Actual source code: test6.c

slepc-3.21.1 2024-04-26
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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:   PetscFunctionBeginUser;
 43:   PetscCall(SlepcInitialize(&argc,&argv,(char*)0,help));
 44:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL));
 45:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,&flg));
 46:   if (!flg) n=m+2;
 47:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nRectangular bidiagonal matrix, m=%" PetscInt_FMT " n=%" PetscInt_FMT "\n\n",m,n));

 49:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 50:         Generate the matrix
 51:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

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

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

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

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

 95:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 96:                     Display solution and clean up
 97:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 98:   PetscCall(SVDErrorView(svd,SVD_ERROR_NORM,PETSC_VIEWER_STDOUT_WORLD));
 99:   PetscCall(SVDDestroy(&svd));
100:   PetscCall(EPSDestroy(&eps));
101:   PetscCall(MatDestroy(&A));
102:   PetscCall(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*/