Date: 2021-09-20T09:43:58+00:00

Actual source code: ex10.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: */

     11: static char help[] = "Illustrates the use of shell spectral transformations. "
     12:   "The problem to be solved is the same as ex1.c and"
     13:   "corresponds to the Laplacian operator in 1 dimension.\n\n"
     14:   "The command line options are:\n"
     15:   "  -n <n>, where <n> = number of grid subdivisions = matrix dimension.\n\n";

     17: #include <slepceps.h>

     19: /* Define context for user-provided spectral transformation */
     20: typedef struct {
     21:   KSP        ksp;
     22: } SampleShellST;

     24: /* Declare routines for user-provided spectral transformation */
     25: PetscErrorCode STCreate_User(SampleShellST**);
     26: PetscErrorCode STSetUp_User(SampleShellST*,ST);
     27: PetscErrorCode STApply_User(ST,Vec,Vec);
     28: PetscErrorCode STApplyTranspose_User(ST,Vec,Vec);
     29: PetscErrorCode STBackTransform_User(ST,PetscInt,PetscScalar*,PetscScalar*);
     30: PetscErrorCode STDestroy_User(SampleShellST*);

     32: int main (int argc,char **argv)
     33: {
     34:   Mat            A;               /* operator matrix */
     35:   EPS            eps;             /* eigenproblem solver context */
     36:   ST             st;              /* spectral transformation context */
     37:   SampleShellST  *shell;          /* user-defined spectral transform context */
     38:   EPSType        type;
     39:   PetscInt       n=30,i,Istart,Iend,nev;
     40:   PetscBool      isShell,terse;

     43:   SlepcInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;

     45:   PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);
     46:   PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem (shell-enabled), n=%D\n\n",n);

     48:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     49:      Compute the operator matrix that defines the eigensystem, Ax=kx
     50:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     52:   MatCreate(PETSC_COMM_WORLD,&A);
     53:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n);
     54:   MatSetFromOptions(A);
     55:   MatSetUp(A);

     57:   MatGetOwnershipRange(A,&Istart,&Iend);
     58:   for (i=Istart;i<Iend;i++) {
     59:     if (i>0) { MatSetValue(A,i,i-1,-1.0,INSERT_VALUES); }
     60:     if (i<n-1) { MatSetValue(A,i,i+1,-1.0,INSERT_VALUES); }
     61:     MatSetValue(A,i,i,2.0,INSERT_VALUES);
     62:   }
     63:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     64:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

     66:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     67:                 Create the eigensolver and set various options
     68:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     70:   /*
     71:      Create eigensolver context
     72:   */
     73:   EPSCreate(PETSC_COMM_WORLD,&eps);

     75:   /*
     76:      Set operators. In this case, it is a standard eigenvalue problem
     77:   */
     78:   EPSSetOperators(eps,A,NULL);
     79:   EPSSetProblemType(eps,EPS_HEP);

     81:   /*
     82:      Set solver parameters at runtime
     83:   */
     84:   EPSSetFromOptions(eps);

     86:   /*
     87:      Initialize shell spectral transformation if selected by user
     88:   */
     89:   EPSGetST(eps,&st);
     90:   PetscObjectTypeCompare((PetscObject)st,STSHELL,&isShell);
     91:   if (isShell) {
     92:     /* Change sorting criterion since this ST example computes values
     93:        closest to 0 */
     94:     EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL);

     96:     /* (Required) Create a context for the user-defined spectral transform;
     97:        this context can be defined to contain any application-specific data. */
     98:     STCreate_User(&shell);
     99:     STShellSetContext(st,shell);

    101:     /* (Required) Set the user-defined routine for applying the operator */
    102:     STShellSetApply(st,STApply_User);

    104:     /* (Optional) Set the user-defined routine for applying the transposed operator */
    105:     STShellSetApplyTranspose(st,STApplyTranspose_User);

    107:     /* (Optional) Set the user-defined routine for back-transformation */
    108:     STShellSetBackTransform(st,STBackTransform_User);

    110:     /* (Optional) Set a name for the transformation, used for STView() */
    111:     PetscObjectSetName((PetscObject)st,"MyTransformation");

    113:     /* (Optional) Do any setup required for the new transformation */
    114:     STSetUp_User(shell,st);
    115:   }

    117:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    118:                       Solve the eigensystem
    119:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    121:   EPSSolve(eps);

    123:   /*
    124:      Optional: Get some information from the solver and display it
    125:   */
    126:   EPSGetType(eps,&type);
    127:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
    128:   EPSGetDimensions(eps,&nev,NULL,NULL);
    129:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %D\n",nev);

    131:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    132:                     Display solution and clean up
    133:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    135:   /* show detailed info unless -terse option is given by user */
    136:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    137:   if (terse) {
    138:     EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
    139:   } else {
    140:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
    141:     EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
    142:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
    143:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
    144:   }
    145:   if (isShell) {
    146:     STDestroy_User(shell);
    147:   }
    148:   EPSDestroy(&eps);
    149:   MatDestroy(&A);
    150:   SlepcFinalize();
    151:   return ierr;
    152: }

    154: /***********************************************************************/
    155: /*     Routines for a user-defined shell spectral transformation       */
    156: /***********************************************************************/

    158: /*
    159:    STCreate_User - This routine creates a user-defined
    160:    spectral transformation context.

    162:    Output Parameter:
    163: .  shell - user-defined spectral transformation context
    164: */
    165: PetscErrorCode STCreate_User(SampleShellST **shell)
    166: {
    167:   SampleShellST  *newctx;

    171:   PetscNew(&newctx);
    172:   KSPCreate(PETSC_COMM_WORLD,&newctx->ksp);
    173:   KSPAppendOptionsPrefix(newctx->ksp,"st_");
    174:   *shell = newctx;
    175:   return(0);
    176: }
    177: /* ------------------------------------------------------------------- */
    178: /*
    179:    STSetUp_User - This routine sets up a user-defined
    180:    spectral transformation context.

    182:    Input Parameters:
    183: +  shell - user-defined spectral transformation context
    184: -  st    - spectral transformation context containing the operator matrices

    186:    Output Parameter:
    187: .  shell - fully set up user-defined transformation context

    189:    Notes:
    190:    In this example, the user-defined transformation is simply OP=A^-1.
    191:    Therefore, the eigenpairs converge in reversed order. The KSP object
    192:    used for the solution of linear systems with A is handled via the
    193:    user-defined context SampleShellST.
    194: */
    195: PetscErrorCode STSetUp_User(SampleShellST *shell,ST st)
    196: {
    197:   Mat            A;

    201:   STGetMatrix(st,0,&A);
    202:   KSPSetOperators(shell->ksp,A,A);
    203:   KSPSetFromOptions(shell->ksp);
    204:   return(0);
    205: }
    206: /* ------------------------------------------------------------------- */
    207: /*
    208:    STApply_User - This routine demonstrates the use of a
    209:    user-provided spectral transformation.

    211:    Input Parameters:
    212: +  st - spectral transformation context
    213: -  x - input vector

    215:    Output Parameter:
    216: .  y - output vector

    218:    Notes:
    219:    The transformation implemented in this code is just OP=A^-1 and
    220:    therefore it is of little use, merely as an example of working with
    221:    a STSHELL.
    222: */
    223: PetscErrorCode STApply_User(ST st,Vec x,Vec y)
    224: {
    225:   SampleShellST  *shell;

    229:   STShellGetContext(st,(void**)&shell);
    230:   KSPSolve(shell->ksp,x,y);
    231:   return(0);
    232: }
    233: /* ------------------------------------------------------------------- */
    234: /*
    235:    STApplyTranspose_User - This is not required unless using a two-sided
    236:    eigensolver.

    238:    Input Parameters:
    239: +  st - spectral transformation context
    240: -  x - input vector

    242:    Output Parameter:
    243: .  y - output vector
    244: */
    245: PetscErrorCode STApplyTranspose_User(ST st,Vec x,Vec y)
    246: {
    247:   SampleShellST  *shell;

    251:   STShellGetContext(st,(void**)&shell);
    252:   KSPSolveTranspose(shell->ksp,x,y);
    253:   return(0);
    254: }
    255: /* ------------------------------------------------------------------- */
    256: /*
    257:    STBackTransform_User - This routine demonstrates the use of a
    258:    user-provided spectral transformation.

    260:    Input Parameters:
    261: +  st - spectral transformation context
    262: -  n  - number of eigenvalues to transform

    264:    Input/Output Parameters:
    265: +  eigr - pointer to real part of eigenvalues
    266: -  eigi - pointer to imaginary part of eigenvalues

    268:    Notes:
    269:    This code implements the back transformation of eigenvalues in
    270:    order to retrieve the eigenvalues of the original problem. In this
    271:    example, simply set k_i = 1/k_i.
    272: */
    273: PetscErrorCode STBackTransform_User(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
    274: {
    275:   PetscInt j;

    278:   for (j=0;j<n;j++) {
    279:     eigr[j] = 1.0 / eigr[j];
    280:   }
    281:   return(0);
    282: }
    283: /* ------------------------------------------------------------------- */
    284: /*
    285:    STDestroy_User - This routine destroys a user-defined
    286:    spectral transformation context.

    288:    Input Parameter:
    289: .  shell - user-defined spectral transformation context
    290: */
    291: PetscErrorCode STDestroy_User(SampleShellST *shell)
    292: {

    296:   KSPDestroy(&shell->ksp);
    297:   PetscFree(shell);
    298:   return(0);
    299: }

    301: /*TEST

    303:    testset:
    304:       args: -eps_nev 5 -eps_non_hermitian -terse
    305:       output_file: output/ex10_1.out
    306:       test:
    307:          suffix: 1_sinvert
    308:          args: -st_type sinvert
    309:       test:
    310:          suffix: 1_sinvert_twoside
    311:          args: -st_type sinvert -eps_balance twoside
    312:          requires: !single
    313:       test:
    314:          suffix: 1_shell
    315:          args: -st_type shell
    316:          requires: !single
    317:       test:
    318:          suffix: 1_shell_twoside
    319:          args: -st_type shell -eps_balance twoside

    321: TEST*/