Line data    Source code

       1             : /*
       2             :    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
       3             :    SLEPc - Scalable Library for Eigenvalue Problem Computations
       4             :    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain
       5             : 
       6             :    This file is part of SLEPc.
       7             :    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
       8             :    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
       9             : */
      10             : 
      11             : static char help[] = "Tests multiple calls to SVDSolve changing ncv.\n\n"
      12             :   "The command line options are:\n"
      13             :   "  -n <n>, where <n> = matrix dimension.\n\n";
      14             : 
      15             : #include <slepcsvd.h>
      16             : 
      17             : /*
      18             :    This example computes the singular values of an nxn Grcar matrix,
      19             :    which is a nonsymmetric Toeplitz matrix:
      20             : 
      21             :               |  1  1  1  1               |
      22             :               | -1  1  1  1  1            |
      23             :               |    -1  1  1  1  1         |
      24             :               |       .  .  .  .  .       |
      25             :           A = |          .  .  .  .  .    |
      26             :               |            -1  1  1  1  1 |
      27             :               |               -1  1  1  1 |
      28             :               |                  -1  1  1 |
      29             :               |                     -1  1 |
      30             : 
      31             :  */
      32             : 
      33           6 : int main(int argc,char **argv)
      34             : {
      35           6 :   Mat            A;
      36           6 :   SVD            svd;
      37           6 :   PetscInt       N=30,Istart,Iend,i,col[5],nsv,ncv;
      38           6 :   PetscScalar    value[] = { -1, 1, 1, 1, 1 };
      39             : 
      40           6 :   PetscFunctionBeginUser;
      41           6 :   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
      42           6 :   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&N,NULL));
      43           6 :   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nSingular values of a Grcar matrix, n=%" PetscInt_FMT,N));
      44           6 :   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\n\n"));
      45             : 
      46             :   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      47             :         Generate the matrix
      48             :      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
      49             : 
      50           6 :   PetscCall(MatCreate(PETSC_COMM_WORLD,&A));
      51           6 :   PetscCall(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,N));
      52           6 :   PetscCall(MatSetFromOptions(A));
      53             : 
      54           6 :   PetscCall(MatGetOwnershipRange(A,&Istart,&Iend));
      55         186 :   for (i=Istart;i<Iend;i++) {
      56         180 :     col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
      57         180 :     if (i==0) PetscCall(MatSetValues(A,1,&i,4,col+1,value+1,INSERT_VALUES));
      58         180 :     else PetscCall(MatSetValues(A,1,&i,PetscMin(5,N-i+1),col,value,INSERT_VALUES));
      59             :   }
      60             : 
      61           6 :   PetscCall(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY));
      62           6 :   PetscCall(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY));
      63             : 
      64             :   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      65             :          Create the singular value solver and set the solution method
      66             :      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
      67             : 
      68           6 :   PetscCall(SVDCreate(PETSC_COMM_WORLD,&svd));
      69           6 :   PetscCall(SVDSetOperators(svd,A,NULL));
      70           6 :   PetscCall(SVDSetTolerances(svd,1e-6,1000));
      71           6 :   PetscCall(SVDSetWhichSingularTriplets(svd,SVD_LARGEST));
      72           6 :   PetscCall(SVDSetFromOptions(svd));
      73             : 
      74             :   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      75             :                       Compute the singular values
      76             :      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
      77             : 
      78             :   /* First solve */
      79           6 :   PetscCall(SVDSolve(svd));
      80           6 :   PetscCall(PetscPrintf(PETSC_COMM_WORLD," - - - First solve, default subspace dimension - - -\n"));
      81           6 :   PetscCall(SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL));
      82             : 
      83             :   /* Second solve */
      84           6 :   PetscCall(SVDGetDimensions(svd,&nsv,&ncv,NULL));
      85           6 :   PetscCall(SVDSetDimensions(svd,nsv,ncv+2,PETSC_DETERMINE));
      86           6 :   PetscCall(SVDSolve(svd));
      87           6 :   PetscCall(PetscPrintf(PETSC_COMM_WORLD," - - - Second solve, subspace of increased size - - -\n"));
      88           6 :   PetscCall(SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL));
      89             : 
      90             :   /* Free work space */
      91           6 :   PetscCall(SVDDestroy(&svd));
      92           6 :   PetscCall(MatDestroy(&A));
      93           6 :   PetscCall(SlepcFinalize());
      94             :   return 0;
      95             : }
      96             : 
      97             : /*TEST
      98             : 
      99             :    test:
     100             :       suffix: 1
     101             :       args: -svd_type {{lanczos trlanczos cross cyclic lapack randomized}} -svd_nsv 3 -svd_ncv 12
     102             :       requires: !single
     103             : 
     104             : TEST*/