Use bytes instead of strings for internal buffers (#4)

This ensures compatibility with OCaml >= 4.06.
Changed opam package to request OCaml >= 4.02.3.

Changes

@@ -1,3 +1,11 @@
+Version 1.03:
+- Ensure compatibility with OCaml 4.06 and up by using bytes instead of strings for internal buffers.
+  The API does not change.
+  (Contributed by Anthony Scemama, review by Timothy Bourke)
+
+Version 1.02:
+- OPAM Packaging
+
 Version 1.01:
 - Relicensed under the LGPL
 - Modernized build and installation procedure.

collcomm.c

@@ -273,7 +273,7 @@ value caml_mpi_reduce_intarray(value data, value result, value op,
                                value root, value comm)
 {
   mlsize_t len = Wosize_val(data);
-  int i, myrank;
+  int myrank;
   /* Decode data at all nodes in place */
   caml_mpi_decode_intarray(data, len);
   /* Do the reduce */

mpi.ml

@@ -181,25 +181,25 @@ external barrier : communicator -> unit = "caml_mpi_barrier"
 
 (* Broadcast *)
 
-external broadcast_string: string -> int -> communicator -> unit
+external broadcast_bytes: bytes -> int -> communicator -> unit
 	 = "caml_mpi_broadcast"
 external broadcast_int: int -> int -> communicator -> int
 	 = "caml_mpi_broadcast_int"
 
 let broadcast v root comm =
   let myself = comm_rank comm in
   if myself = root then begin
-    let data = Marshal.to_string v [Marshal.Closures] in
-    ignore(broadcast_int (String.length data) root comm);
-    broadcast_string data root comm;
+    let data = Marshal.to_bytes v [Marshal.Closures] in
+    ignore(broadcast_int (Bytes.length data) root comm);
+    broadcast_bytes data root comm;
     v
   end else begin
     (* Other processes receive length, allocate buffer, receive data,
        and unmarshal it. *)
     let len = broadcast_int 0 root comm in
-    let data = String.create len in
-    broadcast_string data root comm;
-    Marshal.from_string data 0
+    let data = Bytes.create len in
+    broadcast_bytes data root comm;
+    Marshal.from_bytes data 0
   end
 
 let broadcast_opt data root comm =
@@ -223,8 +223,8 @@ external broadcast_float_array:
 
 (* Scatter *)
 
-external scatter_string:
-  string -> int array -> string -> int -> communicator -> unit
+external scatter_bytes:
+  bytes -> int array -> bytes -> int -> communicator -> unit
   = "caml_mpi_scatter"
 
 external scatter_int: int array -> int -> communicator -> int
@@ -237,36 +237,36 @@ let scatter data root comm =
     (* Check correct length for array *)
     if Array.length data <> nprocs
     then mpi_error "Mpi.scatter: wrong array size";
-    (* Marshal data to strings *)
+    (* Marshal data to bytes *)
     let buffers =
-      Array.map (fun d -> Marshal.to_string d [Marshal.Closures]) data in
-    (* Determine lengths of strings *)
-    let lengths = Array.map String.length buffers in
+      Array.map (fun d -> Marshal.to_bytes d [Marshal.Closures]) data in
+    (* Determine lengths of bytes *)
+    let lengths = Array.map Bytes.length buffers in
     (* Scatter those lengths *)
     ignore(scatter_int lengths root comm);
     (* Build single buffer with all data *)
     let total_len = Array.fold_left (+) 0 lengths in
-    let send_buffer = String.create total_len in
+    let send_buffer = Bytes.create total_len in
     let pos = ref 0 in
     for i = 0 to nprocs - 1 do
-      String.blit buffers.(i) 0 send_buffer !pos lengths.(i);
+      Bytes.blit buffers.(i) 0 send_buffer !pos lengths.(i);
       pos := !pos + lengths.(i)
     done;
     (* Allocate receive buffer *)
-    let recv_buffer = String.create lengths.(myself) in
+    let recv_buffer = Bytes.create lengths.(myself) in
     (* Do the scatter *)
-    scatter_string send_buffer lengths recv_buffer root comm;
+    scatter_bytes send_buffer lengths recv_buffer root comm;
     (* Return value for root *)
     data.(myself)
   end else begin
     (* Get our length *)
     let len = scatter_int [||] root comm in
     (* Allocate receive buffer *)
-    let recv_buffer = String.create len in
+    let recv_buffer = Bytes.create len in
     (* Do the scatter *)
-    scatter_string "" [||] recv_buffer root comm;
+    scatter_bytes Bytes.empty [||] recv_buffer root comm;
     (* Return value received *)
-    Marshal.from_string recv_buffer 0
+    Marshal.from_bytes recv_buffer 0
   end
 
 external scatter_float:
@@ -292,8 +292,8 @@ let scatter_float_array src dst rank comm =
 
 (* Gather *)
 
-external gather_string:
-  string -> string -> int array -> int -> communicator -> unit
+external gather_bytes:
+  bytes -> bytes -> int array -> int -> communicator -> unit
   = "caml_mpi_gather"
 
 external gather_int: int -> int array -> int -> communicator -> unit
@@ -302,30 +302,30 @@ external gather_int: int -> int array -> int -> communicator -> unit
 let gather data root comm =
   let myself = comm_rank comm in
   let nprocs = comm_size comm in
-  let send_buffer = Marshal.to_string data [Marshal.Closures] in
+  let send_buffer = Marshal.to_bytes data [Marshal.Closures] in
   if myself = root then begin
     (* Gather lengths for all data *)
     let lengths = Array.make nprocs 0 in
-    gather_int (String.length send_buffer) lengths root comm;
+    gather_int (Bytes.length send_buffer) lengths root comm;
     (* Allocate receive buffer big enough to hold all data *)
     let total_len = Array.fold_left (+) 0 lengths in
-    let recv_buffer = String.create total_len in
+    let recv_buffer = Bytes.create total_len in
     (* Gather the data *)
-    gather_string send_buffer recv_buffer lengths root comm;
+    gather_bytes send_buffer recv_buffer lengths root comm;
     (* Build array of results *)
-    let res0 = Marshal.from_string recv_buffer 0 in
+    let res0 = Marshal.from_bytes recv_buffer 0 in
     let res = Array.make nprocs res0 in
     let pos = ref 0 in
     for i = 1 to nprocs - 1 do
       pos := !pos + lengths.(i - 1);
-      res.(i) <- Marshal.from_string recv_buffer !pos
+      res.(i) <- Marshal.from_bytes recv_buffer !pos
     done;
     res
   end else begin
     (* Send our length *)
-    gather_int (String.length send_buffer) [||] root comm;
+    gather_int (Bytes.length send_buffer) [||] root comm;
     (* Send our data *)
-    gather_string send_buffer "" [||] root comm;
+    gather_bytes send_buffer Bytes.empty [||] root comm;
     (* Return dummy results *)
     [||]
   end
@@ -365,32 +365,31 @@ let gather_float_array src dst rank comm =
 
 (* Gather to all *)
 
-external allgather_string:
-  string -> string -> int array -> communicator -> unit
+external allgather_bytes:
+  bytes -> bytes -> int array -> communicator -> unit
   = "caml_mpi_allgather"
 
 external allgather_int: int -> int array -> communicator -> unit
   = "caml_mpi_allgather_int"
 
 let allgather data comm =
-  (*let myself = comm_rank comm in*)
   let nprocs = comm_size comm in
-  let send_buffer = Marshal.to_string data [Marshal.Closures] in
+  let send_buffer = Marshal.to_bytes data [Marshal.Closures] in
   (* Gather lengths for all data *)
   let lengths = Array.make nprocs 0 in
-  allgather_int (String.length send_buffer) lengths comm;
+  allgather_int (Bytes.length send_buffer) lengths comm;
   (* Allocate receive buffer big enough to hold all data *)
   let total_len = Array.fold_left (+) 0 lengths in
-  let recv_buffer = String.create total_len in
+  let recv_buffer = Bytes.create total_len in
   (* Gather the data *)
-  allgather_string send_buffer recv_buffer lengths comm;
+  allgather_bytes send_buffer recv_buffer lengths comm;
   (* Build array of results *)
-  let res0 = Marshal.from_string recv_buffer 0 in
+  let res0 = Marshal.from_bytes recv_buffer 0 in
   let res = Array.make nprocs res0 in
   let pos = ref 0 in
   for i = 1 to nprocs - 1 do
     pos := !pos + lengths.(i - 1);
-    res.(i) <- Marshal.from_string recv_buffer !pos
+    res.(i) <- Marshal.from_bytes recv_buffer !pos
   done;
   res
 

opam

@@ -1,9 +1,11 @@
 opam-version: "1.2"
+version: "1.03"
 maintainer: "xavier.leroy@inria.fr"
 authors: ["Xavier Leroy"]
 homepage: "https://github.com/xavierleroy/ocamlmpi"
 bug-reports: "https://github.com/xavierleroy/ocamlmpi/issues"
 dev-repo: "git://github.com/xavierleroy/ocamlmpi"
+license: "LGPL"
 
 build: [
   [make "all" "opt"
@@ -20,4 +22,4 @@ depexts: [
   [["debian"] ["mpi-default-dev"]]
   [["ubuntu"] ["mpi-default-dev"]]
 ]
-
+available: [[ ocaml-version >= "4.02.3" ]]

test.ml

@@ -141,7 +141,7 @@ let test_broadcast broadcastfun printfun data =
   if myrank = 0 then begin
     printf "0: broadcasting %a" printfun data; print_newline()
   end;
-  let res = broadcastfun data 0 comm_world in
+  ignore (broadcastfun data 0 comm_world);
   printf "%d: received %a" myrank printfun data; print_newline()
 
 let _ =