mp_comm_split_direct Subroutine

   SUBROUTINE mp_comm_split_direct(comm, sub_comm, color, key)
      !! the direct way to split a communicator each color is a sub_comm,
      !! the rank order is accoring to the order in the orig comm

      INTEGER, INTENT(in)                                :: comm
      INTEGER, INTENT(OUT)                               :: sub_comm
      INTEGER, INTENT(in)                                :: color
      INTEGER, INTENT(in), OPTIONAL                      :: key

      CHARACTER(LEN=*), PARAMETER :: routineN = 'mp_comm_split_direct'

      INTEGER                                            :: handle, ierr, my_key

      ierr = 0
      CALL timeset(routineN, handle)

      my_key = 0
#if defined(__parallel)
      IF (PRESENT(key)) my_key = key
      CALL mpi_comm_split(comm, color, my_key, sub_comm, ierr)
      debug_comm_count = debug_comm_count + 1
      IF (ierr /= mpi_success) CALL mp_stop(ierr, routineN)
#else
      CALL mp_comm_dup(comm, sub_comm)
      MARK_USED(color)
      MARK_USED(key)
#endif
      CALL timestop(handle)

   END SUBROUTINE mp_comm_split_direct