Actual source code: ex14.c

  1: /*
  2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3:       SLEPc - Scalable Library for Eigenvalue Problem Computations
  4:       Copyright (c) 2002-2007, Universidad Politecnica de Valencia, Spain

  6:       This file is part of SLEPc. See the README file for conditions of use
  7:       and additional information.
  8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  9: */

 11: static char help[] = "Solves a singular value problem with the matrix loaded from a file.\n"
 12:   "This example works for both real and complex numbers.\n\n"
 13:   "The command line options are:\n"
 14:   "  -file <filename>, where <filename> = matrix file in PETSc binary form.\n\n";

 16:  #include slepcsvd.h

 20: int main( int argc, char **argv )
 21: {
 22:   Mat                  A;                  /* operator matrix */
 23:   SVD                  svd;                  /* singular value problem solver context */
 24:   SVDType              type;
 25:   PetscReal            error, tol, sigma;
 27:   int                  nsv, maxit, i, its, nconv;
 28:   char                 filename[256];
 29:   PetscViewer          viewer;
 30:   PetscTruth           flg;


 33:   SlepcInitialize(&argc,&argv,(char*)0,help);

 35:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 36:         Load the operator matrix that defines the singular value problem
 37:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 39:   PetscPrintf(PETSC_COMM_WORLD,"\nSingular value problem stored in file.\n\n");
 40:   PetscOptionsGetString(PETSC_NULL,"-file",filename,256,&flg);
 41:   if (!flg) {
 42:     SETERRQ(1,"Must indicate a file name with the -file option.");
 43:   }

 45: #if defined(PETSC_USE_COMPLEX)
 46:   PetscPrintf(PETSC_COMM_WORLD," Reading COMPLEX matrix from a binary file...\n");
 47: #else
 48:   PetscPrintf(PETSC_COMM_WORLD," Reading REAL matrix from a binary file...\n");
 49: #endif
 50:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer);
 51:   MatLoad(viewer,MATAIJ,&A);
 52:   PetscViewerDestroy(viewer);

 54:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 55:                 Create the singular value solver and set various options
 56:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 58:   /* 
 59:      Create singular value solver context
 60:   */
 61:   SVDCreate(PETSC_COMM_WORLD,&svd);

 63:   /* 
 64:      Set operator
 65:   */
 66:   SVDSetOperator(svd,A);

 68:   /*
 69:      Set solver parameters at runtime
 70:   */
 71:   SVDSetFromOptions(svd);

 73:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 74:                       Solve the singular value system
 75:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 77:   SVDSolve(svd);
 78:   SVDGetIterationNumber(svd, &its);
 79:   PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);

 81:   /*
 82:      Optional: Get some information from the solver and display it
 83:   */
 84:   SVDGetType(svd,&type);
 85:   PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);
 86:   SVDGetDimensions(svd,&nsv,PETSC_NULL);
 87:   PetscPrintf(PETSC_COMM_WORLD," Number of requested singular values: %d\n",nsv);
 88:   SVDGetTolerances(svd,&tol,&maxit);
 89:   PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);

 91:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
 92:                     Display solution and clean up
 93:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

 95:   /* 
 96:      Get number of converged singular triplets
 97:   */
 98:   SVDGetConverged(svd,&nconv);
 99:   PetscPrintf(PETSC_COMM_WORLD," Number of converged approximate singular triplets: %d\n\n",nconv);

101:   if (nconv>0) {
102:     /*
103:        Display singular values and relative errors
104:     */
105:     PetscPrintf(PETSC_COMM_WORLD,
106:          "          sigma           residual norm\n"
107:          "  --------------------- ------------------\n" );
108:     for( i=0; i<nconv; i++ ) {
109:       /* 
110:          Get converged singular triplets: i-th singular value is stored in sigma
111:       */
112:       SVDGetSingularTriplet(svd,i,&sigma,PETSC_NULL,PETSC_NULL);

114:       /*
115:          Compute the error associated to each singular triplet 
116:       */
117:       SVDComputeRelativeError(svd,i,&error);
118:       PetscPrintf(PETSC_COMM_WORLD,"       % 6f      ",sigma);
119:       PetscPrintf(PETSC_COMM_WORLD," % 12g\n",error);
120:     }
121:     PetscPrintf(PETSC_COMM_WORLD,"\n" );
122:   }
123: 
124:   /* 
125:      Free work space
126:   */
127:   SVDDestroy(svd);
128:   MatDestroy(A);
129:   SlepcFinalize();
130:   return 0;
131: }