Date: 2026-05-01T10:02:31+00:00

Actual source code: test20.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[] = "Tests multiple calls to EPSSolve changing ncv.\n\n";

     13: #include <slepceps.h>

     15: int main(int argc,char **argv)
     16: {
     17:   Mat            A;
     18:   EPS            eps;
     19:   PetscReal      tol=PetscMax(1000*PETSC_MACHINE_EPSILON,1e-9);
     20:   PetscInt       n=30,i,Istart,Iend,nev,ncv;

     22:   PetscFunctionBeginUser;
     23:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
     24:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     25:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\n1-D Laplacian Eigenproblem, n=%" PetscInt_FMT "\n\n",n));

     27:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     28:      Compute the operator matrix that defines the eigensystem, Ax=kx
     29:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     31:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     32:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
     33:   PetscCall(MatSetFromOptions(A));
     34:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
     35:   for (i=Istart;i<Iend;i++) {
     36:     if (i>0) PetscCall(MatSetValue(A,i,i-1,-1.0,INSERT_VALUES));
     37:     if (i<n-1) PetscCall(MatSetValue(A,i,i+1,-1.0,INSERT_VALUES));
     38:     PetscCall(MatSetValue(A,i,i,2.0,INSERT_VALUES));
     39:   }
     40:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
     41:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));

     43:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     44:              Create the solver, call EPSSolve() twice
     45:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     46:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
     47:   PetscCall(EPSSetOperators(eps,A,NULL));
     48:   PetscCall(EPSSetProblemType(eps,EPS_HEP));
     49:   PetscCall(EPSSetTolerances(eps,tol,PETSC_CURRENT));
     50:   PetscCall(EPSSetWhichEigenpairs(eps,EPS_SMALLEST_REAL));
     51:   PetscCall(EPSSetFromOptions(eps));

     53:   /* First solve */
     54:   PetscCall(EPSSolve(eps));
     55:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," - - - First solve, default subspace dimension - - -\n"));
     56:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));

     58:   /* Second solve */
     59:   PetscCall(EPSGetDimensions(eps,&nev,&ncv,NULL));
     60:   PetscCall(EPSSetDimensions(eps,nev,ncv+2,PETSC_DETERMINE));
     61:   PetscCall(EPSSolve(eps));
     62:   PetscCall(PetscPrintf(PETSC_COMM_WORLD," - - - Second solve, subspace of increased size - - -\n"));
     63:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));

     65:   PetscCall(EPSDestroy(&eps));
     66:   PetscCall(MatDestroy(&A));
     67:   PetscCall(SlepcFinalize());
     68:   return 0;
     69: }

     71: /*TEST

     73:    test:
     74:       suffix: 1
     75:       args: -n 18 -eps_type {{krylovschur arnoldi gd jd rqcg lobpcg lapack}} -eps_max_it 1500
     76:       output_file: output/test20_1.out

     78:    test:
     79:       suffix: 1_lanczos
     80:       args: -n 18 -eps_type lanczos -eps_lanczos_reorthog full -eps_max_it 1500
     81:       output_file: output/test20_1.out

     83: TEST*/