program cart_coords_example    ! mpirun -np 6 cart_coords_example
      implicit none
      integer nv, mv, i, j
      integer p, reorder, ierr, new_comm
      integer Iam, rank, ndim, root
      parameter (nv=3, mv=2, ndim=2, reorder=1)
      include "mpif.h"  !! This brings in pre-defined MPI constants, ...
      integer dims(ndim), coords(0:ndim-1)
      logical periods(ndim)

      data root/0/      !! designate root process to be process 0
      data periods/.true.,.false./  !! no circular shift permited in y-direction

c**Starts MPI processes ...
      call MPI_Init(ierr)                            !! starts MPI
      call MPI_Comm_rank(MPI_COMM_WORLD, Iam, ierr)  !! get current process id
      call MPI_Comm_size(MPI_COMM_WORLD, p, ierr)    !! get number of processes
c**create cartesian topology for processes
      dims(1) = nv      !! number of rows
      dims(2) = mv      !! number of columns
      call MPI_Cart_create(MPI_COMM_WORLD, ndim, dims, 
     &       periods, reorder, new_comm, ierr)

      if(Iam .eq. root) then
        write(*,*)'   rank       i       j'
        do rank=0,p-1
          call MPI_Cart_coords(new_comm, rank, ndim, coords, ierr)
          write(*,'(3i8)')rank, coords
        enddo
      endif

      call MPI_Finalize(ierr)                        !! let MPI finish up ...

      end