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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.15 by jsr166, Fri Jul 24 22:05:22 2009 UTC vs.
Revision 1.41 by dl, Wed Aug 5 23:37:32 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	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 63 | Line 68 | import java.lang.reflect.*;
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
98	<	* 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
111	<	* 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 245 | 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 366 | 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 377 | 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);
380	–	if (Thread.interrupted())
381	–	throw new InterruptedException();
409		}
410		return getRawResult();
411		}
#	Line 389 | 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();
402	<	throw new TimeoutException();
429	>	else
430	>	throw new TimeoutException();
431		}
432
433		// internal execution methods
#	Line 484 | 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.
532	>	* Returns the result of the computation when it {@link #isDone is done}.
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 512 | 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		*
517	–	* @throws Throwable (a RuntimeException, Error, or unchecked
518	–	* exception) if the underlying computation did so
551		* @return the computed result
552		*/
553		public final V invoke() {
#	Line 526 | 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
558	<	* @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 591 | 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
604	–	* @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 641 | Line 694 | public abstract class ForkJoinTask<V> im
694		}
695		if (ex != null)
696		rethrowException(ex);
697	+	return tasks;
698		}
699
700		/**
701	<	* Returns true if the computation performed by this task has
702	<	* completed (or has been cancelled).
703	<	*
704	<	* @return true if this computation has completed
705	<	*/
706	<	public final boolean isDone() {
707	<	return status < 0;
654	<	}
655	<
656	<	/**
657	<	* Returns true if this task was cancelled.
658	<	*
659	<	* @return true if this task was cancelled
660	<	*/
661	<	public final boolean isCancelled() {
662	<	return (status & COMPLETION_MASK) == CANCELLED;
663	<	}
664	<
665	<	/**
666	<	* Asserts that the results of this task's computation will not be
667	<	* used. If a cancellation occurs before attempting to execute this
668	<	* task, then execution will be suppressed, {@code isCancelled}
669	<	* will report true, and {@code join} will result in a
670	<	* {@code CancellationException} being thrown. Otherwise, when
671	<	* cancellation races with completion, there are no guarantees
672	<	* about whether {@code isCancelled} will report true, whether
673	<	* {@code join} will return normally or via an exception, or
674	<	* whether these behaviors will remain consistent upon repeated
675	<	* invocation.
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 cancel method itself must not throw exceptions.
711	>	* the {@code cancel} method itself must not throw exceptions.
712		*
713	<	* <p> This method is designed to be invoked by <em>other</em>
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 {@code completeExceptionally}.
716	>	* invoke {@link #completeExceptionally}.
717		*
718		* @param mayInterruptIfRunning this value is ignored in the
719	<	* default implementation because tasks are not in general
719	>	* default implementation because tasks are not
720		* cancelled via interruption
721		*
722	<	* @return true if this task is now cancelled
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	+	public final boolean isDone() {
730	+	return status < 0;
731	+	}
732	+
733	+	public final boolean isCancelled() {
734	+	return (status & COMPLETION_MASK) == CANCELLED;
735	+	}
736	+
737		/**
738	<	* Returns true if this task threw an exception or was cancelled.
738	>	* Returns {@code true} if this task threw an exception or was cancelled.
739		*
740	<	* @return true if this task threw an exception or was cancelled
740	>	* @return {@code true} if this task threw an exception or was cancelled
741		*/
742		public final boolean isCompletedAbnormally() {
743		return (status & COMPLETION_MASK) < NORMAL;
744		}
745
746		/**
747	+	* Returns {@code true} if this task completed without throwing an
748	+	* exception and was not cancelled.
749	+	*
750	+	* @return {@code true} if this task completed without throwing an
751	+	* exception and was not cancelled
752	+	*/
753	+	public final boolean isCompletedNormally() {
754	+	return (status & COMPLETION_MASK) == NORMAL;
755	+	}
756	+
757	+	/**
758	+	* Returns {@code true} if this task threw an exception.
759	+	*
760	+	* @return {@code true} if this task threw an exception
761	+	*/
762	+	public final boolean isCompletedExceptionally() {
763	+	return (status & COMPLETION_MASK) == EXCEPTIONAL;
764	+	}
765	+
766	+	/**
767		* Returns the exception thrown by the base computation, or a
768	<	* CancellationException if cancelled, or null if none or if the
769	<	* method has not yet completed.
768	>	* {@code CancellationException} if cancelled, or {@code null} if
769	>	* none or if the method has not yet completed.
770		*
771	<	* @return the exception, or null if none
771	>	* @return the exception, or {@code null} if none
772		*/
773		public final Throwable getException() {
774		int s = status & COMPLETION_MASK;
775	<	if (s >= NORMAL)
776	<	return null;
777	<	if (s == CANCELLED)
718	<	return new CancellationException();
719	<	return exceptionMap.get(this);
775	>	return ((s >= NORMAL)    ? null :
776	>	(s == CANCELLED) ? new CancellationException() :
777	>	exceptionMap.get(this));
778		}
779
780		/**
#	Line 725 | Line 783 | public abstract class ForkJoinTask<V> im
783		* {@code join} and related operations. This method may be used
784		* to induce exceptions in asynchronous tasks, or to force
785		* completion of tasks that would not otherwise complete.  Its use
786	<	* in other situations is likely to be wrong.  This method is
786	>	* in other situations is discouraged.  This method is
787		* overridable, but overridden versions must invoke {@code super}
788		* implementation to maintain guarantees.
789		*
#	Line 745 | Line 803 | public abstract class ForkJoinTask<V> im
803		* operations. This method may be used to provide results for
804		* asynchronous tasks, or to provide alternative handling for
805		* tasks that would not otherwise complete normally. Its use in
806	<	* other situations is likely to be wrong. This method is
806	>	* other situations is discouraged. This method is
807		* overridable, but overridden versions must invoke {@code super}
808		* implementation to maintain guarantees.
809		*
#	Line 770 | Line 828 | public abstract class ForkJoinTask<V> im
828
829		public final V get(long timeout, TimeUnit unit)
830		throws InterruptedException, ExecutionException, TimeoutException {
831	+	long nanos = unit.toNanos(timeout);
832		ForkJoinWorkerThread w = getWorker();
833		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
834	<	awaitDone(w, unit.toNanos(timeout));
834	>	awaitDone(w, nanos);
835		return reportTimedFutureResult();
836		}
837
838		/**
839	<	* Possibly executes other tasks until this task is ready, then
840	<	* returns the result of the computation.  This method may be more
841	<	* efficient than {@code join}, but is only applicable when
842	<	* there are no potential dependencies between continuation of the
843	<	* current task and that of any other task that might be executed
844	<	* while helping. (This usually holds for pure divide-and-conquer
845	<	* tasks). This method may be invoked only from within
846	<	* ForkJoinTask computations (as may be determined using method
847	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
848	<	* result in exceptions or errors, possibly including
849	<	* ClassCastException.
839	>	* Possibly executes other tasks until this task {@link #isDone is
840	>	* done}, then returns the result of the computation.  This method
841	>	* may be more efficient than {@code join}, but is only applicable
842	>	* when there are no potential dependencies between continuation
843	>	* of the current task and that of any other task that might be
844	>	* executed while helping. (This usually holds for pure
845	>	* divide-and-conquer tasks).
846	>	*
847	>	* <p>This method may be invoked only from within {@code
848	>	* ForkJoinTask} computations (as may be determined using method
849	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
850	>	* result in exceptions or errors, possibly including {@code
851	>	* ClassCastException}.
852		*
853		* @return the computed result
854		*/
#	Line 799 | Line 860 | public abstract class ForkJoinTask<V> im
860		}
861
862		/**
863	<	* Possibly executes other tasks until this task is ready.  This
864	<	* method may be invoked only from within ForkJoinTask
865	<	* computations (as may be determined using method {@link
866	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
867	<	* in exceptions or errors, possibly including ClassCastException.
863	>	* Possibly executes other tasks until this task {@link #isDone is
864	>	* done}.  This method may be useful when processing collections
865	>	* of tasks when some have been cancelled or otherwise known to
866	>	* have aborted.
867	>	*
868	>	* <p>This method may be invoked only from within {@code
869	>	* ForkJoinTask} computations (as may be determined using method
870	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
871	>	* result in exceptions or errors, possibly including {@code
872	>	* ClassCastException}.
873		*/
874		public final void quietlyHelpJoin() {
875		if (status >= 0) {
#	Line 842 | Line 908 | public abstract class ForkJoinTask<V> im
908
909		/**
910		* Possibly executes tasks until the pool hosting the current task
911	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
912	<	* designs in which many tasks are forked, but none are explicitly
913	<	* joined, instead executing them until all are processed.
911	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
912	>	* be of use in designs in which many tasks are forked, but none
913	>	* are explicitly joined, instead executing them until all are
914	>	* processed.
915	>	*
916	>	* <p>This method may be invoked only from within {@code
917	>	* ForkJoinTask} computations (as may be determined using method
918	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
919	>	* result in exceptions or errors, possibly including {@code
920	>	* ClassCastException}.
921		*/
922		public static void helpQuiesce() {
923		((ForkJoinWorkerThread) Thread.currentThread())
#	Line 857 | Line 930 | public abstract class ForkJoinTask<V> im
930		* this task, but only if reuse occurs when this task has either
931		* never been forked, or has been forked, then completed and all
932		* outstanding joins of this task have also completed. Effects
933	<	* under any other usage conditions are not guaranteed, and are
934	<	* almost surely wrong. This method may be useful when executing
933	>	* under any other usage conditions are not guaranteed.
934	>	* This method may be useful when executing
935		* pre-constructed trees of subtasks in loops.
936		*/
937		public void reinitialize() {
#	Line 871 | Line 944 | public abstract class ForkJoinTask<V> im
944		* Returns the pool hosting the current task execution, or null
945		* if this task is executing outside of any ForkJoinPool.
946		*
947	<	* @return the pool, or null if none
947	>	* @see #inForkJoinPool
948	>	* @return the pool, or {@code null} if none
949		*/
950		public static ForkJoinPool getPool() {
951		Thread t = Thread.currentThread();
#	Line 896 | Line 970 | public abstract class ForkJoinTask<V> im
970		* by the current thread, and has not commenced executing in
971		* another thread.  This method may be useful when arranging
972		* alternative local processing of tasks that could have been, but
973	<	* were not, stolen. This method may be invoked only from within
974	<	* ForkJoinTask computations (as may be determined using method
975	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
976	<	* result in exceptions or errors, possibly including
977	<	* ClassCastException.
973	>	* were not, stolen.
974	>	*
975	>	* <p>This method may be invoked only from within {@code
976	>	* ForkJoinTask} computations (as may be determined using method
977	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
978	>	* result in exceptions or errors, possibly including {@code
979	>	* ClassCastException}.
980		*
981	<	* @return true if unforked
981	>	* @return {@code true} if unforked
982		*/
983		public boolean tryUnfork() {
984		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 915 | Line 991 | public abstract class ForkJoinTask<V> im
991		* value may be useful for heuristic decisions about whether to
992		* fork other tasks.
993		*
994	+	* <p>This method may be invoked only from within {@code
995	+	* ForkJoinTask} computations (as may be determined using method
996	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
997	+	* result in exceptions or errors, possibly including {@code
998	+	* ClassCastException}.
999	+	*
1000		* @return the number of tasks
1001		*/
1002		public static int getQueuedTaskCount() {
#	Line 932 | Line 1014 | public abstract class ForkJoinTask<V> im
1014		* tasks, and to process computations locally if this threshold is
1015		* exceeded.
1016		*
1017	+	* <p>This method may be invoked only from within {@code
1018	+	* ForkJoinTask} computations (as may be determined using method
1019	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1020	+	* result in exceptions or errors, possibly including {@code
1021	+	* ClassCastException}.
1022	+	*
1023		* @return the surplus number of tasks, which may be negative
1024		*/
1025		public static int getSurplusQueuedTaskCount() {
#	Line 942 | Line 1030 | public abstract class ForkJoinTask<V> im
1030		// Extension methods
1031
1032		/**
1033	<	* Returns the result that would be returned by {@code join},
1034	<	* even if this task completed abnormally, or null if this task is
1035	<	* not known to have been completed.  This method is designed to
1036	<	* aid debugging, as well as to support extensions. Its use in any
1037	<	* other context is discouraged.
1033	>	* Returns the result that would be returned by {@link #join}, even
1034	>	* if this task completed abnormally, or {@code null} if this task
1035	>	* is not known to have been completed.  This method is designed
1036	>	* to aid debugging, as well as to support extensions. Its use in
1037	>	* any other context is discouraged.
1038		*
1039	<	* @return the result, or null if not completed
1039	>	* @return the result, or {@code null} if not completed
1040		*/
1041		public abstract V getRawResult();
1042
#	Line 967 | Line 1055 | public abstract class ForkJoinTask<V> im
1055		* called otherwise. The return value controls whether this task
1056		* is considered to be done normally. It may return false in
1057		* asynchronous actions that require explicit invocations of
1058	<	* {@code complete} to become joinable. It may throw exceptions
1059	<	* to indicate abnormal exit.
1058	>	* {@link #complete} to become joinable. It may also throw an
1059	>	* (unchecked) exception to indicate abnormal exit.
1060		*
1061	<	* @return true if completed normally
974	<	* @throws Error or RuntimeException if encountered during computation
1061	>	* @return {@code true} if completed normally
1062		*/
1063		protected abstract boolean exec();
1064
1065		/**
1066	<	* Returns, but does not unschedule or execute, the task queued by
1067	<	* the current thread but not yet executed, if one is
1066	>	* Returns, but does not unschedule or execute, a task queued by
1067	>	* the current thread but not yet executed, if one is immediately
1068		* available. There is no guarantee that this task will actually
1069	<	* be polled or executed next.  This method is designed primarily
1070	<	* to support extensions, and is unlikely to be useful otherwise.
1071	<	* This method may be invoked only from within ForkJoinTask
1072	<	* computations (as may be determined using method {@link
1073	<	* #inForkJoinPool}). Attempts to invoke in other contexts result
987	<	* in exceptions or errors, possibly including ClassCastException.
1069	>	* be polled or executed next. Conversely, this method may return
1070	>	* null even if a task exists but cannot be accessed without
1071	>	* contention with other threads.  This method is designed
1072	>	* primarily to support extensions, and is unlikely to be useful
1073	>	* otherwise.
1074		*
1075	<	* @return the next task, or null if none are available
1075	>	* <p>This method may be invoked only from within {@code
1076	>	* ForkJoinTask} computations (as may be determined using method
1077	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1078	>	* result in exceptions or errors, possibly including {@code
1079	>	* ClassCastException}.
1080	>	*
1081	>	* @return the next task, or {@code null} if none are available
1082		*/
1083		protected static ForkJoinTask<?> peekNextLocalTask() {
1084		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 997 | Line 1089 | public abstract class ForkJoinTask<V> im
1089		* Unschedules and returns, without executing, the next task
1090		* queued by the current thread but not yet executed.  This method
1091		* is designed primarily to support extensions, and is unlikely to
1092	<	* be useful otherwise.  This method may be invoked only from
1093	<	* within ForkJoinTask computations (as may be determined using
1094	<	* method {@link #inForkJoinPool}). Attempts to invoke in other
1095	<	* contexts result in exceptions or errors, possibly including
1096	<	* ClassCastException.
1092	>	* be useful otherwise.
1093	>	*
1094	>	* <p>This method may be invoked only from within {@code
1095	>	* ForkJoinTask} computations (as may be determined using method
1096	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1097	>	* result in exceptions or errors, possibly including {@code
1098	>	* ClassCastException}.
1099		*
1100	<	* @return the next task, or null if none are available
1100	>	* @return the next task, or {@code null} if none are available
1101		*/
1102		protected static ForkJoinTask<?> pollNextLocalTask() {
1103		return ((ForkJoinWorkerThread) Thread.currentThread())
#	Line 1018 | Line 1112 | public abstract class ForkJoinTask<V> im
1112		* {@code null} result does not necessarily imply quiescence
1113		* of the pool this task is operating in.  This method is designed
1114		* primarily to support extensions, and is unlikely to be useful
1115	<	* otherwise.  This method may be invoked only from within
1116	<	* ForkJoinTask computations (as may be determined using method
1117	<	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1118	<	* result in exceptions or errors, possibly including
1119	<	* ClassCastException.
1115	>	* otherwise.
1116	>	*
1117	>	* <p>This method may be invoked only from within {@code
1118	>	* ForkJoinTask} computations (as may be determined using method
1119	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1120	>	* result in exceptions or errors, possibly including {@code
1121	>	* ClassCastException}.
1122		*
1123	<	* @return a task, or null if none are available
1123	>	* @return a task, or {@code null} if none are available
1124		*/
1125		protected static ForkJoinTask<?> pollTask() {
1126		return ((ForkJoinWorkerThread) Thread.currentThread())
1127		.pollTask();
1128		}
1129
1130	+	/**
1131	+	* Adaptor for Runnables. This implements RunnableFuture
1132	+	* to be compliant with AbstractExecutorService constraints
1133	+	* when used in ForkJoinPool.
1134	+	*/
1135	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1136	+	implements RunnableFuture<T> {
1137	+	final Runnable runnable;
1138	+	final T resultOnCompletion;
1139	+	T result;
1140	+	AdaptedRunnable(Runnable runnable, T result) {
1141	+	if (runnable == null) throw new NullPointerException();
1142	+	this.runnable = runnable;
1143	+	this.resultOnCompletion = result;
1144	+	}
1145	+	public T getRawResult() { return result; }
1146	+	public void setRawResult(T v) { result = v; }
1147	+	public boolean exec() {
1148	+	runnable.run();
1149	+	result = resultOnCompletion;
1150	+	return true;
1151	+	}
1152	+	public void run() { invoke(); }
1153	+	private static final long serialVersionUID = 5232453952276885070L;
1154	+	}
1155	+
1156	+	/**
1157	+	* Adaptor for Callables
1158	+	*/
1159	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1160	+	implements RunnableFuture<T> {
1161	+	final Callable<? extends T> callable;
1162	+	T result;
1163	+	AdaptedCallable(Callable<? extends T> callable) {
1164	+	if (callable == null) throw new NullPointerException();
1165	+	this.callable = callable;
1166	+	}
1167	+	public T getRawResult() { return result; }
1168	+	public void setRawResult(T v) { result = v; }
1169	+	public boolean exec() {
1170	+	try {
1171	+	result = callable.call();
1172	+	return true;
1173	+	} catch (Error err) {
1174	+	throw err;
1175	+	} catch (RuntimeException rex) {
1176	+	throw rex;
1177	+	} catch (Exception ex) {
1178	+	throw new RuntimeException(ex);
1179	+	}
1180	+	}
1181	+	public void run() { invoke(); }
1182	+	private static final long serialVersionUID = 2838392045355241008L;
1183	+	}
1184	+
1185	+	/**
1186	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1187	+	* method of the given {@code Runnable} as its action, and returns
1188	+	* a null result upon {@link #join}.
1189	+	*
1190	+	* @param runnable the runnable action
1191	+	* @return the task
1192	+	*/
1193	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1194	+	return new AdaptedRunnable<Void>(runnable, null);
1195	+	}
1196	+
1197	+	/**
1198	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1199	+	* method of the given {@code Runnable} as its action, and returns
1200	+	* the given result upon {@link #join}.
1201	+	*
1202	+	* @param runnable the runnable action
1203	+	* @param result the result upon completion
1204	+	* @return the task
1205	+	*/
1206	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1207	+	return new AdaptedRunnable<T>(runnable, result);
1208	+	}
1209	+
1210	+	/**
1211	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1212	+	* method of the given {@code Callable} as its action, and returns
1213	+	* its result upon {@link #join}, translating any checked exceptions
1214	+	* encountered into {@code RuntimeException}.
1215	+	*
1216	+	* @param callable the callable action
1217	+	* @return the task
1218	+	*/
1219	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1220	+	return new AdaptedCallable<T>(callable);
1221	+	}
1222	+
1223		// Serialization support
1224
1225		private static final long serialVersionUID = -7721805057305804111L;
#	Line 1039 | Line 1228 | public abstract class ForkJoinTask<V> im
1228		* Save the state to a stream.
1229		*
1230		* @serialData the current run status and the exception thrown
1231	<	* during execution, or null if none
1231	>	* during execution, or {@code null} if none
1232		* @param s the stream
1233		*/
1234		private void writeObject(java.io.ObjectOutputStream s)
#	Line 1063 | Line 1252 | public abstract class ForkJoinTask<V> im
1252		setDoneExceptionally((Throwable) ex);
1253		}
1254
1255	<	// Temporary Unsafe mechanics for preliminary release
1256	<	private static Unsafe getUnsafe() throws Throwable {
1255	>	// Unsafe mechanics
1256	>
1257	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1258	>	private static final long statusOffset =
1259	>	objectFieldOffset("status", ForkJoinTask.class);
1260	>
1261	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1262		try {
1263	<	return Unsafe.getUnsafe();
1263	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1264	>	} catch (NoSuchFieldException e) {
1265	>	// Convert Exception to corresponding Error
1266	>	NoSuchFieldError error = new NoSuchFieldError(field);
1267	>	error.initCause(e);
1268	>	throw error;
1269	>	}
1270	>	}
1271	>
1272	>	/**
1273	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1274	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1275	>	* into a jdk.
1276	>	*
1277	>	* @return a sun.misc.Unsafe
1278	>	*/
1279	>	private static sun.misc.Unsafe getUnsafe() {
1280	>	try {
1281	>	return sun.misc.Unsafe.getUnsafe();
1282		} catch (SecurityException se) {
1283		try {
1284		return java.security.AccessController.doPrivileged
1285	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1286	<	public Unsafe run() throws Exception {
1287	<	return getUnsafePrivileged();
1285	>	(new java.security
1286	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1287	>	public sun.misc.Unsafe run() throws Exception {
1288	>	java.lang.reflect.Field f = sun.misc
1289	>	.Unsafe.class.getDeclaredField("theUnsafe");
1290	>	f.setAccessible(true);
1291	>	return (sun.misc.Unsafe) f.get(null);
1292		}});
1293		} catch (java.security.PrivilegedActionException e) {
1294	<	throw e.getCause();
1294	>	throw new RuntimeException("Could not initialize intrinsics",
1295	>	e.getCause());
1296		}
1297		}
1298		}
1082	–
1083	–	private static Unsafe getUnsafePrivileged()
1084	–	throws NoSuchFieldException, IllegalAccessException {
1085	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1086	–	f.setAccessible(true);
1087	–	return (Unsafe) f.get(null);
1088	–	}
1089	–
1090	–	private static long fieldOffset(String fieldName)
1091	–	throws NoSuchFieldException {
1092	–	return UNSAFE.objectFieldOffset
1093	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1094	–	}
1095	–
1096	–	static final Unsafe UNSAFE;
1097	–	static final long statusOffset;
1098	–
1099	–	static {
1100	–	try {
1101	–	UNSAFE = getUnsafe();
1102	–	statusOffset = fieldOffset("status");
1103	–	} catch (Throwable e) {
1104	–	throw new RuntimeException("Could not initialize intrinsics", e);
1105	–	}
1106	–	}
1107	–
1299		}

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