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;

--- a/src/Pure/Concurrent/task_queue.ML	Tue Sep 09 16:17:08 2008 +0200
+++ b/src/Pure/Concurrent/task_queue.ML	Tue Sep 09 16:29:32 2008 +0200
@@ -12,12 +12,10 @@
   val new_group: unit -> group
   type queue
   val empty: queue
-  val enqueue: group option -> task list -> (unit -> bool) -> queue -> task * queue
-  val dequeue: Thread.thread -> queue -> (task * group option * (unit -> bool)) option * queue
-  val finished: task -> queue -> queue
-  val interrupt_task: queue -> task -> unit
-  val interrupt_group: queue -> group -> unit
-  val interrupt_task_group: queue -> task -> unit
+  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 =
@@ -31,83 +29,80 @@
 fun new_group () = Group (serial ());
 
 
-(* queue of dependent jobs *)
+(* jobs *)
 
 datatype job =
-  Job of unit -> bool |
+  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
-  {jobs: (group option * job) IntGraph.T,                         (*job dependency graph*)
-   cache: (task * group option * (unit -> bool)) Queue.T option,  (*cache of ready tasks*)
-   groups: task list Inttab.table};                               (*active group members*)
+ {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 jobs cache groups =
-  Queue {jobs = jobs, cache = cache, groups = groups};
+fun make_queue groups jobs cache =
+  Queue {groups = groups, jobs = jobs, cache = cache};
+
+val empty = make_queue Inttab.empty IntGraph.empty NONE;
 
 
 (* queue operations *)
 
-val empty = make_queue IntGraph.empty NONE Inttab.empty;
-
-fun enqueue group deps job (Queue {jobs, groups, ...}) =
+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 job)) |> fold add_dep deps;
+    val jobs' = jobs |> IntGraph.new_node (id, (group, Job (true, job))) |> fold add_dep deps;
+  in (task, make_queue groups' jobs' NONE) end;
 
-    val groups' =
-      (case group of
-        NONE => groups
-      | SOME (Group gid) => Inttab.cons_list (gid, task) groups);
-  in (task, make_queue jobs' NONE groups') end;
-
-fun dequeue thread (queue as Queue {jobs, cache, groups}) =
+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 =>
-          let
-            fun add (id, ((group, Job job), ([], _))) = Queue.enqueue (Task id, group, job)
-              | add _ = I;
-          in IntGraph.fold add jobs Queue.empty end);
+      | NONE => IntGraph.fold add_ready jobs Queue.empty);
   in
-    if Queue.is_empty ready then (NONE, make_queue jobs (SOME ready) groups)
-    else
-      let
-        val (result as (Task id, _, _), ready') = Queue.dequeue ready;
-        val jobs' = IntGraph.map_node id (fn (group, _) => (group, Running thread)) jobs;
-      in (SOME result, make_queue jobs' (SOME ready') groups) end
+    (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;
 
-fun finished (task as Task id) (Queue {jobs, groups, ...}) =
-  let
-    val groups' =
-      (case #1 (IntGraph.get_node jobs id) of
-        NONE => groups
-      | SOME (Group gid) => Inttab.remove_list (op =) (gid, task) groups);
-    val jobs' = IntGraph.del_nodes [id] jobs;
-  in make_queue jobs' NONE groups' end;
 
-
-(* interrupt *)
+(* termination *)
 
-fun interrupt_task (Queue {jobs, ...}) (Task id) =
-  (case IntGraph.get_node jobs id of
-    (_, Running thread) => (Thread.interrupt thread handle Thread _ => ())
-  | _ => ())
-  handle IntGraph.UNDEF _ => ();
+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 interrupt_group (queue as Queue {groups, ...}) (Group gid) =
-  List.app (interrupt_task queue) (Inttab.lookup_list groups gid);
-
-fun interrupt_task_group (queue as Queue {jobs, ...}) (task as Task id) =
-  (case IntGraph.get_node jobs id of
-    (NONE, _) => interrupt_task queue task
-  | (SOME group, _) => interrupt_group queue group);
+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;