Date: 2026-01-20T11:35:40+00:00

Actual source code: test6.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[] = "Diagonal eigenproblem.\n\n"
     12:   "The command line options are:\n"
     13:   "  -n <n>, where <n> = matrix dimension.\n"
     14:   "  -seed <s>, where <s> = seed for random number generation.\n\n";

     16: #include <slepceps.h>

     18: int main(int argc,char **argv)
     19: {
     20:   Mat            A;           /* problem matrix */
     21:   EPS            eps;         /* eigenproblem solver context */
     22:   Vec            v0;          /* initial vector */
     23:   PetscRandom    rand;
     24:   PetscReal      tol=PETSC_SMALL;
     25:   PetscInt       n=30,i,Istart,Iend,seed=0x12345678;

     27:   PetscFunctionBeginUser;
     28:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     30:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     31:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nDiagonal Eigenproblem, n=%" PetscInt_FMT "\n\n",n));

     33:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     34:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n));
     35:   PetscCall(MatSetFromOptions(A));
     36:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
     37:   for (i=Istart;i<Iend;i++) PetscCall(MatSetValue(A,i,i,i+1,INSERT_VALUES));
     38:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
     39:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));

     41:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     42:                       Solve the eigensystem
     43:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     44:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));
     45:   PetscCall(EPSSetOperators(eps,A,NULL));
     46:   PetscCall(EPSSetProblemType(eps,EPS_HEP));
     47:   PetscCall(EPSSetTolerances(eps,tol,PETSC_CURRENT));
     48:   PetscCall(EPSSetFromOptions(eps));
     49:   /* set random initial vector */
     50:   PetscCall(MatCreateVecs(A,&v0,NULL));
     51:   PetscCall(PetscRandomCreate(PETSC_COMM_WORLD,&rand));
     52:   PetscCall(PetscRandomSetFromOptions(rand));
     53:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-seed",&seed,NULL));
     54:   PetscCall(PetscRandomSetSeed(rand,seed));
     55:   PetscCall(PetscRandomSeed(rand));
     56:   PetscCall(VecSetRandom(v0,rand));
     57:   PetscCall(EPSSetInitialSpace(eps,1,&v0));
     58:   /* call the solver */
     59:   PetscCall(EPSSolve(eps));

     61:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     62:                     Display solution and clean up
     63:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     64:   PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
     65:   PetscCall(EPSDestroy(&eps));
     66:   PetscCall(MatDestroy(&A));
     67:   PetscCall(VecDestroy(&v0));
     68:   PetscCall(PetscRandomDestroy(&rand));
     69:   PetscCall(SlepcFinalize());
     70:   return 0;
     71: }

     73: /*TEST

     75:    testset:
     76:       args: -eps_nev 4
     77:       requires: !single
     78:       output_file: output/test6_1.out
     79:       test:
     80:          suffix: 1
     81:          args: -eps_type {{krylovschur subspace arnoldi gd}}
     82:       test:
     83:          suffix: 1_power
     84:          args: -eps_type power -eps_max_it 20000
     85:       test:
     86:          suffix: 1_gd2
     87:          args: -eps_type gd -eps_gd_double_expansion
     88:       test:
     89:          suffix: 1_arpack
     90:          args: -eps_type arpack
     91:          requires: arpack

     93: TEST*/