Added Node module in parallel

Parallel_mpi/Parallel.ml

@@ -55,6 +55,26 @@ let broadcast_vec x =
   Lacaml.D.Vec.of_array a
 
 
+module Node = struct
+
+  let name = Unix.gethostname ()
+
+  let comm_node = 
+    Mpi.allgather (name, rank) Mpi.comm_world
+    |> Array.to_list
+    |> List.filter (fun (n, r) -> name = n)
+    |> List.map snd
+    |> Array.of_list
+    |> Mpi.(group_incl (comm_group comm_world))
+    |> Mpi.(comm_create comm_world)
+
+  let rank = 
+    Mpi.comm_rank comm_node
+
+  let master = rank = 0
+  
+end
+
 
 module Vec = struct