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 a = Array.init 41 (fun i -> float_of_int (i+1)) |> Lacaml.D.Vec.of_array in
  let b = Array.init 41 (fun i -> float_of_int (3*i+1)) |> Lacaml.D.Vec.of_array in
  let v1 = Parallel.Vec.of_vec a in
  let v2 = Parallel.Vec.of_vec b in
  let d1 = Parallel.dot v1 v2 |> Parallel.broadcast_float in
  let d2 = Lacaml.D.dot a b in
  (*
  let w = Parallel.Vec.to_vec v in
  Format.printf "%a" Parallel.Vec.pp v;
  if Parallel.master then
      Format.printf "@[%a@]@;" (Lacaml.Io.pp_lfvec ()) w;
  *)
  Printf.printf "%f %f\n" d1 d2;
  print_newline ();