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(* Classical philosopher dinning problem written in STM. Launch it with [./phil
n], where n is the number of philosophers and chopsticks.
*)
module Thread=Cothread (* Or use Thread directly *)
open Stm
(* Number of philosophers and chopsticks, the degree *)
let n =
try int_of_string Sys.argv.(1)
with Invalid_argument _ ->
prerr_endline "Launch the program with a single int, e.g. ./phil 5";
exit 1
let chopstick = Array.init n (fun _ -> tvar true)
let left x = x and right x = (x + 1) mod n
let check b = if b then return () else retry
(* Actions: think, eat, takeup, putdown*)
let think x =
Printf.printf "Phil %d begins his THINKING ...\n" x; flush stdout;
Thread.delay (Random.float 0.1)
let eat x =
Printf.printf "Phil %d begins to EAT -----> \n" x;
Thread.delay (Random.float 0.02);
Printf.printf "Phil %d now finish EAT <----- \n" x; flush stdout
let chop_act x s l r =
Printf.printf "Phil %d %s chopstick %d and %d\n" x s l r
let takeup id =
read_tvar chopstick.(id) >>= check >> write_tvar chopstick.(id) false
let putdown id =
write_tvar chopstick.(id) true
(* Philosopher thread function *)
let phil x =
let l,r = (left x, right x) in
let rec run () =
think x;
atom (takeup l >> takeup r);
chop_act x "take up" l r;
eat x;
atom (putdown l >> putdown r);
chop_act x "put down" l r;
run () in
Random.self_init ();
run ()
let main () =
let phils = Array.init n (Thread.create phil) in
Array.iter Thread.join phils
let _ = main ()
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