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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 1.29 by jsr166, Sun Aug 2 17:19:24 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.Map;
16	>	import java.util.WeakHashMap;
17
18		/**
19	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
20	<	* ForkJoinTask is a thread-like entity that is much lighter weight
21	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
22	<	* hosted by a small number of actual threads in a ForkJoinPool,
23	<	* at the price of some usage limitations.
19	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
20	>	* A {@code ForkJoinTask} is a thread-like entity that is much
21	>	* lighter weight than a normal thread.  Huge numbers of tasks and
22	>	* subtasks may be hosted by a small number of actual threads in a
23	>	* ForkJoinPool, at the price of some usage limitations.
24		*
25	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
26	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
27	<	* set of restrictions (that are only partially statically
28	<	* enforceable) reflecting their intended use as computational tasks
29	<	* calculating pure functions or operating on purely isolated objects.
30	<	* The primary coordination mechanisms supported for ForkJoinTasks are
31	<	* <tt>fork</tt>, that arranges asynchronous execution, and
32	<	* <tt>join</tt>, that doesn't proceed until the task's result has
33	<	* 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
34	<	* synchronizers such as Phasers that are advertised to cooperate with
35	<	* fork/join scheduling. Tasks should also not perform blocking IO,
36	<	* and should ideally access variables that are completely independent
37	<	* of those accessed by other running tasks. Minor breaches of these
38	<	* restrictions, for example using shared output streams, may be
39	<	* tolerable in practice, but frequent use may result in poor
40	<	* performance, and the potential to indefinitely stall if the number
41	<	* of threads not waiting for external synchronization becomes
42	<	* exhausted. This usage restriction is in part enforced by not
43	<	* permitting checked exceptions such as IOExceptions to be
44	<	* thrown. However, computations may still encounter unchecked
45	<	* exceptions, that are rethrown to callers attempting join
46	<	* them. These exceptions may additionally include
47	<	* RejectedExecutionExceptions stemming from internal resource
48	<	* exhaustion such as failure to allocate internal task queues.
25	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
26	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
27	>	* start other subtasks.  As indicated by the name of this class,
28	>	* many programs using {@code ForkJoinTask} employ only methods
29	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
30	>	* #invokeAll}.  However, this class also provides a number of other
31	>	* methods that can come into play in advanced usages, as well as
32	>	* extension mechanics that allow support of new forms of fork/join
33	>	* processing.
34		*
35	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
36	<	* subclassed.  Instead, you subclass one of the abstract classes that
37	<	* support different styles of fork/join processing.  Normally, a
38	<	* concrete ForkJoinTask subclass declares fields comprising its
39	<	* parameters, established in a constructor, and then defines a
40	<	* <tt>compute</tt> method that somehow uses the control methods
41	<	* supplied by this base class. While these methods have
42	<	* <tt>public</tt> access, some of them may only be called from within
43	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
44	<	* result in exceptions or errors including ClassCastException.  The
45	<	* only way to invoke a "main" driver task is to submit it to a
46	<	* ForkJoinPool. Once started, this will usually in turn start other
47	<	* subtasks.
35	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
36	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
37	>	* restrictions (that are only partially statically enforceable)
38	>	* reflecting their intended use as computational tasks calculating
39	>	* pure functions or operating on purely isolated objects.  The
40	>	* primary coordination mechanisms are {@link #fork}, that arranges
41	>	* asynchronous execution, and {@link #join}, that doesn't proceed
42	>	* until the task's result has been computed.  Computations should
43	>	* avoid {@code synchronized} methods or blocks, and should minimize
44	>	* other blocking synchronization apart from joining other tasks or
45	>	* using synchronizers such as Phasers that are advertised to
46	>	* cooperate with fork/join scheduling. Tasks should also not perform
47	>	* blocking IO, and should ideally access variables that are
48	>	* completely independent of those accessed by other running
49	>	* tasks. Minor breaches of these restrictions, for example using
50	>	* shared output streams, may be tolerable in practice, but frequent
51	>	* use may result in poor performance, and the potential to
52	>	* indefinitely stall if the number of threads not waiting for IO or
53	>	* other external synchronization becomes exhausted. This usage
54	>	* restriction is in part enforced by not permitting checked
55	>	* exceptions such as {@code IOExceptions} to be thrown. However,
56	>	* computations may still encounter unchecked exceptions, that are
57	>	* rethrown to callers attempting join them. These exceptions may
58	>	* additionally include RejectedExecutionExceptions stemming from
59	>	* internal resource exhaustion such as failure to allocate internal
60	>	* task queues.
61		*
62	<	* <p>Most base support methods are <tt>final</tt> because their
62	>	* <p>The primary method for awaiting completion and extracting
63	>	* results of a task is {@link #join}, but there are several variants:
64	>	* The {@link Future#get} methods support interruptible and/or timed
65	>	* waits for completion and report results using {@code Future}
66	>	* conventions. Method {@link #helpJoin} enables callers to actively
67	>	* execute other tasks while awaiting joins, which is sometimes more
68	>	* efficient but only applies when all subtasks are known to be
69	>	* strictly tree-structured. Method {@link #invoke} is semantically
70	>	* equivalent to {@code fork(); join()} but always attempts to
71	>	* begin execution in the current thread. The "<em>quiet</em>" forms
72	>	* of these methods do not extract results or report exceptions. These
73	>	* may be useful when a set of tasks are being executed, and you need
74	>	* to delay processing of results or exceptions until all complete.
75	>	* Method {@code invokeAll} (available in multiple versions)
76	>	* performs the most common form of parallel invocation: forking a set
77	>	* of tasks and joining them all.
78	>	*
79	>	* <p>The ForkJoinTask class is not usually directly subclassed.
80	>	* Instead, you subclass one of the abstract classes that support a
81	>	* particular style of fork/join processing, typically {@link
82	>	* RecursiveAction} for computations that do not return results, or
83	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
84	>	* ForkJoinTask subclass declares fields comprising its parameters,
85	>	* established in a constructor, and then defines a {@code compute}
86	>	* method that somehow uses the control methods supplied by this base
87	>	* class. While these methods have {@code public} access (to allow
88	>	* instances of different task subclasses to call each others
89	>	* methods), some of them may only be called from within other
90	>	* ForkJoinTasks (as may be determined using method {@link
91	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
92	>	* result in exceptions or errors, possibly including
93	>	* ClassCastException.
94	>	*
95	>	* <p>Most base support methods are {@code final} because their
96		* implementations are intrinsically tied to the underlying
97		* lightweight task scheduling framework, and so cannot be overridden.
98		* Developers creating new basic styles of fork/join processing should
99	<	* minimally implement protected methods <tt>exec</tt>,
100	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
101	<	* introducing an abstract computational method that can be
102	<	* implemented in its subclasses. To support such extensions,
103	<	* instances of ForkJoinTasks maintain an atomically updated
104	<	* <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.
99	>	* minimally implement {@code protected} methods
100	>	* {@link #exec}, {@link #setRawResult}, and
101	>	* {@link #getRawResult}, while also introducing an abstract
102	>	* computational method that can be implemented in its subclasses,
103	>	* possibly relying on other {@code protected} methods provided
104	>	* by this class.
105		*
106		* <p>ForkJoinTasks should perform relatively small amounts of
107	<	* computations, othewise splitting into smaller tasks. As a very
107	>	* computations, otherwise splitting into smaller tasks. As a very
108		* rough rule of thumb, a task should perform more than 100 and less
109		* than 10000 basic computational steps. If tasks are too big, then
110	<	* parellelism cannot improve throughput. If too small, then memory
110	>	* parallelism cannot improve throughput. If too small, then memory
111		* and internal task maintenance overhead may overwhelm processing.
112		*
113	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
114	<	* be used in extensions such as remote execution frameworks. However,
115	<	* it is in general safe to serialize tasks only before or after, but
113	>	* <p>This class provides {@code adapt} methods for {@link
114	>	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
115	>	* may be of use when mixing execution of ForkJoinTasks with other
116	>	* kinds of tasks. When all tasks are of this form, consider using a
117	>	* pool in {@link ForkJoinPool#setAsyncMode}.
118	>	*
119	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
120	>	* to be used in extensions such as remote execution frameworks. It is
121	>	* in general sensible to serialize tasks only before or after, but
122		* not during execution. Serialization is not relied on during
123		* execution itself.
124	+	*
125	+	* @since 1.7
126	+	* @author Doug Lea
127		*/
128		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
129	+
130		/**
131	<	* Status field holding all run status. We pack this into a single
132	<	* int both to minimize footprint overhead and to ensure atomicity
133	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
131	>	* Run control status bits packed into a single int to minimize
132	>	* footprint and to ensure atomicity (via CAS).  Status is
133	>	* initially zero, and takes on nonnegative values until
134		* completed, upon which status holds COMPLETED. CANCELLED, or
135		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
136		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 145 | public abstract class ForkJoinTask<V> im
145		* currently unused. Also value 0x80000000 is available as spare
146		* completion value.
147		*/
148	<	volatile int status; // accessed directy by pool and workers
148	>	volatile int status; // accessed directly by pool and workers
149
150		static final int COMPLETION_MASK      = 0xe0000000;
151		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 158 | public abstract class ForkJoinTask<V> im
158		/**
159		* Table of exceptions thrown by tasks, to enable reporting by
160		* callers. Because exceptions are rare, we don't directly keep
161	<	* them with task objects, but instead us a weak ref table.  Note
161	>	* them with task objects, but instead use a weak ref table.  Note
162		* that cancellation exceptions don't appear in the table, but are
163		* instead recorded as status values.
164	<	* Todo: Use ConcurrentReferenceHashMap
164	>	* TODO: Use ConcurrentReferenceHashMap
165		*/
166		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
167		Collections.synchronizedMap
#	Line 136 | Line 170 | public abstract class ForkJoinTask<V> im
170		// within-package utilities
171
172		/**
173	<	* Get current worker thread, or null if not a worker thread
173	>	* Gets current worker thread, or null if not a worker thread.
174		*/
175		static ForkJoinWorkerThread getWorker() {
176		Thread t = Thread.currentThread();
177	<	return ((t instanceof ForkJoinWorkerThread)?
178	<	(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);
177	>	return ((t instanceof ForkJoinWorkerThread) ?
178	>	(ForkJoinWorkerThread) t : null);
179		}
180
181		final boolean casStatus(int cmp, int val) {
182	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
182	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183		}
184
185		/**
#	Line 162 | Line 187 | public abstract class ForkJoinTask<V> im
187		*/
188		static void rethrowException(Throwable ex) {
189		if (ex != null)
190	<	_unsafe.throwException(ex);
190	>	UNSAFE.throwException(ex);
191		}
192
193		// Setting completion status
194
195		/**
196	<	* Mark completion and wake up threads waiting to join this task.
196	>	* Marks completion and wakes up threads waiting to join this task.
197	>	*
198		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
199		*/
200		final void setCompletion(int completion) {
201	<	ForkJoinPool pool = getWorkerPool();
201	>	ForkJoinPool pool = getPool();
202		if (pool != null) {
203		int s; // Clear signal bits while setting completion status
204	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
204	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
205
206		if ((s & SIGNAL_MASK) != 0) {
207		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208		pool.updateRunningCount(s);
209	<	synchronized(this) { notifyAll(); }
209	>	synchronized (this) { notifyAll(); }
210		}
211		}
212		else
#	Line 193 | Line 219 | public abstract class ForkJoinTask<V> im
219		*/
220		private void externallySetCompletion(int completion) {
221		int s;
222	<	do;while ((s = status) >= 0 &&
223	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	<	synchronized(this) { notifyAll(); }
222	>	do {} while ((s = status) >= 0 &&
223	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	>	synchronized (this) { notifyAll(); }
225		}
226
227		/**
228	<	* Sets status to indicate normal completion
228	>	* Sets status to indicate normal completion.
229		*/
230		final void setNormalCompletion() {
231		// Try typical fast case -- single CAS, no signal, not already done.
232		// Manually expand casStatus to improve chances of inlining it
233	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
233	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
234		setCompletion(NORMAL);
235		}
236
237		// internal waiting and notification
238
239		/**
240	<	* Performs the actual monitor wait for awaitDone
240	>	* Performs the actual monitor wait for awaitDone.
241		*/
242		private void doAwaitDone() {
243		// Minimize lock bias and in/de-flation effects by maximizing
244		// chances of waiting inside sync
245		try {
246		while (status >= 0)
247	<	synchronized(this) { if (status >= 0) wait(); }
247	>	synchronized (this) { if (status >= 0) wait(); }
248		} catch (InterruptedException ie) {
249		onInterruptedWait();
250		}
251		}
252
253		/**
254	<	* Performs the actual monitor wait for awaitDone
254	>	* Performs the actual timed monitor wait for awaitDone.
255		*/
256		private void doAwaitDone(long startTime, long nanos) {
257	<	synchronized(this) {
257	>	synchronized (this) {
258		try {
259		while (status >= 0) {
260	<	long nt = nanos - System.nanoTime() - startTime;
260	>	long nt = nanos - (System.nanoTime() - startTime);
261		if (nt <= 0)
262		break;
263	<	wait(nt / 1000000, (int)(nt % 1000000));
263	>	wait(nt / 1000000, (int) (nt % 1000000));
264		}
265		} catch (InterruptedException ie) {
266		onInterruptedWait();
#	Line 247 | Line 273 | public abstract class ForkJoinTask<V> im
273		/**
274		* Sets status to indicate there is joiner, then waits for join,
275		* surrounded with pool notifications.
276	+	*
277		* @return status upon exit
278		*/
279	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
280	<	ForkJoinPool pool = w == null? null : w.pool;
279	>	private int awaitDone(ForkJoinWorkerThread w,
280	>	boolean maintainParallelism) {
281	>	ForkJoinPool pool = (w == null) ? null : w.pool;
282		int s;
283		while ((s = status) >= 0) {
284	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
284	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
285		if (pool == null || !pool.preJoin(this, maintainParallelism))
286		doAwaitDone();
287		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 294 | public abstract class ForkJoinTask<V> im
294
295		/**
296		* Timed version of awaitDone
297	+	*
298		* @return status upon exit
299		*/
300	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = w == null? null : w.pool;
300	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	>	ForkJoinPool pool = (w == null) ? null : w.pool;
302		int s;
303		while ((s = status) >= 0) {
304	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
304	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
305		long startTime = System.nanoTime();
306		if (pool == null || !pool.preJoin(this, false))
307		doAwaitDone(startTime, nanos);
#	Line 289 | Line 318 | public abstract class ForkJoinTask<V> im
318		}
319
320		/**
321	<	* Notify pool that thread is unblocked. Called by signalled
321	>	* Notifies pool that thread is unblocked. Called by signalled
322		* threads when woken by non-FJ threads (which is atypical).
323		*/
324		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
325		int s;
326	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
326	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
327		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
328		pool.updateRunningCount(s);
329		}
330
331		/**
332	<	* Notify pool to adjust counts on cancelled or timed out wait
332	>	* Notifies pool to adjust counts on cancelled or timed out wait.
333		*/
334		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
335		if (pool != null) {
#	Line 314 | Line 343 | public abstract class ForkJoinTask<V> im
343		}
344		}
345
346	+	/**
347	+	* Handles interruptions during waits.
348	+	*/
349		private void onInterruptedWait() {
350	<	Thread t = Thread.currentThread();
351	<	if (t instanceof ForkJoinWorkerThread) {
352	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
353	<	if (w.isTerminating())
354	<	cancelIgnoreExceptions();
355	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
350	>	ForkJoinWorkerThread w = getWorker();
351	>	if (w == null)
352	>	Thread.currentThread().interrupt(); // re-interrupt
353	>	else if (w.isTerminating())
354	>	cancelIgnoringExceptions();
355	>	// else if FJworker, ignore interrupt
356		}
357
358		// Recording and reporting exceptions
#	Line 337 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Throws the exception associated with status s;
366	>	* Throws the exception associated with status s.
367	>	*
368		* @throws the exception
369		*/
370		private void reportException(int s) {
#	Line 350 | Line 377 | public abstract class ForkJoinTask<V> im
377		}
378
379		/**
380	<	* Returns result or throws exception using j.u.c.Future conventions
381	<	* Only call when isDone known to be true.
380	>	* Returns result or throws exception using j.u.c.Future conventions.
381	>	* Only call when {@code isDone} known to be true.
382		*/
383		private V reportFutureResult()
384		throws ExecutionException, InterruptedException {
#	Line 370 | Line 397 | public abstract class ForkJoinTask<V> im
397
398		/**
399		* Returns result or throws exception using j.u.c.Future conventions
400	<	* with timeouts
400	>	* with timeouts.
401		*/
402		private V reportTimedFutureResult()
403		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 391 | Line 418 | public abstract class ForkJoinTask<V> im
418
419		/**
420		* Calls exec, recording completion, and rethrowing exception if
421	<	* encountered. Caller should normally check status before calling
421	>	* encountered. Caller should normally check status before calling.
422	>	*
423		* @return true if completed normally
424		*/
425		private boolean tryExec() {
#	Line 409 | Line 437 | public abstract class ForkJoinTask<V> im
437
438		/**
439		* Main execution method used by worker threads. Invokes
440	<	* base computation unless already complete
440	>	* base computation unless already complete.
441		*/
442		final void quietlyExec() {
443		if (status >= 0) {
444		try {
445		if (!exec())
446		return;
447	<	} catch(Throwable rex) {
447	>	} catch (Throwable rex) {
448		setDoneExceptionally(rex);
449		return;
450		}
#	Line 425 | Line 453 | public abstract class ForkJoinTask<V> im
453		}
454
455		/**
456	<	* Calls exec, recording but not rethrowing exception
457	<	* Caller should normally check status before calling
456	>	* Calls exec(), recording but not rethrowing exception.
457	>	* Caller should normally check status before calling.
458	>	*
459		* @return true if completed normally
460		*/
461		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 471 | public abstract class ForkJoinTask<V> im
471		}
472
473		/**
474	<	* Cancel, ignoring any exceptions it throws
474	>	* Cancels, ignoring any exceptions it throws.
475		*/
476	<	final void cancelIgnoreExceptions() {
476	>	final void cancelIgnoringExceptions() {
477		try {
478		cancel(false);
479	<	} catch(Throwable ignore) {
479	>	} catch (Throwable ignore) {
480		}
481		}
482
483	+	/**
484	+	* Main implementation of helpJoin
485	+	*/
486	+	private int busyJoin(ForkJoinWorkerThread w) {
487	+	int s;
488	+	ForkJoinTask<?> t;
489	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
490	+	t.quietlyExec();
491	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
492	+	}
493	+
494		// public methods
495
496		/**
497		* Arranges to asynchronously execute this task.  While it is not
498		* necessarily enforced, it is a usage error to fork a task more
499		* than once unless it has completed and been reinitialized.  This
500	<	* method may be invoked only from within other ForkJoinTask
501	<	* computations. Attempts to invoke in other contexts result in
502	<	* exceptions or errors including ClassCastException.
500	>	* method may be invoked only from within ForkJoinTask
501	>	* computations (as may be determined using method {@link
502	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
503	>	* in exceptions or errors, possibly including ClassCastException.
504	>	*
505	>	* @return {@code this}, to simplify usage.
506		*/
507	<	public final void fork() {
508	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
507	>	public final ForkJoinTask<V> fork() {
508	>	((ForkJoinWorkerThread) Thread.currentThread())
509	>	.pushTask(this);
510	>	return this;
511		}
512
513		/**
514		* Returns the result of the computation when it is ready.
515	<	* This method differs from <tt>get</tt> in that abnormal
515	>	* This method differs from {@code get} in that abnormal
516		* completion results in RuntimeExceptions or Errors, not
517		* ExecutionExceptions.
518		*
#	Line 480 | Line 525 | public abstract class ForkJoinTask<V> im
525		return getRawResult();
526		}
527
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	–
528		/**
529	<	* Possibly executes other tasks until this task is ready, then
530	<	* returns the result of the computation.  This method may be more
531	<	* 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.
529	>	* Commences performing this task, awaits its completion if
530	>	* necessary, and return its result.
531	>	*
532		* @throws Throwable (a RuntimeException, Error, or unchecked
533	<	* exception) if the underlying computation did so.
533	>	* exception) if the underlying computation did so
534		* @return the computed result
535		*/
536		public final V invoke() {
#	Line 527 | Line 541 | public abstract class ForkJoinTask<V> im
541		}
542
543		/**
544	<	* Joins this task, without returning its result or throwing an
545	<	* exception. This method may be useful when processing
546	<	* collections of tasks when some have been cancelled or otherwise
547	<	* known to have aborted.
544	>	* Forks the given tasks, returning when {@code isDone} holds for
545	>	* each task or an exception is encountered. This method may be
546	>	* invoked only from within ForkJoinTask computations (as may be
547	>	* determined using method {@link #inForkJoinPool}). Attempts to
548	>	* invoke in other contexts result in exceptions or errors,
549	>	* possibly including ClassCastException.
550	>	*
551	>	* @param t1 the first task
552	>	* @param t2 the second task
553	>	* @throws NullPointerException if any task is null
554	>	* @throws RuntimeException or Error if a task did so
555		*/
556	<	public final void quietlyJoin() {
557	<	if (status >= 0) {
558	<	ForkJoinWorkerThread w = getWorker();
559	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
556	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
557	>	t2.fork();
558	>	t1.invoke();
559	>	t2.join();
560		}
561
562		/**
563	<	* Possibly executes other tasks until this task is ready.
563	>	* Forks the given tasks, returning when {@code isDone} holds for
564	>	* each task or an exception is encountered. If any task
565	>	* encounters an exception, others may be, but are not guaranteed
566	>	* to be, cancelled.  This method may be invoked only from within
567	>	* ForkJoinTask computations (as may be determined using method
568	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
569	>	* result in exceptions or errors, possibly including
570	>	* ClassCastException.
571	>	*
572	>	* Overloadings of this method exist for the special cases
573	>	* of one to four arguments.
574	>	*
575	>	* @param tasks the tasks
576	>	* @throws NullPointerException if tasks or any element are null
577	>	* @throws RuntimeException or Error if any task did so
578		*/
579	<	public final void quietlyHelpJoin() {
580	<	if (status >= 0) {
581	<	ForkJoinWorkerThread w =
582	<	(ForkJoinWorkerThread)(Thread.currentThread());
583	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
584	<	w.helpJoinTask(this);
579	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
580	>	Throwable ex = null;
581	>	int last = tasks.length - 1;
582	>	for (int i = last; i >= 0; --i) {
583	>	ForkJoinTask<?> t = tasks[i];
584	>	if (t == null) {
585	>	if (ex == null)
586	>	ex = new NullPointerException();
587	>	}
588	>	else if (i != 0)
589	>	t.fork();
590	>	else {
591	>	t.quietlyInvoke();
592	>	if (ex == null)
593	>	ex = t.getException();
594	>	}
595	>	}
596	>	for (int i = 1; i <= last; ++i) {
597	>	ForkJoinTask<?> t = tasks[i];
598	>	if (t != null) {
599	>	if (ex != null)
600	>	t.cancel(false);
601	>	else {
602	>	t.quietlyJoin();
603	>	if (ex == null)
604	>	ex = t.getException();
605	>	}
606	>	}
607		}
608	+	if (ex != null)
609	+	rethrowException(ex);
610		}
611
612		/**
613	<	* Performs this task and awaits its completion if necessary,
614	<	* without returning its result or throwing an exception. This
615	<	* method may be useful when processing collections of tasks when
616	<	* some have been cancelled or otherwise known to have aborted.
617	<	*/
618	<	public final void quietlyInvoke() {
619	<	if (status >= 0 && !tryQuietlyInvoke())
620	<	quietlyJoin();
613	>	* Forks all tasks in the collection, returning when {@code
614	>	* isDone} holds for each task or an exception is encountered. If
615	>	* any task encounters an exception, others may be, but are not
616	>	* guaranteed to be, cancelled.  This method may be invoked only
617	>	* from within ForkJoinTask computations (as may be determined
618	>	* using method {@link #inForkJoinPool}). Attempts to invoke in
619	>	* other contexts result in exceptions or errors, possibly
620	>	* including ClassCastException.
621	>	*
622	>	* @param tasks the collection of tasks
623	>	* @return the tasks argument, to simplify usage
624	>	* @throws NullPointerException if tasks or any element are null
625	>	* @throws RuntimeException or Error if any task did so
626	>	*/
627	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
628	>	if (!(tasks instanceof List<?>)) {
629	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
630	>	return tasks;
631	>	}
632	>	@SuppressWarnings("unchecked")
633	>	List<? extends ForkJoinTask<?>> ts =
634	>	(List<? extends ForkJoinTask<?>>) tasks;
635	>	Throwable ex = null;
636	>	int last = ts.size() - 1;
637	>	for (int i = last; i >= 0; --i) {
638	>	ForkJoinTask<?> t = ts.get(i);
639	>	if (t == null) {
640	>	if (ex == null)
641	>	ex = new NullPointerException();
642	>	}
643	>	else if (i != 0)
644	>	t.fork();
645	>	else {
646	>	t.quietlyInvoke();
647	>	if (ex == null)
648	>	ex = t.getException();
649	>	}
650	>	}
651	>	for (int i = 1; i <= last; ++i) {
652	>	ForkJoinTask<?> t = ts.get(i);
653	>	if (t != null) {
654	>	if (ex != null)
655	>	t.cancel(false);
656	>	else {
657	>	t.quietlyJoin();
658	>	if (ex == null)
659	>	ex = t.getException();
660	>	}
661	>	}
662	>	}
663	>	if (ex != null)
664	>	rethrowException(ex);
665	>	return tasks;
666		}
667
668		/**
669	<	* Returns true if the computation performed by this task has
670	<	* completed (or has been cancelled).
671	<	* @return true if this computation has completed
669	>	* Returns {@code true} if the computation performed by this task
670	>	* has completed (or has been cancelled).
671	>	*
672	>	* @return {@code true} if this computation has completed
673		*/
674		public final boolean isDone() {
675		return status < 0;
676		}
677
678		/**
679	<	* Returns true if this task was cancelled.
680	<	* @return true if this task was cancelled
679	>	* Returns {@code true} if this task was cancelled.
680	>	*
681	>	* @return {@code true} if this task was cancelled
682		*/
683		public final boolean isCancelled() {
684		return (status & COMPLETION_MASK) == CANCELLED;
685		}
686
687		/**
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	–	/**
688		* Asserts that the results of this task's computation will not be
689	<	* used. If a cancellation occurs before this task is processed,
690	<	* then its <tt>compute</tt> method will not be executed,
691	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
692	<	* result in a CancellationException being thrown. Otherwise, when
689	>	* used. If a cancellation occurs before attempting to execute this
690	>	* task, execution will be suppressed, {@link #isCancelled}
691	>	* will report true, and {@link #join} will result in a
692	>	* {@code CancellationException} being thrown. Otherwise, when
693		* cancellation races with completion, there are no guarantees
694	<	* about whether <tt>isCancelled</tt> will report true, whether
695	<	* <tt>join</tt> will return normally or via an exception, or
696	<	* whether these behaviors will remain consistent upon repeated
694	>	* about whether {@code isCancelled} will report {@code true},
695	>	* whether {@code join} will return normally or via an exception,
696	>	* or whether these behaviors will remain consistent upon repeated
697		* invocation.
698		*
699		* <p>This method may be overridden in subclasses, but if so, must
700		* still ensure that these minimal properties hold. In particular,
701	<	* the cancel method itself must not throw exceptions.
701	>	* the {@code cancel} method itself must not throw exceptions.
702		*
703	<	* <p> This method is designed to be invoked by <em>other</em>
703	>	* <p>This method is designed to be invoked by <em>other</em>
704		* tasks. To terminate the current task, you can just return or
705		* throw an unchecked exception from its computation method, or
706	<	* invoke <tt>completeExceptionally(someException)</tt>.
706	>	* invoke {@link #completeExceptionally}.
707		*
708		* @param mayInterruptIfRunning this value is ignored in the
709		* default implementation because tasks are not in general
710	<	* cancelled via interruption.
710	>	* cancelled via interruption
711		*
712	<	* @return true if this task is now cancelled
712	>	* @return {@code true} if this task is now cancelled
713		*/
714		public boolean cancel(boolean mayInterruptIfRunning) {
715		setCompletion(CANCELLED);
#	Line 636 | Line 717 | public abstract class ForkJoinTask<V> im
717		}
718
719		/**
720	+	* Returns {@code true} if this task threw an exception or was cancelled.
721	+	*
722	+	* @return {@code true} if this task threw an exception or was cancelled
723	+	*/
724	+	public final boolean isCompletedAbnormally() {
725	+	return (status & COMPLETION_MASK) < NORMAL;
726	+	}
727	+
728	+	/**
729	+	* Returns the exception thrown by the base computation, or a
730	+	* {@code CancellationException} if cancelled, or {@code null} if
731	+	* none or if the method has not yet completed.
732	+	*
733	+	* @return the exception, or {@code null} if none
734	+	*/
735	+	public final Throwable getException() {
736	+	int s = status & COMPLETION_MASK;
737	+	if (s >= NORMAL)
738	+	return null;
739	+	if (s == CANCELLED)
740	+	return new CancellationException();
741	+	return exceptionMap.get(this);
742	+	}
743	+
744	+	/**
745		* Completes this task abnormally, and if not already aborted or
746		* cancelled, causes it to throw the given exception upon
747	<	* <tt>join</tt> and related operations. This method may be used
747	>	* {@code join} and related operations. This method may be used
748		* to induce exceptions in asynchronous tasks, or to force
749	<	* completion of tasks that would not otherwise complete.  This
750	<	* method is overridable, but overridden versions must invoke
751	<	* <tt>super</tt> implementation to maintain guarantees.
749	>	* completion of tasks that would not otherwise complete.  Its use
750	>	* in other situations is discouraged.  This method is
751	>	* overridable, but overridden versions must invoke {@code super}
752	>	* implementation to maintain guarantees.
753	>	*
754		* @param ex the exception to throw. If this exception is
755		* not a RuntimeException or Error, the actual exception thrown
756		* will be a RuntimeException with cause ex.
757		*/
758		public void completeExceptionally(Throwable ex) {
759		setDoneExceptionally((ex instanceof RuntimeException) ||
760	<	(ex instanceof Error)? ex :
760	>	(ex instanceof Error) ? ex :
761		new RuntimeException(ex));
762		}
763
764		/**
765		* Completes this task, and if not already aborted or cancelled,
766	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
766	>	* returning a {@code null} result upon {@code join} and related
767		* operations. This method may be used to provide results for
768		* asynchronous tasks, or to provide alternative handling for
769	<	* tasks that would not otherwise complete normally.
769	>	* tasks that would not otherwise complete normally. Its use in
770	>	* other situations is discouraged. This method is
771	>	* overridable, but overridden versions must invoke {@code super}
772	>	* implementation to maintain guarantees.
773		*
774	<	* @param value the result value for this task.
774	>	* @param value the result value for this task
775		*/
776		public void complete(V value) {
777		try {
778		setRawResult(value);
779	<	} catch(Throwable rex) {
779	>	} catch (Throwable rex) {
780		setDoneExceptionally(rex);
781		return;
782		}
783		setNormalCompletion();
784		}
785
786	+	public final V get() throws InterruptedException, ExecutionException {
787	+	ForkJoinWorkerThread w = getWorker();
788	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
789	+	awaitDone(w, true);
790	+	return reportFutureResult();
791	+	}
792	+
793	+	public final V get(long timeout, TimeUnit unit)
794	+	throws InterruptedException, ExecutionException, TimeoutException {
795	+	long nanos = unit.toNanos(timeout);
796	+	ForkJoinWorkerThread w = getWorker();
797	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
798	+	awaitDone(w, nanos);
799	+	return reportTimedFutureResult();
800	+	}
801	+
802	+	/**
803	+	* Possibly executes other tasks until this task is ready, then
804	+	* returns the result of the computation.  This method may be more
805	+	* efficient than {@code join}, but is only applicable when
806	+	* there are no potential dependencies between continuation of the
807	+	* current task and that of any other task that might be executed
808	+	* while helping. (This usually holds for pure divide-and-conquer
809	+	* tasks). This method may be invoked only from within
810	+	* ForkJoinTask computations (as may be determined using method
811	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
812	+	* result in exceptions or errors, possibly including
813	+	* ClassCastException.
814	+	*
815	+	* @return the computed result
816	+	*/
817	+	public final V helpJoin() {
818	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
819	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
820	+	reportException(busyJoin(w));
821	+	return getRawResult();
822	+	}
823	+
824	+	/**
825	+	* Possibly executes other tasks until this task is ready.  This
826	+	* method may be invoked only from within ForkJoinTask
827	+	* computations (as may be determined using method {@link
828	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
829	+	* in exceptions or errors, possibly including ClassCastException.
830	+	*/
831	+	public final void quietlyHelpJoin() {
832	+	if (status >= 0) {
833	+	ForkJoinWorkerThread w =
834	+	(ForkJoinWorkerThread) Thread.currentThread();
835	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
836	+	busyJoin(w);
837	+	}
838	+	}
839	+
840	+	/**
841	+	* Joins this task, without returning its result or throwing an
842	+	* exception. This method may be useful when processing
843	+	* collections of tasks when some have been cancelled or otherwise
844	+	* known to have aborted.
845	+	*/
846	+	public final void quietlyJoin() {
847	+	if (status >= 0) {
848	+	ForkJoinWorkerThread w = getWorker();
849	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
850	+	awaitDone(w, true);
851	+	}
852	+	}
853	+
854	+	/**
855	+	* Commences performing this task and awaits its completion if
856	+	* necessary, without returning its result or throwing an
857	+	* exception. This method may be useful when processing
858	+	* collections of tasks when some have been cancelled or otherwise
859	+	* known to have aborted.
860	+	*/
861	+	public final void quietlyInvoke() {
862	+	if (status >= 0 && !tryQuietlyInvoke())
863	+	quietlyJoin();
864	+	}
865	+
866	+	/**
867	+	* Possibly executes tasks until the pool hosting the current task
868	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
869	+	* designs in which many tasks are forked, but none are explicitly
870	+	* joined, instead executing them until all are processed.  This
871	+	* method may be invoked only from within ForkJoinTask
872	+	* computations (as may be determined using method {@link
873	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
874	+	* in exceptions or errors, possibly including ClassCastException.
875	+	*/
876	+	public static void helpQuiesce() {
877	+	((ForkJoinWorkerThread) Thread.currentThread())
878	+	.helpQuiescePool();
879	+	}
880	+
881		/**
882		* Resets the internal bookkeeping state of this task, allowing a
883	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
883	>	* subsequent {@code fork}. This method allows repeated reuse of
884		* this task, but only if reuse occurs when this task has either
885		* never been forked, or has been forked, then completed and all
886		* outstanding joins of this task have also completed. Effects
887		* under any other usage conditions are not guaranteed, and are
888	<	* almost surely wrong. This method may be useful when executing
888	>	* discouraged. This method may be useful when executing
889		* pre-constructed trees of subtasks in loops.
890		*/
891		public void reinitialize() {
#	Line 689 | Line 895 | public abstract class ForkJoinTask<V> im
895		}
896
897		/**
898	<	* Tries to unschedule this task for execution. This method will
899	<	* typically succeed if this task is the next task that would be
900	<	* executed by the current thread, and will typically fail (return
901	<	* false) otherwise. This method may be useful when arranging
902	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
898	>	* Returns the pool hosting the current task execution, or null
899	>	* if this task is executing outside of any ForkJoinPool.
900	>	*
901	>	* @see #inForkJoinPool
902	>	* @return the pool, or {@code null} if none
903		*/
904	<	public boolean tryUnfork() {
905	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
904	>	public static ForkJoinPool getPool() {
905	>	Thread t = Thread.currentThread();
906	>	return (t instanceof ForkJoinWorkerThread) ?
907	>	((ForkJoinWorkerThread) t).pool : null;
908		}
909
910		/**
911	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
912	<	* of them or an exception is encountered. This method may be
913	<	* invoked only from within other ForkJoinTask
914	<	* computations. Attempts to invoke in other contexts result in
915	<	* 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.
911	>	* Returns {@code true} if the current thread is executing as a
912	>	* ForkJoinPool computation.
913	>	*
914	>	* @return {@code true} if the current thread is executing as a
915	>	* ForkJoinPool computation, or false otherwise
916		*/
917	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
918	<	t2.fork();
717	<	t1.invoke();
718	<	t2.join();
917	>	public static boolean inForkJoinPool() {
918	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
919		}
920
921		/**
922	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
923	<	* all of them. If any task encounters an exception, others may be
924	<	* cancelled.  This method may be invoked only from within other
925	<	* ForkJoinTask computations. Attempts to invoke in other contexts
926	<	* result in exceptions or errors including ClassCastException.
927	<	* @param tasks the array of tasks
928	<	* @throws NullPointerException if tasks or any element are null.
929	<	* @throws RuntimeException or Error if any task did so.
930	<	*/
931	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
932	<	Throwable ex = null;
933	<	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.
922	>	* Tries to unschedule this task for execution. This method will
923	>	* typically succeed if this task is the most recently forked task
924	>	* by the current thread, and has not commenced executing in
925	>	* another thread.  This method may be useful when arranging
926	>	* alternative local processing of tasks that could have been, but
927	>	* were not, stolen. This method may be invoked only from within
928	>	* ForkJoinTask computations (as may be determined using method
929	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
930	>	* result in exceptions or errors, possibly including
931	>	* ClassCastException.
932	>	*
933	>	* @return {@code true} if unforked
934		*/
935	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
936	<	if (!(tasks instanceof List)) {
937	<	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);
935	>	public boolean tryUnfork() {
936	>	return ((ForkJoinWorkerThread) Thread.currentThread())
937	>	.unpushTask(this);
938		}
939
940		/**
941	<	* Possibly executes tasks until the pool hosting the current task
942	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
943	<	* designs in which many tasks are forked, but none are explicitly
944	<	* joined, instead executing them until all are processed.
941	>	* Returns an estimate of the number of tasks that have been
942	>	* forked by the current worker thread but not yet executed. This
943	>	* value may be useful for heuristic decisions about whether to
944	>	* fork other tasks.  This method may be invoked only from within
945	>	* ForkJoinTask computations (as may be determined using method
946	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
947	>	* result in exceptions or errors, possibly including
948	>	* ClassCastException.
949	>	* @return the number of tasks
950		*/
951	<	public static void helpQuiesce() {
952	<	((ForkJoinWorkerThread)(Thread.currentThread())).
953	<	helpQuiescePool();
951	>	public static int getQueuedTaskCount() {
952	>	return ((ForkJoinWorkerThread) Thread.currentThread())
953	>	.getQueueSize();
954		}
955
956		/**
957	<	* Returns a estimate of how many more locally queued tasks are
957	>	* Returns an estimate of how many more locally queued tasks are
958		* held by the current worker thread than there are other worker
959	<	* threads that might want to steal them.  This value may be
960	<	* useful for heuristic decisions about whether to fork other
961	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
962	<	* worker should aim to maintain a small constant surplus (for
963	<	* example, 3) of tasks, and to process computations locally if
964	<	* this threshold is exceeded.
959	>	* threads that might steal them.  This value may be useful for
960	>	* heuristic decisions about whether to fork other tasks. In many
961	>	* usages of ForkJoinTasks, at steady state, each worker should
962	>	* aim to maintain a small constant surplus (for example, 3) of
963	>	* tasks, and to process computations locally if this threshold is
964	>	* exceeded.  This method may be invoked only from within
965	>	* ForkJoinTask computations (as may be determined using method
966	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
967	>	* result in exceptions or errors, possibly including
968	>	* ClassCastException.  *
969		* @return the surplus number of tasks, which may be negative
970		*/
971	<	public static int surplus() {
972	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
971	>	public static int getSurplusQueuedTaskCount() {
972	>	return ((ForkJoinWorkerThread) Thread.currentThread())
973		.getEstimatedSurplusTaskCount();
974		}
975
976	<	// Extension kit
976	>	// Extension methods
977
978		/**
979	<	* Returns the result that would be returned by <tt>join</tt>, or
980	<	* null if this task is not known to have been completed.  This
981	<	* method is designed to aid debugging, as well as to support
982	<	* extensions. Its use in any other context is discouraged.
979	>	* Returns the result that would be returned by {@link #join}, even
980	>	* if this task completed abnormally, or {@code null} if this task
981	>	* is not known to have been completed.  This method is designed
982	>	* to aid debugging, as well as to support extensions. Its use in
983	>	* any other context is discouraged.
984		*
985	<	* @return the result, or null if not completed.
985	>	* @return the result, or {@code null} if not completed
986		*/
987		public abstract V getRawResult();
988
#	Line 865 | Line 1001 | public abstract class ForkJoinTask<V> im
1001		* called otherwise. The return value controls whether this task
1002		* is considered to be done normally. It may return false in
1003		* asynchronous actions that require explicit invocations of
1004	<	* <tt>complete</tt> to become joinable. It may throw exceptions
1004	>	* {@link #complete} to become joinable. It may throw exceptions
1005		* to indicate abnormal exit.
1006	<	* @return true if completed normally
1006	>	*
1007	>	* @return {@code true} if completed normally
1008		* @throws Error or RuntimeException if encountered during computation
1009		*/
1010		protected abstract boolean exec();
1011
1012	+	/**
1013	+	* Returns, but does not unschedule or execute, a task queued by
1014	+	* the current thread but not yet executed, if one is immediately
1015	+	* available. There is no guarantee that this task will actually
1016	+	* be polled or executed next. Conversely, this method may return
1017	+	* null even if a task exists but cannot be accessed without
1018	+	* contention with other threads.  This method is designed
1019	+	* primarily to support extensions, and is unlikely to be useful
1020	+	* otherwise.  This method may be invoked only from within
1021	+	* ForkJoinTask computations (as may be determined using method
1022	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1023	+	* result in exceptions or errors, possibly including
1024	+	* ClassCastException.
1025	+	*
1026	+	* @return the next task, or {@code null} if none are available
1027	+	*/
1028	+	protected static ForkJoinTask<?> peekNextLocalTask() {
1029	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1030	+	.peekTask();
1031	+	}
1032	+
1033	+	/**
1034	+	* Unschedules and returns, without executing, the next task
1035	+	* queued by the current thread but not yet executed.  This method
1036	+	* is designed primarily to support extensions, and is unlikely to
1037	+	* be useful otherwise.  This method may be invoked only from
1038	+	* within ForkJoinTask computations (as may be determined using
1039	+	* method {@link #inForkJoinPool}). Attempts to invoke in other
1040	+	* contexts result in exceptions or errors, possibly including
1041	+	* ClassCastException.
1042	+	*
1043	+	* @return the next task, or {@code null} if none are available
1044	+	*/
1045	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1046	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1047	+	.pollLocalTask();
1048	+	}
1049	+
1050	+	/**
1051	+	* Unschedules and returns, without executing, the next task
1052	+	* queued by the current thread but not yet executed, if one is
1053	+	* available, or if not available, a task that was forked by some
1054	+	* other thread, if available. Availability may be transient, so a
1055	+	* {@code null} result does not necessarily imply quiescence
1056	+	* of the pool this task is operating in.  This method is designed
1057	+	* primarily to support extensions, and is unlikely to be useful
1058	+	* otherwise.  This method may be invoked only from within
1059	+	* ForkJoinTask computations (as may be determined using method
1060	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1061	+	* result in exceptions or errors, possibly including
1062	+	* ClassCastException.
1063	+	*
1064	+	* @return a task, or {@code null} if none are available
1065	+	*/
1066	+	protected static ForkJoinTask<?> pollTask() {
1067	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1068	+	.pollTask();
1069	+	}
1070	+
1071	+	/**
1072	+	* Adaptor for Runnables. This implements RunnableFuture
1073	+	* to be compliant with AbstractExecutorService constraints
1074	+	* when used in ForkJoinPool.
1075	+	*/
1076	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1077	+	implements RunnableFuture<T> {
1078	+	final Runnable runnable;
1079	+	final T resultOnCompletion;
1080	+	T result;
1081	+	AdaptedRunnable(Runnable runnable, T result) {
1082	+	if (runnable == null) throw new NullPointerException();
1083	+	this.runnable = runnable;
1084	+	this.resultOnCompletion = result;
1085	+	}
1086	+	public T getRawResult() { return result; }
1087	+	public void setRawResult(T v) { result = v; }
1088	+	public boolean exec() {
1089	+	runnable.run();
1090	+	result = resultOnCompletion;
1091	+	return true;
1092	+	}
1093	+	public void run() { invoke(); }
1094	+	private static final long serialVersionUID = 5232453952276885070L;
1095	+	}
1096	+
1097	+	/**
1098	+	* Adaptor for Callables
1099	+	*/
1100	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1101	+	implements RunnableFuture<T> {
1102	+	final Callable<? extends T> callable;
1103	+	T result;
1104	+	AdaptedCallable(Callable<? extends T> callable) {
1105	+	if (callable == null) throw new NullPointerException();
1106	+	this.callable = callable;
1107	+	}
1108	+	public T getRawResult() { return result; }
1109	+	public void setRawResult(T v) { result = v; }
1110	+	public boolean exec() {
1111	+	try {
1112	+	result = callable.call();
1113	+	return true;
1114	+	} catch (Error err) {
1115	+	throw err;
1116	+	} catch (RuntimeException rex) {
1117	+	throw rex;
1118	+	} catch (Exception ex) {
1119	+	throw new RuntimeException(ex);
1120	+	}
1121	+	}
1122	+	public void run() { invoke(); }
1123	+	private static final long serialVersionUID = 2838392045355241008L;
1124	+	}
1125	+
1126	+	/**
1127	+	* Returns a new ForkJoinTask that performs the {@code run}
1128	+	* method of the given Runnable as its action, and returns a null
1129	+	* result upon {@code join}.
1130	+	*
1131	+	* @param runnable the runnable action
1132	+	* @return the task
1133	+	*/
1134	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1135	+	return new AdaptedRunnable<Void>(runnable, null);
1136	+	}
1137	+
1138	+	/**
1139	+	* Returns a new ForkJoinTask that performs the {@code run}
1140	+	* method of the given Runnable as its action, and returns the
1141	+	* given result upon {@code join}.
1142	+	*
1143	+	* @param runnable the runnable action
1144	+	* @param result the result upon completion
1145	+	* @return the task
1146	+	*/
1147	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1148	+	return new AdaptedRunnable<T>(runnable, result);
1149	+	}
1150	+
1151	+	/**
1152	+	* Returns a new ForkJoinTask that performs the {@code call}
1153	+	* method of the given Callable as its action, and returns its
1154	+	* result upon {@code join}, translating any checked
1155	+	* exceptions encountered into {@code RuntimeException}.
1156	+	*
1157	+	* @param callable the callable action
1158	+	* @return the task
1159	+	*/
1160	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1161	+	return new AdaptedCallable<T>(callable);
1162	+	}
1163	+
1164		// Serialization support
1165
1166		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1169 | public abstract class ForkJoinTask<V> im
1169		* Save the state to a stream.
1170		*
1171		* @serialData the current run status and the exception thrown
1172	<	* during execution, or null if none.
1172	>	* during execution, or {@code null} if none
1173		* @param s the stream
1174		*/
1175		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1180 | public abstract class ForkJoinTask<V> im
1180
1181		/**
1182		* Reconstitute the instance from a stream.
1183	+	*
1184		* @param s the stream
1185		*/
1186		private void readObject(java.io.ObjectInputStream s)
1187		throws java.io.IOException, ClassNotFoundException {
1188		s.defaultReadObject();
1189	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1189	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1190	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1191		Object ex = s.readObject();
1192		if (ex != null)
1193	<	setDoneExceptionally((Throwable)ex);
1193	>	setDoneExceptionally((Throwable) ex);
1194		}
1195
1196	<	// Temporary Unsafe mechanics for preliminary release
1196	>	// Unsafe mechanics
1197
1198	<	static final Unsafe _unsafe;
1199	<	static final long statusOffset;
1198	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1199	>	private static final long statusOffset =
1200	>	objectFieldOffset("status", ForkJoinTask.class);
1201
1202	<	static {
1202	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1203		try {
1204	<	if (ForkJoinTask.class.getClassLoader() != null) {
1205	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1206	<	f.setAccessible(true);
1207	<	_unsafe = (Unsafe)f.get(null);
1208	<	}
1209	<	else
1210	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1204	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1205	>	} catch (NoSuchFieldException e) {
1206	>	// Convert Exception to corresponding Error
1207	>	NoSuchFieldError error = new NoSuchFieldError(field);
1208	>	error.initCause(e);
1209	>	throw error;
1210	>	}
1211		}
1212
1213	+	/**
1214	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1215	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1216	+	* into a jdk.
1217	+	*
1218	+	* @return a sun.misc.Unsafe
1219	+	*/
1220	+	private static sun.misc.Unsafe getUnsafe() {
1221	+	try {
1222	+	return sun.misc.Unsafe.getUnsafe();
1223	+	} catch (SecurityException se) {
1224	+	try {
1225	+	return java.security.AccessController.doPrivileged
1226	+	(new java.security
1227	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1228	+	public sun.misc.Unsafe run() throws Exception {
1229	+	java.lang.reflect.Field f = sun.misc
1230	+	.Unsafe.class.getDeclaredField("theUnsafe");
1231	+	f.setAccessible(true);
1232	+	return (sun.misc.Unsafe) f.get(null);
1233	+	}});
1234	+	} catch (java.security.PrivilegedActionException e) {
1235	+	throw new RuntimeException("Could not initialize intrinsics",
1236	+	e.getCause());
1237	+	}
1238	+	}
1239	+	}
1240		}

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