Date: 2022-03-31T15:29:22+00:00

Actual source code: test6.c
slepc-3.17.0 2022-03-31
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      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[] = "SVD via the cross-product matrix with a user-provided EPS.\n\n"
     12:   "The command line options are:\n"
     13:   "  -m <m>, where <m> = matrix rows.\n"
     14:   "  -n <n>, where <n> = matrix columns (defaults to m+2).\n\n";

     16: #include <slepcsvd.h>

     18: /*
     19:    This example computes the singular values of a rectangular bidiagonal matrix

     21:               |  1  2                     |
     22:               |     1  2                  |
     23:               |        1  2               |
     24:           A = |          .  .             |
     25:               |             .  .          |
     26:               |                1  2       |
     27:               |                   1  2    |
     28:  */

     30: int main(int argc,char **argv)
     31: {
     32:   Mat            A;
     33:   SVD            svd;
     34:   EPS            eps;
     35:   ST             st;
     36:   KSP            ksp;
     37:   PC             pc;
     38:   PetscInt       m=20,n,Istart,Iend,i,col[2];
     39:   PetscScalar    value[] = { 1, 2 };
     40:   PetscBool      flg,expmat;

     42:   SlepcInitialize(&argc,&argv,(char*)0,help);
     43:   PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);
     44:   PetscOptionsGetInt(NULL,NULL,"-n",&n,&flg);
     45:   if (!flg) n=m+2;
     46:   PetscPrintf(PETSC_COMM_WORLD,"\nRectangular bidiagonal matrix, m=%" PetscInt_FMT " n=%" PetscInt_FMT "\n\n",m,n);

     48:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     49:         Generate the matrix
     50:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     52:   MatCreate(PETSC_COMM_WORLD,&A);
     53:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,m,n);
     54:   MatSetFromOptions(A);
     55:   MatSetUp(A);
     56:   MatGetOwnershipRange(A,&Istart,&Iend);
     57:   for (i=Istart;i<Iend;i++) {
     58:     col[0]=i; col[1]=i+1;
     59:     if (i<n-1) MatSetValues(A,1,&i,2,col,value,INSERT_VALUES);
     60:     else if (i==n-1) MatSetValue(A,i,col[0],value[0],INSERT_VALUES);
     61:   }
     62:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     63:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

     65:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     66:         Create a standalone EPS with appropriate settings
     67:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     69:   EPSCreate(PETSC_COMM_WORLD,&eps);
     70:   EPSGetST(eps,&st);
     71:   STSetType(st,STSINVERT);
     72:   STGetKSP(st,&ksp);
     73:   KSPSetType(ksp,KSPBCGS);
     74:   KSPGetPC(ksp,&pc);
     75:   PCSetType(pc,PCJACOBI);
     76:   EPSSetFromOptions(eps);

     78:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     79:         Compute singular values
     80:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     82:   SVDCreate(PETSC_COMM_WORLD,&svd);
     83:   SVDSetOperators(svd,A,NULL);
     84:   SVDSetType(svd,SVDCROSS);
     85:   SVDCrossSetEPS(svd,eps);
     86:   SVDSetWhichSingularTriplets(svd,SVD_SMALLEST);
     87:   SVDSetFromOptions(svd);
     88:   PetscObjectTypeCompare((PetscObject)svd,SVDCROSS,&flg);
     89:   if (flg) {
     90:     SVDCrossGetExplicitMatrix(svd,&expmat);
     91:     if (expmat) PetscPrintf(PETSC_COMM_WORLD," Using explicit matrix with cross solver\n");
     92:   }
     93:   SVDSolve(svd);

     95:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     96:                     Display solution and clean up
     97:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
     98:   SVDErrorView(svd,SVD_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
     99:   SVDDestroy(&svd);
    100:   EPSDestroy(&eps);
    101:   MatDestroy(&A);
    102:   SlepcFinalize();
    103:   return 0;
    104: }

    106: /*TEST

    108:    testset:
    109:       output_file: output/test6_1.out
    110:       test:
    111:          suffix: 1_subspace
    112:          args: -eps_type subspace
    113:       test:
    114:          suffix: 1_lobpcg
    115:          args: -eps_type lobpcg -st_type precond
    116:       test:
    117:          suffix: 2_cuda
    118:          args: -eps_type subspace -mat_type aijcusparse
    119:          requires: cuda

    121: TEST*/