!=======================================================================
! RCS Header:
!   Revision     [$Revision: 1.2.2.1 $]     Named [$Name: release#2_9_b5 $]
!   Last checkin [$Date: 2001/12/06 10:14:18 $]
!   Author       [$Author: frpb $]
!=======================================================================

! *****************************COPYRIGHT*******************************
! (c) CROWN COPYRIGHT 2001, Met Office, All Rights Reserved.           
! Please refer to Copyright file in top level GCOM directory
!                 for further details
! *****************************COPYRIGHT*******************************

#include "gcg_prolog.h"    

      INTEGER FUNCTION GCG_ME (GID)
!     ******************************************************************
!     * Purpose:
!     *  
!     *  Return the rank of my node in this group, in the 
!     *  range 0...groupsize(GID)-1 or -1 of invalid GID / not a member.
!     *
!     * Input:
!     *  GID     - processor group ID 
!     *
!     * Output:
!     *
!     * NOTES:       
!     * 
!     ******************************************************************

      IMPLICIT NONE
      INTEGER GID

#if defined(SHM_SRC)
#include "gcg__grstore_common.h"

      INTEGER IGID, ILOC, ME, GC_ME
#endif
#if defined(MPI_SRC)
      INCLUDE 'mpif.h'
      INTEGER ISTAT, IGID, GRANK
#endif


#if defined(SHM_SRC)
      IF (GID .EQ. GCG__ALLGROUP) THEN
         GCG_ME = GC_ME()
         RETURN
      ELSE IF (GID .GT. GCG__ALLGROUP) THEN
         DO IGID = 1, MAX_GROUP
            IF (GR_ID(IGID) .EQ. GID) THEN
               ME = GC_ME()
               DO ILOC = GR_LOC(IGID), GR_LOC(IGID)+GR_SZ(IGID)-1
                  IF (ME .EQ. GR_MEM(ILOC)) THEN
                     GCG_ME = ILOC - GR_LOC(IGID)
                     RETURN
                  ENDIF
               ENDDO
            ENDIF
         ENDDO
      ENDIF

      GCG_ME = -1
#endif

#if defined(MPI_SRC)
      IF (GID .EQ. GCG__ALLGROUP) THEN
         IGID = MPI_COMM_WORLD
      ELSE
         IGID = GID
      ENDIF
      CALL MPI_COMM_RANK(IGID, GRANK, ISTAT)
      GCG_ME = GRANK
#endif

#if defined(SERIAL_SRC)
      GCG_ME = 0
#endif

      RETURN
      END