Actual source code: test6.c

slepc-3.18.1 2022-11-02
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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;

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

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

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

 66:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 67:         Create a standalone EPS with appropriate settings
 68:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 79:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 80:         Compute singular values
 81:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

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

 96:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 97:                     Display solution and clean up
 98:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
 99:   SVDErrorView(svd,SVD_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD);
100:   SVDDestroy(&svd);
101:   EPSDestroy(&eps);
102:   MatDestroy(&A);
103:   SlepcFinalize();
104:   return 0;
105: }

107: /*TEST

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

122: TEST*/