subroutine create_MPI_data_type(nx,ny,nz,locnx,locnz,
     *                                twoslice,subslice,myid,comm)
 
c     Routine to create a specialized data type for MPI data swaps
c     between processors. See real and complex data maps for details.
 
      implicit none
#include "mpif.h"
      integer nx,ny,nz,locnx,locnz
      integer myid,comm,ierr
      integer sizeofreal,oneslice,twoslice,subslice

      call MPI_TYPE_EXTENT(MPI_REAL,sizeofreal,ierr)


c     data type for 1d section of basic data slice: 2*locnx
      call MPI_TYPE_VECTOR(2*locnx,1,1,MPI_REAL,oneslice,ierr)

c     data type for 2d section of basic data slice: ny+1 1d sections
      call MPI_TYPE_HVECTOR(ny+1,1,(nx+2)*sizeofreal,oneslice,twoslice,ierr)
      if( myid .eq. 0 ) then
       if( ierr .ne. 0 ) write(6,*) ' TYPE_HVECTOR twoslice failure'
      endif
      call MPI_TYPE_COMMIT(twoslice,ierr)

c     data type for 3d section of basic data slice: locnz 2d sections
      call MPI_TYPE_HVECTOR(locnz,1,(nx+2)*(ny+1)*sizeofreal,
     *                      twoslice,subslice,ierr)
      if( myid .eq. 0 ) then
       if( ierr .ne. 0 ) write(6,*) ' TYPE_HVECTOR subslice failure'
      endif
      call MPI_TYPE_COMMIT(subslice,ierr)

      return
      end