(* Title: Pure/Concurrent/task_queue.ML
ID: $Id$
Author: Makarius
Ordered queue of grouped tasks.
*)
signature TASK_QUEUE =
sig
eqtype task
val str_of_task: task -> string
eqtype group
val new_group: unit -> group
val str_of_group: group -> string
type queue
val empty: queue
val is_empty: queue -> bool
val enqueue: group -> task list -> bool -> (bool -> bool) -> queue -> task * queue
val depend: task list -> task -> queue -> queue
val focus: task list -> queue -> queue
val dequeue: queue -> (task * group * (unit -> bool)) option * queue
val dequeue_towards: task list -> queue -> (task * group * (unit -> bool)) option * queue
val interrupt: queue -> task -> unit
val interrupt_external: queue -> string -> unit
val finish: task -> queue -> queue
val cancel: queue -> group -> bool
end;
structure TaskQueue: TASK_QUEUE =
struct
(* identifiers *)
datatype task = Task of serial;
fun str_of_task (Task i) = string_of_int i;
datatype group = Group of serial * bool ref;
fun new_group () = Group (serial (), ref true);
fun str_of_group (Group (i, ref ok)) =
if ok then string_of_int i else enclose "(" ")" (string_of_int i);
(* jobs *)
datatype job =
Job of bool * (bool -> bool) | (*priority, job: status -> status*)
Running of Thread.thread;
type jobs = (group * job) IntGraph.T;
fun get_group (jobs: jobs) (Task id) = #1 (IntGraph.get_node jobs id);
fun get_job (jobs: jobs) (Task id) = #2 (IntGraph.get_node jobs id);
fun map_job (Task id) f (jobs: jobs) = IntGraph.map_node id (apsnd f) jobs;
fun add_job (Task id) (Task dep) (jobs: jobs) =
IntGraph.add_edge_acyclic (dep, id) jobs handle IntGraph.UNDEF _ => jobs;
fun check_job (jobs: jobs) (task as Task id) =
if can (IntGraph.get_node jobs) id then SOME task else NONE;
(* queue of grouped jobs *)
datatype queue = Queue of
{groups: task list Inttab.table, (*groups with presently active members*)
jobs: jobs, (*job dependency graph*)
focus: task list}; (*particular collection of high-priority tasks*)
fun make_queue groups jobs focus = Queue {groups = groups, jobs = jobs, focus = focus};
val empty = make_queue Inttab.empty IntGraph.empty [];
fun is_empty (Queue {jobs, ...}) = IntGraph.is_empty jobs;
(* enqueue *)
fun enqueue (group as Group (gid, _)) deps pri job (Queue {groups, jobs, focus}) =
let
val id = serial ();
val task = Task id;
val groups' = Inttab.cons_list (gid, task) groups;
val jobs' = jobs
|> IntGraph.new_node (id, (group, Job (pri, job))) |> fold (add_job task) deps;
in (task, make_queue groups' jobs' focus) end;
fun depend deps task (Queue {groups, jobs, focus}) =
make_queue groups (fold (add_job task) deps jobs) focus;
fun focus tasks (Queue {groups, jobs, ...}) =
make_queue groups jobs (map_filter (check_job jobs) tasks);
(* dequeue *)
local
fun dequeue_result NONE queue = (NONE, queue)
| dequeue_result (SOME (result as (task, _, _))) (Queue {groups, jobs, focus}) =
(SOME result, make_queue groups (map_job task (K (Running (Thread.self ()))) jobs) focus);
fun dequeue_global req_pri (queue as Queue {jobs, ...}) =
let
fun ready (id, ((group as Group (_, ref ok), Job (pri, job)), ([], _))) =
if pri = req_pri then SOME (Task id, group, (fn () => job ok)) else NONE
| ready _ = NONE;
in dequeue_result (IntGraph.get_first ready jobs) queue end;
fun dequeue_local focus (queue as Queue {jobs, ...}) =
let
fun ready id =
(case IntGraph.get_node jobs id of
(group as Group (_, ref ok), Job (_, job)) =>
if null (IntGraph.imm_preds jobs id) then SOME (Task id, group, (fn () => job ok))
else NONE
| _ => NONE);
val ids = map (fn Task id => id) focus;
in dequeue_result (get_first ready (IntGraph.all_preds jobs ids)) queue end;
in
fun dequeue (queue as Queue {focus, ...}) =
(case dequeue_local focus queue of
(NONE, _) =>
(case dequeue_global true queue of (NONE, _) => dequeue_global false queue | res => res)
| res => res);
fun dequeue_towards tasks (queue as Queue {jobs, ...}) =
dequeue_local (map_filter (check_job jobs) tasks) queue;
end;
(* sporadic interrupts *)
fun interrupt_thread thread = Thread.interrupt thread handle Thread _ => ();
fun interrupt (Queue {jobs, ...}) task =
(case try (get_job jobs) task of SOME (Running thread) => interrupt_thread thread | _ => ());
fun interrupt_external queue str =
(case Int.fromString str of SOME id => interrupt queue (Task id) | NONE => ());
(* misc operations *)
fun cancel (Queue {groups, jobs, ...}) (Group (gid, ok)) =
let
val _ = ok := false; (*invalidate any future group members*)
val tasks = Inttab.lookup_list groups gid;
val running = fold (get_job jobs #> (fn Running thread => cons thread | _ => I)) tasks [];
val _ = List.app interrupt_thread running;
in null running end;
fun finish (task as Task id) (Queue {groups, jobs, focus}) =
let
val Group (gid, _) = get_group jobs task;
val groups' = Inttab.remove_list (op =) (gid, task) groups;
val jobs' = IntGraph.del_node id jobs;
val focus' = remove (op =) task focus;
in make_queue groups' jobs' focus' end;
end;