Trying out Domainslib

main.ml

let long_computation () =
  for i = 0 to 1_000_000_000 do
    ()
  done

(* No parallelism *)
(*
  ________________________________________________________
  Executed in   36.09 secs    fish           external
    usr time   36.08 secs    1.27 millis   36.08 secs
    sys time    0.01 secs    0.09 millis    0.01 secs 
  
*)
(* ________________________________________________________
   Executed in   84.26 secs    fish           external
      usr time   84.22 secs    0.17 millis   84.22 secs
      sys time    0.02 secs    1.10 millis    0.02 secs
*)
let example () =
  for i = 0 to 200 do
    long_computation ()
  done;
  print_endline "Done"

(* Inefficient spawning parellelism of domains *)
(*
   ________________________________________________________
   Executed in    9.29 secs    fish           external
      usr time   71.62 secs  491.00 micros   71.62 secs
      sys time    0.24 secs  824.00 micros    0.24 secs
*)
let example1 () =
  let handles : unit Domain.t list ref = ref [] in

  for i = 0 to 200 do
    let result = Domain.spawn (fun _ -> long_computation ()) in
    handles := result :: !handles
  done;

  !handles |> List.iter (fun d -> Domain.join d);

  print_endline "Done"

let example2 () =
  let open Domainslib in
  let _num_domains = Domain.recommended_domain_count () in
  let pool = Task.setup_pool ~num_domains:4 () in

  let () =
    Task.run pool (fun _ ->
        Task.parallel_for ~start:0 ~finish:200
          ~body:(fun i -> long_computation ())
          pool)
  in
  print_endline "Done"

let () =
  (* let open Domainslib in
     let pool = Task.setup_pool ~num_domains:3 () in

     pool |> Task.teardown_pool;

     print_endline "Done" *)
  example2 ()