Subversion Repositories slepc-dev

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!  SLEPc - Scalable Library for Eigenvalue Problem Computations
!  Copyright (c) 2002-2010, Universidad 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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!
!  Program usage: mpirun -np n ex1f90 [-help] [-n <n>] [all SLEPc options] 
!
!  Description: Simple example that solves an eigensystem with the EPS object.
!  The standard symmetric eigenvalue problem to be solved corresponds to the 
!  Laplacian operator in 1 dimension. 
!
!  The command line options are:
!    -n <n>, where <n> = number of grid points = matrix size
!
! ---------------------------------------------------------------------- 
!
      program main

#include "finclude/petscdef.h"      
#include "finclude/slepcepsdef.h"
      use slepceps

      implicit none

! For usage without modules, uncomment the following lines and remove 
! the previous lines between 'program main' and 'implicit none'
!
!#include "finclude/petsc.h"
!#include "finclude/petscvec.h"
!#include "finclude/petscvec.h90"
!#include "finclude/petscmat.h"
!#include "finclude/petscmat.h90"
!#include "finclude/slepc.h"
!#include "finclude/slepceps.h"
!#include "finclude/slepceps.h90"

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!     Declarations
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!
!  Variables:
!     A      operator matrix
!     solver eigenproblem solver context

#if defined(PETSC_USE_FORTRAN_DATATYPES)
      type(Mat)      A
      type(EPS)      solver
#else
      Mat            A
      EPS            solver
#endif
      EPSType        tname
      PetscReal      tol, error
      PetscScalar    kr, ki
      PetscInt       n, i, Istart, Iend
      PetscInt       nev, maxit, its, nconv
      PetscInt       row(1), col(3)
      PetscMPIInt    rank
      PetscErrorCode ierr
      PetscTruth     flg
      PetscScalar    value(3)

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!     Beginning of program
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      call SlepcInitialize(PETSC_NULL_CHARACTER,ierr)
      call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr)
      n = 30
      call PetscOptionsGetInt(PETSC_NULL_CHARACTER,'-n',n,flg,ierr)

      if (rank .eq. 0) then
        write(*,100) n
      endif
 100  format (/'1-D Laplacian Eigenproblem, n =',I4,' (Fortran)')

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!     Compute the operator matrix that defines the eigensystem, Ax=kx
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      call MatCreate(PETSC_COMM_WORLD,A,ierr)
      call MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n,ierr)
      call MatSetFromOptions(A,ierr)

      call MatGetOwnershipRange(A,Istart,Iend,ierr)
      if (Istart .eq. 0) then 
        row(1) = 0
        col(1) = 0
        col(2) = 1
        value(1) =  2.0
        value(2) = -1.0
        call MatSetValues(A,1,row,2,col,value,INSERT_VALUES,ierr)
        Istart = Istart+1
      endif
      if (Iend .eq. n) then 
        row(1) = n-1
        col(1) = n-2
        col(2) = n-1
        value(1) = -1.0
        value(2) =  2.0
        call MatSetValues(A,1,row,2,col,value,INSERT_VALUES,ierr)
        Iend = Iend-1
      endif
      value(1) = -1.0
      value(2) =  2.0
      value(3) = -1.0
      do i=Istart,Iend-1
        row(1) = i
        col(1) = i-1
        col(2) = i
        col(3) = i+1
        call MatSetValues(A,1,row,3,col,value,INSERT_VALUES,ierr)
      enddo

      call MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY,ierr)
      call MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY,ierr)

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!     Create the eigensolver and display info
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!     ** Create eigensolver context
      call EPSCreate(PETSC_COMM_WORLD,solver,ierr)

!     ** Set operators. In this case, it is a standard eigenvalue problem
      call EPSSetOperators(solver,A,PETSC_NULL_OBJECT,ierr)
      call EPSSetProblemType(solver,EPS_HEP,ierr)

!     ** Set solver parameters at runtime
      call EPSSetFromOptions(solver,ierr)

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!     Solve the eigensystem
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      call EPSSolve(solver,ierr) 
      call EPSGetIterationNumber(solver,its,ierr)
      if (rank .eq. 0) then
        write(*,110) its
      endif
 110  format (/' Number of iterations of the method:',I4)
  
!     ** Optional: Get some information from the solver and display it
      call EPSGetType(solver,tname,ierr)
      if (rank .eq. 0) then
        write(*,120) tname
      endif
 120  format (' Solution method: ',A)
      call EPSGetDimensions(solver,nev,PETSC_NULL_INTEGER,              &
                            PETSC_NULL_INTEGER,ierr)
      if (rank .eq. 0) then
        write(*,130) nev
      endif
 130  format (' Number of requested eigenvalues:',I4)
      call EPSGetTolerances(solver,tol,maxit,ierr)
      if (rank .eq. 0) then
        write(*,140) tol, maxit
      endif
 140  format (' Stopping condition: tol=',1P,E10.4,', maxit=',I4)

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!     Display solution and clean up
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!     ** Get number of converged eigenpairs
      call EPSGetConverged(solver,nconv,ierr)
      if (rank .eq. 0) then
        write(*,150) nconv
      endif
 150  format (' Number of converged eigenpairs:',I4/)

!     ** Display eigenvalues and relative errors
      if (nconv.gt.0) then
        if (rank .eq. 0) then
          write(*,*) '         k          ||Ax-kx||/||kx||'
          write(*,*) ' ----------------- ------------------'
        endif
        do i=0,nconv-1
!         ** Get converged eigenpairs: i-th eigenvalue is stored in kr 
!         ** (real part) and ki (imaginary part)
          call EPSGetEigenpair(solver,i,kr,ki,PETSC_NULL_OBJECT,        &
     &                         PETSC_NULL_OBJECT,ierr)

!         ** Compute the relative error associated to each eigenpair
          call EPSComputeRelativeError(solver,i,error,ierr)
          if (rank .eq. 0) then
            write(*,160) PetscRealPart(kr), error
          endif
 160      format (1P,'   ',E12.4,'       ',E12.4)

        enddo
        if (rank .eq. 0) then
          write(*,*)
        endif
      endif

!     ** Free work space
      call EPSDestroy(solver,ierr)
      call MatDestroy(A,ierr)

      call SlepcFinalize(ierr)
      end