mp_isum_iv Subroutine

      SUBROUTINE mp_isum_iv(msg, gid, request)
      !! Element-wise sum of a rank-1 array on all processes.
      !! @note see mp_sum_i

         INTEGER(KIND=int_4), CONTIGUOUS, INTENT(INOUT)     :: msg(:)
         !! Vector to sum and result
         INTEGER, INTENT(IN)                      :: gid
         INTEGER, INTENT(INOUT)                   :: request

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

         INTEGER                                  :: handle, ierr
#if defined(__parallel)
         INTEGER                                  :: msglen
#endif

         ierr = 0
         CALL timeset(routineN, handle)

#if defined(__parallel)
         msglen = SIZE(msg)
         IF (msglen > 0) THEN
            CALL mpi_iallreduce(MPI_IN_PLACE, msg, msglen, MPI_INTEGER, MPI_SUM, gid, request, ierr)
            IF (ierr /= 0) CALL mp_stop(ierr, "mpi_iallreduce @ "//routineN)
         ELSE
            request = mp_request_null
         END IF
         CALL add_perf(perf_id=23, msg_size=msglen*int_4_size)
#else
         MARK_USED(msg)
         MARK_USED(gid)
         request = mp_request_null
#endif
         CALL timestop(handle)
      END SUBROUTINE mp_isum_iv