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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.15 by jsr166, Fri Jul 24 22:05:22 2009 UTC

#	Line 13 | Line 13 | import sun.misc.Unsafe;
13		import java.lang.reflect.*;
14
15		/**
16	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
17	<	* ForkJoinTask is a thread-like entity that is much lighter weight
18	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
19	<	* hosted by a small number of actual threads in a ForkJoinPool,
20	<	* at the price of some usage limitations.
16	>	* Abstract base class for tasks that run within a {@link
17	>	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
18	>	* lighter weight than a normal thread.  Huge numbers of tasks and
19	>	* subtasks may be hosted by a small number of actual threads in a
20	>	* ForkJoinPool, at the price of some usage limitations.
21		*
22	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
23	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
24	<	* set of restrictions (that are only partially statically
25	<	* enforceable) reflecting their intended use as computational tasks
26	<	* calculating pure functions or operating on purely isolated objects.
27	<	* The primary coordination mechanisms supported for ForkJoinTasks are
28	<	* <tt>fork</tt>, that arranges asynchronous execution, and
29	<	* <tt>join</tt>, that doesn't proceed until the task's result has
30	<	* been computed. (Cancellation is also supported).  The computation
31	<	* defined in the <tt>compute</tt> method should avoid
32	<	* <tt>synchronized</tt> methods or blocks, and should minimize
33	<	* blocking synchronization apart from joining other tasks or using
22	>	* <p> A "main" ForkJoinTask begins execution when submitted to a
23	>	* {@link ForkJoinPool}. Once started, it will usually in turn start
24	>	* other subtasks.  As indicated by the name of this class, many
25	>	* programs using ForkJoinTasks employ only methods {@code fork}
26	>	* and {@code join}, or derivatives such as
27	>	* {@code invokeAll}.  However, this class also provides a number
28	>	* of other methods that can come into play in advanced usages, as
29	>	* well as extension mechanics that allow support of new forms of
30	>	* fork/join processing.
31	>	*
32	>	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
33	>	* efficiency of ForkJoinTasks stems from a set of restrictions (that
34	>	* are only partially statically enforceable) reflecting their
35	>	* intended use as computational tasks calculating pure functions or
36	>	* operating on purely isolated objects.  The primary coordination
37	>	* mechanisms are {@link #fork}, that arranges asynchronous execution,
38	>	* and {@link #join}, that doesn't proceed until the task's result has
39	>	* been computed.  Computations should avoid {@code synchronized}
40	>	* methods or blocks, and should minimize other blocking
41	>	* synchronization apart from joining other tasks or using
42		* synchronizers such as Phasers that are advertised to cooperate with
43		* fork/join scheduling. Tasks should also not perform blocking IO,
44		* and should ideally access variables that are completely independent
#	Line 38 | Line 46 | import java.lang.reflect.*;
46		* restrictions, for example using shared output streams, may be
47		* tolerable in practice, but frequent use may result in poor
48		* performance, and the potential to indefinitely stall if the number
49	<	* of threads not waiting for external synchronization becomes
50	<	* exhausted. This usage restriction is in part enforced by not
51	<	* permitting checked exceptions such as IOExceptions to be
52	<	* thrown. However, computations may still encounter unchecked
49	>	* of threads not waiting for IO or other external synchronization
50	>	* becomes exhausted. This usage restriction is in part enforced by
51	>	* not permitting checked exceptions such as {@code IOExceptions}
52	>	* to be thrown. However, computations may still encounter unchecked
53		* exceptions, that are rethrown to callers attempting join
54		* them. These exceptions may additionally include
55		* RejectedExecutionExceptions stemming from internal resource
56		* exhaustion such as failure to allocate internal task queues.
57		*
58	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
59	<	* subclassed.  Instead, you subclass one of the abstract classes that
60	<	* support different styles of fork/join processing.  Normally, a
61	<	* concrete ForkJoinTask subclass declares fields comprising its
62	<	* parameters, established in a constructor, and then defines a
63	<	* <tt>compute</tt> method that somehow uses the control methods
64	<	* supplied by this base class. While these methods have
65	<	* <tt>public</tt> access, some of them may only be called from within
66	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
67	<	* result in exceptions or errors including ClassCastException.  The
68	<	* only way to invoke a "main" driver task is to submit it to a
69	<	* ForkJoinPool. Once started, this will usually in turn start other
70	<	* subtasks.
58	>	* <p>The primary method for awaiting completion and extracting
59	>	* results of a task is {@link #join}, but there are several variants:
60	>	* The {@link Future#get} methods support interruptible and/or timed
61	>	* waits for completion and report results using {@code Future}
62	>	* conventions. Method {@link #helpJoin} enables callers to actively
63	>	* execute other tasks while awaiting joins, which is sometimes more
64	>	* efficient but only applies when all subtasks are known to be
65	>	* strictly tree-structured. Method {@link #invoke} is semantically
66	>	* equivalent to {@code fork(); join()} but always attempts to
67	>	* begin execution in the current thread. The "<em>quiet</em>" forms
68	>	* of these methods do not extract results or report exceptions. These
69	>	* may be useful when a set of tasks are being executed, and you need
70	>	* to delay processing of results or exceptions until all complete.
71	>	* Method {@code invokeAll} (available in multiple versions)
72	>	* performs the most common form of parallel invocation: forking a set
73	>	* of tasks and joining them all.
74	>	*
75	>	* <p> The ForkJoinTask class is not usually directly subclassed.
76	>	* Instead, you subclass one of the abstract classes that support a
77	>	* particular style of fork/join processing.  Normally, a concrete
78	>	* ForkJoinTask subclass declares fields comprising its parameters,
79	>	* established in a constructor, and then defines a {@code compute}
80	>	* method that somehow uses the control methods supplied by this base
81	>	* class. While these methods have {@code public} access (to allow
82	>	* instances of different task subclasses to call each others
83	>	* methods), some of them may only be called from within other
84	>	* ForkJoinTasks (as may be determined using method {@link
85	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
86	>	* result in exceptions or errors, possibly including
87	>	* ClassCastException.
88		*
89	<	* <p>Most base support methods are <tt>final</tt> because their
89	>	* <p>Most base support methods are {@code final} because their
90		* implementations are intrinsically tied to the underlying
91		* lightweight task scheduling framework, and so cannot be overridden.
92		* Developers creating new basic styles of fork/join processing should
93	<	* minimally implement protected methods <tt>exec</tt>,
94	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
95	<	* introducing an abstract computational method that can be
96	<	* implemented in its subclasses. To support such extensions,
97	<	* instances of ForkJoinTasks maintain an atomically updated
98	<	* <tt>short</tt> representing user-defined control state.  Control
74	<	* state is guaranteed initially to be zero, and to be negative upon
75	<	* completion, but may otherwise be used for any other control
76	<	* purposes, such as maintaining join counts.  The {@link
77	<	* ForkJoinWorkerThread} class supports additional inspection and
78	<	* tuning methods that can be useful when developing extensions.
93	>	* minimally implement {@code protected} methods
94	>	* {@code exec}, {@code setRawResult}, and
95	>	* {@code getRawResult}, while also introducing an abstract
96	>	* computational method that can be implemented in its subclasses,
97	>	* possibly relying on other {@code protected} methods provided
98	>	* by this class.
99		*
100		* <p>ForkJoinTasks should perform relatively small amounts of
101	<	* computations, othewise splitting into smaller tasks. As a very
101	>	* computations, otherwise splitting into smaller tasks. As a very
102		* rough rule of thumb, a task should perform more than 100 and less
103		* than 10000 basic computational steps. If tasks are too big, then
104	<	* parellelism cannot improve throughput. If too small, then memory
104	>	* parallelism cannot improve throughput. If too small, then memory
105		* and internal task maintenance overhead may overwhelm processing.
106		*
107	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
108	<	* be used in extensions such as remote execution frameworks. However,
109	<	* it is in general safe to serialize tasks only before or after, but
107	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
108	>	* to be used in extensions such as remote execution frameworks. It is
109	>	* in general sensible to serialize tasks only before or after, but
110		* not during execution. Serialization is not relied on during
111		* execution itself.
112	+	*
113	+	* @since 1.7
114	+	* @author Doug Lea
115		*/
116		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
117	+
118		/**
119	<	* Status field holding all run status. We pack this into a single
120	<	* int both to minimize footprint overhead and to ensure atomicity
121	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
119	>	* Run control status bits packed into a single int to minimize
120	>	* footprint and to ensure atomicity (via CAS).  Status is
121	>	* initially zero, and takes on nonnegative values until
122		* completed, upon which status holds COMPLETED. CANCELLED, or
123		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
124		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 133 | public abstract class ForkJoinTask<V> im
133		* currently unused. Also value 0x80000000 is available as spare
134		* completion value.
135		*/
136	<	volatile int status; // accessed directy by pool and workers
136	>	volatile int status; // accessed directly by pool and workers
137
138		static final int COMPLETION_MASK      = 0xe0000000;
139		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 146 | public abstract class ForkJoinTask<V> im
146		/**
147		* Table of exceptions thrown by tasks, to enable reporting by
148		* callers. Because exceptions are rare, we don't directly keep
149	<	* them with task objects, but instead us a weak ref table.  Note
149	>	* them with task objects, but instead use a weak ref table.  Note
150		* that cancellation exceptions don't appear in the table, but are
151		* instead recorded as status values.
152	<	* Todo: Use ConcurrentReferenceHashMap
152	>	* TODO: Use ConcurrentReferenceHashMap
153		*/
154		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
155		Collections.synchronizedMap
#	Line 136 | Line 158 | public abstract class ForkJoinTask<V> im
158		// within-package utilities
159
160		/**
161	<	* Get current worker thread, or null if not a worker thread
161	>	* Gets current worker thread, or null if not a worker thread.
162		*/
163		static ForkJoinWorkerThread getWorker() {
164		Thread t = Thread.currentThread();
165	<	return ((t instanceof ForkJoinWorkerThread)?
166	<	(ForkJoinWorkerThread)t : null);
145	<	}
146	<
147	<	/**
148	<	* Get pool of current worker thread, or null if not a worker thread
149	<	*/
150	<	static ForkJoinPool getWorkerPool() {
151	<	Thread t = Thread.currentThread();
152	<	return ((t instanceof ForkJoinWorkerThread)?
153	<	((ForkJoinWorkerThread)t).pool : null);
165	>	return ((t instanceof ForkJoinWorkerThread) ?
166	>	(ForkJoinWorkerThread) t : null);
167		}
168
169		final boolean casStatus(int cmp, int val) {
170	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
170	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
171		}
172
173		/**
#	Line 162 | Line 175 | public abstract class ForkJoinTask<V> im
175		*/
176		static void rethrowException(Throwable ex) {
177		if (ex != null)
178	<	_unsafe.throwException(ex);
178	>	UNSAFE.throwException(ex);
179		}
180
181		// Setting completion status
182
183		/**
184	<	* Mark completion and wake up threads waiting to join this task.
184	>	* Marks completion and wakes up threads waiting to join this task.
185	>	*
186		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
187		*/
188		final void setCompletion(int completion) {
189	<	ForkJoinPool pool = getWorkerPool();
189	>	ForkJoinPool pool = getPool();
190		if (pool != null) {
191		int s; // Clear signal bits while setting completion status
192	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
192	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
193
194		if ((s & SIGNAL_MASK) != 0) {
195		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
196		pool.updateRunningCount(s);
197	<	synchronized(this) { notifyAll(); }
197	>	synchronized (this) { notifyAll(); }
198		}
199		}
200		else
#	Line 193 | Line 207 | public abstract class ForkJoinTask<V> im
207		*/
208		private void externallySetCompletion(int completion) {
209		int s;
210	<	do;while ((s = status) >= 0 &&
211	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
212	<	synchronized(this) { notifyAll(); }
210	>	do {} while ((s = status) >= 0 &&
211	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
212	>	synchronized (this) { notifyAll(); }
213		}
214
215		/**
216	<	* Sets status to indicate normal completion
216	>	* Sets status to indicate normal completion.
217		*/
218		final void setNormalCompletion() {
219		// Try typical fast case -- single CAS, no signal, not already done.
220		// Manually expand casStatus to improve chances of inlining it
221	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
221	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
222		setCompletion(NORMAL);
223		}
224
225		// internal waiting and notification
226
227		/**
228	<	* Performs the actual monitor wait for awaitDone
228	>	* Performs the actual monitor wait for awaitDone.
229		*/
230		private void doAwaitDone() {
231		// Minimize lock bias and in/de-flation effects by maximizing
232		// chances of waiting inside sync
233		try {
234		while (status >= 0)
235	<	synchronized(this) { if (status >= 0) wait(); }
235	>	synchronized (this) { if (status >= 0) wait(); }
236		} catch (InterruptedException ie) {
237		onInterruptedWait();
238		}
239		}
240
241		/**
242	<	* Performs the actual monitor wait for awaitDone
242	>	* Performs the actual timed monitor wait for awaitDone.
243		*/
244		private void doAwaitDone(long startTime, long nanos) {
245	<	synchronized(this) {
245	>	synchronized (this) {
246		try {
247		while (status >= 0) {
248		long nt = nanos - System.nanoTime() - startTime;
249		if (nt <= 0)
250		break;
251	<	wait(nt / 1000000, (int)(nt % 1000000));
251	>	wait(nt / 1000000, (int) (nt % 1000000));
252		}
253		} catch (InterruptedException ie) {
254		onInterruptedWait();
#	Line 247 | Line 261 | public abstract class ForkJoinTask<V> im
261		/**
262		* Sets status to indicate there is joiner, then waits for join,
263		* surrounded with pool notifications.
264	+	*
265		* @return status upon exit
266		*/
267	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
268	<	ForkJoinPool pool = w == null? null : w.pool;
267	>	private int awaitDone(ForkJoinWorkerThread w,
268	>	boolean maintainParallelism) {
269	>	ForkJoinPool pool = (w == null) ? null : w.pool;
270		int s;
271		while ((s = status) >= 0) {
272	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
272	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
273		if (pool == null || !pool.preJoin(this, maintainParallelism))
274		doAwaitDone();
275		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 282 | public abstract class ForkJoinTask<V> im
282
283		/**
284		* Timed version of awaitDone
285	+	*
286		* @return status upon exit
287		*/
288	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
289	<	ForkJoinPool pool = w == null? null : w.pool;
288	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
289	>	ForkJoinPool pool = (w == null) ? null : w.pool;
290		int s;
291		while ((s = status) >= 0) {
292	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
292	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
293		long startTime = System.nanoTime();
294		if (pool == null || !pool.preJoin(this, false))
295		doAwaitDone(startTime, nanos);
#	Line 289 | Line 306 | public abstract class ForkJoinTask<V> im
306		}
307
308		/**
309	<	* Notify pool that thread is unblocked. Called by signalled
309	>	* Notifies pool that thread is unblocked. Called by signalled
310		* threads when woken by non-FJ threads (which is atypical).
311		*/
312		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
313		int s;
314	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
314	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
315		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
316		pool.updateRunningCount(s);
317		}
318
319		/**
320	<	* Notify pool to adjust counts on cancelled or timed out wait
320	>	* Notifies pool to adjust counts on cancelled or timed out wait.
321		*/
322		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
323		if (pool != null) {
#	Line 314 | Line 331 | public abstract class ForkJoinTask<V> im
331		}
332		}
333
334	+	/**
335	+	* Handles interruptions during waits.
336	+	*/
337		private void onInterruptedWait() {
338	<	Thread t = Thread.currentThread();
339	<	if (t instanceof ForkJoinWorkerThread) {
340	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
341	<	if (w.isTerminating())
342	<	cancelIgnoreExceptions();
343	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
338	>	ForkJoinWorkerThread w = getWorker();
339	>	if (w == null)
340	>	Thread.currentThread().interrupt(); // re-interrupt
341	>	else if (w.isTerminating())
342	>	cancelIgnoringExceptions();
343	>	// else if FJworker, ignore interrupt
344		}
345
346		// Recording and reporting exceptions
#	Line 337 | Line 351 | public abstract class ForkJoinTask<V> im
351		}
352
353		/**
354	<	* Throws the exception associated with status s;
354	>	* Throws the exception associated with status s.
355	>	*
356		* @throws the exception
357		*/
358		private void reportException(int s) {
#	Line 350 | Line 365 | public abstract class ForkJoinTask<V> im
365		}
366
367		/**
368	<	* Returns result or throws exception using j.u.c.Future conventions
369	<	* Only call when isDone known to be true.
368	>	* Returns result or throws exception using j.u.c.Future conventions.
369	>	* Only call when {@code isDone} known to be true.
370		*/
371		private V reportFutureResult()
372		throws ExecutionException, InterruptedException {
#	Line 370 | Line 385 | public abstract class ForkJoinTask<V> im
385
386		/**
387		* Returns result or throws exception using j.u.c.Future conventions
388	<	* with timeouts
388	>	* with timeouts.
389		*/
390		private V reportTimedFutureResult()
391		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 391 | Line 406 | public abstract class ForkJoinTask<V> im
406
407		/**
408		* Calls exec, recording completion, and rethrowing exception if
409	<	* encountered. Caller should normally check status before calling
409	>	* encountered. Caller should normally check status before calling.
410	>	*
411		* @return true if completed normally
412		*/
413		private boolean tryExec() {
#	Line 409 | Line 425 | public abstract class ForkJoinTask<V> im
425
426		/**
427		* Main execution method used by worker threads. Invokes
428	<	* base computation unless already complete
428	>	* base computation unless already complete.
429		*/
430		final void quietlyExec() {
431		if (status >= 0) {
432		try {
433		if (!exec())
434		return;
435	<	} catch(Throwable rex) {
435	>	} catch (Throwable rex) {
436		setDoneExceptionally(rex);
437		return;
438		}
#	Line 425 | Line 441 | public abstract class ForkJoinTask<V> im
441		}
442
443		/**
444	<	* Calls exec, recording but not rethrowing exception
445	<	* Caller should normally check status before calling
444	>	* Calls exec(), recording but not rethrowing exception.
445	>	* Caller should normally check status before calling.
446	>	*
447		* @return true if completed normally
448		*/
449		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 459 | public abstract class ForkJoinTask<V> im
459		}
460
461		/**
462	<	* Cancel, ignoring any exceptions it throws
462	>	* Cancels, ignoring any exceptions it throws.
463		*/
464	<	final void cancelIgnoreExceptions() {
464	>	final void cancelIgnoringExceptions() {
465		try {
466		cancel(false);
467	<	} catch(Throwable ignore) {
467	>	} catch (Throwable ignore) {
468		}
469		}
470
471	+	/**
472	+	* Main implementation of helpJoin
473	+	*/
474	+	private int busyJoin(ForkJoinWorkerThread w) {
475	+	int s;
476	+	ForkJoinTask<?> t;
477	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
478	+	t.quietlyExec();
479	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
480	+	}
481	+
482		// public methods
483
484		/**
485		* Arranges to asynchronously execute this task.  While it is not
486		* necessarily enforced, it is a usage error to fork a task more
487		* than once unless it has completed and been reinitialized.  This
488	<	* method may be invoked only from within other ForkJoinTask
489	<	* computations. Attempts to invoke in other contexts result in
490	<	* exceptions or errors including ClassCastException.
488	>	* method may be invoked only from within ForkJoinTask
489	>	* computations (as may be determined using method {@link
490	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
491	>	* in exceptions or errors, possibly including ClassCastException.
492		*/
493		public final void fork() {
494	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
494	>	((ForkJoinWorkerThread) Thread.currentThread())
495	>	.pushTask(this);
496		}
497
498		/**
499		* Returns the result of the computation when it is ready.
500	<	* This method differs from <tt>get</tt> in that abnormal
500	>	* This method differs from {@code get} in that abnormal
501		* completion results in RuntimeExceptions or Errors, not
502		* ExecutionExceptions.
503		*
#	Line 480 | Line 510 | public abstract class ForkJoinTask<V> im
510		return getRawResult();
511		}
512
483	–	public final V get() throws InterruptedException, ExecutionException {
484	–	ForkJoinWorkerThread w = getWorker();
485	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
486	–	awaitDone(w, true);
487	–	return reportFutureResult();
488	–	}
489	–
490	–	public final V get(long timeout, TimeUnit unit)
491	–	throws InterruptedException, ExecutionException, TimeoutException {
492	–	ForkJoinWorkerThread w = getWorker();
493	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
494	–	awaitDone(w, unit.toNanos(timeout));
495	–	return reportTimedFutureResult();
496	–	}
497	–
513		/**
514	<	* Possibly executes other tasks until this task is ready, then
515	<	* returns the result of the computation.  This method may be more
516	<	* efficient than <tt>join</tt>, but is only applicable when there
502	<	* are no potemtial dependencies between continuation of the
503	<	* current task and that of any other task that might be executed
504	<	* while helping. (This usually holds for pure divide-and-conquer
505	<	* tasks).
506	<	* @return the computed result
507	<	*/
508	<	public final V helpJoin() {
509	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
510	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
511	<	reportException(w.helpJoinTask(this));
512	<	return getRawResult();
513	<	}
514	<
515	<	/**
516	<	* Performs this task, awaits its completion if necessary, and
517	<	* return its result.
514	>	* Commences performing this task, awaits its completion if
515	>	* necessary, and return its result.
516	>	*
517		* @throws Throwable (a RuntimeException, Error, or unchecked
518	<	* exception) if the underlying computation did so.
518	>	* exception) if the underlying computation did so
519		* @return the computed result
520		*/
521		public final V invoke() {
#	Line 527 | Line 526 | public abstract class ForkJoinTask<V> im
526		}
527
528		/**
529	<	* Joins this task, without returning its result or throwing an
530	<	* exception. This method may be useful when processing
531	<	* collections of tasks when some have been cancelled or otherwise
532	<	* known to have aborted.
529	>	* Forks both tasks, returning when {@code isDone} holds for
530	>	* both of them or an exception is encountered. This method may be
531	>	* invoked only from within ForkJoinTask computations (as may be
532	>	* determined using method {@link #inForkJoinPool}). Attempts to
533	>	* invoke in other contexts result in exceptions or errors,
534	>	* possibly including ClassCastException.
535	>	*
536	>	* @param t1 one task
537	>	* @param t2 the other task
538	>	* @throws NullPointerException if t1 or t2 are null
539	>	* @throws RuntimeException or Error if either task did so
540		*/
541	<	public final void quietlyJoin() {
542	<	if (status >= 0) {
543	<	ForkJoinWorkerThread w = getWorker();
544	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
541	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
542	>	t2.fork();
543	>	t1.invoke();
544	>	t2.join();
545		}
546
547		/**
548	<	* Possibly executes other tasks until this task is ready.
548	>	* Forks the given tasks, returning when {@code isDone} holds
549	>	* for all of them. If any task encounters an exception, others
550	>	* may be cancelled.  This method may be invoked only from within
551	>	* ForkJoinTask computations (as may be determined using method
552	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
553	>	* result in exceptions or errors, possibly including
554	>	* ClassCastException.
555	>	*
556	>	* @param tasks the array of tasks
557	>	* @throws NullPointerException if tasks or any element are null
558	>	* @throws RuntimeException or Error if any task did so
559		*/
560	<	public final void quietlyHelpJoin() {
561	<	if (status >= 0) {
562	<	ForkJoinWorkerThread w =
563	<	(ForkJoinWorkerThread)(Thread.currentThread());
564	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
565	<	w.helpJoinTask(this);
560	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
561	>	Throwable ex = null;
562	>	int last = tasks.length - 1;
563	>	for (int i = last; i >= 0; --i) {
564	>	ForkJoinTask<?> t = tasks[i];
565	>	if (t == null) {
566	>	if (ex == null)
567	>	ex = new NullPointerException();
568	>	}
569	>	else if (i != 0)
570	>	t.fork();
571	>	else {
572	>	t.quietlyInvoke();
573	>	if (ex == null)
574	>	ex = t.getException();
575	>	}
576	>	}
577	>	for (int i = 1; i <= last; ++i) {
578	>	ForkJoinTask<?> t = tasks[i];
579	>	if (t != null) {
580	>	if (ex != null)
581	>	t.cancel(false);
582	>	else {
583	>	t.quietlyJoin();
584	>	if (ex == null)
585	>	ex = t.getException();
586	>	}
587	>	}
588		}
589	+	if (ex != null)
590	+	rethrowException(ex);
591		}
592
593		/**
594	<	* Performs this task and awaits its completion if necessary,
595	<	* without returning its result or throwing an exception. This
596	<	* method may be useful when processing collections of tasks when
597	<	* some have been cancelled or otherwise known to have aborted.
594	>	* Forks all tasks in the collection, returning when
595	>	* {@code isDone} holds for all of them. If any task
596	>	* encounters an exception, others may be cancelled.  This method
597	>	* may be invoked only from within ForkJoinTask computations (as
598	>	* may be determined using method {@link
599	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
600	>	* in exceptions or errors, possibly including ClassCastException.
601	>	*
602	>	* @param tasks the collection of tasks
603	>	* @throws NullPointerException if tasks or any element are null
604	>	* @throws RuntimeException or Error if any task did so
605		*/
606	<	public final void quietlyInvoke() {
607	<	if (status >= 0 && !tryQuietlyInvoke())
608	<	quietlyJoin();
606	>	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
607	>	if (!(tasks instanceof List<?>)) {
608	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
609	>	return;
610	>	}
611	>	@SuppressWarnings("unchecked")
612	>	List<? extends ForkJoinTask<?>> ts =
613	>	(List<? extends ForkJoinTask<?>>) tasks;
614	>	Throwable ex = null;
615	>	int last = ts.size() - 1;
616	>	for (int i = last; i >= 0; --i) {
617	>	ForkJoinTask<?> t = ts.get(i);
618	>	if (t == null) {
619	>	if (ex == null)
620	>	ex = new NullPointerException();
621	>	}
622	>	else if (i != 0)
623	>	t.fork();
624	>	else {
625	>	t.quietlyInvoke();
626	>	if (ex == null)
627	>	ex = t.getException();
628	>	}
629	>	}
630	>	for (int i = 1; i <= last; ++i) {
631	>	ForkJoinTask<?> t = ts.get(i);
632	>	if (t != null) {
633	>	if (ex != null)
634	>	t.cancel(false);
635	>	else {
636	>	t.quietlyJoin();
637	>	if (ex == null)
638	>	ex = t.getException();
639	>	}
640	>	}
641	>	}
642	>	if (ex != null)
643	>	rethrowException(ex);
644		}
645
646		/**
647		* Returns true if the computation performed by this task has
648		* completed (or has been cancelled).
649	+	*
650		* @return true if this computation has completed
651		*/
652		public final boolean isDone() {
#	Line 574 | Line 655 | public abstract class ForkJoinTask<V> im
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() {
#	Line 581 | Line 663 | public abstract class ForkJoinTask<V> im
663		}
664
665		/**
584	–	* Returns true if this task threw an exception or was cancelled
585	–	* @return true if this task threw an exception or was cancelled
586	–	*/
587	–	public final boolean completedAbnormally() {
588	–	return (status & COMPLETION_MASK) < NORMAL;
589	–	}
590	–
591	–	/**
592	–	* Returns the exception thrown by the base computation, or a
593	–	* CancellationException if cancelled, or null if none or if the
594	–	* method has not yet completed.
595	–	* @return the exception, or null if none
596	–	*/
597	–	public final Throwable getException() {
598	–	int s = status & COMPLETION_MASK;
599	–	if (s >= NORMAL)
600	–	return null;
601	–	if (s == CANCELLED)
602	–	return new CancellationException();
603	–	return exceptionMap.get(this);
604	–	}
605	–
606	–	/**
666		* Asserts that the results of this task's computation will not be
667	<	* used. If a cancellation occurs before this task is processed,
668	<	* then its <tt>compute</tt> method will not be executed,
669	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
670	<	* result in a CancellationException being thrown. Otherwise, when
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 <tt>isCancelled</tt> will report true, whether
673	<	* <tt>join</tt> will return normally or via an exception, or
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.
676		*
#	Line 622 | Line 681 | public abstract class ForkJoinTask<V> im
681		* <p> This method is designed to be invoked by <em>other</em>
682		* tasks. To terminate the current task, you can just return or
683		* throw an unchecked exception from its computation method, or
684	<	* invoke <tt>completeExceptionally(someException)</tt>.
684	>	* invoke {@code completeExceptionally}.
685		*
686		* @param mayInterruptIfRunning this value is ignored in the
687		* default implementation because tasks are not in general
688	<	* cancelled via interruption.
688	>	* cancelled via interruption
689		*
690		* @return true if this task is now cancelled
691		*/
#	Line 636 | Line 695 | public abstract class ForkJoinTask<V> im
695		}
696
697		/**
698	+	* Returns true if this task threw an exception or was cancelled.
699	+	*
700	+	* @return true if this task threw an exception or was cancelled
701	+	*/
702	+	public final boolean isCompletedAbnormally() {
703	+	return (status & COMPLETION_MASK) < NORMAL;
704	+	}
705	+
706	+	/**
707	+	* Returns the exception thrown by the base computation, or a
708	+	* CancellationException if cancelled, or null if none or if the
709	+	* method has not yet completed.
710	+	*
711	+	* @return the exception, or null if none
712	+	*/
713	+	public final Throwable getException() {
714	+	int s = status & COMPLETION_MASK;
715	+	if (s >= NORMAL)
716	+	return null;
717	+	if (s == CANCELLED)
718	+	return new CancellationException();
719	+	return exceptionMap.get(this);
720	+	}
721	+
722	+	/**
723		* Completes this task abnormally, and if not already aborted or
724		* cancelled, causes it to throw the given exception upon
725	<	* <tt>join</tt> and related operations. This method may be used
725	>	* {@code join} and related operations. This method may be used
726		* to induce exceptions in asynchronous tasks, or to force
727	<	* completion of tasks that would not otherwise complete.  This
728	<	* method is overridable, but overridden versions must invoke
729	<	* <tt>super</tt> implementation to maintain guarantees.
727	>	* completion of tasks that would not otherwise complete.  Its use
728	>	* in other situations is likely to be wrong.  This method is
729	>	* overridable, but overridden versions must invoke {@code super}
730	>	* implementation to maintain guarantees.
731	>	*
732		* @param ex the exception to throw. If this exception is
733		* not a RuntimeException or Error, the actual exception thrown
734		* will be a RuntimeException with cause ex.
735		*/
736		public void completeExceptionally(Throwable ex) {
737		setDoneExceptionally((ex instanceof RuntimeException) ||
738	<	(ex instanceof Error)? ex :
738	>	(ex instanceof Error) ? ex :
739		new RuntimeException(ex));
740		}
741
742		/**
743		* Completes this task, and if not already aborted or cancelled,
744	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
744	>	* returning a {@code null} result upon {@code join} and related
745		* operations. This method may be used to provide results for
746		* asynchronous tasks, or to provide alternative handling for
747	<	* tasks that would not otherwise complete normally.
747	>	* tasks that would not otherwise complete normally. Its use in
748	>	* other situations is likely to be wrong. This method is
749	>	* overridable, but overridden versions must invoke {@code super}
750	>	* implementation to maintain guarantees.
751		*
752	<	* @param value the result value for this task.
752	>	* @param value the result value for this task
753		*/
754		public void complete(V value) {
755		try {
756		setRawResult(value);
757	<	} catch(Throwable rex) {
757	>	} catch (Throwable rex) {
758		setDoneExceptionally(rex);
759		return;
760		}
761		setNormalCompletion();
762		}
763
764	+	public final V get() throws InterruptedException, ExecutionException {
765	+	ForkJoinWorkerThread w = getWorker();
766	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
767	+	awaitDone(w, true);
768	+	return reportFutureResult();
769	+	}
770	+
771	+	public final V get(long timeout, TimeUnit unit)
772	+	throws InterruptedException, ExecutionException, TimeoutException {
773	+	ForkJoinWorkerThread w = getWorker();
774	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
775	+	awaitDone(w, unit.toNanos(timeout));
776	+	return reportTimedFutureResult();
777	+	}
778	+
779	+	/**
780	+	* Possibly executes other tasks until this task is ready, then
781	+	* returns the result of the computation.  This method may be more
782	+	* efficient than {@code join}, but is only applicable when
783	+	* there are no potential dependencies between continuation of the
784	+	* current task and that of any other task that might be executed
785	+	* while helping. (This usually holds for pure divide-and-conquer
786	+	* tasks). This method may be invoked only from within
787	+	* ForkJoinTask computations (as may be determined using method
788	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
789	+	* result in exceptions or errors, possibly including
790	+	* ClassCastException.
791	+	*
792	+	* @return the computed result
793	+	*/
794	+	public final V helpJoin() {
795	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
796	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
797	+	reportException(busyJoin(w));
798	+	return getRawResult();
799	+	}
800	+
801	+	/**
802	+	* Possibly executes other tasks until this task is ready.  This
803	+	* method may be invoked only from within ForkJoinTask
804	+	* computations (as may be determined using method {@link
805	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
806	+	* in exceptions or errors, possibly including ClassCastException.
807	+	*/
808	+	public final void quietlyHelpJoin() {
809	+	if (status >= 0) {
810	+	ForkJoinWorkerThread w =
811	+	(ForkJoinWorkerThread) Thread.currentThread();
812	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
813	+	busyJoin(w);
814	+	}
815	+	}
816	+
817	+	/**
818	+	* Joins this task, without returning its result or throwing an
819	+	* exception. This method may be useful when processing
820	+	* collections of tasks when some have been cancelled or otherwise
821	+	* known to have aborted.
822	+	*/
823	+	public final void quietlyJoin() {
824	+	if (status >= 0) {
825	+	ForkJoinWorkerThread w = getWorker();
826	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
827	+	awaitDone(w, true);
828	+	}
829	+	}
830	+
831	+	/**
832	+	* Commences performing this task and awaits its completion if
833	+	* necessary, without returning its result or throwing an
834	+	* exception. This method may be useful when processing
835	+	* collections of tasks when some have been cancelled or otherwise
836	+	* known to have aborted.
837	+	*/
838	+	public final void quietlyInvoke() {
839	+	if (status >= 0 && !tryQuietlyInvoke())
840	+	quietlyJoin();
841	+	}
842	+
843	+	/**
844	+	* Possibly executes tasks until the pool hosting the current task
845	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
846	+	* designs in which many tasks are forked, but none are explicitly
847	+	* joined, instead executing them until all are processed.
848	+	*/
849	+	public static void helpQuiesce() {
850	+	((ForkJoinWorkerThread) Thread.currentThread())
851	+	.helpQuiescePool();
852	+	}
853	+
854		/**
855		* Resets the internal bookkeeping state of this task, allowing a
856	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
856	>	* subsequent {@code fork}. This method allows repeated reuse of
857		* this task, but only if reuse occurs when this task has either
858		* never been forked, or has been forked, then completed and all
859		* outstanding joins of this task have also completed. Effects
#	Line 689 | Line 868 | public abstract class ForkJoinTask<V> im
868		}
869
870		/**
871	<	* Tries to unschedule this task for execution. This method will
872	<	* typically succeed if this task is the next task that would be
873	<	* executed by the current thread, and will typically fail (return
874	<	* false) otherwise. This method may be useful when arranging
696	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
871	>	* Returns the pool hosting the current task execution, or null
872	>	* if this task is executing outside of any ForkJoinPool.
873	>	*
874	>	* @return the pool, or null if none
875		*/
876	<	public boolean tryUnfork() {
877	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
876	>	public static ForkJoinPool getPool() {
877	>	Thread t = Thread.currentThread();
878	>	return (t instanceof ForkJoinWorkerThread) ?
879	>	((ForkJoinWorkerThread) t).pool : null;
880		}
881
882		/**
883	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
884	<	* of them or an exception is encountered. This method may be
885	<	* invoked only from within other ForkJoinTask
886	<	* computations. Attempts to invoke in other contexts result in
887	<	* exceptions or errors including ClassCastException.
710	<	* @param t1 one task
711	<	* @param t2 the other task
712	<	* @throws NullPointerException if t1 or t2 are null
713	<	* @throws RuntimeException or Error if either task did so.
883	>	* Returns {@code true} if the current thread is executing as a
884	>	* ForkJoinPool computation.
885	>	*
886	>	* @return {@code true} if the current thread is executing as a
887	>	* ForkJoinPool computation, or false otherwise
888		*/
889	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
890	<	t2.fork();
717	<	t1.invoke();
718	<	t2.join();
889	>	public static boolean inForkJoinPool() {
890	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
891		}
892
893		/**
894	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
895	<	* all of them. If any task encounters an exception, others may be
896	<	* cancelled.  This method may be invoked only from within other
897	<	* ForkJoinTask computations. Attempts to invoke in other contexts
898	<	* result in exceptions or errors including ClassCastException.
899	<	* @param tasks the array of tasks
900	<	* @throws NullPointerException if tasks or any element are null.
901	<	* @throws RuntimeException or Error if any task did so.
902	<	*/
903	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
904	<	Throwable ex = null;
905	<	int last = tasks.length - 1;
734	<	for (int i = last; i >= 0; --i) {
735	<	ForkJoinTask<?> t = tasks[i];
736	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
759	<	}
760	<	if (ex != null)
761	<	rethrowException(ex);
762	<	}
763	<
764	<	/**
765	<	* Forks all tasks in the collection, returning when
766	<	* <tt>isDone</tt> holds for all of them. If any task encounters
767	<	* an exception, others may be cancelled.  This method may be
768	<	* invoked only from within other ForkJoinTask
769	<	* computations. Attempts to invoke in other contexts result in
770	<	* exceptions or errors including ClassCastException.
771	<	* @param tasks the collection of tasks
772	<	* @throws NullPointerException if tasks or any element are null.
773	<	* @throws RuntimeException or Error if any task did so.
894	>	* Tries to unschedule this task for execution. This method will
895	>	* typically succeed if this task is the most recently forked task
896	>	* by the current thread, and has not commenced executing in
897	>	* another thread.  This method may be useful when arranging
898	>	* alternative local processing of tasks that could have been, but
899	>	* were not, stolen. This method may be invoked only from within
900	>	* ForkJoinTask computations (as may be determined using method
901	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
902	>	* result in exceptions or errors, possibly including
903	>	* ClassCastException.
904	>	*
905	>	* @return true if unforked
906		*/
907	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
908	<	if (!(tasks instanceof List)) {
909	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
778	<	return;
779	<	}
780	<	List<? extends ForkJoinTask<?>> ts =
781	<	(List<? extends ForkJoinTask<?>>)tasks;
782	<	Throwable ex = null;
783	<	int last = ts.size() - 1;
784	<	for (int i = last; i >= 0; --i) {
785	<	ForkJoinTask<?> t = ts.get(i);
786	<	if (t == null) {
787	<	if (ex == null)
788	<	ex = new NullPointerException();
789	<	}
790	<	else if (i != 0)
791	<	t.fork();
792	<	else {
793	<	t.quietlyInvoke();
794	<	if (ex == null)
795	<	ex = t.getException();
796	<	}
797	<	}
798	<	for (int i = 1; i <= last; ++i) {
799	<	ForkJoinTask<?> t = ts.get(i);
800	<	if (t != null) {
801	<	if (ex != null)
802	<	t.cancel(false);
803	<	else {
804	<	t.quietlyJoin();
805	<	if (ex == null)
806	<	ex = t.getException();
807	<	}
808	<	}
809	<	}
810	<	if (ex != null)
811	<	rethrowException(ex);
907	>	public boolean tryUnfork() {
908	>	return ((ForkJoinWorkerThread) Thread.currentThread())
909	>	.unpushTask(this);
910		}
911
912		/**
913	<	* Possibly executes tasks until the pool hosting the current task
914	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
915	<	* designs in which many tasks are forked, but none are explicitly
916	<	* joined, instead executing them until all are processed.
913	>	* Returns an estimate of the number of tasks that have been
914	>	* forked by the current worker thread but not yet executed. This
915	>	* value may be useful for heuristic decisions about whether to
916	>	* fork other tasks.
917	>	*
918	>	* @return the number of tasks
919		*/
920	<	public static void helpQuiesce() {
921	<	((ForkJoinWorkerThread)(Thread.currentThread())).
922	<	helpQuiescePool();
920	>	public static int getQueuedTaskCount() {
921	>	return ((ForkJoinWorkerThread) Thread.currentThread())
922	>	.getQueueSize();
923		}
924
925		/**
926	<	* Returns a estimate of how many more locally queued tasks are
926	>	* Returns an estimate of how many more locally queued tasks are
927		* held by the current worker thread than there are other worker
928	<	* threads that might want to steal them.  This value may be
929	<	* useful for heuristic decisions about whether to fork other
930	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
931	<	* worker should aim to maintain a small constant surplus (for
932	<	* example, 3) of tasks, and to process computations locally if
933	<	* this threshold is exceeded.
928	>	* threads that might steal them.  This value may be useful for
929	>	* heuristic decisions about whether to fork other tasks. In many
930	>	* usages of ForkJoinTasks, at steady state, each worker should
931	>	* aim to maintain a small constant surplus (for example, 3) of
932	>	* tasks, and to process computations locally if this threshold is
933	>	* exceeded.
934	>	*
935		* @return the surplus number of tasks, which may be negative
936		*/
937	<	public static int surplus() {
938	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
937	>	public static int getSurplusQueuedTaskCount() {
938	>	return ((ForkJoinWorkerThread) Thread.currentThread())
939		.getEstimatedSurplusTaskCount();
940		}
941
942	<	// Extension kit
942	>	// Extension methods
943
944		/**
945	<	* Returns the result that would be returned by <tt>join</tt>, or
946	<	* null if this task is not known to have been completed.  This
947	<	* method is designed to aid debugging, as well as to support
948	<	* extensions. Its use in any other context is discouraged.
945	>	* Returns the result that would be returned by {@code join},
946	>	* even if this task completed abnormally, or null if this task is
947	>	* not known to have been completed.  This method is designed to
948	>	* aid debugging, as well as to support extensions. Its use in any
949	>	* other context is discouraged.
950		*
951	<	* @return the result, or null if not completed.
951	>	* @return the result, or null if not completed
952		*/
953		public abstract V getRawResult();
954
#	Line 865 | Line 967 | public abstract class ForkJoinTask<V> im
967		* called otherwise. The return value controls whether this task
968		* is considered to be done normally. It may return false in
969		* asynchronous actions that require explicit invocations of
970	<	* <tt>complete</tt> to become joinable. It may throw exceptions
970	>	* {@code complete} to become joinable. It may throw exceptions
971		* to indicate abnormal exit.
972	+	*
973		* @return true if completed normally
974		* @throws Error or RuntimeException if encountered during computation
975		*/
976		protected abstract boolean exec();
977
978	+	/**
979	+	* Returns, but does not unschedule or execute, the task queued by
980	+	* the current thread but not yet executed, if one is
981	+	* available. There is no guarantee that this task will actually
982	+	* be polled or executed next.  This method is designed primarily
983	+	* to support extensions, and is unlikely to be useful otherwise.
984	+	* This method may be invoked only from within ForkJoinTask
985	+	* computations (as may be determined using method {@link
986	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
987	+	* in exceptions or errors, possibly including ClassCastException.
988	+	*
989	+	* @return the next task, or null if none are available
990	+	*/
991	+	protected static ForkJoinTask<?> peekNextLocalTask() {
992	+	return ((ForkJoinWorkerThread) Thread.currentThread())
993	+	.peekTask();
994	+	}
995	+
996	+	/**
997	+	* Unschedules and returns, without executing, the next task
998	+	* queued by the current thread but not yet executed.  This method
999	+	* is designed primarily to support extensions, and is unlikely to
1000	+	* be useful otherwise.  This method may be invoked only from
1001	+	* within ForkJoinTask computations (as may be determined using
1002	+	* method {@link #inForkJoinPool}). Attempts to invoke in other
1003	+	* contexts result in exceptions or errors, possibly including
1004	+	* ClassCastException.
1005	+	*
1006	+	* @return the next task, or null if none are available
1007	+	*/
1008	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1009	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1010	+	.pollLocalTask();
1011	+	}
1012	+
1013	+	/**
1014	+	* Unschedules and returns, without executing, the next task
1015	+	* queued by the current thread but not yet executed, if one is
1016	+	* available, or if not available, a task that was forked by some
1017	+	* other thread, if available. Availability may be transient, so a
1018	+	* {@code null} result does not necessarily imply quiescence
1019	+	* of the pool this task is operating in.  This method is designed
1020	+	* primarily to support extensions, and is unlikely to be useful
1021	+	* otherwise.  This method may be invoked only from within
1022	+	* ForkJoinTask computations (as may be determined using method
1023	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1024	+	* result in exceptions or errors, possibly including
1025	+	* ClassCastException.
1026	+	*
1027	+	* @return a task, or null if none are available
1028	+	*/
1029	+	protected static ForkJoinTask<?> pollTask() {
1030	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1031	+	.pollTask();
1032	+	}
1033	+
1034		// Serialization support
1035
1036		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1039 | public abstract class ForkJoinTask<V> im
1039		* Save the state to a stream.
1040		*
1041		* @serialData the current run status and the exception thrown
1042	<	* during execution, or null if none.
1042	>	* during execution, or null if none
1043		* @param s the stream
1044		*/
1045		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1050 | public abstract class ForkJoinTask<V> im
1050
1051		/**
1052		* Reconstitute the instance from a stream.
1053	+	*
1054		* @param s the stream
1055		*/
1056		private void readObject(java.io.ObjectInputStream s)
1057		throws java.io.IOException, ClassNotFoundException {
1058		s.defaultReadObject();
1059	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1059	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1060	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1061		Object ex = s.readObject();
1062		if (ex != null)
1063	<	setDoneExceptionally((Throwable)ex);
1063	>	setDoneExceptionally((Throwable) ex);
1064		}
1065
1066		// Temporary Unsafe mechanics for preliminary release
1067	+	private static Unsafe getUnsafe() throws Throwable {
1068	+	try {
1069	+	return Unsafe.getUnsafe();
1070	+	} catch (SecurityException se) {
1071	+	try {
1072	+	return java.security.AccessController.doPrivileged
1073	+	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1074	+	public Unsafe run() throws Exception {
1075	+	return getUnsafePrivileged();
1076	+	}});
1077	+	} catch (java.security.PrivilegedActionException e) {
1078	+	throw e.getCause();
1079	+	}
1080	+	}
1081	+	}
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;
1096	>	static final Unsafe UNSAFE;
1097		static final long statusOffset;
1098
1099		static {
1100		try {
1101	<	if (ForkJoinTask.class.getClassLoader() != null) {
1102	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1103	<	f.setAccessible(true);
1104	<	_unsafe = (Unsafe)f.get(null);
1105	<	}
917	<	else
918	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1101	>	UNSAFE = getUnsafe();
1102	>	statusOffset = fieldOffset("status");
1103	>	} catch (Throwable e) {
1104	>	throw new RuntimeException("Could not initialize intrinsics", e);
1105	>	}
1106		}
1107
1108		}

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