Date: 2022-08-09T09:05:41+00:00

Actual source code: ex10.c
slepc-3.17.2 2022-08-09
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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[] = "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;

     42:   SlepcInitialize(&argc,&argv,(char*)0,help);

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

     47:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     48:      Compute the operator matrix that defines the eigensystem, Ax=kx
     49:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

     65:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     66:                 Create the eigensolver and set various options
     67:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     69:   /*
     70:      Create eigensolver context
     71:   */
     72:   EPSCreate(PETSC_COMM_WORLD,&eps);

     74:   /*
     75:      Set operators. In this case, it is a standard eigenvalue problem
     76:   */
     77:   EPSSetOperators(eps,A,NULL);
     78:   EPSSetProblemType(eps,EPS_HEP);

     80:   /*
     81:      Set solver parameters at runtime
     82:   */
     83:   EPSSetFromOptions(eps);

     85:   /*
     86:      Initialize shell spectral transformation if selected by user
     87:   */
     88:   EPSGetST(eps,&st);
     89:   PetscObjectTypeCompare((PetscObject)st,STSHELL,&isShell);
     90:   if (isShell) {
     91:     /* Change sorting criterion since this ST example computes values
     92:        closest to 0 */
     93:     EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL);

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

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

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

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

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

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

    116:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    117:                       Solve the eigensystem
    118:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    120:   EPSSolve(eps);

    122:   /*
    123:      Optional: Get some information from the solver and display it
    124:   */
    125:   EPSGetType(eps,&type);
    126:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
    127:   EPSGetDimensions(eps,&nev,NULL,NULL);
    128:   PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %" PetscInt_FMT "\n",nev);

    130:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    131:                     Display solution and clean up
    132:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    134:   /* show detailed info unless -terse option is given by user */
    135:   PetscOptionsHasName(NULL,NULL,"-terse",&terse);
    136:   if (terse) EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL);
    137:   else {
    138:     PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL);
    139:     EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD);
    140:     EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
    141:     PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD);
    142:   }
    143:   if (isShell) STDestroy_User(shell);
    144:   EPSDestroy(&eps);
    145:   MatDestroy(&A);
    146:   SlepcFinalize();
    147:   return 0;
    148: }

    150: /***********************************************************************/
    151: /*     Routines for a user-defined shell spectral transformation       */
    152: /***********************************************************************/

    154: /*
    155:    STCreate_User - This routine creates a user-defined
    156:    spectral transformation context.

    158:    Output Parameter:
    159: .  shell - user-defined spectral transformation context
    160: */
    161: PetscErrorCode STCreate_User(SampleShellST **shell)
    162: {
    163:   SampleShellST  *newctx;

    166:   PetscNew(&newctx);
    167:   KSPCreate(PETSC_COMM_WORLD,&newctx->ksp);
    168:   KSPAppendOptionsPrefix(newctx->ksp,"st_");
    169:   *shell = newctx;
    170:   PetscFunctionReturn(0);
    171: }
    172: /* ------------------------------------------------------------------- */
    173: /*
    174:    STSetUp_User - This routine sets up a user-defined
    175:    spectral transformation context.

    177:    Input Parameters:
    178: +  shell - user-defined spectral transformation context
    179: -  st    - spectral transformation context containing the operator matrices

    181:    Output Parameter:
    182: .  shell - fully set up user-defined transformation context

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

    195:   STGetMatrix(st,0,&A);
    196:   KSPSetOperators(shell->ksp,A,A);
    197:   KSPSetFromOptions(shell->ksp);
    198:   PetscFunctionReturn(0);
    199: }
    200: /* ------------------------------------------------------------------- */
    201: /*
    202:    STApply_User - This routine demonstrates the use of a
    203:    user-provided spectral transformation.

    205:    Input Parameters:
    206: +  st - spectral transformation context
    207: -  x - input vector

    209:    Output Parameter:
    210: .  y - output vector

    212:    Notes:
    213:    The transformation implemented in this code is just OP=A^-1 and
    214:    therefore it is of little use, merely as an example of working with
    215:    a STSHELL.
    216: */
    217: PetscErrorCode STApply_User(ST st,Vec x,Vec y)
    218: {
    219:   SampleShellST  *shell;

    222:   STShellGetContext(st,&shell);
    223:   KSPSolve(shell->ksp,x,y);
    224:   PetscFunctionReturn(0);
    225: }
    226: /* ------------------------------------------------------------------- */
    227: /*
    228:    STApplyTranspose_User - This is not required unless using a two-sided
    229:    eigensolver.

    231:    Input Parameters:
    232: +  st - spectral transformation context
    233: -  x - input vector

    235:    Output Parameter:
    236: .  y - output vector
    237: */
    238: PetscErrorCode STApplyTranspose_User(ST st,Vec x,Vec y)
    239: {
    240:   SampleShellST  *shell;

    243:   STShellGetContext(st,&shell);
    244:   KSPSolveTranspose(shell->ksp,x,y);
    245:   PetscFunctionReturn(0);
    246: }
    247: /* ------------------------------------------------------------------- */
    248: /*
    249:    STBackTransform_User - This routine demonstrates the use of a
    250:    user-provided spectral transformation.

    252:    Input Parameters:
    253: +  st - spectral transformation context
    254: -  n  - number of eigenvalues to transform

    256:    Input/Output Parameters:
    257: +  eigr - pointer to real part of eigenvalues
    258: -  eigi - pointer to imaginary part of eigenvalues

    260:    Notes:
    261:    This code implements the back transformation of eigenvalues in
    262:    order to retrieve the eigenvalues of the original problem. In this
    263:    example, simply set k_i = 1/k_i.
    264: */
    265: PetscErrorCode STBackTransform_User(ST st,PetscInt n,PetscScalar *eigr,PetscScalar *eigi)
    266: {
    267:   PetscInt j;

    270:   for (j=0;j<n;j++) {
    271:     eigr[j] = 1.0 / eigr[j];
    272:   }
    273:   PetscFunctionReturn(0);
    274: }
    275: /* ------------------------------------------------------------------- */
    276: /*
    277:    STDestroy_User - This routine destroys a user-defined
    278:    spectral transformation context.

    280:    Input Parameter:
    281: .  shell - user-defined spectral transformation context
    282: */
    283: PetscErrorCode STDestroy_User(SampleShellST *shell)
    284: {
    286:   KSPDestroy(&shell->ksp);
    287:   PetscFree(shell);
    288:   PetscFunctionReturn(0);
    289: }

    291: /*TEST

    293:    testset:
    294:       args: -eps_nev 5 -eps_non_hermitian -terse
    295:       output_file: output/ex10_1.out
    296:       test:
    297:          suffix: 1_sinvert
    298:          args: -st_type sinvert
    299:       test:
    300:          suffix: 1_sinvert_twoside
    301:          args: -st_type sinvert -eps_balance twoside
    302:          requires: !single
    303:       test:
    304:          suffix: 1_shell
    305:          args: -st_type shell
    306:          requires: !single
    307:       test:
    308:          suffix: 1_shell_twoside
    309:          args: -st_type shell -eps_balance twoside

    311: TEST*/