A micro-benchmark to compare modulo, arbitrary-precised, and saturation arithmetics

let repeat n f =
  let rec aux accu k =
    if k = 0 then accu else aux (f () :: accu) (k - 1)
  in
  aux [] n

open! Core
open Core_bench

let rec random () =
  match Int64.to_int (Random.int64 (Int64.of_int Int.max_value)) with
  | None -> random ()
  | Some x -> x

let inputs =
  Array.of_list (repeat 10000 (fun () -> (random (), random ())))

let zinputs =
  Array.map ~f:(fun (x, y) -> (Z.of_int x, Z.of_int y)) inputs

let rec compose k op x y =
  if k = 0 then
    op x y
  else
    compose (k - 1) op (op x y) y

let test op = Array.map ~f:(fun (x, y) -> compose 10 op x y)

let ztest op = test op zinputs

let itest op = test op inputs

let zarith_add_test () =
  ignore (Array.length (ztest Z.add))

let native_add_test () =
  ignore (Array.length (itest Stdlib.( + )))

let saturation_add_test () =
  itest Saturation_repr.add

let zarith_sub_test () =
  ignore (Array.length (ztest Z.sub))

let native_sub_test () =
  ignore (Array.length (itest Stdlib.( - )))

let saturation_sub_test () =
  itest Saturation_repr.sub

let zarith_mul_test () =
  ignore (Array.length (ztest Z.mul))

let native_mul_test () =
  ignore (Array.length (itest Stdlib.( * )))

let saturation_mul_test () =
  itest Saturation_repr.mul

let zarith_div_test () =
  ignore (Array.length (ztest Z.div))

let native_div_test () =
  ignore (Array.length (itest Stdlib.( / )))

let saturation_div_test () =
  itest Saturation_repr.ediv


let () =
  Random.self_init ();

  Command.run (Bench.make_command [
      Bench.Test.create ~name:"Zarith add" zarith_add_test;
      Bench.Test.create ~name:"Native add" native_add_test;
      Bench.Test.create ~name:"Saturation add" saturation_add_test
    ]);

  Command.run (Bench.make_command [
      Bench.Test.create ~name:"Zarith sub" zarith_sub_test;
      Bench.Test.create ~name:"Native sub" native_sub_test;
      Bench.Test.create ~name:"Saturation sub" saturation_sub_test;
    ]);

    Command.run (Bench.make_command [
      Bench.Test.create ~name:"Zarith mul" zarith_mul_test;
      Bench.Test.create ~name:"Native mul" native_mul_test;
      Bench.Test.create ~name:"Saturation mul" saturation_mul_test;
    ]);

    Command.run (Bench.make_command [
      Bench.Test.create ~name:"Zarith div" zarith_div_test;
      Bench.Test.create ~name:"Native div" native_div_test;
      Bench.Test.create ~name:"Saturation div" saturation_div_test;
    ])