job: explicit 'ok' status -- false for canceled jobs;
group is now non-optional;
tuned signature;
replaced low-level interrupts by group cancel operation;
misc tuning;
(* Title: Pure/Concurrent/task_queue.ML
ID: $Id$
Author: Makarius
Ordered queue of grouped tasks.
*)
signature TASK_QUEUE =
sig
eqtype task
eqtype group
val new_group: unit -> group
type queue
val empty: queue
val enqueue: group -> task list -> (bool -> bool) -> queue -> task * queue
val dequeue: Thread.thread -> queue -> (task * group * (unit -> bool)) option * queue
val cancel: group -> queue -> Thread.thread list * queue
val finish: task -> queue -> queue
end;
structure TaskQueue: TASK_QUEUE =
struct
(* identifiers *)
datatype task = Task of serial;
datatype group = Group of serial;
fun new_group () = Group (serial ());
(* jobs *)
datatype job =
Job of bool * (bool -> bool) |
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;
(* queue of grouped jobs *)
datatype queue = Queue of
{groups: task list Inttab.table, (*groups with presently active members*)
jobs: jobs, (*job dependency graph*)
cache: (task * group * (unit -> bool)) Queue.T option}; (*cache of ready tasks*)
fun make_queue groups jobs cache =
Queue {groups = groups, jobs = jobs, cache = cache};
val empty = make_queue Inttab.empty IntGraph.empty NONE;
(* queue operations *)
fun enqueue (group as Group gid) deps job (Queue {groups, jobs, ...}) =
let
val id = serial ();
val task = Task id;
val groups' = Inttab.cons_list (gid, task) groups;
fun add_dep (Task dep) G = IntGraph.add_edge_acyclic (dep, id) G
handle IntGraph.UNDEF _ => G;
val jobs' = jobs |> IntGraph.new_node (id, (group, Job (true, job))) |> fold add_dep deps;
in (task, make_queue groups' jobs' NONE) end;
fun dequeue thread (queue as Queue {groups, jobs, cache}) =
let
fun add_ready (id, ((group, Job (ok, job)), ([], _))) =
Queue.enqueue (Task id, group, (fn () => job ok))
| add_ready _ = I;
val ready =
(case cache of
SOME ready => ready
| NONE => IntGraph.fold add_ready jobs Queue.empty);
in
(case try Queue.dequeue ready of
NONE => (NONE, make_queue groups jobs (SOME ready))
| SOME (result, ready') =>
let val jobs' = map_job (#1 result) (K (Running thread)) jobs
in (SOME result, make_queue groups jobs' (SOME ready')) end)
end;
(* termination *)
fun cancel (group as Group gid) (Queue {groups, jobs, ...}) =
let
val tasks = Inttab.lookup_list groups gid;
val running = fold (get_job jobs #> (fn Running thread => cons thread | _ => I)) tasks [];
val jobs' = fold (fn task =>
(case get_job jobs task of
Job (true, job) => map_job task (K (Job (false, job)))
| _ => I)) tasks jobs;
in (running, make_queue groups jobs' NONE) end;
fun finish (task as Task id) (Queue {groups, jobs, ...}) =
let
val Group gid = get_group jobs task;
val groups' = Inttab.remove_list (op =) (gid, task) groups;
val jobs' = IntGraph.del_nodes [id] jobs;
in make_queue groups' jobs' NONE end;
end;