Date: 2026-05-01T10:02:38+00:00

Actual source code: ex43.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[] = "Generalized eigenproblem, illustrates setting MUMPS options.\n\n"
     12:   "The problem is Ax = lambda Bx, with:\n"
     13:   "   A = Laplacian operator in 2-D\n"
     14:   "   B = diagonal matrix with all values equal to 4\n\n"
     15:   "The command line options are:\n"
     16:   "  -n <n>, where <n> = number of grid subdivisions in x dimension.\n"
     17:   "  -m <m>, where <m> = number of grid subdivisions in y dimension.\n\n";

     19: #include <slepceps.h>

     21: int main(int argc,char **argv)
     22: {
     23:   Mat            A,B;
     24: #if defined(PETSC_HAVE_MUMPS)
     25:   Mat            K;
     26: #endif
     27:   EPS            eps;
     28:   EPSType        type;
     29:   ST             st;
     30:   KSP            ksp;
     31:   PC             pc;
     32:   PetscInt       N,n=10,m=12,Istart,Iend,II,nev,i,j;
     33:   PetscBool      flag,terse;

     35:   PetscFunctionBeginUser;
     36:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     38:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
     39:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-m",&m,&flag));
     40:   N = n*m;
     41:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nGeneralized Eigenproblem, N=%" PetscInt_FMT " (%" PetscInt_FMT "x%" PetscInt_FMT " grid)\n\n",N,n,m));

     43:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     44:      Compute the matrices that define the eigensystem, Ax=kBx
     45:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     47:   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
     48:   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N));
     49:   PetscCall(MatSetFromOptions(A));

     51:   PetscCall(MatCreate(PETSC_COMM_WORLD,&B));
     52:   PetscCall(MatSetSizes(B,PETSC_DECIDE,PETSC_DECIDE,N,N));
     53:   PetscCall(MatSetFromOptions(B));

     55:   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
     56:   for (II=Istart;II<Iend;II++) {
     57:     i = II/n; j = II-i*n;
     58:     if (i>0) PetscCall(MatSetValue(A,II,II-n,-1.0,INSERT_VALUES));
     59:     if (i<m-1) PetscCall(MatSetValue(A,II,II+n,-1.0,INSERT_VALUES));
     60:     if (j>0) PetscCall(MatSetValue(A,II,II-1,-1.0,INSERT_VALUES));
     61:     if (j<n-1) PetscCall(MatSetValue(A,II,II+1,-1.0,INSERT_VALUES));
     62:     PetscCall(MatSetValue(A,II,II,4.0,INSERT_VALUES));
     63:     PetscCall(MatSetValue(B,II,II,4.0,INSERT_VALUES));
     64:   }

     66:   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
     67:   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
     68:   PetscCall(MatAssemblyBegin(B,MAT_FINAL_ASSEMBLY));
     69:   PetscCall(MatAssemblyEnd(B,MAT_FINAL_ASSEMBLY));

     71:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     72:                 Create the eigensolver and set various options
     73:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     75:   /*
     76:      Create eigensolver context
     77:   */
     78:   PetscCall(EPSCreate(PETSC_COMM_WORLD,&eps));

     80:   /*
     81:      Set operators. In this case, it is a generalized eigenvalue problem
     82:   */
     83:   PetscCall(EPSSetOperators(eps,A,B));
     84:   PetscCall(EPSSetProblemType(eps,EPS_GNHEP));

     86:   /*
     87:      Set some solver options
     88:   */
     89:   PetscCall(EPSSetTarget(eps,1.3));
     90:   PetscCall(EPSSetDimensions(eps,2,PETSC_DETERMINE,PETSC_DETERMINE));
     91:   PetscCall(EPSGetST(eps,&st));
     92:   PetscCall(STSetType(st,STSINVERT));

     94:   PetscCall(STGetKSP(st,&ksp));
     95:   PetscCall(KSPSetType(ksp,KSPPREONLY));
     96:   PetscCall(KSPGetPC(ksp,&pc));
     97:   PetscCall(PCSetType(pc,PCLU));

     99:   /*
    100:      Set MUMPS options if available
    101:   */
    102: #if defined(PETSC_HAVE_MUMPS)
    103:   PetscCall(PCFactorSetMatSolverType(pc,MATSOLVERMUMPS));
    104:   /* the next line is required to force the creation of the ST operator and its passing to KSP */
    105:   PetscCall(STGetOperator(st,NULL));
    106:   PetscCall(PCFactorSetUpMatSolverType(pc));
    107:   PetscCall(PCFactorGetMatrix(pc,&K));
    108:   PetscCall(MatMumpsSetIcntl(K,14,50));
    109:   PetscCall(MatMumpsSetCntl(K,3,1e-12));
    110: #endif

    112:   /*
    113:      Let the user change settings at runtime
    114:   */
    115:   PetscCall(EPSSetFromOptions(eps));

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

    121:   PetscCall(EPSSolve(eps));

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

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

    135:   /* show detailed info unless -terse option is given by user */
    136:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
    137:   if (terse) PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,NULL));
    138:   else {
    139:     PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
    140:     PetscCall(EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD));
    141:     PetscCall(EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
    142:     PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
    143:   }
    144:   PetscCall(EPSDestroy(&eps));
    145:   PetscCall(MatDestroy(&A));
    146:   PetscCall(MatDestroy(&B));
    147:   PetscCall(SlepcFinalize());
    148:   return 0;
    149: }

    151: /*TEST

    153:    testset:
    154:       args: -terse
    155:       output_file: output/ex43_1.out
    156:       test:
    157:          suffix: 1
    158:       test:
    159:          suffix: 2
    160:          nsize: 2
    161:          args: -st_pc_factor_mat_solver_type mumps
    162:          requires: mumps

    164: TEST*/