static char help[]="This program illustrates the use of PETSc-fftw interface for real DFT\n";
#include <petscmat.h>
#include <fftw3-mpi.h>

extern PetscErrorCode InputTransformFFT(Mat,Vec,Vec);
extern PetscErrorCode OutputTransformFFT(Mat,Vec,Vec);
int main(int argc,char **args)
{
  PetscErrorCode ierr;
  PetscMPIInt    rank,size;
  PetscInt       N0=3,N1=3,N2=3,N=N0*N1*N2;
  PetscRandom    rdm;
  PetscScalar    a;
  PetscReal      enorm;
  Vec            x,y,z,input,output;
  PetscBool      view=PETSC_FALSE,use_interface=PETSC_TRUE;
  Mat            A;
  PetscInt       DIM, dim[3],vsize;
  PetscReal      fac;

  ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
#if defined(PETSC_USE_COMPLEX)
  SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers");
#endif

  ierr = MPI_Comm_size(PETSC_COMM_WORLD, &size);CHKERRMPI(ierr);
  ierr = MPI_Comm_rank(PETSC_COMM_WORLD, &rank);CHKERRMPI(ierr);

  ierr = PetscRandomCreate(PETSC_COMM_WORLD, &rdm);CHKERRQ(ierr);
  ierr = PetscRandomSetFromOptions(rdm);CHKERRQ(ierr);

  ierr = VecCreate(PETSC_COMM_WORLD,&input);CHKERRQ(ierr);
  ierr = VecSetSizes(input,PETSC_DECIDE,N);CHKERRQ(ierr);
  ierr = VecSetFromOptions(input);CHKERRQ(ierr);
  ierr = VecSetRandom(input,rdm);CHKERRQ(ierr);
  ierr = VecDuplicate(input,&output);CHKERRQ(ierr);
/*  ierr = VecGetSize(input,&vsize);CHKERRQ(ierr); */
/*  printf("Size of the input Vector is %d\n",vsize); */

  DIM    = 3;
  dim[0] = N0; dim[1] = N1; dim[2] = N2;

  ierr = MatCreateFFT(PETSC_COMM_WORLD,DIM,dim,MATFFTW,&A);CHKERRQ(ierr);
  ierr = MatCreateVecs(A,&x,&y);CHKERRQ(ierr);
  ierr = MatCreateVecs(A,&z,NULL);CHKERRQ(ierr);
  ierr = VecGetSize(y,&vsize);CHKERRQ(ierr);
  printf("The vector size from the main routine is %d\n",vsize);

  ierr = InputTransformFFT(A,input,x);CHKERRQ(ierr);
  ierr = MatMult(A,x,y);CHKERRQ(ierr);
  ierr = MatMultTranspose(A,y,z);CHKERRQ(ierr);
  ierr = OutputTransformFFT(A,z,output);CHKERRQ(ierr);

  fac  = 1.0/(PetscReal)N;
  ierr = VecScale(output,fac);CHKERRQ(ierr);

  ierr = VecAssemblyBegin(input);CHKERRQ(ierr);
  ierr = VecAssemblyEnd(input);CHKERRQ(ierr);
  ierr = VecAssemblyBegin(output);CHKERRQ(ierr);
  ierr = VecAssemblyEnd(output);CHKERRQ(ierr);

  ierr = VecView(input,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);
  ierr = VecView(output,PETSC_VIEWER_STDOUT_WORLD);CHKERRQ(ierr);

  ierr = VecAXPY(output,-1.0,input);CHKERRQ(ierr);
  ierr = VecNorm(output,NORM_1,&enorm);CHKERRQ(ierr);
/*  if (enorm > 1.e-14) { */
  if (rank == 0) {
    ierr = PetscPrintf(PETSC_COMM_SELF,"  Error norm of |x - z| %e\n",enorm);CHKERRQ(ierr);
  }
/*      } */

/* ierr = MatCreateVecs(A,&z,NULL);CHKERRQ(ierr); */
/*  printf("Vector size from ex148 %d\n",vsize); */
/*  ierr = PetscObjectSetName((PetscObject) x, "Real space vector");CHKERRQ(ierr); */
/*      ierr = PetscObjectSetName((PetscObject) y, "Frequency space vector");CHKERRQ(ierr); */
/*      ierr = PetscObjectSetName((PetscObject) z, "Reconstructed vector");CHKERRQ(ierr); */

  ierr = PetscFinalize();
  return ierr;

}