Date: 2024-12-02T08:57:10+00:00

Actual source code: ex9.c
slepc-3.22.2 2024-12-02
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      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: */

     11: static char help[] = "Solves a problem associated to the Brusselator wave model in chemical reactions, illustrating the use of shell matrices.\n\n"
     12:   "The command line options are:\n"
     13:   "  -n <n>, where <n> = block dimension of the 2x2 block matrix.\n"
     14:   "  -L <L>, where <L> = bifurcation parameter.\n"
     15:   "  -alpha <alpha>, -beta <beta>, -delta1 <delta1>,  -delta2 <delta2>,\n"
     16:   "       where <alpha> <beta> <delta1> <delta2> = model parameters.\n\n";

     18: #include <slepceps.h>

     20: /*
     21:    This example computes the eigenvalues with largest real part of the
     22:    following matrix

     24:         A = [ tau1*T+(beta-1)*I     alpha^2*I
     25:                   -beta*I        tau2*T-alpha^2*I ],

     27:    where

     29:         T = tridiag{1,-2,1}
     30:         h = 1/(n+1)
     31:         tau1 = delta1/(h*L)^2
     32:         tau2 = delta2/(h*L)^2
     33: */

     35: /*
     36:    Matrix operations
     37: */
     38: PetscErrorCode MatMult_Brussel(Mat,Vec,Vec);
     39: PetscErrorCode MatMultTranspose_Brussel(Mat,Vec,Vec);
     40: PetscErrorCode MatGetDiagonal_Brussel(Mat,Vec);

     42: typedef struct {
     43:   Mat         T;
     44:   Vec         x1,x2,y1,y2;
     45:   PetscScalar alpha,beta,tau1,tau2,sigma;
     46: } CTX_BRUSSEL;

     48: int main(int argc,char **argv)
     49: {
     50:   Mat            A;               /* eigenvalue problem matrix */
     51:   EPS            eps;             /* eigenproblem solver context */
     52:   EPSType        type;
     53:   PetscScalar    delta1,delta2,L,h;
     54:   PetscInt       N=30,n,i,Istart,Iend,nev;
     55:   CTX_BRUSSEL    *ctx;
     56:   PetscBool      terse;
     57:   PetscViewer    viewer;

     59:   PetscFunctionBeginUser;
     60:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     62:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL));
     63:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nBrusselator wave model, n=%" PetscInt_FMT "\n\n",N));

     65:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     66:         Generate the matrix
     67:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     69:   /*
     70:      Create shell matrix context and set default parameters
     71:   */
     72:   PetscCall(PetscNew(&ctx));
     73:   ctx->alpha = 2.0;
     74:   ctx->beta  = 5.45;
     75:   delta1     = 0.008;
     76:   delta2     = 0.004;
     77:   L          = 0.51302;

     79:   /*
     80:      Look the command line for user-provided parameters
     81:   */
     82:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-L",&L,NULL));
     83:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-alpha",&ctx->alpha,NULL));
     84:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-beta",&ctx->beta,NULL));
     85:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-delta1",&delta1,NULL));
     86:   PetscCall(PetscOptionsGetScalar(NULL,NULL,"-delta2",&delta2,NULL));

     88:   /*
     89:      Create matrix T
     90:   */
     91:   PetscCall(MatCreate(PETSC_COMM_WORLD,&ctx->T));
     92:   PetscCall(MatSetSizes(ctx->T,PETSC_DECIDE,PETSC_DECIDE,N,N));
     93:   PetscCall(MatSetFromOptions(ctx->T));

     95:   PetscCall(MatGetOwnershipRange(ctx->T,&Istart,&Iend));
     96:   for (i=Istart;i<Iend;i++) {
     97:     if (i>0) PetscCall(MatSetValue(ctx->T,i,i-1,1.0,INSERT_VALUES));
     98:     if (i<N-1) PetscCall(MatSetValue(ctx->T,i,i+1,1.0,INSERT_VALUES));
     99:     PetscCall(MatSetValue(ctx->T,i,i,-2.0,INSERT_VALUES));
    100:   }
    101:   PetscCall(MatAssemblyBegin(ctx->T,MAT_FINAL_ASSEMBLY));
    102:   PetscCall(MatAssemblyEnd(ctx->T,MAT_FINAL_ASSEMBLY));
    103:   PetscCall(MatGetLocalSize(ctx->T,&n,NULL));

    105:   /*
    106:      Fill the remaining information in the shell matrix context
    107:      and create auxiliary vectors
    108:   */
    109:   h = 1.0 / (PetscReal)(N+1);
    110:   ctx->tau1 = delta1 / ((h*L)*(h*L));
    111:   ctx->tau2 = delta2 / ((h*L)*(h*L));
    112:   ctx->sigma = 0.0;
    113:   PetscCall(VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,PETSC_DECIDE,NULL,&ctx->x1));
    114:   PetscCall(VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,PETSC_DECIDE,NULL,&ctx->x2));
    115:   PetscCall(VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,PETSC_DECIDE,NULL,&ctx->y1));
    116:   PetscCall(VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,PETSC_DECIDE,NULL,&ctx->y2));

    118:   /*
    119:      Create the shell matrix
    120:   */
    121:   PetscCall(MatCreateShell(PETSC_COMM_WORLD,2*n,2*n,2*N,2*N,(void*)ctx,&A));
    122:   PetscCall(MatShellSetOperation(A,MATOP_MULT,(void(*)(void))MatMult_Brussel));
    123:   PetscCall(MatShellSetOperation(A,MATOP_MULT_TRANSPOSE,(void(*)(void))MatMultTranspose_Brussel));
    124:   PetscCall(MatShellSetOperation(A,MATOP_GET_DIAGONAL,(void(*)(void))MatGetDiagonal_Brussel));

    126:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    127:                 Create the eigensolver and set various options
    128:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    130:   /*
    131:      Create eigensolver context
    132:   */
    133:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));

    135:   /*
    136:      Set operators. In this case, it is a standard eigenvalue problem
    137:   */
    138:   PetscCall(EPSSetOperators(eps,A,NULL));
    139:   PetscCall(EPSSetProblemType(eps,EPS_NHEP));

    141:   /*
    142:      Ask for the rightmost eigenvalues
    143:   */
    144:   PetscCall(EPSSetWhichEigenpairs(eps,EPS_LARGEST_REAL));

    146:   /*
    147:      Set other solver options at runtime
    148:   */
    149:   PetscCall(EPSSetFromOptions(eps));

    151:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    152:                       Solve the eigensystem
    153:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    155:   PetscCall(EPSSolve(eps));

    157:   /*
    158:      Optional: Get some information from the solver and display it
    159:   */
    160:   PetscCall(EPSGetType(eps,&type));
    161:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type));
    162:   PetscCall(EPSGetDimensions(eps,&nev,NULL,NULL));
    163:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev));

    165:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    166:                     Display solution and clean up
    167:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    169:   /* show detailed info unless -terse option is given by user */
    170:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
    171:   if (terse) PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
    172:   else {
    173:     PetscCall(PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer));
    174:     PetscCall(PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_INFO_DETAIL));
    175:     PetscCall(EPSConvergedReasonView(eps,viewer));
    176:     PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,viewer));
    177:     PetscCall(PetscViewerPopFormat(viewer));
    178:   }
    179:   PetscCall(EPSDestroy(&eps));
    180:   PetscCall(MatDestroy(&A));
    181:   PetscCall(MatDestroy(&ctx->T));
    182:   PetscCall(VecDestroy(&ctx->x1));
    183:   PetscCall(VecDestroy(&ctx->x2));
    184:   PetscCall(VecDestroy(&ctx->y1));
    185:   PetscCall(VecDestroy(&ctx->y2));
    186:   PetscCall(PetscFree(ctx));
    187:   PetscCall(SlepcFinalize());
    188:   return 0;
    189: }

    191: PetscErrorCode MatMult_Brussel(Mat A,Vec x,Vec y)
    192: {
    193:   PetscInt          n;
    194:   const PetscScalar *px;
    195:   PetscScalar       *py;
    196:   CTX_BRUSSEL       *ctx;

    198:   PetscFunctionBeginUser;
    199:   PetscCall(MatShellGetContext(A,&ctx));
    200:   PetscCall(MatGetLocalSize(ctx->T,&n,NULL));
    201:   PetscCall(VecGetArrayRead(x,&px));
    202:   PetscCall(VecGetArray(y,&py));
    203:   PetscCall(VecPlaceArray(ctx->x1,px));
    204:   PetscCall(VecPlaceArray(ctx->x2,px+n));
    205:   PetscCall(VecPlaceArray(ctx->y1,py));
    206:   PetscCall(VecPlaceArray(ctx->y2,py+n));

    208:   PetscCall(MatMult(ctx->T,ctx->x1,ctx->y1));
    209:   PetscCall(VecScale(ctx->y1,ctx->tau1));
    210:   PetscCall(VecAXPY(ctx->y1,ctx->beta-1.0+ctx->sigma,ctx->x1));
    211:   PetscCall(VecAXPY(ctx->y1,ctx->alpha*ctx->alpha,ctx->x2));

    213:   PetscCall(MatMult(ctx->T,ctx->x2,ctx->y2));
    214:   PetscCall(VecScale(ctx->y2,ctx->tau2));
    215:   PetscCall(VecAXPY(ctx->y2,-ctx->beta,ctx->x1));
    216:   PetscCall(VecAXPY(ctx->y2,-ctx->alpha*ctx->alpha+ctx->sigma,ctx->x2));

    218:   PetscCall(VecRestoreArrayRead(x,&px));
    219:   PetscCall(VecRestoreArray(y,&py));
    220:   PetscCall(VecResetArray(ctx->x1));
    221:   PetscCall(VecResetArray(ctx->x2));
    222:   PetscCall(VecResetArray(ctx->y1));
    223:   PetscCall(VecResetArray(ctx->y2));
    224:   PetscFunctionReturn(PETSC_SUCCESS);
    225: }

    227: PetscErrorCode MatMultTranspose_Brussel(Mat A,Vec x,Vec y)
    228: {
    229:   PetscInt          n;
    230:   const PetscScalar *px;
    231:   PetscScalar       *py;
    232:   CTX_BRUSSEL       *ctx;

    234:   PetscFunctionBeginUser;
    235:   PetscCall(MatShellGetContext(A,&ctx));
    236:   PetscCall(MatGetLocalSize(ctx->T,&n,NULL));
    237:   PetscCall(VecGetArrayRead(x,&px));
    238:   PetscCall(VecGetArray(y,&py));
    239:   PetscCall(VecPlaceArray(ctx->x1,px));
    240:   PetscCall(VecPlaceArray(ctx->x2,px+n));
    241:   PetscCall(VecPlaceArray(ctx->y1,py));
    242:   PetscCall(VecPlaceArray(ctx->y2,py+n));

    244:   PetscCall(MatMultTranspose(ctx->T,ctx->x1,ctx->y1));
    245:   PetscCall(VecScale(ctx->y1,ctx->tau1));
    246:   PetscCall(VecAXPY(ctx->y1,ctx->beta-1.0+ctx->sigma,ctx->x1));
    247:   PetscCall(VecAXPY(ctx->y1,-ctx->beta,ctx->x2));

    249:   PetscCall(MatMultTranspose(ctx->T,ctx->x2,ctx->y2));
    250:   PetscCall(VecScale(ctx->y2,ctx->tau2));
    251:   PetscCall(VecAXPY(ctx->y2,ctx->alpha*ctx->alpha,ctx->x1));
    252:   PetscCall(VecAXPY(ctx->y2,-ctx->alpha*ctx->alpha+ctx->sigma,ctx->x2));

    254:   PetscCall(VecRestoreArrayRead(x,&px));
    255:   PetscCall(VecRestoreArray(y,&py));
    256:   PetscCall(VecResetArray(ctx->x1));
    257:   PetscCall(VecResetArray(ctx->x2));
    258:   PetscCall(VecResetArray(ctx->y1));
    259:   PetscCall(VecResetArray(ctx->y2));
    260:   PetscFunctionReturn(PETSC_SUCCESS);
    261: }

    263: PetscErrorCode MatGetDiagonal_Brussel(Mat A,Vec diag)
    264: {
    265:   Vec            d1,d2;
    266:   PetscInt       n;
    267:   PetscScalar    *pd;
    268:   MPI_Comm       comm;
    269:   CTX_BRUSSEL    *ctx;

    271:   PetscFunctionBeginUser;
    272:   PetscCall(MatShellGetContext(A,&ctx));
    273:   PetscCall(PetscObjectGetComm((PetscObject)A,&comm));
    274:   PetscCall(MatGetLocalSize(ctx->T,&n,NULL));
    275:   PetscCall(VecGetArray(diag,&pd));
    276:   PetscCall(VecCreateMPIWithArray(comm,1,n,PETSC_DECIDE,pd,&d1));
    277:   PetscCall(VecCreateMPIWithArray(comm,1,n,PETSC_DECIDE,pd+n,&d2));

    279:   PetscCall(VecSet(d1,-2.0*ctx->tau1 + ctx->beta - 1.0 + ctx->sigma));
    280:   PetscCall(VecSet(d2,-2.0*ctx->tau2 - ctx->alpha*ctx->alpha + ctx->sigma));

    282:   PetscCall(VecDestroy(&d1));
    283:   PetscCall(VecDestroy(&d2));
    284:   PetscCall(VecRestoreArray(diag,&pd));
    285:   PetscFunctionReturn(PETSC_SUCCESS);
    286: }

    288: /*TEST

    290:    test:
    291:       suffix: 1
    292:       args: -n 50 -eps_nev 4 -eps_two_sided {{0 1}} -eps_type {{krylovschur lapack}} -terse
    293:       requires: !single
    294:       filter: grep -v method

    296:    test:
    297:       suffix: 2
    298:       args: -eps_nev 8 -eps_max_it 300 -eps_target -28 -rg_type interval -rg_interval_endpoints -40,-20,-.1,.1 -terse
    299:       requires: !single

    301:    test:
    302:       suffix: 3
    303:       args: -n 50 -eps_nev 4 -eps_balance twoside -terse
    304:       requires: double
    305:       filter: grep -v method
    306:       output_file: output/ex9_1.out

    308:    test:
    309:       suffix: 4
    310:       args: -eps_smallest_imaginary -eps_ncv 24 -terse
    311:       requires: !complex !single

    313:    test:
    314:       suffix: 4_complex
    315:       args: -eps_smallest_imaginary -eps_ncv 24 -terse
    316:       requires: complex !single

    318:    test:
    319:       suffix: 5
    320:       args: -eps_nev 4 -eps_target_real -eps_target -3 -terse
    321:       requires: !single

    323:    test:
    324:       suffix: 6
    325:       args: -eps_nev 2 -eps_target_imaginary -eps_target 3i -terse
    326:       requires: complex !single

    328:    test:
    329:       suffix: 7
    330:       args: -n 40 -eps_nev 1 -eps_type arnoldi -eps_smallest_real -eps_refined -eps_ncv 42 -eps_max_it 300 -terse
    331:       requires: double

    333:    test:
    334:       suffix: 8
    335:       args: -eps_nev 2 -eps_target -30 -eps_type jd -st_matmode shell -eps_jd_fix 0.0001 -eps_jd_const_correction_tol 0 -terse
    336:       requires: !single
    337:       filter: sed -e "s/[+-]0\.0*i//g"
    338:       timeoutfactor: 2

    340:    test:
    341:       suffix: 9
    342:       args: -eps_largest_imaginary -eps_ncv 24 -terse
    343:       requires: !single

    345: TEST*/