Scatter OK

Parallel/Parallel.ml

@@ -42,7 +42,7 @@ module Vec = struct
     ()
 
   let create n = 
-    let step = n / size + 1 in
+    let step = (n-1) / size + 1 in
     let local_first = step * rank + 1 in
     let local_last = min (local_first + step - 1) n  in
     {
@@ -50,7 +50,7 @@ module Vec = struct
       global_last  = n ;
       local_first  ;
       local_last   ;
-      data         = Lacaml.D.Vec.create (local_last - local_first + 1)
+      data         = Lacaml.D.Vec.create (max 0 (local_last - local_first + 1))
     }
 
 
@@ -73,4 +73,25 @@ module Vec = struct
           (Lacaml.D.Vec.dim result.data)
           (fun i -> f (i+result.local_first-1))
     }
+
+
+  let of_array a =
+    let la = Array.length a in
+    let a = 
+      let n = la mod size in
+      if n > 0 then
+        Array.concat [ a ; Array.make (size-n) 0. ]
+      else
+        a
+    in
+    let result = create la in
+    let () = Mpi.barrier Mpi.comm_world in
+    Printf.printf "%d\n%!" rank;
+    let a_local = Array.make ((Array.length a)/size) 0. in
+    Printf.printf "%d\n%!" (Array.length a_local);
+    let () = Mpi.scatter_float_array a a_local 0 Mpi.comm_world in
+    { result with data =
+        Lacaml.D.Vec.of_array a_local
+    }
+    
 end

Parallel/Parallel.mli

@@ -39,10 +39,10 @@ module Vec : sig
   (** [init n f] @return a distributed vector containing [n] elements, where
       each element at position [i] is initialized by the result of calling [f i].  *)
 
-(*
   val of_array : float array -> t
   (** [of_array ar] @return a distributed vector initialized from array [ar]. *)
 
+(*
   val to_array : t -> float array
   (** [to_array v] @return an array initialized from vector [v]. *)
 

run_parallel.ml

@@ -2,6 +2,10 @@
 let () =
   Printf.printf "Hello from rank %d of %d.\n" Parallel.rank Parallel.size;
   let () = Parallel.barrier () in
-  let v = Parallel.Vec.init 47 (fun i -> float_of_int i) in
+(*
+let v = Parallel.Vec.init 47 (fun i -> float_of_int i) in
+*)
+  let a = Array.init 6 (fun i -> float_of_int (i+1)) in
+  let v = Parallel.Vec.of_array a in
   Format.printf "%a" Parallel.Vec.pp v;