dequeue_towards: always return active tasks;
join_work: imitate worker more closely, keep active if queue appears to be blocked for the moment -- it may become free again after some worker_finished event;
(* Title: Pure/Concurrent/task_queue.ML
Author: Makarius
Ordered queue of grouped tasks.
*)
signature TASK_QUEUE =
sig
type task
val new_task: int -> task
val pri_of_task: task -> int
val str_of_task: task -> string
type group
val new_group: group option -> group
val group_id: group -> int
val eq_group: group * group -> bool
val cancel_group: group -> exn -> unit
val is_canceled: group -> bool
val group_status: group -> exn list
val str_of_group: group -> string
type queue
val empty: queue
val is_empty: queue -> bool
val status: queue -> {ready: int, pending: int, running: int}
val cancel: queue -> group -> bool
val cancel_all: queue -> group list
val enqueue: group -> task list -> int -> (bool -> bool) -> queue -> (task * bool) * queue
val extend: task -> (bool -> bool) -> queue -> queue option
val dequeue: queue -> (task * group * (bool -> bool) list) option * queue
val dequeue_towards: task list -> queue ->
(((task * group * (bool -> bool) list) option * task list) * queue)
val finish: task -> queue -> bool * queue
end;
structure Task_Queue:> TASK_QUEUE =
struct
(* tasks *)
datatype task = Task of int * serial;
fun new_task pri = Task (pri, serial ());
fun pri_of_task (Task (pri, _)) = pri;
fun str_of_task (Task (_, i)) = string_of_int i;
fun task_ord (Task t1, Task t2) = prod_ord (rev_order o int_ord) int_ord (t1, t2);
structure Task_Graph = Graph(type key = task val ord = task_ord);
(* nested groups *)
datatype group = Group of
{parent: group option,
id: serial,
status: exn list ref};
fun make_group (parent, id, status) = Group {parent = parent, id = id, status = status};
fun new_group parent = make_group (parent, serial (), ref []);
fun group_id (Group {id, ...}) = id;
fun eq_group (group1, group2) = group_id group1 = group_id group2;
fun group_ancestry (Group {parent, id, ...}) =
id :: (case parent of NONE => [] | SOME group => group_ancestry group);
(* group status *)
fun cancel_group (Group {status, ...}) exn = CRITICAL (fn () =>
(case exn of
Exn.Interrupt => if null (! status) then status := [exn] else ()
| _ => change status (cons exn)));
fun is_canceled (Group {parent, status, ...}) = (*non-critical*)
not (null (! status)) orelse (case parent of NONE => false | SOME group => is_canceled group);
fun group_status (Group {parent, status, ...}) = (*non-critical*)
! status @ (case parent of NONE => [] | SOME group => group_status group);
fun str_of_group group =
(is_canceled group ? enclose "(" ")") (string_of_int (group_id group));
(* jobs *)
datatype job =
Job of (bool -> bool) list |
Running of Thread.thread;
type jobs = (group * job) Task_Graph.T;
fun get_group (jobs: jobs) task = #1 (Task_Graph.get_node jobs task);
fun get_job (jobs: jobs) task = #2 (Task_Graph.get_node jobs task);
fun set_job task job (jobs: jobs) = Task_Graph.map_node task (fn (group, _) => (group, job)) jobs;
(* queue of grouped jobs *)
datatype result = Unknown | Result of task | No_Result;
datatype queue = Queue of
{groups: task list Inttab.table, (*groups with presently active members*)
jobs: jobs, (*job dependency graph*)
cache: result}; (*last dequeue result*)
fun make_queue groups jobs cache = Queue {groups = groups, jobs = jobs, cache = cache};
val empty = make_queue Inttab.empty Task_Graph.empty No_Result;
fun is_empty (Queue {jobs, ...}) = Task_Graph.is_empty jobs;
(* queue status *)
fun status (Queue {jobs, ...}) =
let
val (x, y, z) =
Task_Graph.fold (fn (task, ((_, job), (deps, _))) => fn (x, y, z) =>
(case job of
Job _ => if null deps then (x + 1, y, z) else (x, y + 1, z)
| Running _ => (x, y, z + 1)))
jobs (0, 0, 0);
in {ready = x, pending = y, running = z} end;
(* cancel -- peers and sub-groups *)
fun cancel (Queue {groups, jobs, ...}) group =
let
val _ = cancel_group group Exn.Interrupt;
val tasks = Inttab.lookup_list groups (group_id group);
val running =
fold (get_job jobs #> (fn Running t => insert Thread.equal t | _ => I)) tasks [];
val _ = List.app SimpleThread.interrupt running;
in null running end;
fun cancel_all (Queue {jobs, ...}) =
let
fun cancel_job (group, job) (groups, running) =
(cancel_group group Exn.Interrupt;
(case job of Running t => (insert eq_group group groups, insert Thread.equal t running)
| _ => (groups, running)));
val (groups, running) = Task_Graph.fold (cancel_job o #1 o #2) jobs ([], []);
val _ = List.app SimpleThread.interrupt running;
in groups end;
(* enqueue *)
fun add_job task dep (jobs: jobs) =
Task_Graph.add_edge (dep, task) jobs handle Task_Graph.UNDEF _ => jobs;
fun get_deps (jobs: jobs) task =
Task_Graph.imm_preds jobs task handle Task_Graph.UNDEF _ => [];
fun enqueue group deps pri job (Queue {groups, jobs, cache}) =
let
val task = new_task pri;
val groups' = groups
|> fold (fn gid => Inttab.cons_list (gid, task)) (group_ancestry group);
val jobs' = jobs
|> Task_Graph.new_node (task, (group, Job [job]))
|> fold (add_job task) deps
|> fold (fold (add_job task) o get_deps jobs) deps;
val minimal = null (get_deps jobs' task);
val cache' =
(case cache of
Result last =>
if task_ord (last, task) = LESS
then cache else Unknown
| _ => Unknown);
in ((task, minimal), make_queue groups' jobs' cache') end;
fun extend task job (Queue {groups, jobs, cache}) =
(case try (get_job jobs) task of
SOME (Job list) => SOME (make_queue groups (set_job task (Job (job :: list)) jobs) cache)
| _ => NONE);
(* dequeue *)
fun dequeue (queue as Queue {groups, jobs, cache}) =
let
fun ready (task, ((group, Job list), ([], _))) = SOME (task, group, rev list)
| ready _ = NONE;
fun deq boundary =
(case Task_Graph.get_first boundary ready jobs of
NONE => (NONE, make_queue groups jobs No_Result)
| SOME (result as (task, _, _)) =>
let
val jobs' = set_job task (Running (Thread.self ())) jobs;
val cache' = Result task;
in (SOME result, make_queue groups jobs' cache') end);
in
(case cache of
Unknown => deq NONE
| Result last => deq (SOME last)
| No_Result => (NONE, queue))
end;
(* dequeue_towards -- adhoc dependencies *)
fun dequeue_towards deps (queue as Queue {groups, jobs, ...}) =
let
fun ready task =
(case Task_Graph.get_node jobs task of
(group, Job list) =>
if null (Task_Graph.imm_preds jobs task)
then SOME (task, group, rev list)
else NONE
| _ => NONE);
val tasks = filter (can (Task_Graph.get_node jobs)) deps;
fun result (res as (task, _, _)) =
let
val jobs' = set_job task (Running (Thread.self ())) jobs;
val cache' = Unknown;
in ((SOME res, tasks), make_queue groups jobs' cache') end;
in
(case get_first ready tasks of
SOME res => result res
| NONE =>
(case get_first (get_first ready o Task_Graph.imm_preds jobs) tasks of
SOME res => result res
| NONE => ((NONE, tasks), queue)))
end;
(* finish *)
fun finish task (Queue {groups, jobs, cache}) =
let
val group = get_group jobs task;
val groups' = groups
|> fold (fn gid => Inttab.remove_list (op =) (gid, task)) (group_ancestry group);
val jobs' = Task_Graph.del_node task jobs;
val maximal = null (Task_Graph.imm_succs jobs task);
val cache' = if maximal then cache else Unknown;
in (maximal, make_queue groups' jobs' cache') end;
end;