Date: 2026-05-01T10:02:30+00:00

Actual source code: test13.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: */

     11: static char help[] = "Test EPSSetArbitrarySelection.\n\n";

     13: #include <slepceps.h>

     15: PetscErrorCode MyArbitrarySelection(PetscScalar eigr,PetscScalar eigi,Vec xr,Vec xi,PetscScalar *rr,PetscScalar *ri,void *ctx)
     16: {
     17:   Vec             xref = *(Vec*)ctx;

     19:   PetscFunctionBeginUser;
     20:   PetscCall(VecDot(xr,xref,rr));
     21:   *rr = PetscAbsScalar(*rr);
     22:   if (ri) *ri = 0.0;
     23:   PetscFunctionReturn(PETSC_SUCCESS);
     24: }

     26: PetscErrorCode MyArbitrarySelectionDestroy(PetscCtxRt ctx)
     27: {
     28:   Vec             xref = **(Vec**)ctx;

     30:   PetscFunctionBeginUser;
     31:   PetscCall(VecDestroy(&xref));
     32:   PetscFunctionReturn(PETSC_SUCCESS);
     33: }

     35: int main(int argc,char **argv)
     36: {
     37:   Mat            A;           /* problem matrices */
     38:   EPS            eps;         /* eigenproblem solver context */
     39:   PetscScalar    seigr,seigi;
     40:   PetscReal      tol=1000*PETSC_MACHINE_EPSILON;
     41:   Vec            sxr,sxi;
     42:   PetscInt       n=30,i,Istart,Iend,nconv;

     44:   PetscFunctionBeginUser;
     45:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     47:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     48:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nTridiagonal with zero diagonal, n=%" PetscInt_FMT "\n\n",n));

     50:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     51:            Create matrix tridiag([-1 0 -1])
     52:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     53:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     54:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
     55:   PetscCall(MatSetFromOptions(A));

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

     65:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     66:                         Create the eigensolver
     67:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     68:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
     69:   PetscCall(EPSSetProblemType(eps,EPS_HEP));
     70:   PetscCall(EPSSetTolerances(eps,tol,PETSC_CURRENT));
     71:   PetscCall(EPSSetOperators(eps,A,NULL));
     72:   PetscCall(EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL));
     73:   PetscCall(EPSSetFromOptions(eps));

     75:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     76:                 Solve eigenproblem and store some solution
     77:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     78:   PetscCall(EPSSolve(eps));
     79:   PetscCall(EPSGetConverged(eps,&nconv));
     80:   if (nconv>0) {
     81:     PetscCall(MatCreateVecs(A,&sxr,NULL));
     82:     PetscCall(MatCreateVecs(A,&sxi,NULL));
     83:     PetscCall(EPSGetEigenpair(eps,0,&seigr,&seigi,sxr,sxi));
     84:     PetscCall(VecDestroy(&sxi));
     85:     PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));

     87:     /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     88:                  Solve eigenproblem using an arbitrary selection
     89:        - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     90:     PetscCall(EPSSetArbitrarySelection(eps,MyArbitrarySelection,&sxr));
     91:     PetscCall(EPSSetArbitrarySelectionContextDestroy(eps,MyArbitrarySelectionDestroy));
     92:     PetscCall(EPSSetWhichEigenpairs(eps,EPS_LARGEST_MAGNITUDE));
     93:     PetscCall(EPSSolve(eps));
     94:     PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
     95:   } else PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Problem: no eigenpairs converged.\n"));

     97:   PetscCall(EPSDestroy(&eps));
     98:   PetscCall(MatDestroy(&A));
     99:   PetscCall(SlepcFinalize());
    100:   return 0;
    101: }

    103: /*TEST

    105:    testset:
    106:       args: -eps_max_it 5000 -st_pc_type jacobi
    107:       output_file: output/test13_1.out
    108:       filter: sed -e "s/-1.98975/-1.98974/"
    109:       test:
    110:          suffix: 1
    111:          args: -eps_type {{krylovschur gd}}
    112:       test:
    113:          suffix: 1_jd
    114:          args: -eps_type jd -st_ksp_type gmres
    115:       test:
    116:          suffix: 1_gd2
    117:          args: -eps_type gd -eps_gd_double_expansion
    118:       test:
    119:          suffix: 2
    120:          args: -eps_non_hermitian -eps_type {{krylovschur gd jd}}
    121:       test:
    122:          suffix: 2_gd2
    123:          args: -eps_non_hermitian -eps_type gd -eps_gd_double_expansion
    124:          timeoutfactor: 2

    126: TEST*/