author | wenzelm |
Mon, 27 Jul 2009 15:53:43 +0200 | |
changeset 32226 | 23511e4da055 |
parent 32225 | d5d6f47fb018 |
child 32227 | a7e901209005 |
permissions | -rw-r--r-- |
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(* Title: Pure/Concurrent/future.ML |
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Author: Makarius |
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Future values. |
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Notes: |
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* Futures are similar to delayed evaluation, i.e. delay/force is |
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generalized to fork/join (and variants). The idea is to model |
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parallel value-oriented computations, but *not* communicating |
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processes. |
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* Futures are grouped; failure of one group member causes the whole |
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group to be interrupted eventually. Groups are block-structured. |
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* Forked futures are evaluated spontaneously by a farm of worker |
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threads in the background; join resynchronizes the computation and |
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delivers results (values or exceptions). |
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* The pool of worker threads is limited, usually in correlation with |
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the number of physical cores on the machine. Note that allocation |
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of runtime resources is distorted either if workers yield CPU time |
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(e.g. via system sleep or wait operations), or if non-worker |
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threads contend for significant runtime resources independently. |
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*) |
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signature FUTURE = |
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sig |
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val enabled: unit -> bool |
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type task = Task_Queue.task |
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type group = Task_Queue.group |
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val is_worker: unit -> bool |
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val worker_group: unit -> Task_Queue.group option |
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type 'a future |
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val task_of: 'a future -> task |
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val group_of: 'a future -> group |
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val peek: 'a future -> 'a Exn.result option |
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val is_finished: 'a future -> bool |
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val value: 'a -> 'a future |
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val fork: (unit -> 'a) -> 'a future |
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val fork_group: group -> (unit -> 'a) -> 'a future |
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val fork_deps: 'b future list -> (unit -> 'a) -> 'a future |
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val fork_pri: int -> (unit -> 'a) -> 'a future |
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val join_results: 'a future list -> 'a Exn.result list |
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val join_result: 'a future -> 'a Exn.result |
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val join: 'a future -> 'a |
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val map: ('a -> 'b) -> 'a future -> 'b future |
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val interruptible_task: ('a -> 'b) -> 'a -> 'b |
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val cancel_group: group -> unit |
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val cancel: 'a future -> unit |
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val shutdown: unit -> unit |
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end; |
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structure Future: FUTURE = |
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struct |
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(** future values **) |
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fun enabled () = |
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Multithreading.enabled () andalso |
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not (Multithreading.self_critical ()); |
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(* identifiers *) |
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type task = Task_Queue.task; |
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type group = Task_Queue.group; |
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local |
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val tag = Universal.tag () : (string * task * group) option Universal.tag; |
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in |
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fun thread_data () = the_default NONE (Thread.getLocal tag); |
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fun setmp_thread_data data f x = |
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Library.setmp_thread_data tag (thread_data ()) (SOME data) f x; |
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end; |
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val is_worker = is_some o thread_data; |
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val worker_group = Option.map #3 o thread_data; |
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(* datatype future *) |
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datatype 'a future = Future of |
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{task: task, |
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group: group, |
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result: 'a Exn.result option ref}; |
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fun task_of (Future {task, ...}) = task; |
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fun group_of (Future {group, ...}) = group; |
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fun peek (Future {result, ...}) = ! result; |
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fun is_finished x = is_some (peek x); |
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fun value x = Future |
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{task = Task_Queue.new_task 0, |
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group = Task_Queue.new_group NONE, |
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result = ref (SOME (Exn.Result x))}; |
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(** scheduling **) |
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(* global state *) |
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val queue = ref Task_Queue.empty; |
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val next = ref 0; |
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val workers = ref ([]: (Thread.thread * bool) list); |
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val scheduler = ref (NONE: Thread.thread option); |
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val excessive = ref 0; |
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val canceled = ref ([]: Task_Queue.group list); |
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val do_shutdown = ref false; |
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(* synchronization *) |
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val scheduler_event = ConditionVar.conditionVar (); |
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val work_available = ConditionVar.conditionVar (); |
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val work_finished = ConditionVar.conditionVar (); |
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local |
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val lock = Mutex.mutex (); |
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in |
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fun SYNCHRONIZED name = SimpleThread.synchronized name lock; |
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fun wait cond = (*requires SYNCHRONIZED*) |
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ConditionVar.wait (cond, lock); |
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fun wait_timeout cond timeout = (*requires SYNCHRONIZED*) |
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ignore (ConditionVar.waitUntil (cond, lock, Time.+ (Time.now (), timeout))); |
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fun signal cond = (*requires SYNCHRONIZED*) |
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ConditionVar.signal cond; |
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fun broadcast cond = (*requires SYNCHRONIZED*) |
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ConditionVar.broadcast cond; |
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fun broadcast_all () = (*requires SYNCHRONIZED*) |
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(ConditionVar.broadcast scheduler_event; |
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ConditionVar.broadcast work_available; |
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ConditionVar.broadcast work_finished); |
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end; |
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(* worker activity *) |
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fun count_active ws = |
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fold (fn (_, active) => fn i => if active then i + 1 else i) ws 0; |
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fun change_active active = (*requires SYNCHRONIZED*) |
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change workers (AList.update Thread.equal (Thread.self (), active)); |
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fun overloaded () = |
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count_active (! workers) > Multithreading.max_threads_value (); |
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(* execute future jobs *) |
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fun future_job group (e: unit -> 'a) = |
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let |
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val result = ref (NONE: 'a Exn.result option); |
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fun job ok = |
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let |
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val res = |
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if ok then |
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Exn.capture |
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(Multithreading.with_attributes Multithreading.restricted_interrupts |
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(fn _ => fn () => e ())) () |
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else Exn.Exn Exn.Interrupt; |
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val _ = result := SOME res; |
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in |
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(case res of |
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Exn.Exn exn => (Task_Queue.cancel_group group exn; false) |
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| Exn.Result _ => true) |
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end; |
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in (result, job) end; |
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fun do_cancel group = (*requires SYNCHRONIZED*) |
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(change canceled (insert Task_Queue.eq_group group); broadcast scheduler_event); |
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fun execute name (task, group, jobs) = |
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let |
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val valid = not (Task_Queue.is_canceled group); |
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val ok = setmp_thread_data (name, task, group) (fn () => |
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fold (fn job => fn ok => job valid andalso ok) jobs true) (); |
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val _ = SYNCHRONIZED "execute" (fn () => |
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let |
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val maximal = change_result queue (Task_Queue.finish task); |
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val _ = |
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if ok then () |
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else if Task_Queue.cancel (! queue) group then () |
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else do_cancel group; |
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val _ = broadcast work_finished; |
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val _ = if maximal then () else broadcast work_available; |
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in () end); |
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in () end; |
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(* worker threads *) |
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fun worker_wait cond = (*requires SYNCHRONIZED*) |
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(change_active false; broadcast scheduler_event; |
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wait cond; |
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change_active true; broadcast scheduler_event); |
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fun worker_next () = (*requires SYNCHRONIZED*) |
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if ! excessive > 0 then |
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(dec excessive; |
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change workers (filter_out (fn (thread, _) => Thread.equal (thread, Thread.self ()))); |
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broadcast scheduler_event; |
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NONE) |
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else if overloaded () then (worker_wait scheduler_event; worker_next ()) |
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else |
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(case change_result queue Task_Queue.dequeue of |
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NONE => (worker_wait work_available; worker_next ()) |
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| some => some); |
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fun worker_loop name = |
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(case SYNCHRONIZED name (fn () => worker_next ()) of |
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NONE => () |
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| SOME work => (execute name work; worker_loop name)); |
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fun worker_start name = (*requires SYNCHRONIZED*) |
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change workers (cons (SimpleThread.fork false (fn () => worker_loop name), true)); |
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(* scheduler *) |
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val last_status = ref Time.zeroTime; |
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val next_status = Time.fromMilliseconds 450; |
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|
233 |
fun scheduler_next () = (*requires SYNCHRONIZED*) |
28156 | 234 |
let |
32226 | 235 |
(*queue and worker status*) |
236 |
val _ = |
|
237 |
let val now = Time.now () in |
|
238 |
if Time.> (Time.+ (! last_status, next_status), now) then () |
|
239 |
else |
|
240 |
(last_status := now; Multithreading.tracing 1 (fn () => |
|
241 |
let |
|
242 |
val {ready, pending, running} = Task_Queue.status (! queue); |
|
243 |
val total = length (! workers); |
|
244 |
val active = count_active (! workers); |
|
245 |
in |
|
246 |
"SCHEDULE: " ^ |
|
247 |
string_of_int ready ^ " ready, " ^ |
|
248 |
string_of_int pending ^ " pending, " ^ |
|
249 |
string_of_int running ^ " running; " ^ |
|
250 |
string_of_int total ^ " workers, " ^ |
|
251 |
string_of_int active ^ " active" |
|
252 |
end)) |
|
253 |
end; |
|
32053 | 254 |
|
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|
255 |
(*worker threads*) |
28191 | 256 |
val _ = |
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|
257 |
if forall (Thread.isActive o #1) (! workers) then () |
32095 | 258 |
else |
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changeset
|
259 |
(case List.partition (Thread.isActive o #1) (! workers) of |
32095 | 260 |
(_, []) => () |
32220 | 261 |
| (alive, dead) => |
262 |
(workers := alive; Multithreading.tracing 0 (fn () => |
|
263 |
"SCHEDULE: disposed " ^ string_of_int (length dead) ^ " dead worker threads"))); |
|
28191 | 264 |
|
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|
265 |
val m = if ! do_shutdown then 0 else Multithreading.max_threads_value (); |
32095 | 266 |
val mm = (m * 3) div 2; |
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changeset
|
267 |
val l = length (! workers); |
32095 | 268 |
val _ = excessive := l - mm; |
28203 | 269 |
val _ = |
32095 | 270 |
if mm > l then |
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more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
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parents:
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changeset
|
271 |
(funpow (mm - l) (fn () => worker_start ("worker " ^ string_of_int (inc next))) (); |
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more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
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|
272 |
broadcast scheduler_event) |
28203 | 273 |
else (); |
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|
274 |
|
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changeset
|
275 |
(*canceled groups*) |
32225
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cancel: improved reactivity due to more careful broadcasting;
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changeset
|
276 |
val _ = |
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cancel: improved reactivity due to more careful broadcasting;
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changeset
|
277 |
if null (! canceled) then () |
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cancel: improved reactivity due to more careful broadcasting;
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changeset
|
278 |
else (change canceled (filter_out (Task_Queue.cancel (! queue))); broadcast_all ()); |
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changeset
|
279 |
|
32219
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changeset
|
280 |
val timeout = |
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changeset
|
281 |
Time.fromMilliseconds (if not (! do_shutdown) andalso null (! canceled) then 500 else 50); |
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changeset
|
282 |
val _ = interruptible (fn () => wait_timeout scheduler_event timeout) () |
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parents:
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changeset
|
283 |
handle Exn.Interrupt => List.app do_cancel (Task_Queue.cancel_all (! queue)); |
28167 | 284 |
|
32219
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changeset
|
285 |
(*shutdown*) |
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parents:
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diff
changeset
|
286 |
val continue = not (! do_shutdown andalso null (! workers)); |
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parents:
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changeset
|
287 |
val _ = if continue then () else scheduler := NONE; |
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more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
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parents:
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changeset
|
288 |
val _ = broadcast scheduler_event; |
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parents:
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changeset
|
289 |
in continue end; |
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parents:
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changeset
|
290 |
|
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parents:
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diff
changeset
|
291 |
fun scheduler_loop () = |
32107
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future_job: tight scope for interrupts, to prevent shooting ourselves in the foot via cancel_group;
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parents:
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diff
changeset
|
292 |
while SYNCHRONIZED "scheduler" (fn () => scheduler_next ()) do (); |
28156 | 293 |
|
28203 | 294 |
fun scheduler_active () = (*requires SYNCHRONIZED*) |
295 |
(case ! scheduler of NONE => false | SOME thread => Thread.isActive thread); |
|
296 |
||
28464 | 297 |
fun scheduler_check name = SYNCHRONIZED name (fn () => |
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parents:
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diff
changeset
|
298 |
if not (scheduler_active ()) then |
32219
9a2566d1fdbd
more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
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parents:
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diff
changeset
|
299 |
(do_shutdown := false; scheduler := SOME (SimpleThread.fork false scheduler_loop); |
9a2566d1fdbd
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parents:
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diff
changeset
|
300 |
broadcast scheduler_event) |
28206
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parents:
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diff
changeset
|
301 |
else if ! do_shutdown then error "Scheduler shutdown in progress" |
bcd48c6897d4
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parents:
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diff
changeset
|
302 |
else ()); |
28156 | 303 |
|
304 |
||
29366 | 305 |
|
306 |
(** futures **) |
|
28156 | 307 |
|
29366 | 308 |
(* fork *) |
309 |
||
310 |
fun fork_future opt_group deps pri e = |
|
311 |
let |
|
312 |
val _ = scheduler_check "future check"; |
|
313 |
||
32102 | 314 |
val group = |
315 |
(case opt_group of |
|
316 |
SOME group => group |
|
317 |
| NONE => Task_Queue.new_group (worker_group ())); |
|
29366 | 318 |
val (result, job) = future_job group e; |
28192 | 319 |
val task = SYNCHRONIZED "future" (fn () => |
32219
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wenzelm
parents:
32186
diff
changeset
|
320 |
let |
9a2566d1fdbd
more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
wenzelm
parents:
32186
diff
changeset
|
321 |
val (task, minimal) = change_result queue (Task_Queue.enqueue group deps pri job); |
9a2566d1fdbd
more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
wenzelm
parents:
32186
diff
changeset
|
322 |
val _ = if minimal then signal work_available else (); |
9a2566d1fdbd
more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
wenzelm
parents:
32186
diff
changeset
|
323 |
in task end); |
28166
43087721a66e
moved task, thread_data, group, queue to task_queue.ML;
wenzelm
parents:
28163
diff
changeset
|
324 |
in Future {task = task, group = group, result = result} end; |
28162 | 325 |
|
29366 | 326 |
fun fork e = fork_future NONE [] 0 e; |
327 |
fun fork_group group e = fork_future (SOME group) [] 0 e; |
|
328 |
fun fork_deps deps e = fork_future NONE (map task_of deps) 0 e; |
|
329 |
fun fork_pri pri e = fork_future NONE [] pri e; |
|
28186 | 330 |
|
331 |
||
29366 | 332 |
(* join *) |
333 |
||
29551
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
334 |
local |
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
335 |
|
32099 | 336 |
fun get_result x = |
337 |
(case peek x of |
|
32102 | 338 |
NONE => Exn.Exn (SYS_ERROR "unfinished future") |
339 |
| SOME (Exn.Exn Exn.Interrupt) => |
|
340 |
Exn.Exn (Exn.EXCEPTIONS (Exn.flatten_list (Task_Queue.group_status (group_of x)))) |
|
341 |
| SOME res => res); |
|
28186 | 342 |
|
32224 | 343 |
fun join_wait x = |
344 |
if SYNCHRONIZED "join_wait" (fn () => |
|
345 |
is_finished x orelse (wait work_finished; false)) |
|
346 |
then () else join_wait x; |
|
347 |
||
32095 | 348 |
fun join_next deps = (*requires SYNCHRONIZED*) |
32224 | 349 |
if null deps then NONE |
350 |
else if overloaded () then (worker_wait scheduler_event; join_next deps) |
|
351 |
else |
|
352 |
(case change_result queue (Task_Queue.dequeue_towards deps) of |
|
353 |
(NONE, []) => NONE |
|
354 |
| (NONE, deps') => (worker_wait work_finished; join_next deps') |
|
355 |
| (SOME work, deps') => SOME (work, deps')); |
|
32095 | 356 |
|
32224 | 357 |
fun join_work deps = |
32095 | 358 |
(case SYNCHRONIZED "join" (fn () => join_next deps) of |
29551
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
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diff
changeset
|
359 |
NONE => () |
32224 | 360 |
| SOME (work, deps') => (execute "join" work; join_work deps')); |
29551
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
361 |
|
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
362 |
in |
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
363 |
|
29366 | 364 |
fun join_results xs = |
365 |
if forall is_finished xs then map get_result xs |
|
366 |
else uninterruptible (fn _ => fn () => |
|
367 |
let |
|
368 |
val _ = scheduler_check "join check"; |
|
369 |
val _ = Multithreading.self_critical () andalso |
|
370 |
error "Cannot join future values within critical section"; |
|
32224 | 371 |
val _ = |
372 |
if is_worker () then join_work (map task_of xs) |
|
373 |
else List.app join_wait xs; |
|
29366 | 374 |
in map get_result xs end) (); |
28186 | 375 |
|
29551
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
376 |
end; |
95e469919c3e
join_results: when dependencies are resulved (but not finished yet),
wenzelm
parents:
29431
diff
changeset
|
377 |
|
28647
8068cdc84e7e
join_results: allow CRITICAL join of finished futures;
wenzelm
parents:
28645
diff
changeset
|
378 |
fun join_result x = singleton join_results x; |
8068cdc84e7e
join_results: allow CRITICAL join of finished futures;
wenzelm
parents:
28645
diff
changeset
|
379 |
fun join x = Exn.release (join_result x); |
28156 | 380 |
|
29366 | 381 |
|
382 |
(* map *) |
|
383 |
||
29384
a3c7e9ae9b71
more robust propagation of errors through bulk jobs;
wenzelm
parents:
29366
diff
changeset
|
384 |
fun map_future f x = |
29366 | 385 |
let |
386 |
val _ = scheduler_check "map_future check"; |
|
387 |
||
29384
a3c7e9ae9b71
more robust propagation of errors through bulk jobs;
wenzelm
parents:
29366
diff
changeset
|
388 |
val task = task_of x; |
32102 | 389 |
val group = Task_Queue.new_group (SOME (group_of x)); |
29384
a3c7e9ae9b71
more robust propagation of errors through bulk jobs;
wenzelm
parents:
29366
diff
changeset
|
390 |
val (result, job) = future_job group (fn () => f (join x)); |
a3c7e9ae9b71
more robust propagation of errors through bulk jobs;
wenzelm
parents:
29366
diff
changeset
|
391 |
|
29366 | 392 |
val extended = SYNCHRONIZED "map_future" (fn () => |
393 |
(case Task_Queue.extend task job (! queue) of |
|
394 |
SOME queue' => (queue := queue'; true) |
|
395 |
| NONE => false)); |
|
396 |
in |
|
29384
a3c7e9ae9b71
more robust propagation of errors through bulk jobs;
wenzelm
parents:
29366
diff
changeset
|
397 |
if extended then Future {task = task, group = group, result = result} |
32099 | 398 |
else fork_future (SOME group) [task] (Task_Queue.pri_of_task task) (fn () => f (join x)) |
29366 | 399 |
end; |
28979
3ce619d8d432
fork/map: no inheritance of group (structure is nested, not parallel);
wenzelm
parents:
28972
diff
changeset
|
400 |
|
28191 | 401 |
|
29431 | 402 |
(* cancellation *) |
28202
23cb9a974630
added focus, which indicates a particular collection of high-priority tasks;
wenzelm
parents:
28201
diff
changeset
|
403 |
|
30618
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
404 |
fun interruptible_task f x = |
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
405 |
if Multithreading.available then |
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
406 |
Multithreading.with_attributes |
32058 | 407 |
(if is_worker () |
30618
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
408 |
then Multithreading.restricted_interrupts |
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
409 |
else Multithreading.regular_interrupts) |
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
410 |
(fn _ => f) x |
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
411 |
else interruptible f x; |
046f4f986fb5
restricted interrupts for tasks running as future worker thread -- attempt to prevent interrupt race conditions;
wenzelm
parents:
30612
diff
changeset
|
412 |
|
32222 | 413 |
(*cancel_group: present and future group members will be interrupted eventually*) |
29431 | 414 |
fun cancel_group group = |
28464 | 415 |
(scheduler_check "cancel check"; |
32225
d5d6f47fb018
cancel: improved reactivity due to more careful broadcasting;
wenzelm
parents:
32224
diff
changeset
|
416 |
SYNCHRONIZED "cancel" (fn () => do_cancel group)); |
28206
bcd48c6897d4
eliminated requests, use global state variables uniformly;
wenzelm
parents:
28203
diff
changeset
|
417 |
|
29431 | 418 |
fun cancel x = cancel_group (group_of x); |
28206
bcd48c6897d4
eliminated requests, use global state variables uniformly;
wenzelm
parents:
28203
diff
changeset
|
419 |
|
29366 | 420 |
|
421 |
(** global join and shutdown **) |
|
422 |
||
28203 | 423 |
fun shutdown () = |
28276 | 424 |
if Multithreading.available then |
28464 | 425 |
(scheduler_check "shutdown check"; |
28276 | 426 |
SYNCHRONIZED "shutdown" (fn () => |
32219
9a2566d1fdbd
more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
wenzelm
parents:
32186
diff
changeset
|
427 |
(while not (scheduler_active ()) do wait scheduler_event; |
9a2566d1fdbd
more specific conditions: scheduler_event, work_available, work_finished -- considereably reduces overhead with many threads;
wenzelm
parents:
32186
diff
changeset
|
428 |
while not (Task_Queue.is_empty (! queue)) do wait scheduler_event; |
28276 | 429 |
do_shutdown := true; |
32225
d5d6f47fb018
cancel: improved reactivity due to more careful broadcasting;
wenzelm
parents:
32224
diff
changeset
|
430 |
while scheduler_active () do (broadcast_all (); wait scheduler_event)))) |
28276 | 431 |
else (); |
28203 | 432 |
|
29366 | 433 |
|
434 |
(*final declarations of this structure!*) |
|
435 |
val map = map_future; |
|
436 |
||
28156 | 437 |
end; |
28972 | 438 |
|
439 |
type 'a future = 'a Future.future; |
|
440 |