Date: 2016-03-29T14:58:43+00:00

Actual source code: test3.c
slepc-3.6.3 2016-03-29
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-2015, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.

      8:    SLEPc is free software: you can redistribute it and/or modify it under  the
      9:    terms of version 3 of the GNU Lesser General Public License as published by
     10:    the Free Software Foundation.

     12:    SLEPc  is  distributed in the hope that it will be useful, but WITHOUT  ANY
     13:    WARRANTY;  without even the implied warranty of MERCHANTABILITY or  FITNESS
     14:    FOR  A  PARTICULAR PURPOSE. See the GNU Lesser General Public  License  for
     15:    more details.

     17:    You  should have received a copy of the GNU Lesser General  Public  License
     18:    along with SLEPc. If not, see <http://www.gnu.org/licenses/>.
     19:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     20: */

     22: static char help[] = "Test SVD with user-provided initial vectors.\n\n"
     23:   "The command line options are:\n"
     24:   "  -n <n>, where <n> = row dimension.\n"
     25:   "  -m <m>, where <m> = column dimension.\n\n";

     27: #include <slepcsvd.h>

     29: /*
     30:    This example computes the singular values of a rectangular nxm Grcar matrix:

     32:               |  1  1  1  1               |
     33:               | -1  1  1  1  1            |
     34:               |    -1  1  1  1  1         |
     35:           A = |       .  .  .  .  .       |
     36:               |          .  .  .  .  .    |
     37:               |            -1  1  1  1  1 |
     38:               |               -1  1  1  1 |

     40:  */

     44: int main(int argc,char **argv)
     45: {
     46:   Mat            A;               /* Grcar matrix */
     47:   SVD            svd;             /* singular value solver context */
     48:   Vec            v0,w0;           /* initial vectors */
     49:   PetscInt       N=35,M=30,Istart,Iend,i,col[5];
     50:   PetscScalar    value[] = { -1, 1, 1, 1, 1 };

     53:   SlepcInitialize(&argc,&argv,(char*)0,help);
     54:   PetscOptionsGetInt(NULL,"-n",&N,NULL);
     55:   PetscOptionsGetInt(NULL,"-m",&M,NULL);
     56:   PetscPrintf(PETSC_COMM_WORLD,"\nSVD of a rectangular Grcar matrix, %Dx%D\n\n",N,M);

     58:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     59:         Generate the matrix
     60:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     62:   MatCreate(PETSC_COMM_WORLD,&A);
     63:   MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,N,M);
     64:   MatSetFromOptions(A);
     65:   MatSetUp(A);

     67:   MatGetOwnershipRange(A,&Istart,&Iend);
     68:   for (i=Istart;i<Iend;i++) {
     69:     col[0]=i-1; col[1]=i; col[2]=i+1; col[3]=i+2; col[4]=i+3;
     70:     if (i==0) {
     71:       MatSetValues(A,1,&i,PetscMin(4,M-i+1),col+1,value+1,INSERT_VALUES);
     72:     } else {
     73:       MatSetValues(A,1,&i,PetscMin(5,M-i+1),col,value,INSERT_VALUES);
     74:     }
     75:   }
     76:   MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
     77:   MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);

     79:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     80:              Create the SVD context and solve the problem
     81:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     83:   SVDCreate(PETSC_COMM_WORLD,&svd);
     84:   SVDSetOperator(svd,A);
     85:   SVDSetFromOptions(svd);

     87:   /*
     88:      Set the initial vectors. This is optional, if not done the initial
     89:      vectors are set to random values
     90:   */
     91:   MatCreateVecs(A,&v0,&w0);
     92:   VecSet(v0,1.0);
     93:   VecSet(w0,1.0);
     94:   SVDSetInitialSpace(svd,1,&v0);
     95:   SVDSetInitialSpaceLeft(svd,1,&w0);

     97:   /*
     98:      Compute solution
     99:   */
    100:   SVDSolve(svd);
    101:   SVDErrorView(svd,SVD_ERROR_RELATIVE,NULL);

    103:   /*
    104:      Free work space
    105:   */
    106:   VecDestroy(&v0);
    107:   VecDestroy(&w0);
    108:   SVDDestroy(&svd);
    109:   MatDestroy(&A);
    110:   SlepcFinalize();
    111:   return 0;
    112: }