296:       /* use tighter tolerance */
    297:       eps->tol = SLEPC_DEFAULT_TOL*1e-2;
    298: #endif
    299:     }
    300:     if (eps->max_it==PETSC_DETERMINE) eps->max_it = 100;
    301:     if (ctx->nev==1) ctx->nev = PetscMin(40,eps->n);  /* nev not set, use default value */
    302:     PetscCheck(eps->n<=10 || ctx->nev>=10,PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONG,"nev cannot be less than 10 in spectrum slicing runs");
    303:   }
    304:   eps->ops->backtransform = EPSBackTransform_Skip;

    306:   /* create spectrum slicing context and initialize it */
    307:   PetscCall(EPSSliceResetSR(eps));
    308:   PetscCall(PetscNew(&sr));
    309:   ctx->sr = sr;
    310:   sr->itsKs = 0;
    311:   sr->nleap = 0;
    312:   sr->nMAXCompl = eps->nev/4;
    313:   sr->iterCompl = eps->max_it/4;
    314:   sr->sPres = NULL;
    315:   sr->nS = 0;

    317:   if (ctx->npart==1 || ctx->global) {
    318:     /* check presence of ends and finding direction */
    319:     if ((eps->inta > PETSC_MIN_REAL && !(ctx->subintervals && ctx->subintervals[0]==ctx->subintervals[1])) || eps->intb >= PETSC_MAX_REAL) {
    320:       sr->int0 = eps->inta;
    321:       sr->int1 = eps->intb;
    322:       sr->dir = 1;
    323:       if (eps->intb >= PETSC_MAX_REAL) { /* Right-open interval */
    324:         sr->hasEnd = PETSC_FALSE;
    325:       } else sr->hasEnd = PETSC_TRUE;
    326:     } else {
    327:       sr->int0 = eps->intb;
    328:       sr->int1 = eps->inta;
    329:       sr->dir = -1;
    330:       sr->hasEnd = PetscNot(eps->inta <= PETSC_MIN_REAL);
    331:     }
    332:   }
    333:   if (ctx->global) {
    334:     PetscCall(EPSSetDimensions_Default(eps,&ctx->nev,&ctx->ncv,&ctx->mpd));
    335:     /* create subintervals and initialize auxiliary eps for slicing runs */
    336:     PetscCall(EPSKrylovSchurGetChildEPS(eps,&ctx->eps));
    337:     /* prevent computation of factorization in global eps */
    338:     PetscCall(STSetTransform(eps->st,PETSC_FALSE));
    339:     PetscCall(EPSSliceGetEPS(eps));
    340:     sr_loc = ((EPS_KRYLOVSCHUR*)ctx->eps->data)->sr;
    341:     if (ctx->npart>1) {
    342:       PetscCall(PetscSubcommGetChild(ctx->subc,&child));
    343:       if ((sr->dir>0&&ctx->subc->color==0)||(sr->dir<0&&ctx->subc->color==ctx->npart-1)) sr->inertia0 = sr_loc->inertia0;
    344:       PetscCallMPI(MPI_Comm_rank(child,&rank));
    345:       if (!rank) {
    346:         PetscCall(PetscMPIIntCast((sr->dir>0)?0:ctx->npart-1,&aux));
    347:         PetscCallMPI(MPI_Bcast(&sr->inertia0,1,MPIU_INT,aux,ctx->commrank));
    348:       }
    349:       PetscCallMPI(MPI_Bcast(&sr->inertia0,1,MPIU_INT,0,child));
    350:       PetscCall(PetscFree(ctx->nconv_loc));
    351:       PetscCall(PetscMalloc1(ctx->npart,&ctx->nconv_loc));
    352:       PetscCallMPI(MPI_Comm_size(((PetscObject)eps)->comm,&nproc));
    353:       if (sr->dir<0) off = 1;
    354:       if (nproc%ctx->npart==0) { /* subcommunicators with the same size */
    355:         PetscCall(PetscMPIIntCast(sr_loc->numEigs,&aux));
    356:         PetscCallMPI(MPI_Allgather(&aux,1,MPI_INT,ctx->nconv_loc,1,MPI_INT,ctx->commrank));
    357:         PetscCallMPI(MPI_Allgather(sr_loc->dir==sr->dir?&sr_loc->int0:&sr_loc->int1,1,MPIU_REAL,ctx->subintervals+off,1,MPIU_REAL,ctx->commrank));
    358:       } else {
    359:         PetscCallMPI(MPI_Comm_rank(child,&rank));
    360:         if (!rank) {
    361:           PetscCall(PetscMPIIntCast(sr_loc->numEigs,&aux));
    362:           PetscCallMPI(MPI_Allgather(&aux,1,MPI_INT,ctx->nconv_loc,1,MPI_INT,ctx->commrank));
    363:           PetscCallMPI(MPI_Allgather(sr_loc->dir==sr->dir?&sr_loc->int0:&sr_loc->int1,1,MPIU_REAL,ctx->subintervals+off,1,MPIU_REAL,ctx->commrank));
    364:         }
    365:         PetscCall(PetscMPIIntCast(ctx->npart,&aux));
    366:         PetscCallMPI(MPI_Bcast(ctx->nconv_loc,aux,MPI_INT,0,child));
    367:         PetscCallMPI(MPI_Bcast(ctx->subintervals+off,aux,MPIU_REAL,0,child));
    368:       }
    369:       nEigs = 0;
    370:       for (i=0;i<ctx->npart;i++) nEigs += ctx->nconv_loc[i];
    371:     } else {
    372:       nEigs = sr_loc->numEigs;
    373:       sr->inertia0 = sr_loc->inertia0;
    374:       sr->dir = sr_loc->dir;
    375:     }
    376:     sr->inertia1 = sr->inertia0+sr->dir*nEigs;
    377:     sr->numEigs = nEigs;
    378:     eps->nev = nEigs;
    379:     eps->ncv = nEigs;
    380:     eps->mpd = nEigs;
    381:   } else {
    382:     ctx_glob = (EPS_KRYLOVSCHUR*)ctx->eps->data;
    383:     sr_glob = ctx_glob->sr;
    384:     if (ctx->npart>1) {
    385:       sr->dir = sr_glob->dir;
    386:       sr->int0 = (sr->dir==1)?eps->inta:eps->intb;
    387:       sr->int1 = (sr->dir==1)?eps->intb:eps->inta;
    388:       if ((sr->dir>0&&ctx->subc->color==ctx->npart-1)||(sr->dir<0&&ctx->subc->color==0)) sr->hasEnd = sr_glob->hasEnd;
    389:       else sr->hasEnd = PETSC_TRUE;
    390:     }
    391:     /* sets first shift */
    392:     PetscCall(STSetShift(eps->st,(sr->int0==0.0)?10.0/PETSC_MAX_REAL:sr->int0));
    393:     PetscCall(STSetUp(eps->st));

    395:     /* compute inertia0 */
    396:     PetscCall(EPSSliceGetInertia(eps,sr->int0,&sr->inertia0,ctx->detect?&zeros:NULL));
    397:     /* undocumented option to control what to do when an eigenvalue is found:
    398:        - error out if it's the endpoint of the user-provided interval (or sub-interval)
    399:        - if it's an endpoint computed internally:
    400:           + if hiteig=0 error out
    401:           + else if hiteig=1 the subgroup that hit the eigenvalue does nothing
    402:           + otherwise the subgroup that hit the eigenvalue perturbs the shift and recomputes inertia
    403:     */
    404:     PetscCall(PetscOptionsGetInt(NULL,NULL,"-eps_krylovschur_hiteigenvalue",&hiteig,NULL));
    405:     if (zeros) { /* error in factorization */
    406:       PetscCheck(sr->int0!=ctx->eps->inta && sr->int0!=ctx->eps->intb,((PetscObject)eps)->comm,PETSC_ERR_USER,"Found singular matrix for the transformed problem in the interval endpoint");
    407:       PetscCheck(!ctx_glob->subintset || hiteig,((PetscObject)eps)->comm,PETSC_ERR_USER,"Found singular matrix for the transformed problem in an interval endpoint defined by user");
    408:       if (hiteig==1) { /* idle subgroup */
    409:         sr->inertia0 = -1;
    410:       } else { /* perturb shift */
    411:         sr->int0 *= (1.0+SLICE_PTOL);
    412:         PetscCall(EPSSliceGetInertia(eps,sr->int0,&sr->inertia0,&zeros));
    413:         PetscCheck(zeros==0,((PetscObject)eps)->comm,PETSC_ERR_CONV_FAILED,"Inertia computation fails in %g",(double)sr->int1);
    414:       }
    415:     }
    416:     if (ctx->npart>1) {
    417:       PetscCall(PetscSubcommGetChild(ctx->subc,&child));
    418:       /* inertia1 is received from neighbour */
    419:       PetscCallMPI(MPI_Comm_rank(child,&rank));
    420:       if (!rank) {
    421:         if (sr->inertia0!=-1 && ((sr->dir>0 && ctx->subc->color>0) || (sr->dir<0 && ctx->subc->color<ctx->npart-1))) { /* send inertia0 to neighbour0 */
    422:           PetscCall(PetscMPIIntCast(ctx->subc->color-sr->dir,&aux));
    423:           PetscCallMPI(MPIU_Isend(&sr->inertia0,1,MPIU_INT,aux,0,ctx->commrank,&req));
    424:           PetscCallMPI(MPIU_Isend(&sr->int0,1,MPIU_REAL,aux,0,ctx->commrank,&req));
    425:         }
    426:         if ((sr->dir>0 && ctx->subc->color<ctx->npart-1)|| (sr->dir<0 && ctx->subc->color>0)) { /* receive inertia1 from neighbour1 */
    427:           PetscCall(PetscMPIIntCast(ctx->subc->color+sr->dir,&aux));
    428:           PetscCallMPI(MPI_Recv(&sr->inertia1,1,MPIU_INT,aux,0,ctx->commrank,MPI_STATUS_IGNORE));
    429:           PetscCallMPI(MPI_Recv(&sr->int1,1,MPIU_REAL,aux,0,ctx->commrank,MPI_STATUS_IGNORE));
    430:         }
    431:         if (sr->inertia0==-1 && !(sr->dir>0 && ctx->subc->color==ctx->npart-1) && !(sr->dir<0 && ctx->subc->color==0)) {
    432:           sr->inertia0 = sr->inertia1; sr->int0 = sr->int1;
    433:           PetscCall(PetscMPIIntCast(ctx->subc->color-sr->dir,&aux));
    434:           PetscCallMPI(MPIU_Isend(&sr->inertia0,1,MPIU_INT,aux,0,ctx->commrank,&req));
    435:           PetscCallMPI(MPIU_Isend(&sr->int0,1,MPIU_REAL,aux,0,ctx->commrank,&req));
    436:         }
    437:       }
    438:       if ((sr->dir>0 && ctx->subc->color<ctx->npart-1)||(sr->dir<0 && ctx->subc->color>0)) {
    439:         PetscCallMPI(MPI_Bcast(&sr->inertia1,1,MPIU_INT,0,child));
    440:         PetscCallMPI(MPI_Bcast(&sr->int1,1,MPIU_REAL,0,child));
    441:       } else sr_glob->inertia1 = sr->inertia1;
    442:     }

    444:     /* last process in eps comm computes inertia1 */
    445:     if (ctx->npart==1 || ((sr->dir>0 && ctx->subc->color==ctx->npart-1) || (sr->dir<0 && ctx->subc->color==0))) {
    446:       PetscCall(EPSSliceGetInertia(eps,sr->int1,&sr->inertia1,ctx->detect?&zeros:NULL));
    447:       PetscCheck(zeros==0,((PetscObject)eps)->comm,PETSC_ERR_USER,"Found singular matrix for the transformed problem in an interval endpoint defined by user");
    448:       if (!rank && sr->inertia0==-1) {
    449:         sr->inertia0 = sr->inertia1; sr->int0 = sr->int1;
    450:         PetscCall(PetscMPIIntCast(ctx->subc->color-sr->dir,&aux));
    451:         PetscCallMPI(MPIU_Isend(&sr->inertia0,1,MPIU_INT,aux,0,ctx->commrank,&req));
    452:         PetscCallMPI(MPIU_Isend(&sr->int0,1,MPIU_REAL,aux,0,ctx->commrank,&req));
    453:       }
    454:       if (sr->hasEnd) {
    455:         sr->dir = -sr->dir; r = sr->int0; sr->int0 = sr->int1; sr->int1 = r;
    456:         i = sr->inertia0; sr->inertia0 = sr->inertia1; sr->inertia1 = i;
    457:       }
    458:     }

    460:     /* number of eigenvalues in interval */
    461:     sr->numEigs = (sr->dir)*(sr->inertia1 - sr->inertia0);
    462:     if (ctx->npart>1) {
    463:       /* memory allocate for subinterval eigenpairs */
    464:       PetscCall(EPSSliceAllocateSolution(eps,1));
    465:     }
    466:     dssz = eps->ncv+1;
    467:     PetscCall(DSGetParallel(ctx->eps->ds,&ptype));
    468:     PetscCall(DSSetParallel(eps->ds,ptype));
    469:     PetscCall(DSGetMethod(ctx->eps->ds,&method));
    470:     PetscCall(DSSetMethod(eps->ds,method));
    471:   }
    472:   PetscCall(DSSetType(eps->ds,DSHEP));
    473:   PetscCall(DSSetCompact(eps->ds,PETSC_TRUE));
    474:   PetscCall(DSAllocate(eps->ds,dssz));
    475:   /* keep state of subcomm matrices to check that the user does not modify them */
    476:   PetscCall(EPSGetOperators(eps,&A,&B));
    477:   PetscCall(MatGetState(A,&ctx->Astate));
    478:   PetscCall(PetscObjectGetId((PetscObject)A,&ctx->Aid));
    479:   if (B) {
    480:     PetscCall(MatGetState(B,&ctx->Bstate));
    481:     PetscCall(PetscObjectGetId((PetscObject)B,&ctx->Bid));
    482:   } else {
    483:     ctx->Bstate=0;
    484:     ctx->Bid=0;
    485:   }
    486:   PetscFunctionReturn(PETSC_SUCCESS);
    487: }

    489: static PetscErrorCode EPSSliceGatherEigenVectors(EPS eps)
    490: {
    491:   Vec             v,vg,v_loc;
    492:   IS              is1,is2;
    493:   VecScatter      vec_sc;
    494:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    495:   PetscInt        nloc,m0,n0,i,si,idx,*idx1,*idx2,j;
    496:   PetscScalar     *array;
    497:   EPS_SR          sr_loc;
    498:   BV              V_loc;

    500:   PetscFunctionBegin;
    501:   sr_loc = ((EPS_KRYLOVSCHUR*)ctx->eps->data)->sr;
    502:   V_loc = sr_loc->V;

    504:   /* Gather parallel eigenvectors */
    505:   PetscCall(BVGetColumn(eps->V,0,&v));
    506:   PetscCall(VecGetOwnershipRange(v,&n0,&m0));
    507:   PetscCall(BVRestoreColumn(eps->V,0,&v));
    508:   PetscCall(BVGetColumn(ctx->eps->V,0,&v));
    509:   PetscCall(VecGetLocalSize(v,&nloc));
    510:   PetscCall(BVRestoreColumn(ctx->eps->V,0,&v));
    511:   PetscCall(PetscMalloc2(m0-n0,&idx1,m0-n0,&idx2));
    512:   PetscCall(VecCreateMPI(PetscObjectComm((PetscObject)eps),nloc,PETSC_DECIDE,&vg));
    513:   idx = -1;
    514:   for (si=0;si<ctx->npart;si++) {
    515:     j = 0;
    516:     for (i=n0;i<m0;i++) {
    517:       idx1[j]   = i;
    518:       idx2[j++] = i+eps->n*si;
    519:     }
    520:     PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)eps),(m0-n0),idx1,PETSC_COPY_VALUES,&is1));
    521:     PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)eps),(m0-n0),idx2,PETSC_COPY_VALUES,&is2));
    522:     PetscCall(BVGetColumn(eps->V,0,&v));
    523:     PetscCall(VecScatterCreate(v,is1,vg,is2,&vec_sc));
    524:     PetscCall(BVRestoreColumn(eps->V,0,&v));
    525:     PetscCall(ISDestroy(&is1));
    526:     PetscCall(ISDestroy(&is2));
    527:     for (i=0;i<ctx->nconv_loc[si];i++) {
    528:       PetscCall(BVGetColumn(eps->V,++idx,&v));
    529:       if (ctx->subc->color==si) {
    530:         PetscCall(BVGetColumn(V_loc,i,&v_loc));
    531:         PetscCall(VecGetArray(v_loc,&array));
    532:         PetscCall(VecPlaceArray(vg,array));
    533:       }
    534:       PetscCall(VecScatterBegin(vec_sc,vg,v,INSERT_VALUES,SCATTER_REVERSE));
    535:       PetscCall(VecScatterEnd(vec_sc,vg,v,INSERT_VALUES,SCATTER_REVERSE));
    536:       if (ctx->subc->color==si) {
    537:         PetscCall(VecResetArray(vg));
    538:         PetscCall(VecRestoreArray(v_loc,&array));
    539:         PetscCall(BVRestoreColumn(V_loc,i,&v_loc));
    540:       }
    541:       PetscCall(BVRestoreColumn(eps->V,idx,&v));
    542:     }
    543:     PetscCall(VecScatterDestroy(&vec_sc));
    544:   }
    545:   PetscCall(PetscFree2(idx1,idx2));
    546:   PetscCall(VecDestroy(&vg));
    547:   PetscFunctionReturn(PETSC_SUCCESS);
    548: }

    550: /*
    551:   EPSComputeVectors_Slice - Recover Eigenvectors from subcomunicators
    552:  */
    553: PetscErrorCode EPSComputeVectors_Slice(EPS eps)
    554: {
    555:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;

    557:   PetscFunctionBegin;
    558:   if (ctx->global && ctx->npart>1) {
    559:     PetscCall(EPSComputeVectors(ctx->eps));
    560:     PetscCall(EPSSliceGatherEigenVectors(eps));
    561:   }
    562:   PetscFunctionReturn(PETSC_SUCCESS);
    563: }

    565: static PetscErrorCode EPSSliceGetInertias(EPS eps,PetscInt *n,PetscReal **shifts,PetscInt **inertias)
    566: {
    567:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    568:   PetscInt        i=0,j,tmpi;
    569:   PetscReal       v,tmpr;
    570:   EPS_shift       s;

    572:   PetscFunctionBegin;
    573:   PetscCheck(eps->state,PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONGSTATE,"Must call EPSSetUp() first");
    574:   PetscCheck(ctx->sr,PetscObjectComm((PetscObject)eps),PETSC_ERR_ARG_WRONGSTATE,"Only available in interval computations, see EPSSetInterval()");
    575:   if (!ctx->sr->s0) {  /* EPSSolve not called yet */
    576:     *n = 2;
    577:   } else {
    578:     *n = 1;
    579:     s = ctx->sr->s0;
    580:     while (s) {
    581:       (*n)++;
    582:       s = s->neighb[1];
    583:     }
    584:   }
    585:   PetscCall(PetscMalloc1(*n,shifts));
    586:   PetscCall(PetscMalloc1(*n,inertias));
    587:   if (!ctx->sr->s0) {  /* EPSSolve not called yet */
    588:     (*shifts)[0]   = ctx->sr->int0;
    589:     (*shifts)[1]   = ctx->sr->int1;
    590:     (*inertias)[0] = ctx->sr->inertia0;
    591:     (*inertias)[1] = ctx->sr->inertia1;
    592:   } else {
    593:     s = ctx->sr->s0;
    594:     while (s) {
    595:       (*shifts)[i]     = s->value;
    596:       (*inertias)[i++] = s->inertia;
    597:       s = s->neighb[1];
    598:     }
    599:     (*shifts)[i]   = ctx->sr->int1;
    600:     (*inertias)[i] = ctx->sr->inertia1;
    601:   }
    602:   /* remove possible duplicate in last position */
    603:   if ((*shifts)[(*n)-1]==(*shifts)[(*n)-2]) (*n)--;
    604:   /* sort result */
    605:   for (i=0;i<*n;i++) {
    606:     v = (*shifts)[i];
    607:     for (j=i+1;j<*n;j++) {
    608:       if (v > (*shifts)[j]) {
    609:         SlepcSwap((*shifts)[i],(*shifts)[j],tmpr);
    610:         SlepcSwap((*inertias)[i],(*inertias)[j],tmpi);
    611:         v = (*shifts)[i];
    612:       }
    613:     }
    614:   }
    615:   PetscFunctionReturn(PETSC_SUCCESS);
    616: }

    618: static PetscErrorCode EPSSliceGatherSolution(EPS eps)
    619: {
    620:   PetscMPIInt     rank,nproc,*disp,*ns_loc,aux;
    621:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    622:   PetscInt        i,idx,j,*perm_loc,off=0,*inertias_loc,ns;
    623:   PetscScalar     *eigr_loc;
    624:   EPS_SR          sr_loc;
    625:   PetscReal       *shifts_loc;
    626:   MPI_Comm        child;

    628:   PetscFunctionBegin;
    629:   eps->nconv = 0;
    630:   for (i=0;i<ctx->npart;i++) eps->nconv += ctx->nconv_loc[i];
    631:   sr_loc = ((EPS_KRYLOVSCHUR*)ctx->eps->data)->sr;

    633:   /* Gather the shifts used and the inertias computed */
    634:   PetscCall(EPSSliceGetInertias(ctx->eps,&ns,&shifts_loc,&inertias_loc));
    635:   if (ctx->sr->dir>0 && shifts_loc[ns-1]==sr_loc->int1 && ctx->subc->color<ctx->npart-1) ns--;
    636:   if (ctx->sr->dir<0 && shifts_loc[ns-1]==sr_loc->int0 && ctx->subc->color>0) {
    637:     ns--;
    638:     for (i=0;i<ns;i++) {
    639:       inertias_loc[i] = inertias_loc[i+1];
    640:       shifts_loc[i] = shifts_loc[i+1];
    641:     }
    642:   }
    643:   PetscCall(PetscMalloc1(ctx->npart,&ns_loc));
    644:   PetscCall(PetscSubcommGetChild(ctx->subc,&child));
    645:   PetscCallMPI(MPI_Comm_rank(child,&rank));
    646:   PetscCall(PetscMPIIntCast(ns,&aux));
    647:   if (!rank) PetscCallMPI(MPI_Allgather(&aux,1,MPI_INT,ns_loc,1,MPI_INT,ctx->commrank));
    648:   PetscCall(PetscMPIIntCast(ctx->npart,&aux));
    649:   PetscCallMPI(MPI_Bcast(ns_loc,aux,MPI_INT,0,child));
    650:   ctx->nshifts = 0;
    651:   for (i=0;i<ctx->npart;i++) ctx->nshifts += ns_loc[i];
    652:   PetscCall(PetscFree(ctx->inertias));
    653:   PetscCall(PetscFree(ctx->shifts));
    654:   PetscCall(PetscMalloc1(ctx->nshifts,&ctx->inertias));
    655:   PetscCall(PetscMalloc1(ctx->nshifts,&ctx->shifts));

    657:   /* Gather eigenvalues (same ranks have fully set of eigenvalues)*/
    658:   eigr_loc = sr_loc->eigr;
    659:   perm_loc = sr_loc->perm;
    660:   PetscCallMPI(MPI_Comm_size(((PetscObject)eps)->comm,&nproc));
    661:   PetscCall(PetscMalloc1(ctx->npart,&disp));
    662:   disp[0] = 0;
    663:   for (i=1;i<ctx->npart;i++) disp[i] = disp[i-1]+ctx->nconv_loc[i-1];
    664:   if (nproc%ctx->npart==0) { /* subcommunicators with the same size */
    665:     PetscCall(PetscMPIIntCast(sr_loc->numEigs,&aux));
    666:     PetscCallMPI(MPI_Allgatherv(eigr_loc,aux,MPIU_SCALAR,eps->eigr,ctx->nconv_loc,disp,MPIU_SCALAR,ctx->commrank)); /* eigenvalues */
    667:     PetscCallMPI(MPI_Allgatherv(perm_loc,aux,MPIU_INT,eps->perm,ctx->nconv_loc,disp,MPIU_INT,ctx->commrank)); /* perm */
    668:     for (i=1;i<ctx->npart;i++) disp[i] = disp[i-1]+ns_loc[i-1];
    669:     PetscCall(PetscMPIIntCast(ns,&aux));
    670:     PetscCallMPI(MPI_Allgatherv(shifts_loc,aux,MPIU_REAL,ctx->shifts,ns_loc,disp,MPIU_REAL,ctx->commrank)); /* shifts */
    671:     PetscCallMPI(MPI_Allgatherv(inertias_loc,aux,MPIU_INT,ctx->inertias,ns_loc,disp,MPIU_INT,ctx->commrank)); /* inertias */
    672:     PetscCallMPI(MPIU_Allreduce(&sr_loc->itsKs,&eps->its,1,MPIU_INT,MPI_SUM,ctx->commrank));
    673:   } else { /* subcommunicators with different size */
    674:     if (!rank) {
    675:       PetscCall(PetscMPIIntCast(sr_loc->numEigs,&aux));
    676:       PetscCallMPI(MPI_Allgatherv(eigr_loc,aux,MPIU_SCALAR,eps->eigr,ctx->nconv_loc,disp,MPIU_SCALAR,ctx->commrank)); /* eigenvalues */
    677:       PetscCallMPI(MPI_Allgatherv(perm_loc,aux,MPIU_INT,eps->perm,ctx->nconv_loc,disp,MPIU_INT,ctx->commrank)); /* perm */
    678:       for (i=1;i<ctx->npart;i++) disp[i] = disp[i-1]+ns_loc[i-1];
    679:       PetscCall(PetscMPIIntCast(ns,&aux));
    680:       PetscCallMPI(MPI_Allgatherv(shifts_loc,aux,MPIU_REAL,ctx->shifts,ns_loc,disp,MPIU_REAL,ctx->commrank)); /* shifts */
    681:       PetscCallMPI(MPI_Allgatherv(inertias_loc,aux,MPIU_INT,ctx->inertias,ns_loc,disp,MPIU_INT,ctx->commrank)); /* inertias */
    682:       PetscCallMPI(MPIU_Allreduce(&sr_loc->itsKs,&eps->its,1,MPIU_INT,MPI_SUM,ctx->commrank));
    683:     }
    684:     PetscCall(PetscMPIIntCast(eps->nconv,&aux));
    685:     PetscCallMPI(MPI_Bcast(eps->eigr,aux,MPIU_SCALAR,0,child));
    686:     PetscCallMPI(MPI_Bcast(eps->perm,aux,MPIU_INT,0,child));
    687:     PetscCall(PetscMPIIntCast(ctx->nshifts,&aux));
    688:     PetscCallMPI(MPI_Bcast(ctx->shifts,aux,MPIU_REAL,0,child));
    689:     PetscCallMPI(MPI_Bcast(ctx->inertias,aux,MPIU_INT,0,child));
    690:     PetscCallMPI(MPI_Bcast(&eps->its,1,MPIU_INT,0,child));
    691:   }
    692:   /* Update global array eps->perm */
    693:   idx = ctx->nconv_loc[0];
    694:   for (i=1;i<ctx->npart;i++) {
    695:     off += ctx->nconv_loc[i-1];
    696:     for (j=0;j<ctx->nconv_loc[i];j++) eps->perm[idx++] += off;
    697:   }

    699:   /* Gather parallel eigenvectors */
    700:   PetscCall(PetscFree(ns_loc));
    701:   PetscCall(PetscFree(disp));
    702:   PetscCall(PetscFree(shifts_loc));
    703:   PetscCall(PetscFree(inertias_loc));
    704:   PetscFunctionReturn(PETSC_SUCCESS);
    705: }

    707: /*
    708:    Fills the fields of a shift structure
    709: */
    710: static PetscErrorCode EPSCreateShift(EPS eps,PetscReal val,EPS_shift neighb0,EPS_shift neighb1)
    711: {
    712:   EPS_shift       s,*pending2;
    713:   PetscInt        i;
    714:   EPS_SR          sr;
    715:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;

    717:   PetscFunctionBegin;
    718:   sr = ctx->sr;
    719:   if ((neighb0 && val==neighb0->value) || (neighb1 && val==neighb1->value)) {
    720:     sr->nPend++;
    721:     PetscFunctionReturn(PETSC_SUCCESS);
    722:   }
    723:   PetscCall(PetscNew(&s));
    724:   s->value = val;
    725:   s->neighb[0] = neighb0;
    726:   if (neighb0) neighb0->neighb[1] = s;
    727:   s->neighb[1] = neighb1;
    728:   if (neighb1) neighb1->neighb[0] = s;
    729:   s->comp[0] = PETSC_FALSE;
    730:   s->comp[1] = PETSC_FALSE;
    731:   s->index = -1;
    732:   s->neigs = 0;
    733:   s->nconv[0] = s->nconv[1] = 0;
    734:   s->nsch[0] = s->nsch[1]=0;
    735:   /* Inserts in the stack of pending shifts */
    736:   /* If needed, the array is resized */
    737:   if (sr->nPend >= sr->maxPend) {
    738:     sr->maxPend *= 2;
    739:     PetscCall(PetscMalloc1(sr->maxPend,&pending2));
    740:     for (i=0;i<sr->nPend;i++) pending2[i] = sr->pending[i];
    741:     PetscCall(PetscFree(sr->pending));
    742:     sr->pending = pending2;
    743:   }
    744:   sr->pending[sr->nPend++]=s;
    745:   PetscFunctionReturn(PETSC_SUCCESS);
    746: }

    748: /* Prepare for Rational Krylov update */
    749: static PetscErrorCode EPSPrepareRational(EPS eps)
    750: {
    751:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    752:   PetscInt        dir,i,k,ld,nv;
    753:   PetscScalar     *A;
    754:   EPS_SR          sr = ctx->sr;
    755:   Vec             v;

    757:   PetscFunctionBegin;
    758:   PetscCall(DSGetLeadingDimension(eps->ds,&ld));
    759:   dir = (sr->sPres->neighb[0] == sr->sPrev)?1:-1;
    760:   dir*=sr->dir;
    761:   k = 0;
    762:   for (i=0;i<sr->nS;i++) {
    763:     if (dir*PetscRealPart(sr->S[i])>0.0) {
    764:       sr->S[k] = sr->S[i];
    765:       sr->S[sr->nS+k] = sr->S[sr->nS+i];
    766:       PetscCall(BVGetColumn(sr->Vnext,k,&v));
    767:       PetscCall(BVCopyVec(eps->V,eps->nconv+i,v));
    768:       PetscCall(BVRestoreColumn(sr->Vnext,k,&v));
    769:       k++;
    770:       if (k>=sr->nS/2) break;
    771:     }
    772:   }
    773:   /* Copy to DS */
    774:   PetscCall(DSSetCompact(eps->ds,PETSC_FALSE));  /* make sure DS_MAT_A is allocated */
    775:   PetscCall(DSGetArray(eps->ds,DS_MAT_A,&A));
    776:   PetscCall(PetscArrayzero(A,ld*ld));
    777:   for (i=0;i<k;i++) {
    778:     A[i*(1+ld)] = sr->S[i];
    779:     A[k+i*ld] = sr->S[sr->nS+i];
    780:   }
    781:   sr->nS = k;
    782:   PetscCall(DSRestoreArray(eps->ds,DS_MAT_A,&A));
    783:   PetscCall(DSGetDimensions(eps->ds,&nv,NULL,NULL,NULL));
    784:   PetscCall(DSSetDimensions(eps->ds,nv,0,k));
    785:   /* Append u to V */
    786:   PetscCall(BVGetColumn(sr->Vnext,sr->nS,&v));
    787:   PetscCall(BVCopyVec(eps->V,sr->nv,v));
    788:   PetscCall(BVRestoreColumn(sr->Vnext,sr->nS,&v));
    789:   PetscFunctionReturn(PETSC_SUCCESS);
    790: }

    792: /* Provides next shift to be computed */
    793: static PetscErrorCode EPSExtractShift(EPS eps)
    794: {
    795:   PetscInt        iner,zeros=0;
    796:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    797:   EPS_SR          sr;
    798:   PetscReal       newShift,diam,ptol;
    799:   EPS_shift       sPres;

    801:   PetscFunctionBegin;
    802:   sr = ctx->sr;
    803:   if (sr->nPend > 0) {
    804:     if (sr->sPres==sr->pending[sr->nPend-1]) {
    805:       eps->reason = EPS_CONVERGED_ITERATING;
    806:       eps->its = 0;
    807:       sr->nPend--;
    808:       sr->sPres->rep = PETSC_TRUE;
    809:       PetscFunctionReturn(PETSC_SUCCESS);
    810:     }
    811:     sr->sPrev = sr->sPres;
    812:     sr->sPres = sr->pending[--sr->nPend];
    813:     sPres = sr->sPres;
    814:     PetscCall(EPSSliceGetInertia(eps,sPres->value,&iner,ctx->detect?&zeros:NULL));
    815:     if (zeros) {
    816:       diam = PetscMin(PetscAbsReal(sPres->neighb[0]->value-sPres->value),PetscAbsReal(sPres->neighb[1]->value-sPres->value));
    817:       ptol = PetscMin(SLICE_PTOL,diam/2);
    818:       newShift = sPres->value*(1.0+ptol);
    819:       if (sr->dir*(sPres->neighb[0] && newShift-sPres->neighb[0]->value) < 0) newShift = (sPres->value+sPres->neighb[0]->value)/2;
    820:       else if (sPres->neighb[1] && sr->dir*(sPres->neighb[1]->value-newShift) < 0) newShift = (sPres->value+sPres->neighb[1]->value)/2;
    821:       PetscCall(EPSSliceGetInertia(eps,newShift,&iner,&zeros));
    822:       PetscCheck(zeros==0,((PetscObject)eps)->comm,PETSC_ERR_CONV_FAILED,"Inertia computation fails in %g",(double)newShift);
    823:       sPres->value = newShift;
    824:     }
    825:     sr->sPres->inertia = iner;
    826:     eps->target = sr->sPres->value;
    827:     eps->reason = EPS_CONVERGED_ITERATING;
    828:     eps->its = 0;
    829:   } else sr->sPres = NULL;
    830:   PetscFunctionReturn(PETSC_SUCCESS);
    831: }

    833: /*
    834:    Symmetric KrylovSchur adapted to spectrum slicing:
    835:    Allows searching an specific amount of eigenvalues in the subintervals left and right.
    836:    Returns whether the search has succeeded
    837: */
    838: static PetscErrorCode EPSKrylovSchur_Slice(EPS eps)
    839: {
    840:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    841:   PetscInt        i,k,l,ld,nv,*iwork,j,count0,count1,iterCompl=0,n0,n1;
    842:   Mat             U,Op,T;
    843:   PetscScalar     *Q,*A;
    844:   PetscReal       *a,*b,beta,lambda;
    845:   EPS_shift       sPres;
    846:   PetscBool       breakdown,complIterating,sch0,sch1;
    847:   EPS_SR          sr = ctx->sr;

    849:   PetscFunctionBegin;
    850:   /* Spectrum slicing data */
    851:   sPres = sr->sPres;
    852:   complIterating =PETSC_FALSE;
    853:   sch1 = sch0 = PETSC_TRUE;
    854:   PetscCall(DSGetLeadingDimension(eps->ds,&ld));
    855:   PetscCall(PetscMalloc1(2*ld,&iwork));
    856:   count0=0;count1=0; /* Found on both sides */
    857:   if (!sPres->rep && sr->nS > 0 && (sPres->neighb[0] == sr->sPrev || sPres->neighb[1] == sr->sPrev)) {
    858:     /* Rational Krylov */
    859:     PetscCall(DSTranslateRKS(eps->ds,sr->sPrev->value-sPres->value));
    860:     PetscCall(DSGetDimensions(eps->ds,NULL,NULL,&l,NULL));
    861:     PetscCall(DSSetDimensions(eps->ds,l+1,0,0));
    862:     PetscCall(BVSetActiveColumns(eps->V,0,l+1));
    863:     PetscCall(DSGetMat(eps->ds,DS_MAT_Q,&U));
    864:     PetscCall(BVMultInPlace(eps->V,U,0,l+1));
    865:     PetscCall(DSRestoreMat(eps->ds,DS_MAT_Q,&U));
    866:   } else {
    867:     /* Get the starting Lanczos vector */
    868:     PetscCall(EPSGetStartVector(eps,0,NULL));
    869:     l = 0;
    870:   }
    871:   /* Restart loop */
    872:   while (eps->reason == EPS_CONVERGED_ITERATING) {
    873:     eps->its++; sr->itsKs++;
    874:     /* Compute an nv-step Lanczos factorization */
    875:     nv = PetscMin(eps->nconv+eps->mpd,eps->ncv);
    876:     PetscCall(DSSetDimensions(eps->ds,nv,eps->nconv,eps->nconv+l));
    877:     PetscCall(DSGetMat(eps->ds,DS_MAT_T,&T));
    878:     PetscCall(STGetOperator(eps->st,&Op));
    879:     PetscCall(BVMatLanczos(eps->V,Op,T,eps->nconv+l,&nv,&beta,&breakdown));
    880:     PetscCall(STRestoreOperator(eps->st,&Op));
    881:     sr->nv = nv;
    882:     PetscCall(DSRestoreMat(eps->ds,DS_MAT_T,&T));
    883:     PetscCall(DSSetDimensions(eps->ds,nv,eps->nconv,eps->nconv+l));
    884:     if (l==0) PetscCall(DSSetState(eps->ds,DS_STATE_INTERMEDIATE));
    885:     else PetscCall(DSSetState(eps->ds,DS_STATE_RAW));
    886:     PetscCall(BVSetActiveColumns(eps->V,eps->nconv,nv));

    888:     /* Solve projected problem and compute residual norm estimates */
    889:     if (eps->its == 1 && l > 0) { /* After rational update, DS_MAT_A is available */
    890:       PetscCall(DSGetArray(eps->ds,DS_MAT_A,&A));
    891:       PetscCall(DSGetArrayReal(eps->ds,DS_MAT_T,&a));
    892:       b = a + ld;
    893:       k = eps->nconv+l;
    894:       A[k*ld+k-1] = A[(k-1)*ld+k];
    895:       A[k*ld+k] = a[k];
    896:       for (j=k+1; j< nv; j++) {
    897:         A[j*ld+j] = a[j];
    898:         A[j*ld+j-1] = b[j-1] ;
    899:         A[(j-1)*ld+j] = b[j-1];
    900:       }
    901:       PetscCall(DSRestoreArray(eps->ds,DS_MAT_A,&A));
    902:       PetscCall(DSRestoreArrayReal(eps->ds,DS_MAT_T,&a));
    903:       PetscCall(DSSolve(eps->ds,eps->eigr,NULL));
    904:       PetscCall(DSSort(eps->ds,eps->eigr,NULL,NULL,NULL,NULL));
    905:       PetscCall(DSSetCompact(eps->ds,PETSC_TRUE));
    906:     } else { /* Restart */
    907:       PetscCall(DSSolve(eps->ds,eps->eigr,NULL));
    908:       PetscCall(DSSort(eps->ds,eps->eigr,NULL,NULL,NULL,NULL));
    909:     }
    910:     PetscCall(DSSynchronize(eps->ds,eps->eigr,NULL));

    912:     /* Residual */
    913:     PetscCall(EPSKrylovConvergence(eps,PETSC_TRUE,eps->nconv,nv-eps->nconv,beta,0.0,1.0,&k));
    914:     /* Checking values obtained for completing */
    915:     for (i=0;i<k;i++) {
    916:       sr->back[i]=eps->eigr[i];
    917:     }
    918:     PetscCall(STBackTransform(eps->st,k,sr->back,eps->eigi));
    919:     count0=count1=0;
    920:     for (i=0;i<k;i++) {
    921:       lambda = PetscRealPart(sr->back[i]);
    922:       if ((sr->dir*(sPres->value - lambda) > 0) && (sr->dir*(lambda - sPres->ext[0]) > 0)) count0++;
    923:       if ((sr->dir*(lambda - sPres->value) > 0) && (sr->dir*(sPres->ext[1] - lambda) > 0)) count1++;
    924:     }
    925:     if (k>eps->nev && eps->ncv-k<5) eps->reason = EPS_CONVERGED_TOL;
    926:     else {
    927:       /* Checks completion */
    928:       if ((!sch0||count0 >= sPres->nsch[0]) && (!sch1 ||count1 >= sPres->nsch[1])) {
    929:         eps->reason = EPS_CONVERGED_TOL;
    930:       } else {
    931:         if (!complIterating && eps->its >= eps->max_it) eps->reason = EPS_DIVERGED_ITS;
    932:         if (complIterating) {
    933:           if (--iterCompl <= 0) eps->reason = EPS_DIVERGED_ITS;
    934:         } else if (k >= eps->nev) {
    935:           n0 = sPres->nsch[0]-count0;
    936:           n1 = sPres->nsch[1]-count1;
    937:           if (sr->iterCompl>0 && ((n0>0 && n0<= sr->nMAXCompl)||(n1>0&&n1<=sr->nMAXCompl))) {
    938:             /* Iterating for completion*/
    939:             complIterating = PETSC_TRUE;
    940:             if (n0 >sr->nMAXCompl)sch0 = PETSC_FALSE;
    941:             if (n1 >sr->nMAXCompl)sch1 = PETSC_FALSE;
    942:             iterCompl = sr->iterCompl;
    943:           } else eps->reason = EPS_CONVERGED_TOL;
    944:         }
    945:       }
    946:     }
    947:     /* Update l */
    948:     if (eps->reason == EPS_CONVERGED_ITERATING) l = PetscMax(1,(PetscInt)((nv-k)*ctx->keep));
    949:     else l = nv-k;
    950:     if (breakdown) l=0;
    951:     if (!ctx->lock && l>0 && eps->reason == EPS_CONVERGED_ITERATING) { l += k; k = 0; } /* non-locking variant: reset no. of converged pairs */

    953:     if (eps->reason == EPS_CONVERGED_ITERATING) {
    954:       if (breakdown) {
    955:         /* Start a new Lanczos factorization */
    956:         PetscCall(PetscInfo(eps,"Breakdown in Krylov-Schur method (it=%" PetscInt_FMT " norm=%g)\n",eps->its,(double)beta));
    957:         PetscCall(EPSGetStartVector(eps,k,&breakdown));
    958:         if (breakdown) {
    959:           eps->reason = EPS_DIVERGED_BREAKDOWN;
    960:           PetscCall(PetscInfo(eps,"Unable to generate more start vectors\n"));
    961:         }
    962:       } else {
    963:         /* Prepare the Rayleigh quotient for restart */
    964:         PetscCall(DSGetArrayReal(eps->ds,DS_MAT_T,&a));
    965:         PetscCall(DSGetArray(eps->ds,DS_MAT_Q,&Q));
    966:         b = a + ld;
    967:         for (i=k;i<k+l;i++) {
    968:           a[i] = PetscRealPart(eps->eigr[i]);
    969:           b[i] = PetscRealPart(Q[nv-1+i*ld]*beta);
    970:         }
    971:         PetscCall(DSRestoreArrayReal(eps->ds,DS_MAT_T,&a));
    972:         PetscCall(DSRestoreArray(eps->ds,DS_MAT_Q,&Q));
    973:       }
    974:     }
    975:     /* Update the corresponding vectors V(:,idx) = V*Q(:,idx) */
    976:     PetscCall(DSGetMat(eps->ds,DS_MAT_Q,&U));
    977:     PetscCall(BVMultInPlace(eps->V,U,eps->nconv,k+l));
    978:     PetscCall(DSRestoreMat(eps->ds,DS_MAT_Q,&U));

    980:     /* Normalize u and append it to V */
    981:     if (eps->reason == EPS_CONVERGED_ITERATING && !breakdown) PetscCall(BVCopyColumn(eps->V,nv,k+l));
    982:     eps->nconv = k;
    983:     if (eps->reason != EPS_CONVERGED_ITERATING) {
    984:       /* Store approximated values for next shift */
    985:       PetscCall(DSGetArray(eps->ds,DS_MAT_Q,&Q));
    986:       sr->nS = l;
    987:       for (i=0;i<l;i++) {
    988:         sr->S[i] = eps->eigr[i+k];/* Diagonal elements */
    989:         sr->S[i+l] = Q[nv-1+(i+k)*ld]*beta; /* Out of diagonal elements */
    990:       }
    991:       PetscCall(DSRestoreArray(eps->ds,DS_MAT_Q,&Q));
    992:     }
    993:   }
    994:   /* Check for completion */
    995:   for (i=0;i< eps->nconv; i++) {
    996:     if (sr->dir*PetscRealPart(eps->eigr[i])>0) sPres->nconv[1]++;
    997:     else sPres->nconv[0]++;
    998:   }
    999:   sPres->comp[0] = PetscNot(count0 < sPres->nsch[0]);
    1000:   sPres->comp[1] = PetscNot(count1 < sPres->nsch[1]);
    1001:   PetscCall(PetscInfo(eps,"Lanczos: %" PetscInt_FMT " evals in [%g,%g]%s and %" PetscInt_FMT " evals in [%g,%g]%s\n",count0,(double)(sr->dir==1?sPres->ext[0]:sPres->value),(double)(sr->dir==1?sPres->value:sPres->ext[0]),sPres->comp[0]?"*":"",count1,(double)(sr->dir==1?sPres->value:sPres->ext[1]),(double)(sr->dir==1?sPres->ext[1]:sPres->value),sPres->comp[1]?"*":""));
    1002:   PetscCheck(count0<=sPres->nsch[0] && count1<=sPres->nsch[1],PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Mismatch between number of values found and information from inertia%s",ctx->detect?"":", consider using EPSKrylovSchurSetDetectZeros()");
    1003:   PetscCall(PetscFree(iwork));
    1004:   PetscFunctionReturn(PETSC_SUCCESS);
    1005: }

    1007: /*
    1008:   Obtains value of subsequent shift
    1009: */
    1010: static PetscErrorCode EPSGetNewShiftValue(EPS eps,PetscInt side,PetscReal *newS)
    1011: {
    1012:   PetscReal       lambda,d_prev;
    1013:   PetscInt        i,idxP;
    1014:   EPS_SR          sr;
    1015:   EPS_shift       sPres,s;
    1016:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;

    1018:   PetscFunctionBegin;
    1019:   sr = ctx->sr;
    1020:   sPres = sr->sPres;
    1021:   if (sPres->neighb[side]) {
    1022:     /* Completing a previous interval */
    1023:     *newS = (sPres->value + sPres->neighb[side]->value)/2;
    1024:     if (PetscAbsReal(sPres->value - *newS)/PetscAbsReal(sPres->value)<=100*PETSC_SQRT_MACHINE_EPSILON) *newS = sPres->value;
    1025:   } else { /* (Only for side=1). Creating a new interval. */
    1026:     if (sPres->neigs==0) {/* No value has been accepted*/
    1027:       if (sPres->neighb[0]) {
    1028:         /* Multiplying by 10 the previous distance */
    1029:         *newS = sPres->value + 10*sr->dir*PetscAbsReal(sPres->value - sPres->neighb[0]->value);
    1030:         sr->nleap++;
    1031:         /* Stops when the interval is open and no values are found in the last 5 shifts (there might be infinite eigenvalues) */
    1032:         PetscCheck(sr->hasEnd || sr->nleap<=5,PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Unable to compute the wanted eigenvalues with open interval");
    1033:       } else { /* First shift */
    1034:         PetscCheck(eps->nconv!=0,PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"First shift renders no information");
    1035:         /* Unaccepted values give information for next shift */
    1036:         idxP=0;/* Number of values left from shift */
    1037:         for (i=0;i<eps->nconv;i++) {
    1038:           lambda = PetscRealPart(eps->eigr[i]);
    1039:           if (sr->dir*(lambda - sPres->value) <0) idxP++;
    1040:           else break;
    1041:         }
    1042:         /* Avoiding subtraction of eigenvalues (might be the same).*/
    1043:         if (idxP>0) {
    1044:           d_prev = PetscAbsReal(sPres->value - PetscRealPart(eps->eigr[0]))/(idxP+0.3);
    1045:         } else {
    1046:           d_prev = PetscAbsReal(sPres->value - PetscRealPart(eps->eigr[eps->nconv-1]))/(eps->nconv+0.3);
    1047:         }
    1048:         *newS = sPres->value + (sr->dir*d_prev*eps->nev)/2;
    1049:       }
    1050:     } else { /* Accepted values found */
    1051:       sr->nleap = 0;
    1052:       /* Average distance of values in previous subinterval */
    1053:       s = sPres->neighb[0];
    1054:       while (s && PetscAbs(s->inertia - sPres->inertia)==0) {
    1055:         s = s->neighb[0];/* Looking for previous shifts with eigenvalues within */
    1056:       }
    1057:       if (s) {
    1058:         d_prev = PetscAbsReal((sPres->value - s->value)/(sPres->inertia - s->inertia));
    1059:       } else { /* First shift. Average distance obtained with values in this shift */
    1060:         /* first shift might be too far from first wanted eigenvalue (no values found outside the interval)*/
    1061:         if (sr->dir*(PetscRealPart(sr->eigr[0])-sPres->value)>0 && PetscAbsReal((PetscRealPart(sr->eigr[sr->indexEig-1]) - PetscRealPart(sr->eigr[0]))/PetscRealPart(sr->eigr[0])) > PetscSqrtReal(eps->tol)) {
    1062:           d_prev =  PetscAbsReal((PetscRealPart(sr->eigr[sr->indexEig-1]) - PetscRealPart(sr->eigr[0])))/(sPres->neigs+0.3);
    1063:         } else {
    1064:           d_prev = PetscAbsReal(PetscRealPart(sr->eigr[sr->indexEig-1]) - sPres->value)/(sPres->neigs+0.3);
    1065:         }
    1066:       }
    1067:       /* Average distance is used for next shift by adding it to value on the right or to shift */
    1068:       if (sr->dir*(PetscRealPart(sr->eigr[sPres->index + sPres->neigs -1]) - sPres->value)>0) {
    1069:         *newS = PetscRealPart(sr->eigr[sPres->index + sPres->neigs -1])+ (sr->dir*d_prev*eps->nev)/2;
    1070:       } else { /* Last accepted value is on the left of shift. Adding to shift */
    1071:         *newS = sPres->value + (sr->dir*d_prev*eps->nev)/2;
    1072:       }
    1073:     }
    1074:     /* End of interval can not be surpassed */
    1075:     if (sr->dir*(sr->int1 - *newS) < 0) *newS = sr->int1;
    1076:   }/* of neighb[side]==null */
    1077:   PetscFunctionReturn(PETSC_SUCCESS);
    1078: }

    1080: /*
    1081:   Function for sorting an array of real values
    1082: */
    1083: static PetscErrorCode sortRealEigenvalues(PetscScalar *r,PetscInt *perm,PetscInt nr,PetscBool prev,PetscInt dir)
    1084: {
    1085:   PetscReal re;
    1086:   PetscInt  i,j,tmp;

    1088:   PetscFunctionBegin;
    1089:   if (!prev) for (i=0;i<nr;i++) perm[i] = i;
    1090:   /* Insertion sort */
    1091:   for (i=1;i<nr;i++) {
    1092:     re = PetscRealPart(r[perm[i]]);
    1093:     j = i-1;
    1094:     while (j>=0 && dir*(re - PetscRealPart(r[perm[j]])) <= 0) {
    1095:       tmp = perm[j]; perm[j] = perm[j+1]; perm[j+1] = tmp; j--;
    1096:     }
    1097:   }
    1098:   PetscFunctionReturn(PETSC_SUCCESS);
    1099: }

    1101: /* Stores the pairs obtained since the last shift in the global arrays */
    1102: static PetscErrorCode EPSStoreEigenpairs(EPS eps)
    1103: {
    1104:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    1105:   PetscReal       lambda,err,norm;
    1106:   PetscInt        i,count;
    1107:   PetscBool       iscayley;
    1108:   EPS_SR          sr = ctx->sr;
    1109:   EPS_shift       sPres;
    1110:   Vec             v,w;

    1112:   PetscFunctionBegin;
    1113:   sPres = sr->sPres;
    1114:   sPres->index = sr->indexEig;
    1115:   count = sr->indexEig;
    1116:   /* Back-transform */
    1117:   PetscCall(STBackTransform(eps->st,eps->nconv,eps->eigr,eps->eigi));
    1118:   PetscCall(PetscObjectTypeCompare((PetscObject)eps->st,STCAYLEY,&iscayley));
    1119:   /* Sort eigenvalues */
    1120:   PetscCall(sortRealEigenvalues(eps->eigr,eps->perm,eps->nconv,PETSC_FALSE,sr->dir));
    1121:   /* Values stored in global array */
    1122:   for (i=0;i<eps->nconv;i++) {
    1123:     lambda = PetscRealPart(eps->eigr[eps->perm[i]]);
    1124:     err = eps->errest[eps->perm[i]];

    1126:     if (sr->dir*(lambda - sPres->ext[0]) > 0 && (sr->dir)*(sPres->ext[1] - lambda) > 0) {/* Valid value */
    1127:       PetscCheck(count<sr->numEigs,PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Unexpected error in Spectrum Slicing");
    1128:       sr->eigr[count] = lambda;
    1129:       sr->errest[count] = err;
    1130:       /* Explicit purification */
    1131:       PetscCall(BVGetColumn(eps->V,eps->perm[i],&w));
    1132:       if (eps->purify) {
    1133:         PetscCall(BVGetColumn(sr->V,count,&v));
    1134:         PetscCall(STApply(eps->st,w,v));
    1135:         PetscCall(BVRestoreColumn(sr->V,count,&v));
    1136:       } else PetscCall(BVInsertVec(sr->V,count,w));
    1137:       PetscCall(BVRestoreColumn(eps->V,eps->perm[i],&w));
    1138:       PetscCall(BVNormColumn(sr->V,count,NORM_2,&norm));
    1139:       PetscCall(BVScaleColumn(sr->V,count,1.0/norm));
    1140:       count++;
    1141:     }
    1142:   }
    1143:   sPres->neigs = count - sr->indexEig;
    1144:   sr->indexEig = count;
    1145:   /* Global ordering array updating */
    1146:   PetscCall(sortRealEigenvalues(sr->eigr,sr->perm,count,PETSC_TRUE,sr->dir));
    1147:   PetscFunctionReturn(PETSC_SUCCESS);
    1148: }

    1150: static PetscErrorCode EPSLookForDeflation(EPS eps)
    1151: {
    1152:   PetscReal       val;
    1153:   PetscInt        i,count0=0,count1=0;
    1154:   EPS_shift       sPres;
    1155:   PetscInt        ini,fin,k,idx0,idx1;
    1156:   EPS_SR          sr;
    1157:   Vec             v;
    1158:   EPS_KRYLOVSCHUR *ctx=(EPS_KRYLOVSCHUR*)eps->data;

    1160:   PetscFunctionBegin;
    1161:   sr = ctx->sr;
    1162:   sPres = sr->sPres;

    1164:   if (sPres->neighb[0]) ini = (sr->dir)*(sPres->neighb[0]->inertia - sr->inertia0);
    1165:   else ini = 0;
    1166:   fin = sr->indexEig;
    1167:   /* Selection of ends for searching new values */
    1168:   if (!sPres->neighb[0]) sPres->ext[0] = sr->int0;/* First shift */
    1169:   else sPres->ext[0] = sPres->neighb[0]->value;
    1170:   if (!sPres->neighb[1]) {
    1171:     if (sr->hasEnd) sPres->ext[1] = sr->int1;
    1172:     else sPres->ext[1] = (sr->dir > 0)?PETSC_MAX_REAL:PETSC_MIN_REAL;
    1173:   } else sPres->ext[1] = sPres->neighb[1]->value;
    1174:   /* Selection of values between right and left ends */
    1175:   for (i=ini;i<fin;i++) {
    1176:     val=PetscRealPart(sr->eigr[sr->perm[i]]);
    1177:     /* Values to the right of left shift */
    1178:     if (sr->dir*(val - sPres->ext[1]) < 0) {
    1179:       if (sr->dir*(val - sPres->value) < 0) count0++;
    1180:       else count1++;
    1181:     } else break;
    1182:   }
    1183:   /* The number of values on each side are found */
    1184:   if (sPres->neighb[0]) {
    1185:     sPres->nsch[0] = (sr->dir)*(sPres->inertia - sPres->neighb[0]->inertia)-count0;
    1186:     PetscCheck(sPres->nsch[0]>=0,PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Mismatch between number of values found and information from inertia%s",ctx->detect?"":", consider using EPSKrylovSchurSetDetectZeros()");
    1187:   } else sPres->nsch[0] = 0;

    1189:   if (sPres->neighb[1]) {
    1190:     sPres->nsch[1] = (sr->dir)*(sPres->neighb[1]->inertia - sPres->inertia) - count1;
    1191:     PetscCheck(sPres->nsch[1]>=0,PetscObjectComm((PetscObject)eps),PETSC_ERR_PLIB,"Mismatch between number of values found and information from inertia%s",ctx->detect?"":", consider using EPSKrylovSchurSetDetectZeros()");
    1192:   } else sPres->nsch[1] = (sr->dir)*(sr->inertia1 - sPres->inertia);

    1194:   /* Completing vector of indexes for deflation */
    1195:   idx0 = ini;
    1196:   idx1 = ini+count0+count1;
    1197:   k=0;
    1198:   for (i=idx0;i<idx1;i++) sr->idxDef[k++]=sr->perm[i];
    1199:   PetscCall(BVDuplicateResize(eps->V,k+eps->ncv+1,&sr->Vnext));
    1200:   PetscCall(BVSetNumConstraints(sr->Vnext,k));
    1201:   for (i=0;i<k;i++) {
    1202:     PetscCall(BVGetColumn(sr->Vnext,-i-1,&v));
    1203:     PetscCall(BVCopyVec(sr->V,sr->idxDef[i],v));
    1204:     PetscCall(BVRestoreColumn(sr->Vnext,-i-1,&v));
    1205:   }

    1207:   /* For rational Krylov */
    1208:   if (!sr->sPres->rep && sr->nS>0 && (sr->sPrev == sr->sPres->neighb[0] || sr->sPrev == sr->sPres->neighb[1])) PetscCall(EPSPrepareRational(eps));
    1209:   eps->nconv = 0;
    1210:   /* Get rid of temporary Vnext */
    1211:   PetscCall(BVDestroy(&eps->V));
    1212:   eps->V = sr->Vnext;
    1213:   sr->Vnext = NULL;
    1214:   PetscFunctionReturn(PETSC_SUCCESS);
    1215: }

    1217: PetscErrorCode EPSSolve_KrylovSchur_Slice(EPS eps)
    1218: {
    1219:   PetscInt         i,lds,ti;
    1220:   PetscReal        newS;
    1221:   EPS_KRYLOVSCHUR  *ctx=(EPS_KRYLOVSCHUR*)eps->data;
    1222:   EPS_SR           sr=ctx->sr;
    1223:   Mat              A,B=NULL;
    1224:   PetscObjectState Astate,Bstate=0;
    1225:   PetscObjectId    Aid,Bid=0;

    1227:   PetscFunctionBegin;
    1228:   PetscCall(PetscCitationsRegister(citation,&cited));
    1229:   if (ctx->global) {
    1230:     PetscCall(EPSSolve_KrylovSchur_Slice(ctx->eps));
    1231:     ctx->eps->state = EPS_STATE_SOLVED;
    1232:     eps->reason = EPS_CONVERGED_TOL;
    1233:     if (ctx->npart>1) {
    1234:       /* Gather solution from subsolvers */
    1235:       PetscCall(EPSSliceGatherSolution(eps));
    1236:     } else {
    1237:       eps->nconv = sr->numEigs;
    1238:       eps->its   = ctx->eps->its;
    1239:       PetscCall(PetscFree(ctx->inertias));
    1240:       PetscCall(PetscFree(ctx->shifts));
    1241:       PetscCall(EPSSliceGetInertias(ctx->eps,&ctx->nshifts,&ctx->shifts,&ctx->inertias));
    1242:     }
    1243:   } else {
    1244:     if (ctx->npart==1) {
    1245:       sr->eigr   = ctx->eps->eigr;
    1246:       sr->eigi   = ctx->eps->eigi;
    1247:       sr->perm   = ctx->eps->perm;
    1248:       sr->errest = ctx->eps->errest;
    1249:       sr->V      = ctx->eps->V;
    1250:     }
    1251:     /* Check that the user did not modify subcomm matrices */
    1252:     PetscCall(EPSGetOperators(eps,&A,&B));
    1253:     PetscCall(MatGetState(A,&Astate));
    1254:     PetscCall(PetscObjectGetId((PetscObject)A,&Aid));
    1255:     if (B) {
    1256:       PetscCall(MatGetState(B,&Bstate));
    1257:       PetscCall(PetscObjectGetId((PetscObject)B,&Bid));
    1258:     }
    1259:     PetscCheck(Astate==ctx->Astate && (!B || Bstate==ctx->Bstate) && Aid==ctx->Aid && (!B || Bid==ctx->Bid),PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"Subcomm matrices have been modified by user");
    1260:     /* Only with eigenvalues present in the interval ...*/
    1261:     if (sr->numEigs==0) {
    1262:       eps->reason = EPS_CONVERGED_TOL;
    1263:       PetscFunctionReturn(PETSC_SUCCESS);
    1264:     }
    1265:     /* Array of pending shifts */
    1266:     sr->maxPend = 100; /* Initial size */
    1267:     sr->nPend = 0;
    1268:     PetscCall(PetscMalloc1(sr->maxPend,&sr->pending));
    1269:     PetscCall(EPSCreateShift(eps,sr->int0,NULL,NULL));
    1270:     /* extract first shift */
    1271:     sr->sPrev = NULL;
    1272:     sr->sPres = sr->pending[--sr->nPend];
    1273:     sr->sPres->inertia = sr->inertia0;
    1274:     eps->target = sr->sPres->value;
    1275:     sr->s0 = sr->sPres;
    1276:     sr->indexEig = 0;
    1277:     /* Memory reservation for auxiliary variables */
    1278:     lds = PetscMin(eps->mpd,eps->ncv);
    1279:     PetscCall(PetscCalloc1(lds*lds,&sr->S));
    1280:     PetscCall(PetscMalloc1(eps->ncv,&sr->back));
    1281:     for (i=0;i<sr->numEigs;i++) {
    1282:       sr->eigr[i]   = 0.0;
    1283:       sr->eigi[i]   = 0.0;
    1284:       sr->errest[i] = 0.0;
    1285:       sr->perm[i]   = i;
    1286:     }
    1287:     /* Vectors for deflation */
    1288:     PetscCall(PetscMalloc1(sr->numEigs,&sr->idxDef));
    1289:     sr->indexEig = 0;
    1290:     /* Main loop */
    1291:     while (sr->sPres) {
    1292:       /* Search for deflation */
    1293:       PetscCall(EPSLookForDeflation(eps));
    1294:       /* KrylovSchur */
    1295:       PetscCall(EPSKrylovSchur_Slice(eps));

    1297:       PetscCall(EPSStoreEigenpairs(eps));
    1298:       /* Select new shift */
    1299:       if (!sr->sPres->comp[1]) {
    1300:         PetscCall(EPSGetNewShiftValue(eps,1,&newS));
    1301:         PetscCall(EPSCreateShift(eps,newS,sr->sPres,sr->sPres->neighb[1]));
    1302:       }
    1303:       if (!sr->sPres->comp[0]) {
    1304:         /* Completing earlier interval */
    1305:         PetscCall(EPSGetNewShiftValue(eps,0,&newS));
    1306:         PetscCall(EPSCreateShift(eps,newS,sr->sPres->neighb[0],sr->sPres));
    1307:       }
    1308:       /* Preparing for a new search of values */
    1309:       PetscCall(EPSExtractShift(eps));
    1310:     }

    1312:     /* Updating eps values prior to exit */
    1313:     PetscCall(PetscFree(sr->S));
    1314:     PetscCall(PetscFree(sr->idxDef));
    1315:     PetscCall(PetscFree(sr->pending));
    1316:     PetscCall(PetscFree(sr->back));
    1317:     PetscCall(BVDuplicateResize(eps->V,eps->ncv+1,&sr->Vnext));
    1318:     PetscCall(BVSetNumConstraints(sr->Vnext,0));
    1319:     PetscCall(BVDestroy(&eps->V));
    1320:     eps->V      = sr->Vnext;
    1321:     eps->nconv  = sr->indexEig;
    1322:     eps->reason = EPS_CONVERGED_TOL;
    1323:     eps->its    = sr->itsKs;
    1324:     eps->nds    = 0;
    1325:     if (sr->dir<0) {
    1326:       for (i=0;i<eps->nconv/2;i++) {
    1327:         ti = sr->perm[i]; sr->perm[i] = sr->perm[eps->nconv-1-i]; sr->perm[eps->nconv-1-i] = ti;
    1328:       }
    1329:     }
    1330:   }
    1331:   PetscFunctionReturn(PETSC_SUCCESS);
    1332: }