SUBROUTINE exchange_horiz_2d( ar )

!--------------------------------------------------------------------------------!
! This file is part of PALM.
!
! PALM is free software: you can redistribute it and/or modify it under the terms
! of the GNU General Public License as published by the Free Software Foundation,
! either version 3 of the License, or (at your option) any later version.
!
! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
! A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
!
! You should have received a copy of the GNU General Public License along with
! PALM. If not, see <http://www.gnu.org/licenses/>.
!
! Copyright 1997-2012  Leibniz University Hannover
!--------------------------------------------------------------------------------!
!
! Current revisions:
! -----------------
! 
!
! Former revisions:
! -----------------
! $Id: exchange_horiz_2d.f90 1093 2013-02-02 12:58:49Z witha $
!
! 1092 2013-02-02 11:24:22Z raasch
! unused variables removed
!
! 1036 2012-10-22 13:43:42Z raasch
! code put under GPL (PALM 3.9)
!
! 841 2012-02-28 12:29:49Z maronga
! Excluded routine from compilation of namelist_file_check
!
! 707 2011-03-29 11:39:40Z raasch
! bc_lr/ns replaced by bc_lr/ns_cyc
! 
! 702 2011-03-24 19:33:15Z suehring
! Bugfix in declaration of ar in exchange_horiz_2d_int and number of MPI-blocks
! in MPI_SENDRECV().
!
! 667 2010-12-23 12:06:00Z suehring/gryschka
! Dynamic exchange of ghost points with nbgp, which depends on the advection
! scheme. Exchange between left and right PEs is now done with MPI-vectors.
!
! 73 2007-03-20 08:33:14Z raasch
! Neumann boundary conditions at inflow/outflow in case of non-cyclic boundary
! conditions
!
! RCS Log replace by Id keyword, revision history cleaned up
!
! Revision 1.9  2006/05/12 19:15:52  letzel
! MPI_REAL replaced by MPI_INTEGER in exchange_horiz_2d_int
!
! Revision 1.1  1998/01/23 09:58:21  raasch
! Initial revision
!
!
! Description:
! ------------
! Exchange of lateral (ghost) boundaries (parallel computers) and cyclic
! boundary conditions, respectively, for 2D-arrays.
!------------------------------------------------------------------------------!

    USE control_parameters
    USE cpulog
    USE indices
    USE interfaces
    USE pegrid

    IMPLICIT NONE


    REAL ::  ar(nysg:nyng,nxlg:nxrg)
    INTEGER :: i

#if ! defined( __check )
    CALL cpu_log( log_point_s(13), 'exchange_horiz_2d', 'start' )

#if defined( __parallel )

!
!-- Exchange of lateral boundary values for parallel computers
    IF ( pdims(1) == 1 )  THEN

!
!--    One-dimensional decomposition along y, boundary values can be exchanged
!--    within the PE memory
       ar(:,nxlg:nxl-1) = ar(:,nxr-nbgp+1:nxr)
       ar(:,nxr+1:nxrg) = ar(:,nxl:nxl+nbgp-1)

    ELSE
!
!--    Send left boundary, receive right one

       CALL MPI_SENDRECV( ar(nysg,nxl), 1, type_y, pleft,  0,                 &
                          ar(nysg,nxr+1), 1, type_y, pright, 0,               &
                          comm2d, status, ierr )
!
!--    Send right boundary, receive left one
       CALL MPI_SENDRECV( ar(nysg,nxr+1-nbgp), 1, type_y, pright,  1,         &
                          ar(nysg,nxlg), 1, type_y, pleft,   1,               &
                          comm2d, status, ierr )
                          
     
    ENDIF

    IF ( pdims(2) == 1 )  THEN
!
!--    One-dimensional decomposition along x, boundary values can be exchanged
!--    within the PE memory
       ar(nysg:nys-1,:) = ar(nyn-nbgp+1:nyn,:)
       ar(nyn+1:nyng,:) = ar(nys:nys+nbgp-1,:)

    ELSE
!
!--    Send front boundary, receive rear one

       CALL MPI_SENDRECV( ar(nys,nxlg), 1, type_x, psouth, 0,                 &         
                          ar(nyn+1,nxlg), 1, type_x, pnorth, 0,               &
                          comm2d, status, ierr )
!
!--    Send rear boundary, receive front one
       CALL MPI_SENDRECV( ar(nyn+1-nbgp,nxlg), 1, type_x, pnorth, 1,          &
                          ar(nysg,nxlg), 1, type_x, psouth, 1,                &
                          comm2d, status, ierr )

    ENDIF

#else

!
!-- Lateral boundary conditions in the non-parallel case
    IF ( bc_lr_cyc )  THEN
       ar(:,nxlg:nxl-1) = ar(:,nxr-nbgp+1:nxr)
       ar(:,nxr+1:nxrg) = ar(:,nxl:nxl+nbgp-1)
    ENDIF

    IF ( bc_ns_cyc )  THEN
       ar(nysg:nys-1,:) = ar(nyn-nbgp+1:nyn,:)
       ar(nyn+1:nyng,:) = ar(nys:nys+nbgp-1,:)
    ENDIF


#endif

!
!-- Neumann-conditions at inflow/outflow in case of non-cyclic boundary
!-- conditions
    IF ( inflow_l .OR. outflow_l )  THEN
       DO i=nbgp, 1, -1
         ar(:,nxl-i) = ar(:,nxl)
       END DO
    END IF
    IF ( inflow_r .OR. outflow_r )  THEN 
       DO i=1, nbgp
          ar(:,nxr+i) = ar(:,nxr)
       END DO
    END IF
    IF ( inflow_s .OR. outflow_s )  THEN
       DO i=nbgp, 1, -1
         ar(nys-i,:) = ar(nys,:)
       END DO
    END IF
    IF ( inflow_n .OR. outflow_n )  THEN
       DO i=1, nbgp
         ar(nyn+i,:) = ar(nyn,:)
       END DO
    END IF
    CALL cpu_log( log_point_s(13), 'exchange_horiz_2d', 'stop' )

#endif
 END SUBROUTINE exchange_horiz_2d



 SUBROUTINE exchange_horiz_2d_int( ar )

!------------------------------------------------------------------------------!
! Description:
! ------------
! Exchange of lateral (ghost) boundaries (parallel computers) and cyclic
! boundary conditions, respectively, for 2D integer arrays.
!------------------------------------------------------------------------------!

    USE control_parameters
    USE cpulog
    USE indices
    USE interfaces
    USE pegrid

    IMPLICIT NONE

    INTEGER ::  ar(nysg:nyng,nxlg:nxrg)

#if ! defined( __check )
    CALL cpu_log( log_point_s(13), 'exchange_horiz_2d', 'start' )

#if defined( __parallel )

!
!-- Exchange of lateral boundary values for parallel computers
    IF ( pdims(1) == 1 )  THEN

!
!--    One-dimensional decomposition along y, boundary values can be exchanged
!--    within the PE memory
       ar(:,nxlg:nxl-1) = ar(:,nxr-nbgp+1:nxr)
       ar(:,nxr+1:nxrg) = ar(:,nxl:nxl+nbgp-1)


    ELSE
!
!--    Send left boundary, receive right one
       CALL MPI_SENDRECV( ar(nysg,nxl), 1, type_y_int, pleft,  0,             &
                          ar(nysg,nxr+1), 1, type_y_int, pright, 0,           &
                          comm2d, status, ierr )
!
!--    Send right boundary, receive left one
       CALL MPI_SENDRECV( ar(nysg,nxr+1-nbgp), 1, type_y_int, pright,  1,     &
                          ar(nysg,nxlg), 1, type_y_int, pleft,   1,           &
                          comm2d, status, ierr )

    ENDIF

    IF ( pdims(2) == 1 )  THEN
!
!--    One-dimensional decomposition along x, boundary values can be exchanged
!--    within the PE memory
       ar(nysg:nys-1,:) = ar(nyn+1-nbgp:nyn,:)
       ar(nyn+1:nyng,:) = ar(nys:nys-1+nbgp,:)


    ELSE
!
!--    Send front boundary, receive rear one
       CALL MPI_SENDRECV( ar(nys,nxlg), 1, type_x_int, psouth, 0,             &
                          ar(nyn+1,nxlg), 1, type_x_int, pnorth, 0,           &
                          comm2d, status, ierr )                          

!
!--    Send rear boundary, receive front one
       CALL MPI_SENDRECV( ar(nyn+1-nbgp,nxlg), 1, type_x_int, pnorth, 1,      &
                          ar(nysg,nxlg), 1, type_x_int, psouth, 1,            &
                          comm2d, status, ierr )

    ENDIF

#else

!
!-- Lateral boundary conditions in the non-parallel case
    IF ( bc_lr_cyc )  THEN
       ar(:,nxlg:nxl-1) = ar(:,nxr-nbgp+1:nxr)
       ar(:,nxr+1:nxrg) = ar(:,nxl:nxl+nbgp-1)
    ENDIF

    IF ( bc_ns_cyc )  THEN
       ar(nysg:nys-1,:) = ar(nyn+1-nbgp:nyn,:)
       ar(nyn+1:nyng,:) = ar(nys:nys-1+nbgp,:)
    ENDIF

#endif
    CALL cpu_log( log_point_s(13), 'exchange_horiz_2d', 'stop' )

#endif
 END SUBROUTINE exchange_horiz_2d_int