Subversion Repositories slepc-dev

static char help[] = "Solves an eigensystem loaded from a file.\n\n"

  "This example works for both real and complex numbers.\n\n"

  "The command line options are:\n\n"

  "  -file <filename>, where <filename> = matrix file in PETSc binary form.\n\n";

#include "slepceps.h"

#undef __FUNCT__

#define __FUNCT__ "main"

int main( int argc, char **argv )

{

  Vec         *x;              /* basis vectors */

  Mat         A;               /* operator matrix */

  EPS         eps;             /* eigenproblem solver context */

  EPSType     type;

  PetscReal   *error, tol, re, im;

  PetscScalar *kr, *ki;

  int         nev, ierr, maxit, i, its, nconv;

  char        filename[256];

  PetscViewer viewer;

  PetscTruth  flg;

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

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

        Load the operator matrix that defines the eigensystem, Ax=kx

     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  ierr = PetscPrintf(PETSC_COMM_WORLD,"\nEigenproblem stored in file.\n\n");CHKERRQ(ierr);

  ierr = PetscOptionsGetString(PETSC_NULL,"-file",filename,256,&flg);CHKERRQ(ierr);

  if (!flg) {

    SETERRQ(1,"Must indicate a file name with the -file option.");

  }

#if defined(PETSC_USE_COMPLEX)

  ierr = PetscPrintf(PETSC_COMM_WORLD," Reading COMPLEX matrix from a binary file...\n");CHKERRQ(ierr);

#else

  ierr = PetscPrintf(PETSC_COMM_WORLD," Reading REAL matrix from a binary file...\n");CHKERRQ(ierr);

#endif

  ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,PETSC_BINARY_RDONLY,&viewer);CHKERRQ(ierr);

  ierr = MatLoad(viewer,MATMPIAIJ,&A);CHKERRQ(ierr);

  ierr = PetscViewerDestroy(viewer);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                Create the eigensolver and set various options

     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  /*

     Create eigensolver context

  */

  ierr = EPSCreate(PETSC_COMM_WORLD,&eps);CHKERRQ(ierr);

  /*

     Set operators. In this case, it is a standard eigenvalue problem

  */

  ierr = EPSSetOperators(eps,A,PETSC_NULL);CHKERRQ(ierr);

  /*

     Set solver parameters at runtime

  */

  ierr = EPSSetFromOptions(eps);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                      Solve the eigensystem

     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  ierr = EPSSolve(eps,&its);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD," Number of iterations of the method: %d\n",its);CHKERRQ(ierr);

  /*

     Optional: Get some information from the solver and display it

  */

  ierr = EPSGetType(eps,&type);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD," Solution method: %s\n\n",type);CHKERRQ(ierr);

  ierr = EPSGetDimensions(eps,&nev,PETSC_NULL);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD," Number of requested eigenvalues: %d\n",nev);CHKERRQ(ierr);

  ierr = EPSGetTolerances(eps,&tol,&maxit);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD," Stopping condition: tol=%.4g, maxit=%d\n",tol,maxit);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

                    Display solution and clean up

     - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

  /*

     Get number of converged eigenpairs

  */

  ierr = EPSGetConverged(eps,&nconv);CHKERRQ(ierr);

  ierr = PetscPrintf(PETSC_COMM_WORLD," Number of converged approximate eigenpairs: %d\n\n",nconv);CHKERRQ(ierr);

  if (nconv>0) {

    /*

       Get converged eigenpairs: i-th eigenvalue is stored in kr[i] (real part) and

       ki[i] (imaginary part), and the corresponding eigenvector is stored in x[i]

    */

    ierr = EPSGetSolution(eps,&kr,&ki,&x);CHKERRQ(ierr);

    /*

       Compute the relative error associated to each eigenpair

    */

    ierr = PetscMalloc(nconv*sizeof(PetscReal),&error);CHKERRQ(ierr);

    ierr = EPSComputeError(eps,error);CHKERRQ(ierr);

    /*

       Display eigenvalues and relative errors

    */

    ierr = PetscPrintf(PETSC_COMM_WORLD,

         "           k              ||Ax-kx||/|k|\n"

         "  --------------------- -----------------\n" );CHKERRQ(ierr);

    for( i=0; i<nconv; i++ ) {

#if defined(PETSC_USE_COMPLEX)

      re = PetscRealPart(kr[i]);

      im = PetscImaginaryPart(kr[i]);

#else

      re = kr[i];

      im = ki[i];

#endif

      if( im>0.0 ) ierr = PetscPrintf(PETSC_COMM_WORLD," % 6f + %6f i",re,im);

      else if( im<0.0 ) ierr = PetscPrintf(PETSC_COMM_WORLD," % 6f - %6f i",re,-im);

      else ierr = PetscPrintf(PETSC_COMM_WORLD,"       % 6f      ",re);

      CHKERRQ(ierr);

      ierr = PetscPrintf(PETSC_COMM_WORLD," % 12f\n",error[i]);CHKERRQ(ierr);

    }

    ierr = PetscPrintf(PETSC_COMM_WORLD,"\n" );CHKERRQ(ierr);

    ierr = PetscFree(error);CHKERRQ(ierr);

  }

  /*

     Free work space

  */

  ierr = EPSDestroy(eps);CHKERRQ(ierr);

  ierr = MatDestroy(A);CHKERRQ(ierr);

  ierr = SlepcFinalize();CHKERRQ(ierr);

  return 0;

}