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root/jsr166/jsr166/src/jsr166y/ForkJoinTask.java

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.17 by jsr166, Sat Jul 25 00:34:00 2009 UTC vs.
Revision 1.39 by jsr166, Wed Aug 5 00:57:41 2009 UTC

#	Line 12 | Line 12 | import java.io.Serializable;
12		import java.util.Collection;
13		import java.util.Collections;
14		import java.util.List;
15	+	import java.util.RandomAccess;
16		import java.util.Map;
17		import java.util.WeakHashMap;
18
19		/**
20	<	* Abstract base class for tasks that run within a {@link
21	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22		* lighter weight than a normal thread.  Huge numbers of tasks and
23		* subtasks may be hosted by a small number of actual threads in a
24		* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods {@code fork}
30	<	* and {@code join}, or derivatives such as
31	<	* {@code invokeAll}.  However, this class also provides a number
32	<	* of other methods that can come into play in advanced usages, as
33	<	* well as extension mechanics that allow support of new forms of
34	<	* fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid {@code synchronized}
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as {@code IOExceptions}
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include RejectedExecutionExceptions stemming from
60	>	* internal resource exhaustion such as failure to allocate internal
61	>	* task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
#	Line 66 | Line 68 | import java.util.WeakHashMap;
68		* execute other tasks while awaiting joins, which is sometimes more
69		* efficient but only applies when all subtasks are known to be
70		* strictly tree-structured. Method {@link #invoke} is semantically
71	<	* equivalent to {@code fork(); join()} but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74		* may be useful when a set of tasks are being executed, and you need
75		* to delay processing of results or exceptions until all complete.
76		* Method {@code invokeAll} (available in multiple versions)
77		* performs the most common form of parallel invocation: forking a set
78		* of tasks and joining them all.
79		*
80	<	* <p> The ForkJoinTask class is not usually directly subclassed.
80	>	* <p>The execution status of tasks may be queried at several levels
81	>	* of detail: {@link #isDone} is true if a task completed in any way
82	>	* (including the case where a task was cancelled without executing);
83	>	* {@link #isCancelled} is true if completion was due to cancellation;
84	>	* {@link #isCompletedNormally} is true if a task completed without
85	>	* cancellation or encountering an exception; {@link
86	>	* #isCompletedExceptionally} is true if if the task encountered an
87	>	* exception (in which case {@link #getException} returns the
88	>	* exception); {@link #isCancelled} is true if the task was cancelled
89	>	* (in which case {@link #getException} returns a {@link
90	>	* java.util.concurrent.CancellationException}); and {@link
91	>	* #isCompletedAbnormally} is true if a task was either cancelled or
92	>	* encountered an exception.
93	>	*
94	>	* <p>The ForkJoinTask class is not usually directly subclassed.
95		* Instead, you subclass one of the abstract classes that support a
96	<	* particular style of fork/join processing.  Normally, a concrete
96	>	* particular style of fork/join processing, typically {@link
97	>	* RecursiveAction} for computations that do not return results, or
98	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
99		* ForkJoinTask subclass declares fields comprising its parameters,
100		* established in a constructor, and then defines a {@code compute}
101		* method that somehow uses the control methods supplied by this base
102		* class. While these methods have {@code public} access (to allow
103	<	* instances of different task subclasses to call each others
103	>	* instances of different task subclasses to call each other's
104		* methods), some of them may only be called from within other
105		* ForkJoinTasks (as may be determined using method {@link
106		* #inForkJoinPool}).  Attempts to invoke them in other contexts
107		* result in exceptions or errors, possibly including
108		* ClassCastException.
109		*
110	<	* <p>Most base support methods are {@code final} because their
111	<	* implementations are intrinsically tied to the underlying
112	<	* lightweight task scheduling framework, and so cannot be overridden.
113	<	* Developers creating new basic styles of fork/join processing should
114	<	* minimally implement {@code protected} methods
115	<	* {@code exec}, {@code setRawResult}, and
116	<	* {@code getRawResult}, while also introducing an abstract
117	<	* computational method that can be implemented in its subclasses,
118	<	* possibly relying on other {@code protected} methods provided
101	<	* by this class.
110	>	* <p>Most base support methods are {@code final}, to prevent
111	>	* overriding of implementations that are intrinsically tied to the
112	>	* underlying lightweight task scheduling framework.  Developers
113	>	* creating new basic styles of fork/join processing should minimally
114	>	* implement {@code protected} methods {@link #exec}, {@link
115	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
116	>	* an abstract computational method that can be implemented in its
117	>	* subclasses, possibly relying on other {@code protected} methods
118	>	* provided by this class.
119		*
120		* <p>ForkJoinTasks should perform relatively small amounts of
121	<	* computations, otherwise splitting into smaller tasks. As a very
122	<	* rough rule of thumb, a task should perform more than 100 and less
123	<	* than 10000 basic computational steps. If tasks are too big, then
124	<	* parallelism cannot improve throughput. If too small, then memory
125	<	* and internal task maintenance overhead may overwhelm processing.
121	>	* computation. Large tasks should be split into smaller subtasks,
122	>	* usually via recursive decomposition. As a very rough rule of thumb,
123	>	* a task should perform more than 100 and less than 10000 basic
124	>	* computational steps. If tasks are too big, then parallelism cannot
125	>	* improve throughput. If too small, then memory and internal task
126	>	* maintenance overhead may overwhelm processing.
127	>	*
128	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
129	>	* and {@link Callable}, that may be of use when mixing execution of
130	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
131	>	* are of this form, consider using a pool in
132	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
133		*
134	<	* <p>ForkJoinTasks are {@code Serializable}, which enables them
135	<	* to be used in extensions such as remote execution frameworks. It is
136	<	* in general sensible to serialize tasks only before or after, but
137	<	* not during execution. Serialization is not relied on during
114	<	* execution itself.
134	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
135	>	* used in extensions such as remote execution frameworks. It is
136	>	* sensible to serialize tasks only before or after, but not during,
137	>	* execution. Serialization is not relied on during execution itself.
138		*
139		* @since 1.7
140		* @author Doug Lea
#	Line 248 | Line 271 | public abstract class ForkJoinTask<V> im
271		synchronized (this) {
272		try {
273		while (status >= 0) {
274	<	long nt = nanos - System.nanoTime() - startTime;
274	>	long nt = nanos - (System.nanoTime() - startTime);
275		if (nt <= 0)
276		break;
277		wait(nt / 1000000, (int) (nt % 1000000));
#	Line 369 | Line 392 | public abstract class ForkJoinTask<V> im
392
393		/**
394		* Returns result or throws exception using j.u.c.Future conventions.
395	<	* Only call when {@code isDone} known to be true.
395	>	* Only call when {@code isDone} known to be true or thread known
396	>	* to be interrupted.
397		*/
398		private V reportFutureResult()
399	<	throws ExecutionException, InterruptedException {
399	>	throws InterruptedException, ExecutionException {
400	>	if (Thread.interrupted())
401	>	throw new InterruptedException();
402		int s = status & COMPLETION_MASK;
403		if (s < NORMAL) {
404		Throwable ex;
#	Line 380 | Line 406 | public abstract class ForkJoinTask<V> im
406		throw new CancellationException();
407		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
408		throw new ExecutionException(ex);
383	–	if (Thread.interrupted())
384	–	throw new InterruptedException();
409		}
410		return getRawResult();
411		}
#	Line 392 | Line 416 | public abstract class ForkJoinTask<V> im
416		*/
417		private V reportTimedFutureResult()
418		throws InterruptedException, ExecutionException, TimeoutException {
419	+	if (Thread.interrupted())
420	+	throw new InterruptedException();
421		Throwable ex;
422		int s = status & COMPLETION_MASK;
423		if (s == NORMAL)
424		return getRawResult();
425	<	if (s == CANCELLED)
425	>	else if (s == CANCELLED)
426		throw new CancellationException();
427	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
428		throw new ExecutionException(ex);
429	<	if (Thread.interrupted())
430	<	throw new InterruptedException();
405	<	throw new TimeoutException();
429	>	else
430	>	throw new TimeoutException();
431		}
432
433		// internal execution methods
#	Line 487 | Line 512 | public abstract class ForkJoinTask<V> im
512		/**
513		* Arranges to asynchronously execute this task.  While it is not
514		* necessarily enforced, it is a usage error to fork a task more
515	<	* than once unless it has completed and been reinitialized.  This
516	<	* method may be invoked only from within ForkJoinTask
517	<	* computations (as may be determined using method {@link
518	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
519	<	* in exceptions or errors, possibly including ClassCastException.
515	>	* than once unless it has completed and been reinitialized.
516	>	*
517	>	* <p>This method may be invoked only from within {@code
518	>	* ForkJoinTask} computations (as may be determined using method
519	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
520	>	* result in exceptions or errors, possibly including {@code
521	>	* ClassCastException}.
522	>	*
523	>	* @return {@code this}, to simplify usage
524		*/
525	<	public final void fork() {
525	>	public final ForkJoinTask<V> fork() {
526		((ForkJoinWorkerThread) Thread.currentThread())
527		.pushTask(this);
528	+	return this;
529		}
530
531		/**
532		* Returns the result of the computation when it is ready.
533	<	* This method differs from {@code get} in that abnormal
534	<	* completion results in RuntimeExceptions or Errors, not
535	<	* ExecutionExceptions.
533	>	* This method differs from {@link #get()} in that
534	>	* abnormal completion results in {@code RuntimeException} or
535	>	* {@code Error}, not {@code ExecutionException}.
536		*
537		* @return the computed result
538		*/
#	Line 515 | Line 545 | public abstract class ForkJoinTask<V> im
545
546		/**
547		* Commences performing this task, awaits its completion if
548	<	* necessary, and return its result.
548	>	* necessary, and return its result, or throws an (unchecked)
549	>	* exception if the underlying computation did so.
550		*
520	–	* @throws Throwable (a RuntimeException, Error, or unchecked
521	–	* exception) if the underlying computation did so
551		* @return the computed result
552		*/
553		public final V invoke() {
#	Line 529 | Line 558 | public abstract class ForkJoinTask<V> im
558		}
559
560		/**
561	<	* Forks both tasks, returning when {@code isDone} holds for
562	<	* both of them or an exception is encountered. This method may be
563	<	* invoked only from within ForkJoinTask computations (as may be
564	<	* determined using method {@link #inForkJoinPool}). Attempts to
565	<	* invoke in other contexts result in exceptions or errors,
566	<	* possibly including ClassCastException.
567	<	*
568	<	* @param t1 one task
569	<	* @param t2 the other task
570	<	* @throws NullPointerException if t1 or t2 are null
571	<	* @throws RuntimeException or Error if either task did so
561	>	* Forks the given tasks, returning when {@code isDone} holds for
562	>	* each task or an (unchecked) exception is encountered, in which
563	>	* case the exception is rethrown.  If either task encounters an
564	>	* exception, the other one may be, but is not guaranteed to be,
565	>	* cancelled.  If both tasks throw an exception, then this method
566	>	* throws one of them.  The individual status of each task may be
567	>	* checked using {@link #getException()} and related methods.
568	>	*
569	>	* <p>This method may be invoked only from within {@code
570	>	* ForkJoinTask} computations (as may be determined using method
571	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
572	>	* result in exceptions or errors, possibly including {@code
573	>	* ClassCastException}.
574	>	*
575	>	* @param t1 the first task
576	>	* @param t2 the second task
577	>	* @throws NullPointerException if any task is null
578		*/
579	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
579	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
580		t2.fork();
581		t1.invoke();
582		t2.join();
583		}
584
585		/**
586	<	* Forks the given tasks, returning when {@code isDone} holds
587	<	* for all of them. If any task encounters an exception, others
588	<	* may be cancelled.  This method may be invoked only from within
589	<	* ForkJoinTask computations (as may be determined using method
590	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
591	<	* result in exceptions or errors, possibly including
592	<	* ClassCastException.
586	>	* Forks the given tasks, returning when {@code isDone} holds for
587	>	* each task or an (unchecked) exception is encountered, in which
588	>	* case the exception is rethrown. If any task encounters an
589	>	* exception, others may be, but are not guaranteed to be,
590	>	* cancelled.  If more than one task encounters an exception, then
591	>	* this method throws any one of these exceptions.  The individual
592	>	* status of each task may be checked using {@link #getException()}
593	>	* and related methods.
594	>	*
595	>	* <p>This method may be invoked only from within {@code
596	>	* ForkJoinTask} computations (as may be determined using method
597	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
598	>	* result in exceptions or errors, possibly including {@code
599	>	* ClassCastException}.
600		*
601	<	* @param tasks the array of tasks
602	<	* @throws NullPointerException if tasks or any element are null
561	<	* @throws RuntimeException or Error if any task did so
601	>	* @param tasks the tasks
602	>	* @throws NullPointerException if any task is null
603		*/
604		public static void invokeAll(ForkJoinTask<?>... tasks) {
605		Throwable ex = null;
#	Line 594 | Line 635 | public abstract class ForkJoinTask<V> im
635		}
636
637		/**
638	<	* Forks all tasks in the collection, returning when
639	<	* {@code isDone} holds for all of them. If any task
640	<	* encounters an exception, others may be cancelled.  This method
641	<	* may be invoked only from within ForkJoinTask computations (as
642	<	* may be determined using method {@link
643	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
644	<	* in exceptions or errors, possibly including ClassCastException.
638	>	* Forks all tasks in the specified collection, returning when
639	>	* {@code isDone} holds for each task or an (unchecked) exception
640	>	* is encountered.  If any task encounters an exception, others
641	>	* may be, but are not guaranteed to be, cancelled.  If more than
642	>	* one task encounters an exception, then this method throws any
643	>	* one of these exceptions.  The individual status of each task
644	>	* may be checked using {@link #getException()} and related
645	>	* methods.  The behavior of this operation is undefined if the
646	>	* specified collection is modified while the operation is in
647	>	* progress.
648	>	*
649	>	* <p>This method may be invoked only from within {@code
650	>	* ForkJoinTask} computations (as may be determined using method
651	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
652	>	* result in exceptions or errors, possibly including {@code
653	>	* ClassCastException}.
654		*
655		* @param tasks the collection of tasks
656	+	* @return the tasks argument, to simplify usage
657		* @throws NullPointerException if tasks or any element are null
607	–	* @throws RuntimeException or Error if any task did so
658		*/
659	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
660	<	if (!(tasks instanceof List<?>)) {
659	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
660	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
661		invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
662	<	return;
662	>	return tasks;
663		}
664		@SuppressWarnings("unchecked")
665		List<? extends ForkJoinTask<?>> ts =
#	Line 644 | Line 694 | public abstract class ForkJoinTask<V> im
694		}
695		if (ex != null)
696		rethrowException(ex);
697	+	return tasks;
698	+	}
699	+
700	+	/**
701	+	* Attempts to cancel execution of this task. This attempt will
702	+	* fail if the task has already completed, has already been
703	+	* cancelled, or could not be cancelled for some other reason. If
704	+	* successful, and this task has not started when cancel is
705	+	* called, execution of this task is suppressed, {@link
706	+	* #isCancelled} will report true, and {@link #join} will result
707	+	* in a {@code CancellationException} being thrown.
708	+	*
709	+	* <p>This method may be overridden in subclasses, but if so, must
710	+	* still ensure that these minimal properties hold. In particular,
711	+	* the {@code cancel} method itself must not throw exceptions.
712	+	*
713	+	* <p>This method is designed to be invoked by <em>other</em>
714	+	* tasks. To terminate the current task, you can just return or
715	+	* throw an unchecked exception from its computation method, or
716	+	* invoke {@link #completeExceptionally}.
717	+	*
718	+	* @param mayInterruptIfRunning this value is ignored in the
719	+	* default implementation because tasks are not
720	+	* cancelled via interruption
721	+	*
722	+	* @return {@code true} if this task is now cancelled
723	+	*/
724	+	public boolean cancel(boolean mayInterruptIfRunning) {
725	+	setCompletion(CANCELLED);
726	+	return (status & COMPLETION_MASK) == CANCELLED;
727		}
728
729		/**
730	<	* Returns true if the computation performed by this task has
731	<	* completed (or has been cancelled).
730	>	* Returns {@code true} if the computation performed by this task
731	>	* has completed (or has been cancelled).
732		*
733	<	* @return true if this computation has completed
733	>	* @return {@code true} if this computation has completed
734		*/
735		public final boolean isDone() {
736		return status < 0;
737		}
738
739		/**
740	<	* Returns true if this task was cancelled.
740	>	* Returns {@code true} if this task was cancelled.
741		*
742	<	* @return true if this task was cancelled
742	>	* @return {@code true} if this task was cancelled
743		*/
744		public final boolean isCancelled() {
745		return (status & COMPLETION_MASK) == CANCELLED;
746		}
747
748		/**
749	<	* Asserts that the results of this task's computation will not be
670	<	* used. If a cancellation occurs before attempting to execute this
671	<	* task, then execution will be suppressed, {@code isCancelled}
672	<	* will report true, and {@code join} will result in a
673	<	* {@code CancellationException} being thrown. Otherwise, when
674	<	* cancellation races with completion, there are no guarantees
675	<	* about whether {@code isCancelled} will report true, whether
676	<	* {@code join} will return normally or via an exception, or
677	<	* whether these behaviors will remain consistent upon repeated
678	<	* invocation.
679	<	*
680	<	* <p>This method may be overridden in subclasses, but if so, must
681	<	* still ensure that these minimal properties hold. In particular,
682	<	* the cancel method itself must not throw exceptions.
683	<	*
684	<	* <p> This method is designed to be invoked by <em>other</em>
685	<	* tasks. To terminate the current task, you can just return or
686	<	* throw an unchecked exception from its computation method, or
687	<	* invoke {@code completeExceptionally}.
749	>	* Returns {@code true} if this task threw an exception or was cancelled.
750		*
751	<	* @param mayInterruptIfRunning this value is ignored in the
752	<	* default implementation because tasks are not in general
753	<	* cancelled via interruption
751	>	* @return {@code true} if this task threw an exception or was cancelled
752	>	*/
753	>	public final boolean isCompletedAbnormally() {
754	>	return (status & COMPLETION_MASK) < NORMAL;
755	>	}
756	>
757	>	/**
758	>	* Returns {@code true} if this task completed without throwing an
759	>	* exception and was not cancelled.
760		*
761	<	* @return true if this task is now cancelled
761	>	* @return {@code true} if this task completed without throwing an
762	>	* exception and was not cancelled
763		*/
764	<	public boolean cancel(boolean mayInterruptIfRunning) {
765	<	setCompletion(CANCELLED);
697	<	return (status & COMPLETION_MASK) == CANCELLED;
764	>	public final boolean isCompletedNormally() {
765	>	return (status & COMPLETION_MASK) == NORMAL;
766		}
767
768		/**
769	<	* Returns true if this task threw an exception or was cancelled.
769	>	* Returns {@code true} if this task threw an exception.
770		*
771	<	* @return true if this task threw an exception or was cancelled
771	>	* @return {@code true} if this task threw an exception
772		*/
773	<	public final boolean isCompletedAbnormally() {
774	<	return (status & COMPLETION_MASK) < NORMAL;
773	>	public final boolean isCompletedExceptionally() {
774	>	return (status & COMPLETION_MASK) == EXCEPTIONAL;
775		}
776
777		/**
778		* Returns the exception thrown by the base computation, or a
779	<	* CancellationException if cancelled, or null if none or if the
780	<	* method has not yet completed.
779	>	* {@code CancellationException} if cancelled, or {@code null} if
780	>	* none or if the method has not yet completed.
781		*
782	<	* @return the exception, or null if none
782	>	* @return the exception, or {@code null} if none
783		*/
784		public final Throwable getException() {
785		int s = status & COMPLETION_MASK;
786	<	if (s >= NORMAL)
787	<	return null;
788	<	if (s == CANCELLED)
721	<	return new CancellationException();
722	<	return exceptionMap.get(this);
786	>	return ((s >= NORMAL)    ? null :
787	>	(s == CANCELLED) ? new CancellationException() :
788	>	exceptionMap.get(this));
789		}
790
791		/**
#	Line 728 | Line 794 | public abstract class ForkJoinTask<V> im
794		* {@code join} and related operations. This method may be used
795		* to induce exceptions in asynchronous tasks, or to force
796		* completion of tasks that would not otherwise complete.  Its use
797	<	* in other situations is likely to be wrong.  This method is
797	>	* in other situations is discouraged.  This method is
798		* overridable, but overridden versions must invoke {@code super}
799		* implementation to maintain guarantees.
800		*
#	Line 748 | Line 814 | public abstract class ForkJoinTask<V> im
814		* operations. This method may be used to provide results for
815		* asynchronous tasks, or to provide alternative handling for
816		* tasks that would not otherwise complete normally. Its use in
817	<	* other situations is likely to be wrong. This method is
817	>	* other situations is discouraged. This method is
818		* overridable, but overridden versions must invoke {@code super}
819		* implementation to maintain guarantees.
820		*
#	Line 773 | Line 839 | public abstract class ForkJoinTask<V> im
839
840		public final V get(long timeout, TimeUnit unit)
841		throws InterruptedException, ExecutionException, TimeoutException {
842	+	long nanos = unit.toNanos(timeout);
843		ForkJoinWorkerThread w = getWorker();
844		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
845	<	awaitDone(w, unit.toNanos(timeout));
845	>	awaitDone(w, nanos);
846		return reportTimedFutureResult();
847		}
848
#	Line 786 | Line 853 | public abstract class ForkJoinTask<V> im
853		* there are no potential dependencies between continuation of the
854		* current task and that of any other task that might be executed
855		* while helping. (This usually holds for pure divide-and-conquer
856	<	* tasks). This method may be invoked only from within
857	<	* ForkJoinTask computations (as may be determined using method
858	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
859	<	* result in exceptions or errors, possibly including
860	<	* ClassCastException.
856	>	* tasks).
857	>	*
858	>	* <p>This method may be invoked only from within {@code
859	>	* ForkJoinTask} computations (as may be determined using method
860	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
861	>	* result in exceptions or errors, possibly including {@code
862	>	* ClassCastException}.
863		*
864		* @return the computed result
865		*/
#	Line 803 | Line 872 | public abstract class ForkJoinTask<V> im
872
873		/**
874		* Possibly executes other tasks until this task is ready.  This
875	<	* method may be invoked only from within ForkJoinTask
876	<	* computations (as may be determined using method {@link
877	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
878	<	* in exceptions or errors, possibly including ClassCastException.
875	>	* method may be useful when processing collections of tasks when
876	>	* some have been cancelled or otherwise known to have aborted.
877	>	*
878	>	* <p>This method may be invoked only from within {@code
879	>	* ForkJoinTask} computations (as may be determined using method
880	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
881	>	* result in exceptions or errors, possibly including {@code
882	>	* ClassCastException}.
883		*/
884		public final void quietlyHelpJoin() {
885		if (status >= 0) {
#	Line 845 | Line 918 | public abstract class ForkJoinTask<V> im
918
919		/**
920		* Possibly executes tasks until the pool hosting the current task
921	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
922	<	* designs in which many tasks are forked, but none are explicitly
923	<	* joined, instead executing them until all are processed.
921	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
922	>	* be of use in designs in which many tasks are forked, but none
923	>	* are explicitly joined, instead executing them until all are
924	>	* processed.
925	>	*
926	>	* <p>This method may be invoked only from within {@code
927	>	* ForkJoinTask} computations (as may be determined using method
928	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
929	>	* result in exceptions or errors, possibly including {@code
930	>	* ClassCastException}.
931		*/
932		public static void helpQuiesce() {
933		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 860 | Line 940 | public abstract class ForkJoinTask<V> im
940		* this task, but only if reuse occurs when this task has either
941		* never been forked, or has been forked, then completed and all
942		* outstanding joins of this task have also completed. Effects
943	<	* under any other usage conditions are not guaranteed, and are
944	<	* almost surely wrong. This method may be useful when executing
943	>	* under any other usage conditions are not guaranteed.
944	>	* This method may be useful when executing
945		* pre-constructed trees of subtasks in loops.
946		*/
947		public void reinitialize() {
#	Line 874 | Line 954 | public abstract class ForkJoinTask<V> im
954		* Returns the pool hosting the current task execution, or null
955		* if this task is executing outside of any ForkJoinPool.
956		*
957	<	* @return the pool, or null if none
957	>	* @see #inForkJoinPool
958	>	* @return the pool, or {@code null} if none
959		*/
960		public static ForkJoinPool getPool() {
961		Thread t = Thread.currentThread();
#	Line 899 | Line 980 | public abstract class ForkJoinTask<V> im
980		* by the current thread, and has not commenced executing in
981		* another thread.  This method may be useful when arranging
982		* alternative local processing of tasks that could have been, but
983	<	* were not, stolen. This method may be invoked only from within
903	<	* ForkJoinTask computations (as may be determined using method
904	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
905	<	* result in exceptions or errors, possibly including
906	<	* ClassCastException.
983	>	* were not, stolen.
984		*
985	<	* @return true if unforked
985	>	* <p>This method may be invoked only from within {@code
986	>	* ForkJoinTask} computations (as may be determined using method
987	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
988	>	* result in exceptions or errors, possibly including {@code
989	>	* ClassCastException}.
990	>	*
991	>	* @return {@code true} if unforked
992		*/
993		public boolean tryUnfork() {
994		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 918 | Line 1001 | public abstract class ForkJoinTask<V> im
1001		* value may be useful for heuristic decisions about whether to
1002		* fork other tasks.
1003		*
1004	+	* <p>This method may be invoked only from within {@code
1005	+	* ForkJoinTask} computations (as may be determined using method
1006	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1007	+	* result in exceptions or errors, possibly including {@code
1008	+	* ClassCastException}.
1009	+	*
1010		* @return the number of tasks
1011		*/
1012		public static int getQueuedTaskCount() {
#	Line 935 | Line 1024 | public abstract class ForkJoinTask<V> im
1024		* tasks, and to process computations locally if this threshold is
1025		* exceeded.
1026		*
1027	+	* <p>This method may be invoked only from within {@code
1028	+	* ForkJoinTask} computations (as may be determined using method
1029	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1030	+	* result in exceptions or errors, possibly including {@code
1031	+	* ClassCastException}.
1032	+	*
1033		* @return the surplus number of tasks, which may be negative
1034		*/
1035		public static int getSurplusQueuedTaskCount() {
#	Line 945 | Line 1040 | public abstract class ForkJoinTask<V> im
1040		// Extension methods
1041
1042		/**
1043	<	* Returns the result that would be returned by {@code join},
1044	<	* even if this task completed abnormally, or null if this task is
1045	<	* not known to have been completed.  This method is designed to
1046	<	* aid debugging, as well as to support extensions. Its use in any
1047	<	* other context is discouraged.
1043	>	* Returns the result that would be returned by {@link #join}, even
1044	>	* if this task completed abnormally, or {@code null} if this task
1045	>	* is not known to have been completed.  This method is designed
1046	>	* to aid debugging, as well as to support extensions. Its use in
1047	>	* any other context is discouraged.
1048		*
1049	<	* @return the result, or null if not completed
1049	>	* @return the result, or {@code null} if not completed
1050		*/
1051		public abstract V getRawResult();
1052
#	Line 970 | Line 1065 | public abstract class ForkJoinTask<V> im
1065		* called otherwise. The return value controls whether this task
1066		* is considered to be done normally. It may return false in
1067		* asynchronous actions that require explicit invocations of
1068	<	* {@code complete} to become joinable. It may throw exceptions
1069	<	* to indicate abnormal exit.
1068	>	* {@link #complete} to become joinable. It may also throw an
1069	>	* (unchecked) exception to indicate abnormal exit.
1070		*
1071	<	* @return true if completed normally
977	<	* @throws Error or RuntimeException if encountered during computation
1071	>	* @return {@code true} if completed normally
1072		*/
1073		protected abstract boolean exec();
1074
1075		/**
1076	<	* Returns, but does not unschedule or execute, the task queued by
1077	<	* the current thread but not yet executed, if one is
1076	>	* Returns, but does not unschedule or execute, a task queued by
1077	>	* the current thread but not yet executed, if one is immediately
1078		* available. There is no guarantee that this task will actually
1079	<	* be polled or executed next.  This method is designed primarily
1080	<	* to support extensions, and is unlikely to be useful otherwise.
1081	<	* This method may be invoked only from within ForkJoinTask
1082	<	* computations (as may be determined using method {@link
1083	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
990	<	* in exceptions or errors, possibly including ClassCastException.
1079	>	* be polled or executed next. Conversely, this method may return
1080	>	* null even if a task exists but cannot be accessed without
1081	>	* contention with other threads.  This method is designed
1082	>	* primarily to support extensions, and is unlikely to be useful
1083	>	* otherwise.
1084		*
1085	<	* @return the next task, or null if none are available
1085	>	* <p>This method may be invoked only from within {@code
1086	>	* ForkJoinTask} computations (as may be determined using method
1087	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1088	>	* result in exceptions or errors, possibly including {@code
1089	>	* ClassCastException}.
1090	>	*
1091	>	* @return the next task, or {@code null} if none are available
1092		*/
1093		protected static ForkJoinTask<?> peekNextLocalTask() {
1094		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1000 | Line 1099 | public abstract class ForkJoinTask<V> im
1099		* Unschedules and returns, without executing, the next task
1100		* queued by the current thread but not yet executed.  This method
1101		* is designed primarily to support extensions, and is unlikely to
1102	<	* be useful otherwise.  This method may be invoked only from
1103	<	* within ForkJoinTask computations (as may be determined using
1104	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1105	<	* contexts result in exceptions or errors, possibly including
1106	<	* ClassCastException.
1102	>	* be useful otherwise.
1103	>	*
1104	>	* <p>This method may be invoked only from within {@code
1105	>	* ForkJoinTask} computations (as may be determined using method
1106	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1107	>	* result in exceptions or errors, possibly including {@code
1108	>	* ClassCastException}.
1109		*
1110	<	* @return the next task, or null if none are available
1110	>	* @return the next task, or {@code null} if none are available
1111		*/
1112		protected static ForkJoinTask<?> pollNextLocalTask() {
1113		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1021 | Line 1122 | public abstract class ForkJoinTask<V> im
1122		* {@code null} result does not necessarily imply quiescence
1123		* of the pool this task is operating in.  This method is designed
1124		* primarily to support extensions, and is unlikely to be useful
1125	<	* otherwise.  This method may be invoked only from within
1025	<	* ForkJoinTask computations (as may be determined using method
1026	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1027	<	* result in exceptions or errors, possibly including
1028	<	* ClassCastException.
1125	>	* otherwise.
1126		*
1127	<	* @return a task, or null if none are available
1127	>	* <p>This method may be invoked only from within {@code
1128	>	* ForkJoinTask} computations (as may be determined using method
1129	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1130	>	* result in exceptions or errors, possibly including {@code
1131	>	* ClassCastException}.
1132	>	*
1133	>	* @return a task, or {@code null} if none are available
1134		*/
1135		protected static ForkJoinTask<?> pollTask() {
1136		return ((ForkJoinWorkerThread) Thread.currentThread())
1137		.pollTask();
1138		}
1139
1140	+	/**
1141	+	* Adaptor for Runnables. This implements RunnableFuture
1142	+	* to be compliant with AbstractExecutorService constraints
1143	+	* when used in ForkJoinPool.
1144	+	*/
1145	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1146	+	implements RunnableFuture<T> {
1147	+	final Runnable runnable;
1148	+	final T resultOnCompletion;
1149	+	T result;
1150	+	AdaptedRunnable(Runnable runnable, T result) {
1151	+	if (runnable == null) throw new NullPointerException();
1152	+	this.runnable = runnable;
1153	+	this.resultOnCompletion = result;
1154	+	}
1155	+	public T getRawResult() { return result; }
1156	+	public void setRawResult(T v) { result = v; }
1157	+	public boolean exec() {
1158	+	runnable.run();
1159	+	result = resultOnCompletion;
1160	+	return true;
1161	+	}
1162	+	public void run() { invoke(); }
1163	+	private static final long serialVersionUID = 5232453952276885070L;
1164	+	}
1165	+
1166	+	/**
1167	+	* Adaptor for Callables
1168	+	*/
1169	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1170	+	implements RunnableFuture<T> {
1171	+	final Callable<? extends T> callable;
1172	+	T result;
1173	+	AdaptedCallable(Callable<? extends T> callable) {
1174	+	if (callable == null) throw new NullPointerException();
1175	+	this.callable = callable;
1176	+	}
1177	+	public T getRawResult() { return result; }
1178	+	public void setRawResult(T v) { result = v; }
1179	+	public boolean exec() {
1180	+	try {
1181	+	result = callable.call();
1182	+	return true;
1183	+	} catch (Error err) {
1184	+	throw err;
1185	+	} catch (RuntimeException rex) {
1186	+	throw rex;
1187	+	} catch (Exception ex) {
1188	+	throw new RuntimeException(ex);
1189	+	}
1190	+	}
1191	+	public void run() { invoke(); }
1192	+	private static final long serialVersionUID = 2838392045355241008L;
1193	+	}
1194	+
1195	+	/**
1196	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1197	+	* method of the given {@code Runnable} as its action, and returns
1198	+	* a null result upon {@link #join}.
1199	+	*
1200	+	* @param runnable the runnable action
1201	+	* @return the task
1202	+	*/
1203	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1204	+	return new AdaptedRunnable<Void>(runnable, null);
1205	+	}
1206	+
1207	+	/**
1208	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1209	+	* method of the given {@code Runnable} as its action, and returns
1210	+	* the given result upon {@link #join}.
1211	+	*
1212	+	* @param runnable the runnable action
1213	+	* @param result the result upon completion
1214	+	* @return the task
1215	+	*/
1216	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1217	+	return new AdaptedRunnable<T>(runnable, result);
1218	+	}
1219	+
1220	+	/**
1221	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1222	+	* method of the given {@code Callable} as its action, and returns
1223	+	* its result upon {@link #join}, translating any checked exceptions
1224	+	* encountered into {@code RuntimeException}.
1225	+	*
1226	+	* @param callable the callable action
1227	+	* @return the task
1228	+	*/
1229	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1230	+	return new AdaptedCallable<T>(callable);
1231	+	}
1232	+
1233		// Serialization support
1234
1235		private static final long serialVersionUID = -7721805057305804111L;
#	Line 1042 | Line 1238 | public abstract class ForkJoinTask<V> im
1238		* Save the state to a stream.
1239		*
1240		* @serialData the current run status and the exception thrown
1241	<	* during execution, or null if none
1241	>	* during execution, or {@code null} if none
1242		* @param s the stream
1243		*/
1244		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1066 | Line 1262 | public abstract class ForkJoinTask<V> im
1262		setDoneExceptionally((Throwable) ex);
1263		}
1264
1265	<	// Unsafe mechanics for jsr166y 3rd party package.
1265	>	// Unsafe mechanics
1266	>
1267	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1268	>	private static final long statusOffset =
1269	>	objectFieldOffset("status", ForkJoinTask.class);
1270	>
1271	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1272	>	try {
1273	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1274	>	} catch (NoSuchFieldException e) {
1275	>	// Convert Exception to corresponding Error
1276	>	NoSuchFieldError error = new NoSuchFieldError(field);
1277	>	error.initCause(e);
1278	>	throw error;
1279	>	}
1280	>	}
1281	>
1282	>	/**
1283	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1284	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1285	>	* into a jdk.
1286	>	*
1287	>	* @return a sun.misc.Unsafe
1288	>	*/
1289		private static sun.misc.Unsafe getUnsafe() {
1290		try {
1291		return sun.misc.Unsafe.getUnsafe();
1292		} catch (SecurityException se) {
1293		try {
1294		return java.security.AccessController.doPrivileged
1295	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1295	>	(new java.security
1296	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1297		public sun.misc.Unsafe run() throws Exception {
1298	<	return getUnsafeByReflection();
1298	>	java.lang.reflect.Field f = sun.misc
1299	>	.Unsafe.class.getDeclaredField("theUnsafe");
1300	>	f.setAccessible(true);
1301	>	return (sun.misc.Unsafe) f.get(null);
1302		}});
1303		} catch (java.security.PrivilegedActionException e) {
1304		throw new RuntimeException("Could not initialize intrinsics",
#	Line 1083 | Line 1306 | public abstract class ForkJoinTask<V> im
1306		}
1307		}
1308		}
1086	–
1087	–	private static sun.misc.Unsafe getUnsafeByReflection()
1088	–	throws NoSuchFieldException, IllegalAccessException {
1089	–	java.lang.reflect.Field f =
1090	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1091	–	f.setAccessible(true);
1092	–	return (sun.misc.Unsafe) f.get(null);
1093	–	}
1094	–
1095	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
1096	–	try {
1097	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1098	–	} catch (NoSuchFieldException e) {
1099	–	// Convert Exception to Error
1100	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1101	–	error.initCause(e);
1102	–	throw error;
1103	–	}
1104	–	}
1105	–
1106	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1107	–	static final long statusOffset =
1108	–	fieldOffset("status", ForkJoinTask.class);
1109	–
1309		}

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