let map_anon_memory n () =
  let fd = Unix.openfile "/dev/zero" [ Unix.O_RDWR ] 0 in
  let kind = Bigarray.Char in
  let layout = Bigarray.C_layout in
  let dims = [| n |] in
  let shared = true in
  let pos = None in
  let genarray = UnixLabels.map_file ?pos ~kind ~layout ~dims ~shared fd in
  Bigarray.array1_of_genarray genarray

let spawn_child f () =
  let pid = Unix.fork () in
  if pid = 0 then (
    f () ;
    Unix._exit 0
  ) else pid

let bench_concurrency () =
  let memory = map_anon_memory 1_000 () in
  let get n = memory.{n} in
  let set n c = memory.{n} <- c in
  let aux () =
    for i = 1 to 10 do (
      Unix.sleep 1 ;
      set 0 @@ Char.chr ((Char.code 'A') + i - 1) ;
      Format.printf "Child\tMemory 0 (%f): %c\n%!" (time ()) (get 0) ;
    ) done
  in
  let _pid = spawn_child aux () in
  for _ = 1 to 7  do
    Format.printf "Parent\tMemory 0 (%f): %c\n%!" (time ()) (get 0) ;
    Unix.sleep 2 ;
  done ;
  ()

let () =
  bench_concurrency () ;
  ()