Added SharedMemory

Parallel_mpi/SharedMemory.ml

@@ -0,0 +1,23 @@
+let create ?(temp_dir="/dev/shm")  data_type  size_array =
+    let filename =
+      Parallel.Node.broadcast (lazy (Filename.temp_file ~temp_dir "4idx." ".tmp"))
+    in
+    at_exit (fun () -> try Sys.remove filename with _ -> ());
+
+    if Parallel.Node.master then
+      begin
+        let fd = Unix.openfile filename [Unix.O_RDWR] 0o600 in
+        let result =
+          Unix.map_file fd  data_type  Bigarray.fortran_layout  true  size_array
+        in
+        Bigarray.Genarray.fill result 0.;
+        Parallel.Node.barrier ();
+        result
+      end
+    else
+      begin
+        Parallel.Node.barrier ();
+        let fd = Unix.openfile filename [Unix.O_RDONLY] 0o600 in
+        Unix.map_file fd  data_type  Bigarray.fortran_layout  false  size_array
+      end
+