Date: 2026-03-09T09:11:59+00:00

Actual source code: test9.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[] = "Illustrates use of PEPSetEigenvalueComparison().\n\n"
     12:   "Based on butterfly.c. The command line options are:\n"
     13:   "  -m <m>, grid size, the dimension of the matrices is n=m*m.\n"
     14:   "  -c <array>, problem parameters, must be 10 comma-separated real values.\n\n";

     16: #include <slepcpep.h>

     18: #define NMAT 5

     20: /*
     21:     Function for user-defined eigenvalue ordering criterion.

     23:     Given two eigenvalues ar+i*ai and br+i*bi, the subroutine must choose
     24:     one of them as the preferred one according to the criterion.
     25:     In this example, eigenvalues are sorted by magnitude but those with
     26:     positive real part are preferred.
     27: */
     28: PetscErrorCode MyEigenSort(PetscScalar ar,PetscScalar ai,PetscScalar br,PetscScalar bi,PetscInt *r,void *ctx)
     29: {
     30:   PetscReal rea,reb;

     32:   PetscFunctionBeginUser;
     33: #if defined(PETSC_USE_COMPLEX)
     34:   rea = PetscRealPart(ar); reb = PetscRealPart(br);
     35: #else
     36:   rea = ar; reb = br;
     37: #endif
     38:   *r = rea<0.0? 1: (reb<0.0? -1: PetscSign(SlepcAbsEigenvalue(br,bi)-SlepcAbsEigenvalue(ar,ai)));
     39:   PetscFunctionReturn(PETSC_SUCCESS);
     40: }

     42: int main(int argc,char **argv)
     43: {
     44:   Mat            A[NMAT];         /* problem matrices */
     45:   PEP            pep;             /* polynomial eigenproblem solver context */
     46:   PetscInt       n,m=8,k,II,Istart,Iend,i,j;
     47:   PetscReal      c[10] = { 0.6, 1.3, 1.3, 0.1, 0.1, 1.2, 1.0, 1.0, 1.2, 1.0 };
     48:   PetscBool      flg;
     49:   PetscBool      terse;
     50:   const char     *prefix;

     52:   PetscFunctionBeginUser;
     53:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     55:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL));
     56:   n = m*m;
     57:   k = 10;
     58:   PetscCall(PetscOptionsGetRealArray(NULL,NULL,"-c",c,&k,&flg));
     59:   PetscCheck(!flg || k==10,PETSC_COMM_WORLD,PETSC_ERR_USER,"The number of parameters -c should be 10, you provided %" PetscInt_FMT,k);
     60:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nButterfly problem, n=%" PetscInt_FMT " (m=%" PetscInt_FMT ")\n\n",n,m));

     62:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     63:                      Compute the polynomial matrices
     64:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     66:   /* initialize matrices */
     67:   for (i=0;i<NMAT;i++) {
     68:     PetscCall(MatCreate(PETSC_COMM_WORLD,&A[i]));
     69:     PetscCall(MatSetSizes(A[i],PETSC_DECIDE,PETSC_DECIDE,n,n));
     70:     PetscCall(MatSetFromOptions(A[i]));
     71:   }
     72:   PetscCall(MatGetOwnershipRange(A[0],&Istart,&Iend));

     74:   /* A0 */
     75:   for (II=Istart;II<Iend;II++) {
     76:     i = II/m; j = II-i*m;
     77:     PetscCall(MatSetValue(A[0],II,II,4.0*c[0]/6.0+4.0*c[1]/6.0,INSERT_VALUES));
     78:     if (j>0) PetscCall(MatSetValue(A[0],II,II-1,c[0]/6.0,INSERT_VALUES));
     79:     if (j<m-1) PetscCall(MatSetValue(A[0],II,II+1,c[0]/6.0,INSERT_VALUES));
     80:     if (i>0) PetscCall(MatSetValue(A[0],II,II-m,c[1]/6.0,INSERT_VALUES));
     81:     if (i<m-1) PetscCall(MatSetValue(A[0],II,II+m,c[1]/6.0,INSERT_VALUES));
     82:   }

     84:   /* A1 */
     85:   for (II=Istart;II<Iend;II++) {
     86:     i = II/m; j = II-i*m;
     87:     if (j>0) PetscCall(MatSetValue(A[1],II,II-1,c[2],INSERT_VALUES));
     88:     if (j<m-1) PetscCall(MatSetValue(A[1],II,II+1,-c[2],INSERT_VALUES));
     89:     if (i>0) PetscCall(MatSetValue(A[1],II,II-m,c[3],INSERT_VALUES));
     90:     if (i<m-1) PetscCall(MatSetValue(A[1],II,II+m,-c[3],INSERT_VALUES));
     91:   }

     93:   /* A2 */
     94:   for (II=Istart;II<Iend;II++) {
     95:     i = II/m; j = II-i*m;
     96:     PetscCall(MatSetValue(A[2],II,II,-2.0*c[4]-2.0*c[5],INSERT_VALUES));
     97:     if (j>0) PetscCall(MatSetValue(A[2],II,II-1,c[4],INSERT_VALUES));
     98:     if (j<m-1) PetscCall(MatSetValue(A[2],II,II+1,c[4],INSERT_VALUES));
     99:     if (i>0) PetscCall(MatSetValue(A[2],II,II-m,c[5],INSERT_VALUES));
    100:     if (i<m-1) PetscCall(MatSetValue(A[2],II,II+m,c[5],INSERT_VALUES));
    101:   }

    103:   /* A3 */
    104:   for (II=Istart;II<Iend;II++) {
    105:     i = II/m; j = II-i*m;
    106:     if (j>0) PetscCall(MatSetValue(A[3],II,II-1,c[6],INSERT_VALUES));
    107:     if (j<m-1) PetscCall(MatSetValue(A[3],II,II+1,-c[6],INSERT_VALUES));
    108:     if (i>0) PetscCall(MatSetValue(A[3],II,II-m,c[7],INSERT_VALUES));
    109:     if (i<m-1) PetscCall(MatSetValue(A[3],II,II+m,-c[7],INSERT_VALUES));
    110:   }

    112:   /* A4 */
    113:   for (II=Istart;II<Iend;II++) {
    114:     i = II/m; j = II-i*m;
    115:     PetscCall(MatSetValue(A[4],II,II,2.0*c[8]+2.0*c[9],INSERT_VALUES));
    116:     if (j>0) PetscCall(MatSetValue(A[4],II,II-1,-c[8],INSERT_VALUES));
    117:     if (j<m-1) PetscCall(MatSetValue(A[4],II,II+1,-c[8],INSERT_VALUES));
    118:     if (i>0) PetscCall(MatSetValue(A[4],II,II-m,-c[9],INSERT_VALUES));
    119:     if (i<m-1) PetscCall(MatSetValue(A[4],II,II+m,-c[9],INSERT_VALUES));
    120:   }

    122:   /* assemble matrices */
    123:   for (i=0;i<NMAT;i++) PetscCall(MatAssemblyBegin(A[i],MAT_FINAL_ASSEMBLY));
    124:   for (i=0;i<NMAT;i++) PetscCall(MatAssemblyEnd(A[i],MAT_FINAL_ASSEMBLY));

    126:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    127:                 Create the eigensolver and solve the problem
    128:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    130:   PetscCall(PEPCreate(PETSC_COMM_WORLD,&pep));
    131:   PetscCall(PEPSetOptionsPrefix(pep,"check_"));
    132:   PetscCall(PEPAppendOptionsPrefix(pep,"myprefix_"));
    133:   PetscCall(PEPGetOptionsPrefix(pep,&prefix));
    134:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"PEP prefix is currently: %s\n\n",prefix));

    136:   PetscCall(PEPSetOperators(pep,NMAT,A));
    137:   PetscCall(PEPSetEigenvalueComparison(pep,MyEigenSort,NULL));
    138:   PetscCall(PEPSetFromOptions(pep));
    139:   PetscCall(PEPSolve(pep));

    141:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    142:                     Display solution and clean up
    143:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    145:   /* show detailed info unless -terse option is given by user */
    146:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
    147:   if (terse) PetscCall(PEPErrorView(pep,PEP_ERROR_BACKWARD,NULL));
    148:   else {
    149:     PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
    150:     PetscCall(PEPConvergedReasonView(pep,PETSC_VIEWER_STDOUT_WORLD));
    151:     PetscCall(PEPErrorView(pep,PEP_ERROR_BACKWARD,PETSC_VIEWER_STDOUT_WORLD));
    152:     PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
    153:   }
    154:   PetscCall(PEPDestroy(&pep));
    155:   for (i=0;i<NMAT;i++) PetscCall(MatDestroy(&A[i]));
    156:   PetscCall(SlepcFinalize());
    157:   return 0;
    158: }

    160: /*TEST

    162:    test:
    163:       args: -check_myprefix_pep_nev 4 -terse
    164:       requires: double

    166: TEST*/