source: palm/trunk/SOURCE/exchange_horiz.f90 @ 597

 SUBROUTINE exchange_horiz( ar )

!------------------------------------------------------------------------------!
! Current revisions:
! -----------------
! 
!
! Former revisions:
! -----------------
! $Id: exchange_horiz.f90 484 2010-02-05 07:36:54Z maronga $
!
! 75 2007-03-22 09:54:05Z raasch
! Special cases for additional gridpoints along x or y in case of non-cyclic
! boundary conditions are not regarded any more
!
! RCS Log replace by Id keyword, revision history cleaned up
!
! Revision 1.16  2006/02/23 12:19:08  raasch
! anz_yz renamed ngp_yz
!
! Revision 1.1  1997/07/24 11:13:29  raasch
! Initial revision
!
!
! Description:
! ------------
! Exchange of lateral boundary values (parallel computers) and cyclic
! lateral boundary conditions, respectively.
!------------------------------------------------------------------------------!

    USE control_parameters
    USE cpulog
    USE indices
    USE interfaces
    USE pegrid

    IMPLICIT NONE

#if defined( __parallel )
    INTEGER, DIMENSION(4)                 ::  req
    INTEGER, DIMENSION(MPI_STATUS_SIZE,4) ::  wait_stat
#endif

    REAL ::  ar(nzb:nzt+1,nys-1:nyn+1,nxl-1:nxr+1)


    CALL cpu_log( log_point_s(2), 'exchange_horiz', 'start' )

#if defined( __parallel )

!
!-- Exchange of lateral boundary values for parallel computers
    IF ( pdims(1) == 1  .OR.  mg_switch_to_pe0 )  THEN
!
!--    One-dimensional decomposition along y, boundary values can be exchanged
!--    within the PE memory
       IF ( bc_lr == 'cyclic' )  THEN
          ar(:,nys:nyn,nxl-1) = ar(:,nys:nyn,nxr)
          ar(:,nys:nyn,nxr+1) = ar(:,nys:nyn,nxl)
       ENDIF

    ELSE

       req = 0
!
!--    Send left boundary, receive right one
       CALL MPI_ISEND(                                                     &
               ar(nzb,nys-1,nxl), ngp_yz(grid_level), MPI_REAL, pleft,  0, &
                          comm2d, req(1), ierr )
       CALL MPI_IRECV(                                                       &
               ar(nzb,nys-1,nxr+1), ngp_yz(grid_level), MPI_REAL, pright, 0, &
                          comm2d, req(2), ierr )
!
!--    Send right boundary, receive left one
       CALL MPI_ISEND(                                                     &
               ar(nzb,nys-1,nxr), ngp_yz(grid_level), MPI_REAL, pright, 1, &
                          comm2d, req(3), ierr )
       CALL MPI_IRECV(                                                       &
               ar(nzb,nys-1,nxl-1), ngp_yz(grid_level), MPI_REAL, pleft,  1, &
                          comm2d, req(4), ierr )
       CALL MPI_WAITALL( 4, req, wait_stat, ierr )

    ENDIF


    IF ( pdims(2) == 1  .OR.  mg_switch_to_pe0 )  THEN
!
!--    One-dimensional decomposition along x, boundary values can be exchanged
!--    within the PE memory
       IF ( bc_ns == 'cyclic' )  THEN
          ar(:,nys-1,:) = ar(:,nyn,:)
          ar(:,nyn+1,:) = ar(:,nys,:)
       ENDIF

    ELSE

       req = 0
!
!--    Send front boundary, receive rear one
       CALL MPI_ISEND( ar(nzb,nys,nxl-1),   1, type_xz(grid_level), psouth, 0, &
                       comm2d, req(1), ierr )
       CALL MPI_IRECV( ar(nzb,nyn+1,nxl-1), 1, type_xz(grid_level), pnorth, 0, &
                       comm2d, req(2), ierr )
!
!--    Send rear boundary, receive front one
       CALL MPI_ISEND( ar(nzb,nyn,nxl-1),   1, type_xz(grid_level), pnorth, 1, &
                       comm2d, req(3), ierr )
       CALL MPI_IRECV( ar(nzb,nys-1,nxl-1), 1, type_xz(grid_level), psouth, 1, &
                       comm2d, req(4), ierr )
       call MPI_WAITALL( 4, req, wait_stat, ierr )

    ENDIF


#else

!
!-- Lateral boundary conditions in the non-parallel case
    IF ( bc_lr == 'cyclic' )  THEN
       ar(:,nys:nyn,nxl-1) = ar(:,nys:nyn,nxr)
       ar(:,nys:nyn,nxr+1) = ar(:,nys:nyn,nxl)
    ENDIF

    IF ( bc_ns == 'cyclic' )  THEN
       ar(:,nys-1,:) = ar(:,nyn,:)
       ar(:,nyn+1,:) = ar(:,nys,:)
    ENDIF

#endif

    CALL cpu_log( log_point_s(2), 'exchange_horiz', 'stop' )

 END SUBROUTINE exchange_horiz