/* This program illustrates use of parallel real FFT */
static char help[]="This program illustrates the use of parallel real multi-dimensional fftw (without PETSc interface)";
#include <petscmat.h>
#include <fftw3.h>
#include <fftw3-mpi.h>

int main(int argc,char **args)
{
  ptrdiff_t      N0=2,N1=2,N2=2,N3=2,dim[4],N,D;
  fftw_plan      bplan,fplan;
  fftw_complex   *out;
  double         *in1,*in2;
  ptrdiff_t      alloc_local,local_n0,local_0_start;
  ptrdiff_t      local_n1,local_1_start;
  PetscInt       i,j,indx[100],n1;
  PetscInt       size,rank,n,*in,N_factor;
  PetscScalar    *data_fin,value1,one=1.0,zero=0.0;
  PetscScalar    a,*x_arr,*y_arr,*z_arr,enorm;
  Vec            fin,fout,fout1,x,y;
  PetscRandom    rnd;
  PetscErrorCode ierr;

  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. Your current scalar type is complex");
#endif
  ierr = MPI_Comm_size(PETSC_COMM_WORLD, &size);CHKERRMPI(ierr);
  ierr = MPI_Comm_rank(PETSC_COMM_WORLD, &rank);CHKERRMPI(ierr);

  PetscRandomCreate(PETSC_COMM_WORLD,&rnd);
  D     =4;
  dim[0]=N0;dim[1]=N1;dim[2]=N2;dim[3]=N3/2+1;

  alloc_local = fftw_mpi_local_size_transposed(D,dim,PETSC_COMM_WORLD,&local_n0,&local_0_start,&local_n1,&local_1_start);

  printf("The value alloc_local is %ld from process %d\n",alloc_local,rank);
  printf("The value local_n0 is %ld from process %d\n",local_n0,rank);
  printf("The value local_0_start is  %ld from process %d\n",local_0_start,rank);
  printf("The value local_n1 is  %ld from process %d\n",local_n1,rank);
  printf("The value local_1_start is  %ld from process %d\n",local_1_start,rank);

  /* Allocate space for input and output arrays  */

  in1=(double*)fftw_malloc(sizeof(double)*alloc_local*2);
  in2=(double*)fftw_malloc(sizeof(double)*alloc_local*2);
  out=(fftw_complex*)fftw_malloc(sizeof(fftw_complex)*alloc_local);

  N=2*N0*N1*N2*(N3/2+1);N_factor=N0*N1*N2*N3;
  n=2*local_n0*N1*N2*(N3/2+1);n1=local_n1*N0*2*N1*N2;

/*    printf("The value N is  %d from process %d\n",N,rank); */
/*    printf("The value n is  %d from process %d\n",n,rank); */
/*    printf("The value n1 is  %d from process %d\n",n1,rank); */
  /* Creating data vector and accompanying array with VeccreateMPIWithArray */
  ierr = VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,N,(PetscScalar*)in1,&fin);CHKERRQ(ierr);
  ierr = VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,N,(PetscScalar*)out,&fout);CHKERRQ(ierr);
  ierr = VecCreateMPIWithArray(PETSC_COMM_WORLD,1,n,N,(PetscScalar*)in2,&fout1);CHKERRQ(ierr);

/*    VecGetSize(fin,&size); */
/*    printf("The size is %d\n",size); */

  VecSet(fin,one);
/*    VecAssemblyBegin(fin); */
/*    VecAssemblyEnd(fin); */
/*    VecView(fin,PETSC_VIEWER_STDOUT_WORLD); */

  VecGetArray(fin,&x_arr);
  VecGetArray(fout1,&z_arr);
  VecGetArray(fout,&y_arr);

  dim[3]=N3;

  fplan=fftw_mpi_plan_dft_r2c(D,dim,(double*)x_arr,(fftw_complex*)y_arr,PETSC_COMM_WORLD,FFTW_ESTIMATE);
  bplan=fftw_mpi_plan_dft_c2r(D,dim,(fftw_complex*)y_arr,(double*)z_arr,PETSC_COMM_WORLD,FFTW_ESTIMATE);

  fftw_execute(fplan);
  fftw_execute(bplan);

  VecRestoreArray(fin,&x_arr);
  VecRestoreArray(fout1,&z_arr);
  VecRestoreArray(fout,&y_arr);

/*    a = 1.0/(PetscReal)N_factor; */
/*    ierr = VecScale(fout1,a);CHKERRQ(ierr); */

  VecAssemblyBegin(fout1);
  VecAssemblyEnd(fout1);

  VecView(fout1,PETSC_VIEWER_STDOUT_WORLD);

  fftw_destroy_plan(fplan);
  fftw_destroy_plan(bplan);
  fftw_free(in1); ierr = VecDestroy(&fin);CHKERRQ(ierr);
  fftw_free(out); ierr = VecDestroy(&fout);CHKERRQ(ierr);
  fftw_free(in2); ierr = VecDestroy(&fout1);CHKERRQ(ierr);

  ierr = PetscFinalize();
  return ierr;
}