mg_restrict_buffer_size Subroutine

  subroutine mg_restrict_buffer_size(mg, n_send, n_recv, dsize)
    type(mg_t), intent(inout) :: mg
    integer, intent(out)      :: n_send(0:mg%n_cpu-1)
    integer, intent(out)      :: n_recv(0:mg%n_cpu-1)
    integer, intent(out)      :: dsize
    integer :: n_out(0:mg%n_cpu-1, mg%first_normal_lvl:mg%highest_lvl)
    integer :: n_in(0:mg%n_cpu-1, mg%first_normal_lvl:mg%highest_lvl)
    integer                   :: lvl, i, id, p_id, p_rank
    integer                   :: i_c, c_id, c_rank, min_lvl

    n_out(:, :) = 0
    n_in(:, :)  = 0
    min_lvl = max(mg%lowest_lvl+1, mg%first_normal_lvl)

    do lvl = min_lvl, mg%highest_lvl
       ! Number of messages to receive (at lvl-1)
       do i = 1, size(mg%lvls(lvl-1)%my_parents)
          id = mg%lvls(lvl-1)%my_parents(i)
          do i_c = 1, mg_num_children
             c_id = mg%boxes(id)%children(i_c)

             if (c_id > mg_no_box) then
                c_rank = mg%boxes(c_id)%rank
                if (c_rank /= mg%my_rank) then
                   n_in(c_rank, lvl) = n_in(c_rank, lvl) + 1
                end if
             end if
          end do
       end do

       ! Number of messages to send
       do i = 1, size(mg%lvls(lvl)%my_ids)
          id = mg%lvls(lvl)%my_ids(i)

          p_id = mg%boxes(id)%parent
          p_rank = mg%boxes(p_id)%rank
          if (p_rank /= mg%my_rank) then
             n_out(p_rank, lvl) = n_out(p_rank, lvl) + 1
          end if

       end do
    end do

    allocate(mg%comm_restrict%n_send(0:mg%n_cpu-1,&
        mg%first_normal_lvl:mg%highest_lvl))
    allocate(mg%comm_restrict%n_recv(0:mg%n_cpu-1,&
        mg%first_normal_lvl:mg%highest_lvl))
    mg%comm_restrict%n_send = n_out
    mg%comm_restrict%n_recv = n_in

    dsize  = (mg%box_size/2)**3
    n_send = maxval(n_out, dim=2)
    n_recv = maxval(n_in, dim=2)
  end subroutine mg_restrict_buffer_size