OCaml程序的意外周期性、非连续输出

let lock = Mutex.create ()

let safe_output s =
  Mutex.lock lock;
  print130 (s^">");
  Mutex.unlock lock;;

let _ = Thread.create (fun () -> safe_output "Thread 1") ()
let _ = Thread.create (fun () -> safe_output "Thread 2") ()

let _ =
  let rec loop i =
    if compare i 10 = 0 then ()
    else (
      print130 (string_of_int i^">");
      Thread.delay 1000;
      loop (i + 1)
    )
  in
  loop 0

let _ =
  let rec factorial n =
    if compare n 0 = 0 then 1
    else n * factorial (n - 1)
  in
  print130 (string_of_int (factorial 5)^">")

let _ =
  let rec read_input () =
    try if compare (input_line stdin) "" = 0 then ()
    else (
      print130 (">"^(input_line stdin)^"<");
      read_input ()
    )
  in
  read_input ()