/*
   - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
   SLEPc - Scalable Library for Eigenvalue Problem Computations
   Copyright (c) 2002-2012, Universitat Politecnica de Valencia, Spain

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

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

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

static char help[] = "Solves a standard eigensystem Ax=kx with the matrix loaded from a file.\n"
  "This example works for both real and complex numbers.\n\n"
  "The command line options are:\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)
{
  Mat            A;               /* operator matrix */
  EPS            eps;             /* eigenproblem solver context */
  const EPSType  type;
  PetscReal      tol;
  PetscInt       nev,maxit,its;
  char           filename[PETSC_MAX_PATH_LEN];
  PetscViewer    viewer;
  PetscBool      flg;
  PetscErrorCode ierr;

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

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
        Load the operator matrix that defines the eigensystem, Ax=kx
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  ierr = PetscPrintf(PETSC_COMM_WORLD,"\nEigenproblem stored in file.\n\n");CHKERRQ(ierr);
  ierr = PetscOptionsGetString(PETSC_NULL,"-file",filename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
  if (!flg) SETERRQ(PETSC_COMM_WORLD,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,FILE_MODE_READ,&viewer);CHKERRQ(ierr);
  ierr = MatCreate(PETSC_COMM_WORLD,&A);CHKERRQ(ierr);
  ierr = MatSetFromOptions(A);CHKERRQ(ierr);
  ierr = MatLoad(A,viewer);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);

  /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
                Create the eigensolver and set various options
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  /* 
     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
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  ierr = EPSSolve(eps);CHKERRQ(ierr);
  ierr = EPSGetIterationNumber(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,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
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  ierr = EPSPrintSolution(eps,PETSC_NULL);CHKERRQ(ierr);
  ierr = EPSDestroy(&eps);CHKERRQ(ierr);
  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = SlepcFinalize();CHKERRQ(ierr);
  return 0;
}