Date: 2021-09-20T09:43:47+00:00

Actual source code: cayley.c
slepc-3.15.2 2021-09-20
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2021, 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:    Implements the Cayley spectral transform
     12: */

     14: #include <slepc/private/stimpl.h>

     16: typedef struct {
     17:   PetscScalar nu;
     18:   PetscBool   nu_set;
     19: } ST_CAYLEY;

     21: static PetscErrorCode MatMult_Cayley(Mat B,Vec x,Vec y)
     22: {
     24:   ST             st;
     25:   ST_CAYLEY      *ctx;
     26:   PetscScalar    nu;

     29:   MatShellGetContext(B,(void**)&st);
     30:   ctx = (ST_CAYLEY*)st->data;
     31:   nu = ctx->nu;

     33:   if (st->matmode == ST_MATMODE_INPLACE) { nu = nu + st->sigma; };

     35:   if (st->nmat>1) {
     36:     /* generalized eigenproblem: y = (A + tB)x */
     37:     MatMult(st->A[0],x,y);
     38:     MatMult(st->A[1],x,st->work[1]);
     39:     VecAXPY(y,nu,st->work[1]);
     40:   } else {
     41:     /* standard eigenproblem: y = (A + tI)x */
     42:     MatMult(st->A[0],x,y);
     43:     VecAXPY(y,nu,x);
     44:   }
     45:   return(0);
     46: }

     48: static PetscErrorCode MatMultTranspose_Cayley(Mat B,Vec x,Vec y)
     49: {
     51:   ST             st;
     52:   ST_CAYLEY      *ctx;
     53:   PetscScalar    nu;

     56:   MatShellGetContext(B,(void**)&st);
     57:   ctx = (ST_CAYLEY*)st->data;
     58:   nu = ctx->nu;

     60:   if (st->matmode == ST_MATMODE_INPLACE) { nu = nu + st->sigma; };
     61:   nu = PetscConj(nu);

     63:   if (st->nmat>1) {
     64:     /* generalized eigenproblem: y = (A + tB)x */
     65:     MatMultTranspose(st->A[0],x,y);
     66:     MatMultTranspose(st->A[1],x,st->work[1]);
     67:     VecAXPY(y,nu,st->work[1]);
     68:   } else {
     69:     /* standard eigenproblem: y = (A + tI)x */
     70:     MatMultTranspose(st->A[0],x,y);
     71:     VecAXPY(y,nu,x);
     72:   }
     73:   return(0);
     74: }

     76: PetscErrorCode STGetBilinearForm_Cayley(ST st,Mat *B)
     77: {

     81:   STSetUp(st);
     82:   *B = st->T[0];
     83:   PetscObjectReference((PetscObject)*B);
     84:   return(0);
     85: }

     87: PetscErrorCode STBackTransform_Cayley(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
     88: {
     89:   ST_CAYLEY   *ctx = (ST_CAYLEY*)st->data;
     90:   PetscInt    j;
     91: #if !defined(PETSC_USE_COMPLEX)
     92:   PetscScalar t,i,r;
     93: #endif

     96: #if !defined(PETSC_USE_COMPLEX)
     97:   for (j=0;j<n;j++) {
     98:     if (eigi[j] == 0.0) eigr[j] = (ctx->nu + eigr[j] * st->sigma) / (eigr[j] - 1.0);
     99:     else {
    100:       r = eigr[j];
    101:       i = eigi[j];
    102:       r = st->sigma * (r * r + i * i - r) + ctx->nu * (r - 1);
    103:       i = - st->sigma * i - ctx->nu * i;
    104:       t = i * i + r * (r - 2.0) + 1.0;
    105:       eigr[j] = r / t;
    106:       eigi[j] = i / t;
    107:     }
    108:   }
    109: #else
    110:   for (j=0;j<n;j++) {
    111:     eigr[j] = (ctx->nu + eigr[j] * st->sigma) / (eigr[j] - 1.0);
    112:   }
    113: #endif
    114:   return(0);
    115: }

    117: PetscErrorCode STPostSolve_Cayley(ST st)
    118: {

    122:   if (st->matmode == ST_MATMODE_INPLACE) {
    123:     if (st->nmat>1) {
    124:       MatAXPY(st->A[0],st->sigma,st->A[1],st->str);
    125:     } else {
    126:       MatShift(st->A[0],st->sigma);
    127:     }
    128:     st->Astate[0] = ((PetscObject)st->A[0])->state;
    129:     st->state   = ST_STATE_INITIAL;
    130:     st->opready = PETSC_FALSE;
    131:   }
    132:   return(0);
    133: }

    135: /*
    136:    Operator (cayley):
    137:                Op                  P         M
    138:    if nmat=1:  (A-sI)^-1 (A+tI)    A-sI      A+tI
    139:    if nmat=2:  (A-sB)^-1 (A+tB)    A-sB      A+tI
    140: */
    141: PetscErrorCode STComputeOperator_Cayley(ST st)
    142: {
    144:   PetscInt       n,m;
    145:   ST_CAYLEY      *ctx = (ST_CAYLEY*)st->data;

    148:   /* if the user did not set the shift, use the target value */
    149:   if (!st->sigma_set) st->sigma = st->defsigma;

    151:   if (!ctx->nu_set) ctx->nu = st->sigma;
    152:   if (ctx->nu == 0.0 && st->sigma == 0.0) SETERRQ(PetscObjectComm((PetscObject)st),1,"Values of shift and antishift cannot be zero simultaneously");
    153:   if (ctx->nu == -st->sigma) SETERRQ(PetscObjectComm((PetscObject)st),1,"It is not allowed to set the antishift equal to minus the shift (the target)");

    155:   /* T[0] = A+nu*B */
    156:   if (st->matmode==ST_MATMODE_INPLACE) {
    157:     MatGetLocalSize(st->A[0],&n,&m);
    158:     MatCreateShell(PetscObjectComm((PetscObject)st),n,m,PETSC_DETERMINE,PETSC_DETERMINE,st,&st->T[0]);
    159:     MatShellSetOperation(st->T[0],MATOP_MULT,(void(*)(void))MatMult_Cayley);
    160:     MatShellSetOperation(st->T[0],MATOP_MULT_TRANSPOSE,(void(*)(void))MatMultTranspose_Cayley);
    161:     PetscLogObjectParent((PetscObject)st,(PetscObject)st->T[0]);
    162:   } else {
    163:     STMatMAXPY_Private(st,ctx->nu,0.0,0,NULL,PetscNot(st->state==ST_STATE_UPDATED),&st->T[0]);
    164:   }
    165:   st->M = st->T[0];

    167:   /* T[1] = A-sigma*B */
    168:   STMatMAXPY_Private(st,-st->sigma,0.0,0,NULL,PetscNot(st->state==ST_STATE_UPDATED),&st->T[1]);
    169:   PetscObjectReference((PetscObject)st->T[1]);
    170:   MatDestroy(&st->P);
    171:   st->P = st->T[1];
    172:   return(0);
    173: }

    175: PetscErrorCode STSetUp_Cayley(ST st)
    176: {

    180:   if (st->nmat>2) SETERRQ(PetscObjectComm((PetscObject)st),PETSC_ERR_SUP,"Cayley transform cannot be used in polynomial eigenproblems");
    181:   STSetWorkVecs(st,2);
    182:   KSPSetUp(st->ksp);
    183:   return(0);
    184: }

    186: PetscErrorCode STSetShift_Cayley(ST st,PetscScalar newshift)
    187: {
    189:   ST_CAYLEY      *ctx = (ST_CAYLEY*)st->data;

    192:   if (newshift==0.0 && (!ctx->nu_set || (ctx->nu_set && ctx->nu==0.0))) SETERRQ(PetscObjectComm((PetscObject)st),1,"Values of shift and antishift cannot be zero simultaneously");
    193:   if (ctx->nu == -newshift) SETERRQ(PetscObjectComm((PetscObject)st),1,"It is not allowed to set the shift equal to minus the antishift");

    195:   if (!ctx->nu_set) {
    196:     if (st->matmode!=ST_MATMODE_INPLACE) {
    197:       STMatMAXPY_Private(st,newshift,ctx->nu,0,NULL,PETSC_FALSE,&st->T[0]);
    198:     }
    199:     ctx->nu = newshift;
    200:   }
    201:   STMatMAXPY_Private(st,-newshift,-st->sigma,0,NULL,PETSC_FALSE,&st->T[1]);
    202:   if (st->P!=st->T[1]) {
    203:     PetscObjectReference((PetscObject)st->T[1]);
    204:     MatDestroy(&st->P);
    205:     st->P = st->T[1];
    206:   }
    207:   STKSPSetOperators(st,st->P,st->Pmat?st->Pmat:st->P);
    208:   KSPSetUp(st->ksp);
    209:   return(0);
    210: }

    212: PetscErrorCode STSetFromOptions_Cayley(PetscOptionItems *PetscOptionsObject,ST st)
    213: {
    215:   PetscScalar    nu;
    216:   PetscBool      flg;
    217:   ST_CAYLEY      *ctx = (ST_CAYLEY*)st->data;

    220:   PetscOptionsHead(PetscOptionsObject,"ST Cayley Options");

    222:     PetscOptionsScalar("-st_cayley_antishift","Value of the antishift","STCayleySetAntishift",ctx->nu,&nu,&flg);
    223:     if (flg) { STCayleySetAntishift(st,nu); }

    225:   PetscOptionsTail();
    226:   return(0);
    227: }

    229: static PetscErrorCode STCayleySetAntishift_Cayley(ST st,PetscScalar newshift)
    230: {
    232:   ST_CAYLEY *ctx = (ST_CAYLEY*)st->data;

    235:   if (ctx->nu != newshift) {
    236:     STCheckNotSeized(st,1);
    237:     if (st->state && st->matmode!=ST_MATMODE_INPLACE) {
    238:       STMatMAXPY_Private(st,newshift,ctx->nu,0,NULL,PETSC_FALSE,&st->T[0]);
    239:     }
    240:     ctx->nu = newshift;
    241:   }
    242:   ctx->nu_set = PETSC_TRUE;
    243:   return(0);
    244: }

    246: /*@
    247:    STCayleySetAntishift - Sets the value of the anti-shift for the Cayley
    248:    spectral transformation.

    250:    Logically Collective on st

    252:    Input Parameters:
    253: +  st  - the spectral transformation context
    254: -  nu  - the anti-shift

    256:    Options Database Key:
    257: .  -st_cayley_antishift - Sets the value of the anti-shift

    259:    Level: intermediate

    261:    Note:
    262:    In the generalized Cayley transform, the operator can be expressed as
    263:    OP = inv(A - sigma B)*(A + nu B). This function sets the value of nu.
    264:    Use STSetShift() for setting sigma. The value nu=-sigma is not allowed.

    266: .seealso: STSetShift(), STCayleyGetAntishift()
    267: @*/
    268: PetscErrorCode STCayleySetAntishift(ST st,PetscScalar nu)
    269: {

    275:   PetscTryMethod(st,"STCayleySetAntishift_C",(ST,PetscScalar),(st,nu));
    276:   return(0);
    277: }

    279: static PetscErrorCode STCayleyGetAntishift_Cayley(ST st,PetscScalar *nu)
    280: {
    281:   ST_CAYLEY *ctx = (ST_CAYLEY*)st->data;

    284:   *nu = ctx->nu;
    285:   return(0);
    286: }

    288: /*@
    289:    STCayleyGetAntishift - Gets the value of the anti-shift used in the Cayley
    290:    spectral transformation.

    292:    Not Collective

    294:    Input Parameter:
    295: .  st  - the spectral transformation context

    297:    Output Parameter:
    298: .  nu  - the anti-shift

    300:    Level: intermediate

    302: .seealso: STGetShift(), STCayleySetAntishift()
    303: @*/
    304: PetscErrorCode STCayleyGetAntishift(ST st,PetscScalar *nu)
    305: {

    311:   PetscUseMethod(st,"STCayleyGetAntishift_C",(ST,PetscScalar*),(st,nu));
    312:   return(0);
    313: }

    315: PetscErrorCode STView_Cayley(ST st,PetscViewer viewer)
    316: {
    318:   char           str[50];
    319:   ST_CAYLEY      *ctx = (ST_CAYLEY*)st->data;
    320:   PetscBool      isascii;

    323:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isascii);
    324:   if (isascii) {
    325:     SlepcSNPrintfScalar(str,sizeof(str),ctx->nu,PETSC_FALSE);
    326:     PetscViewerASCIIPrintf(viewer,"  antishift: %s\n",str);
    327:   }
    328:   return(0);
    329: }

    331: PetscErrorCode STDestroy_Cayley(ST st)
    332: {

    336:   PetscFree(st->data);
    337:   PetscObjectComposeFunction((PetscObject)st,"STCayleySetAntishift_C",NULL);
    338:   PetscObjectComposeFunction((PetscObject)st,"STCayleyGetAntishift_C",NULL);
    339:   return(0);
    340: }

    342: SLEPC_EXTERN PetscErrorCode STCreate_Cayley(ST st)
    343: {
    345:   ST_CAYLEY      *ctx;

    348:   PetscNewLog(st,&ctx);
    349:   st->data = (void*)ctx;

    351:   st->usesksp = PETSC_TRUE;

    353:   st->ops->apply           = STApply_Generic;
    354:   st->ops->applytrans      = STApplyTranspose_Generic;
    355:   st->ops->backtransform   = STBackTransform_Cayley;
    356:   st->ops->setshift        = STSetShift_Cayley;
    357:   st->ops->getbilinearform = STGetBilinearForm_Cayley;
    358:   st->ops->setup           = STSetUp_Cayley;
    359:   st->ops->computeoperator = STComputeOperator_Cayley;
    360:   st->ops->setfromoptions  = STSetFromOptions_Cayley;
    361:   st->ops->postsolve       = STPostSolve_Cayley;
    362:   st->ops->destroy         = STDestroy_Cayley;
    363:   st->ops->view            = STView_Cayley;
    364:   st->ops->checknullspace  = STCheckNullSpace_Default;
    365:   st->ops->setdefaultksp   = STSetDefaultKSP_Default;

    367:   PetscObjectComposeFunction((PetscObject)st,"STCayleySetAntishift_C",STCayleySetAntishift_Cayley);
    368:   PetscObjectComposeFunction((PetscObject)st,"STCayleyGetAntishift_C",STCayleyGetAntishift_Cayley);
    369:   return(0);
    370: }