mp_isendrecv_lv Subroutine

      SUBROUTINE mp_isendrecv_lv(msgin, dest, msgout, source, comm, send_request, &
                                             recv_request, tag)
      !! Non-blocking send and receive of a vector
      !!
      !! Implementation
      !! Calls mpi_isend and mpi_irecv.
      !! @note
      !! arrays can be pointers or assumed shape, but they must be contiguous!

         INTEGER(KIND=int_8), CONTIGUOUS, DIMENSION(:)      :: msgin
         !! Vector data to send
         INTEGER, INTENT(IN)                      :: dest
         !! Which process to send to
         INTEGER(KIND=int_8), CONTIGUOUS, DIMENSION(:)      :: msgout
         !! Receive data into this pointer
         INTEGER, INTENT(IN)                      :: source
         !! Process to receive from
         TYPE(mp_comm_type), INTENT(IN)           :: comm
         !! Message passing environment identifier
         TYPE(mp_request_type), INTENT(out)       :: send_request, recv_request
         !! Request handle for the send
         !! Request handle for the receive
         INTEGER, INTENT(in), OPTIONAL            :: tag
         !! tag to differentiate requests

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

         INTEGER                                  :: handle, ierr
#if defined(__parallel)
         INTEGER                                  :: msglen, my_tag
         INTEGER(KIND=int_8)                                :: foo
#endif

         ierr = 0
         CALL timeset(routineN, handle)

#if defined(__parallel)
         my_tag = 0
         IF (PRESENT(tag)) my_tag = tag

         msglen = SIZE(msgout, 1)
         IF (msglen > 0) THEN
            CALL mpi_irecv(msgout, msglen, MPI_INTEGER8, source, my_tag, &
                           comm%handle, recv_request%handle, ierr)
         ELSE
            CALL mpi_irecv(foo, msglen, MPI_INTEGER8, source, my_tag, &
                           comm%handle, recv_request%handle, ierr)
         END IF
         IF (ierr /= 0) CALL mp_stop(ierr, "mpi_irecv @ "//routineN)

         msglen = SIZE(msgin, 1)
         IF (msglen > 0) THEN
            CALL mpi_isend(msgin, msglen, MPI_INTEGER8, dest, my_tag, &
                           comm%handle, send_request%handle, ierr)
         ELSE
            CALL mpi_isend(foo, msglen, MPI_INTEGER8, dest, my_tag, &
                           comm%handle, send_request%handle, ierr)
         END IF
         IF (ierr /= 0) CALL mp_stop(ierr, "mpi_isend @ "//routineN)

         msglen = (msglen + SIZE(msgout, 1) + 1)/2
         CALL add_perf(perf_id=8, msg_size=msglen*int_8_size)
#else
         MARK_USED(dest)
         MARK_USED(source)
         MARK_USED(comm)
         MARK_USED(tag)
         send_request = mp_request_null
         recv_request = mp_request_null
         msgout = msgin
#endif
         CALL timestop(handle)
      END SUBROUTINE mp_isendrecv_lv