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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 1.34 by dl, Tue Aug 4 11:44:33 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.RandomAccess;
16	>	import java.util.Map;
17	>	import java.util.WeakHashMap;
18
19		/**
20	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
21	<	* ForkJoinTask is a thread-like entity that is much lighter weight
22	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
23	<	* hosted by a small number of actual threads in a ForkJoinPool,
24	<	* at the price of some usage limitations.
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22	>	* lighter weight than a normal thread.  Huge numbers of tasks and
23	>	* subtasks may be hosted by a small number of actual threads in a
24	>	* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
27	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
28	<	* set of restrictions (that are only partially statically
29	<	* enforceable) reflecting their intended use as computational tasks
30	<	* calculating pure functions or operating on purely isolated objects.
31	<	* The primary coordination mechanisms supported for ForkJoinTasks are
32	<	* <tt>fork</tt>, that arranges asynchronous execution, and
33	<	* <tt>join</tt>, that doesn't proceed until the task's result has
34	<	* 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.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
37	<	* subclassed.  Instead, you subclass one of the abstract classes that
38	<	* support different styles of fork/join processing.  Normally, a
39	<	* concrete ForkJoinTask subclass declares fields comprising its
40	<	* parameters, established in a constructor, and then defines a
41	<	* <tt>compute</tt> method that somehow uses the control methods
42	<	* supplied by this base class. While these methods have
43	<	* <tt>public</tt> access, some of them may only be called from within
44	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
45	<	* result in exceptions or errors including ClassCastException.  The
46	<	* only way to invoke a "main" driver task is to submit it to a
47	<	* ForkJoinPool. Once started, this will usually in turn start other
48	<	* subtasks.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include RejectedExecutionExceptions stemming from
60	>	* internal resource exhaustion such as failure to allocate internal
61	>	* task queues.
62		*
63	<	* <p>Most base support methods are <tt>final</tt> because their
64	<	* implementations are intrinsically tied to the underlying
65	<	* lightweight task scheduling framework, and so cannot be overridden.
66	<	* Developers creating new basic styles of fork/join processing should
67	<	* minimally implement protected methods <tt>exec</tt>,
68	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
69	<	* introducing an abstract computational method that can be
70	<	* implemented in its subclasses. To support such extensions,
71	<	* instances of ForkJoinTasks maintain an atomically updated
72	<	* <tt>short</tt> representing user-defined control state.  Control
73	<	* state is guaranteed initially to be zero, and to be negative upon
74	<	* completion, but may otherwise be used for any other control
75	<	* purposes, such as maintaining join counts.  The {@link
76	<	* ForkJoinWorkerThread} class supports additional inspection and
77	<	* tuning methods that can be useful when developing extensions.
63	>	* <p>The primary method for awaiting completion and extracting
64	>	* results of a task is {@link #join}, but there are several variants:
65	>	* The {@link Future#get} methods support interruptible and/or timed
66	>	* waits for completion and report results using {@code Future}
67	>	* conventions. Method {@link #helpJoin} enables callers to actively
68	>	* execute other tasks while awaiting joins, which is sometimes more
69	>	* efficient but only applies when all subtasks are known to be
70	>	* strictly tree-structured. Method {@link #invoke} is semantically
71	>	* equivalent to {@code fork(); join()} but always attempts to
72	>	* begin execution in the current thread. The "<em>quiet</em>" forms
73	>	* of these methods do not extract results or report exceptions. These
74	>	* may be useful when a set of tasks are being executed, and you need
75	>	* to delay processing of results or exceptions until all complete.
76	>	* Method {@code invokeAll} (available in multiple versions)
77	>	* performs the most common form of parallel invocation: forking a set
78	>	* of tasks and joining them all.
79	>	*
80	>	* <p>The ForkJoinTask class is not usually directly subclassed.
81	>	* Instead, you subclass one of the abstract classes that support a
82	>	* particular style of fork/join processing, typically {@link
83	>	* RecursiveAction} for computations that do not return results, or
84	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
85	>	* ForkJoinTask subclass declares fields comprising its parameters,
86	>	* established in a constructor, and then defines a {@code compute}
87	>	* method that somehow uses the control methods supplied by this base
88	>	* class. While these methods have {@code public} access (to allow
89	>	* instances of different task subclasses to call each other's
90	>	* methods), some of them may only be called from within other
91	>	* ForkJoinTasks (as may be determined using method {@link
92	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
93	>	* result in exceptions or errors, possibly including
94	>	* ClassCastException.
95	>	*
96	>	* <p>Most base support methods are {@code final}, to prevent
97	>	* overriding of implementations that are intrinsically tied to the
98	>	* underlying lightweight task scheduling framework.  Developers
99	>	* creating new basic styles of fork/join processing should minimally
100	>	* implement {@code protected} methods {@link #exec}, {@link
101	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
102	>	* an abstract computational method that can be implemented in its
103	>	* subclasses, possibly relying on other {@code protected} methods
104	>	* provided by this class.
105		*
106		* <p>ForkJoinTasks should perform relatively small amounts of
107	<	* computations, othewise 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
111	<	* and internal task maintenance overhead may overwhelm processing.
107	>	* computation. Large tasks should be split into smaller subtasks,
108	>	* usually via recursive decomposition. As a very rough rule of thumb,
109	>	* a task should perform more than 100 and less than 10000 basic
110	>	* computational steps. If tasks are too big, then parallelism cannot
111	>	* improve throughput. If too small, then memory and internal task
112	>	* maintenance overhead may overwhelm processing.
113	>	*
114	>	* <p>This class provides {@code adapt} methods for {@link
115	>	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
116	>	* may be of use when mixing execution of ForkJoinTasks with other
117	>	* kinds of tasks. When all tasks are of this form, consider using a
118	>	* pool in {@link ForkJoinPool#setAsyncMode async mode}.
119		*
120	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
121	<	* be used in extensions such as remote execution frameworks. However,
122	<	* it is in general safe to serialize tasks only before or after, but
123	<	* not during execution. Serialization is not relied on during
124	<	* execution itself.
120	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
121	>	* used in extensions such as remote execution frameworks. It is
122	>	* sensible to serialize tasks only before or after, but not during,
123	>	* execution. Serialization is not relied on during 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 {
385	+	if (Thread.interrupted())
386	+	throw new InterruptedException();
387		int s = status & COMPLETION_MASK;
388		if (s < NORMAL) {
389		Throwable ex;
#	Line 362 | Line 391 | public abstract class ForkJoinTask<V> im
391		throw new CancellationException();
392		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
393		throw new ExecutionException(ex);
365	–	if (Thread.interrupted())
366	–	throw new InterruptedException();
394		}
395		return getRawResult();
396		}
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 {
404	+	if (Thread.interrupted())
405	+	throw new InterruptedException();
406		Throwable ex;
407		int s = status & COMPLETION_MASK;
408		if (s == NORMAL)
#	Line 382 | Line 411 | public abstract class ForkJoinTask<V> im
411		throw new CancellationException();
412		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
413		throw new ExecutionException(ex);
385	–	if (Thread.interrupted())
386	–	throw new InterruptedException();
414		throw new TimeoutException();
415		}
416
#	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.
499	>	* than once unless it has completed and been reinitialized.
500	>	*
501	>	* <p>This method may be invoked only from within {@code
502	>	* ForkJoinTask} computations (as may be determined using method
503	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
504	>	* result in exceptions or errors, possibly including {@code
505	>	* ClassCastException}.
506	>	*
507	>	* @return {@code this}, to simplify usage
508		*/
509	<	public final void fork() {
510	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
509	>	public final ForkJoinTask<V> fork() {
510	>	((ForkJoinWorkerThread) Thread.currentThread())
511	>	.pushTask(this);
512	>	return this;
513		}
514
515		/**
516		* Returns the result of the computation when it is ready.
517	<	* This method differs from <tt>get</tt> in that abnormal
518	<	* completion results in RuntimeExceptions or Errors, not
519	<	* ExecutionExceptions.
517	>	* This method differs from {@link #get()} in that
518	>	* abnormal completion results in {@code RuntimeException} or
519	>	* {@code Error}, not {@code ExecutionException}.
520		*
521		* @return the computed result
522		*/
#	Line 480 | Line 527 | public abstract class ForkJoinTask<V> im
527		return getRawResult();
528		}
529
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	–
530		/**
531	<	* Possibly executes other tasks until this task is ready, then
532	<	* returns the result of the computation.  This method may be more
533	<	* efficient than <tt>join</tt>, but is only applicable when there
534	<	* 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.
518	<	* @throws Throwable (a RuntimeException, Error, or unchecked
519	<	* exception) if the underlying computation did so.
531	>	* Commences performing this task, awaits its completion if
532	>	* necessary, and return its result, or throws an (unchecked)
533	>	* exception if the underlying computation did so.
534	>	*
535		* @return the computed result
536		*/
537		public final V invoke() {
#	Line 527 | Line 542 | public abstract class ForkJoinTask<V> im
542		}
543
544		/**
545	<	* Joins this task, without returning its result or throwing an
546	<	* exception. This method may be useful when processing
547	<	* collections of tasks when some have been cancelled or otherwise
548	<	* known to have aborted.
545	>	* Forks the given tasks, returning when {@code isDone} holds for
546	>	* each task or an (unchecked) exception is encountered, in which
547	>	* case the exception is rethrown.  If more than one task
548	>	* encounters an exception, then this method throws any one of
549	>	* these exceptions.  The individual status of each task may be
550	>	* checked using {@link #getException()} and related methods.
551	>	*
552	>	* <p>This method may be invoked only from within {@code
553	>	* ForkJoinTask} computations (as may be determined using method
554	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
555	>	* result in exceptions or errors, possibly including {@code
556	>	* ClassCastException}.
557	>	*
558	>	* @param t1 the first task
559	>	* @param t2 the second task
560	>	* @throws NullPointerException if any task is null
561		*/
562	<	public final void quietlyJoin() {
563	<	if (status >= 0) {
564	<	ForkJoinWorkerThread w = getWorker();
565	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
566	<	awaitDone(w, true);
562	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
563	>	t2.fork();
564	>	t1.invoke();
565	>	t2.join();
566	>	}
567	>
568	>	/**
569	>	* Forks the given tasks, returning when {@code isDone} holds for
570	>	* each task or an (unchecked) exception is encountered, in which
571	>	* case the exception is rethrown. If any task encounters an
572	>	* exception, others may be, but are not guaranteed to be,
573	>	* cancelled.  If more than one task encounters an exception, then
574	>	* this method throws any one of these exceptions.  The individual
575	>	* status of each task may be checked using {@link #getException()}
576	>	* and related methods.
577	>	*
578	>	* <p>This method may be invoked only from within {@code
579	>	* ForkJoinTask} computations (as may be determined using method
580	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
581	>	* result in exceptions or errors, possibly including {@code
582	>	* ClassCastException}.
583	>	*
584	>	* @param tasks the tasks
585	>	* @throws NullPointerException if any task is null
586	>	*/
587	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
588	>	Throwable ex = null;
589	>	int last = tasks.length - 1;
590	>	for (int i = last; i >= 0; --i) {
591	>	ForkJoinTask<?> t = tasks[i];
592	>	if (t == null) {
593	>	if (ex == null)
594	>	ex = new NullPointerException();
595	>	}
596	>	else if (i != 0)
597	>	t.fork();
598	>	else {
599	>	t.quietlyInvoke();
600	>	if (ex == null)
601	>	ex = t.getException();
602	>	}
603		}
604	+	for (int i = 1; i <= last; ++i) {
605	+	ForkJoinTask<?> t = tasks[i];
606	+	if (t != null) {
607	+	if (ex != null)
608	+	t.cancel(false);
609	+	else {
610	+	t.quietlyJoin();
611	+	if (ex == null)
612	+	ex = t.getException();
613	+	}
614	+	}
615	+	}
616	+	if (ex != null)
617	+	rethrowException(ex);
618		}
619
620		/**
621	<	* Possibly executes other tasks until this task is ready.
621	>	* Forks all tasks in the specified collection, returning when
622	>	* {@code isDone} holds for each task or an (unchecked) exception
623	>	* is encountered.  If any task encounters an exception, others
624	>	* may be, but are not guaranteed to be, cancelled.  If more than
625	>	* one task encounters an exception, then this method throws any
626	>	* one of these exceptions.  The individual status of each task
627	>	* may be checked using {@link #getException()} and related
628	>	* methods.  The behavior of this operation is undefined if the
629	>	* specified collection is modified while the operation is in
630	>	* progress.
631	>	*
632	>	* <p>This method may be invoked only from within {@code
633	>	* ForkJoinTask} computations (as may be determined using method
634	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
635	>	* result in exceptions or errors, possibly including {@code
636	>	* ClassCastException}.
637	>	*
638	>	* @param tasks the collection of tasks
639	>	* @return the tasks argument, to simplify usage
640	>	* @throws NullPointerException if tasks or any element are null
641		*/
642	<	public final void quietlyHelpJoin() {
643	<	if (status >= 0) {
644	<	ForkJoinWorkerThread w =
645	<	(ForkJoinWorkerThread)(Thread.currentThread());
646	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
647	<	w.helpJoinTask(this);
642	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
643	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
644	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
645	>	return tasks;
646	>	}
647	>	@SuppressWarnings("unchecked")
648	>	List<? extends ForkJoinTask<?>> ts =
649	>	(List<? extends ForkJoinTask<?>>) tasks;
650	>	Throwable ex = null;
651	>	int last = ts.size() - 1;
652	>	for (int i = last; i >= 0; --i) {
653	>	ForkJoinTask<?> t = ts.get(i);
654	>	if (t == null) {
655	>	if (ex == null)
656	>	ex = new NullPointerException();
657	>	}
658	>	else if (i != 0)
659	>	t.fork();
660	>	else {
661	>	t.quietlyInvoke();
662	>	if (ex == null)
663	>	ex = t.getException();
664	>	}
665		}
666	+	for (int i = 1; i <= last; ++i) {
667	+	ForkJoinTask<?> t = ts.get(i);
668	+	if (t != null) {
669	+	if (ex != null)
670	+	t.cancel(false);
671	+	else {
672	+	t.quietlyJoin();
673	+	if (ex == null)
674	+	ex = t.getException();
675	+	}
676	+	}
677	+	}
678	+	if (ex != null)
679	+	rethrowException(ex);
680	+	return tasks;
681		}
682
683		/**
684	<	* Performs this task and awaits its completion if necessary,
685	<	* without returning its result or throwing an exception. This
686	<	* method may be useful when processing collections of tasks when
687	<	* some have been cancelled or otherwise known to have aborted.
684	>	* Attempts to cancel execution of this task. This attempt will
685	>	* fail if the task has already completed, has already been
686	>	* cancelled, or could not be cancelled for some other reason. If
687	>	* successful, and this task has not started when cancel is
688	>	* called, execution of this task is suppressed, {@link
689	>	* #isCancelled} will report true, and {@link #join} will result
690	>	* in a {@code CancellationException} being thrown.
691	>	*
692	>	* <p>This method may be overridden in subclasses, but if so, must
693	>	* still ensure that these minimal properties hold. In particular,
694	>	* the {@code cancel} method itself must not throw exceptions.
695	>	*
696	>	* <p>This method is designed to be invoked by <em>other</em>
697	>	* tasks. To terminate the current task, you can just return or
698	>	* throw an unchecked exception from its computation method, or
699	>	* invoke {@link #completeExceptionally}.
700	>	*
701	>	* @param mayInterruptIfRunning this value is ignored in the
702	>	* default implementation because tasks are not
703	>	* cancelled via interruption
704	>	*
705	>	* @return {@code true} if this task is now cancelled
706		*/
707	<	public final void quietlyInvoke() {
708	<	if (status >= 0 && !tryQuietlyInvoke())
709	<	quietlyJoin();
707	>	public boolean cancel(boolean mayInterruptIfRunning) {
708	>	setCompletion(CANCELLED);
709	>	return (status & COMPLETION_MASK) == CANCELLED;
710		}
711
712		/**
713	<	* Returns true if the computation performed by this task has
714	<	* completed (or has been cancelled).
715	<	* @return true if this computation has completed
713	>	* Returns {@code true} if the computation performed by this task
714	>	* has completed (or has been cancelled).
715	>	*
716	>	* @return {@code true} if this computation has completed
717		*/
718		public final boolean isDone() {
719		return status < 0;
720		}
721
722		/**
723	<	* Returns true if this task was cancelled.
724	<	* @return true if this task was cancelled
723	>	* Returns {@code true} if this task was cancelled.
724	>	*
725	>	* @return {@code true} if this task was cancelled
726		*/
727		public final boolean isCancelled() {
728		return (status & COMPLETION_MASK) == CANCELLED;
729		}
730
731		/**
732	<	* Returns true if this task threw an exception or was cancelled
733	<	* @return true if this task threw an exception or was cancelled
732	>	* Returns {@code true} if this task threw an exception or was cancelled.
733	>	*
734	>	* @return {@code true} if this task threw an exception or was cancelled
735		*/
736	<	public final boolean completedAbnormally() {
736	>	public final boolean isCompletedAbnormally() {
737		return (status & COMPLETION_MASK) < NORMAL;
738		}
739
740		/**
741	+	* Returns {@code true} if this task completed without throwing an
742	+	* exception and was not cancelled.
743	+	*
744	+	* @return {@code true} if this task completed without throwing an
745	+	* exception and was not cancelled
746	+	*/
747	+	public final boolean isCompletedNormally() {
748	+	return (status & COMPLETION_MASK) == NORMAL;
749	+	}
750	+
751	+	/**
752	+	* Returns {@code true} if this task threw an exception.
753	+	*
754	+	* @return {@code true} if this task threw an exception
755	+	*/
756	+	public final boolean isCompletedExceptionally() {
757	+	return (status & COMPLETION_MASK) == EXCEPTIONAL;
758	+	}
759	+
760	+	/**
761		* Returns the exception thrown by the base computation, or a
762	<	* CancellationException if cancelled, or null if none or if the
763	<	* method has not yet completed.
764	<	* @return the exception, or null if none
762	>	* {@code CancellationException} if cancelled, or {@code null} if
763	>	* none or if the method has not yet completed.
764	>	*
765	>	* @return the exception, or {@code null} if none
766		*/
767		public final Throwable getException() {
768		int s = status & COMPLETION_MASK;
#	Line 604 | Line 774 | public abstract class ForkJoinTask<V> im
774		}
775
776		/**
607	–	* Asserts that the results of this task's computation will not be
608	–	* used. If a cancellation occurs before this task is processed,
609	–	* then its <tt>compute</tt> method will not be executed,
610	–	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
611	–	* result in a CancellationException being thrown. Otherwise, when
612	–	* cancellation races with completion, there are no guarantees
613	–	* about whether <tt>isCancelled</tt> will report true, whether
614	–	* <tt>join</tt> will return normally or via an exception, or
615	–	* whether these behaviors will remain consistent upon repeated
616	–	* invocation.
617	–	*
618	–	* <p>This method may be overridden in subclasses, but if so, must
619	–	* still ensure that these minimal properties hold. In particular,
620	–	* the cancel method itself must not throw exceptions.
621	–	*
622	–	* <p> This method is designed to be invoked by <em>other</em>
623	–	* tasks. To terminate the current task, you can just return or
624	–	* throw an unchecked exception from its computation method, or
625	–	* invoke <tt>completeExceptionally(someException)</tt>.
626	–	*
627	–	* @param mayInterruptIfRunning this value is ignored in the
628	–	* default implementation because tasks are not in general
629	–	* cancelled via interruption.
630	–	*
631	–	* @return true if this task is now cancelled
632	–	*/
633	–	public boolean cancel(boolean mayInterruptIfRunning) {
634	–	setCompletion(CANCELLED);
635	–	return (status & COMPLETION_MASK) == CANCELLED;
636	–	}
637	–
638	–	/**
777		* Completes this task abnormally, and if not already aborted or
778		* cancelled, causes it to throw the given exception upon
779	<	* <tt>join</tt> and related operations. This method may be used
779	>	* {@code join} and related operations. This method may be used
780		* to induce exceptions in asynchronous tasks, or to force
781	<	* completion of tasks that would not otherwise complete.  This
782	<	* method is overridable, but overridden versions must invoke
783	<	* <tt>super</tt> implementation to maintain guarantees.
781	>	* completion of tasks that would not otherwise complete.  Its use
782	>	* in other situations is discouraged.  This method is
783	>	* overridable, but overridden versions must invoke {@code super}
784	>	* implementation to maintain guarantees.
785	>	*
786		* @param ex the exception to throw. If this exception is
787		* not a RuntimeException or Error, the actual exception thrown
788		* will be a RuntimeException with cause ex.
789		*/
790		public void completeExceptionally(Throwable ex) {
791		setDoneExceptionally((ex instanceof RuntimeException) ||
792	<	(ex instanceof Error)? ex :
792	>	(ex instanceof Error) ? ex :
793		new RuntimeException(ex));
794		}
795
796		/**
797		* Completes this task, and if not already aborted or cancelled,
798	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
798	>	* returning a {@code null} result upon {@code join} and related
799		* operations. This method may be used to provide results for
800		* asynchronous tasks, or to provide alternative handling for
801	<	* tasks that would not otherwise complete normally.
801	>	* tasks that would not otherwise complete normally. Its use in
802	>	* other situations is discouraged. This method is
803	>	* overridable, but overridden versions must invoke {@code super}
804	>	* implementation to maintain guarantees.
805		*
806	<	* @param value the result value for this task.
806	>	* @param value the result value for this task
807		*/
808		public void complete(V value) {
809		try {
810		setRawResult(value);
811	<	} catch(Throwable rex) {
811	>	} catch (Throwable rex) {
812		setDoneExceptionally(rex);
813		return;
814		}
815		setNormalCompletion();
816		}
817
818	+	public final V get() throws InterruptedException, ExecutionException {
819	+	ForkJoinWorkerThread w = getWorker();
820	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
821	+	awaitDone(w, true);
822	+	return reportFutureResult();
823	+	}
824	+
825	+	public final V get(long timeout, TimeUnit unit)
826	+	throws InterruptedException, ExecutionException, TimeoutException {
827	+	long nanos = unit.toNanos(timeout);
828	+	ForkJoinWorkerThread w = getWorker();
829	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
830	+	awaitDone(w, nanos);
831	+	return reportTimedFutureResult();
832	+	}
833	+
834	+	/**
835	+	* Possibly executes other tasks until this task is ready, then
836	+	* returns the result of the computation.  This method may be more
837	+	* efficient than {@code join}, but is only applicable when
838	+	* there are no potential dependencies between continuation of the
839	+	* current task and that of any other task that might be executed
840	+	* while helping. (This usually holds for pure divide-and-conquer
841	+	* tasks).
842	+	*
843	+	* <p>This method may be invoked only from within {@code
844	+	* ForkJoinTask} computations (as may be determined using method
845	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
846	+	* result in exceptions or errors, possibly including {@code
847	+	* ClassCastException}.
848	+	*
849	+	* @return the computed result
850	+	*/
851	+	public final V helpJoin() {
852	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
853	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
854	+	reportException(busyJoin(w));
855	+	return getRawResult();
856	+	}
857	+
858	+	/**
859	+	* Possibly executes other tasks until this task is ready.  This
860	+	* method may be useful when processing collections of tasks when
861	+	* some have been cancelled or otherwise known to have aborted.
862	+	*
863	+	* <p>This method may be invoked only from within {@code
864	+	* ForkJoinTask} computations (as may be determined using method
865	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
866	+	* result in exceptions or errors, possibly including {@code
867	+	* ClassCastException}.
868	+	*/
869	+	public final void quietlyHelpJoin() {
870	+	if (status >= 0) {
871	+	ForkJoinWorkerThread w =
872	+	(ForkJoinWorkerThread) Thread.currentThread();
873	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
874	+	busyJoin(w);
875	+	}
876	+	}
877	+
878	+	/**
879	+	* Joins this task, without returning its result or throwing an
880	+	* exception. This method may be useful when processing
881	+	* collections of tasks when some have been cancelled or otherwise
882	+	* known to have aborted.
883	+	*/
884	+	public final void quietlyJoin() {
885	+	if (status >= 0) {
886	+	ForkJoinWorkerThread w = getWorker();
887	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
888	+	awaitDone(w, true);
889	+	}
890	+	}
891	+
892	+	/**
893	+	* Commences performing this task and awaits its completion if
894	+	* necessary, without returning its result or throwing an
895	+	* exception. This method may be useful when processing
896	+	* collections of tasks when some have been cancelled or otherwise
897	+	* known to have aborted.
898	+	*/
899	+	public final void quietlyInvoke() {
900	+	if (status >= 0 && !tryQuietlyInvoke())
901	+	quietlyJoin();
902	+	}
903	+
904	+	/**
905	+	* Possibly executes tasks until the pool hosting the current task
906	+	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
907	+	* be of use in designs in which many tasks are forked, but none
908	+	* are explicitly joined, instead executing them until all are
909	+	* processed.
910	+	*
911	+	* <p>This method may be invoked only from within {@code
912	+	* ForkJoinTask} computations (as may be determined using method
913	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
914	+	* result in exceptions or errors, possibly including {@code
915	+	* ClassCastException}.
916	+	*/
917	+	public static void helpQuiesce() {
918	+	((ForkJoinWorkerThread) Thread.currentThread())
919	+	.helpQuiescePool();
920	+	}
921	+
922		/**
923		* Resets the internal bookkeeping state of this task, allowing a
924	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
924	>	* subsequent {@code fork}. This method allows repeated reuse of
925		* this task, but only if reuse occurs when this task has either
926		* never been forked, or has been forked, then completed and all
927		* outstanding joins of this task have also completed. Effects
928	<	* under any other usage conditions are not guaranteed, and are
929	<	* almost surely wrong. This method may be useful when executing
928	>	* under any other usage conditions are not guaranteed.
929	>	* This method may be useful when executing
930		* pre-constructed trees of subtasks in loops.
931		*/
932		public void reinitialize() {
#	Line 689 | Line 936 | public abstract class ForkJoinTask<V> im
936		}
937
938		/**
939	<	* Tries to unschedule this task for execution. This method will
940	<	* typically succeed if this task is the next task that would be
941	<	* executed by the current thread, and will typically fail (return
942	<	* false) otherwise. This method may be useful when arranging
943	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
699	<	*/
700	<	public boolean tryUnfork() {
701	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
702	<	}
703	<
704	<	/**
705	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
706	<	* of them or an exception is encountered. This method may be
707	<	* invoked only from within other ForkJoinTask
708	<	* computations. Attempts to invoke in other contexts result in
709	<	* 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.
939	>	* Returns the pool hosting the current task execution, or null
940	>	* if this task is executing outside of any ForkJoinPool.
941	>	*
942	>	* @see #inForkJoinPool
943	>	* @return the pool, or {@code null} if none
944		*/
945	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
946	<	t2.fork();
947	<	t1.invoke();
948	<	t2.join();
945	>	public static ForkJoinPool getPool() {
946	>	Thread t = Thread.currentThread();
947	>	return (t instanceof ForkJoinWorkerThread) ?
948	>	((ForkJoinWorkerThread) t).pool : null;
949		}
950
951		/**
952	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
953	<	* all of them. If any task encounters an exception, others may be
954	<	* cancelled.  This method may be invoked only from within other
955	<	* ForkJoinTask computations. Attempts to invoke in other contexts
956	<	* result in exceptions or errors including ClassCastException.
727	<	* @param tasks the array of tasks
728	<	* @throws NullPointerException if tasks or any element are null.
729	<	* @throws RuntimeException or Error if any task did so.
952	>	* Returns {@code true} if the current thread is executing as a
953	>	* ForkJoinPool computation.
954	>	*
955	>	* @return {@code true} if the current thread is executing as a
956	>	* ForkJoinPool computation, or false otherwise
957		*/
958	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
959	<	Throwable ex = null;
733	<	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);
958	>	public static boolean inForkJoinPool() {
959	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
960		}
961
962		/**
963	<	* Forks all tasks in the collection, returning when
964	<	* <tt>isDone</tt> holds for all of them. If any task encounters
965	<	* an exception, others may be cancelled.  This method may be
966	<	* invoked only from within other ForkJoinTask
967	<	* computations. Attempts to invoke in other contexts result in
968	<	* exceptions or errors including ClassCastException.
969	<	* @param tasks the collection of tasks
970	<	* @throws NullPointerException if tasks or any element are null.
971	<	* @throws RuntimeException or Error if any task did so.
963	>	* Tries to unschedule this task for execution. This method will
964	>	* typically succeed if this task is the most recently forked task
965	>	* by the current thread, and has not commenced executing in
966	>	* another thread.  This method may be useful when arranging
967	>	* alternative local processing of tasks that could have been, but
968	>	* were not, stolen.
969	>	*
970	>	* <p>This method may be invoked only from within {@code
971	>	* ForkJoinTask} computations (as may be determined using method
972	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
973	>	* result in exceptions or errors, possibly including {@code
974	>	* ClassCastException}.
975	>	*
976	>	* @return {@code true} if unforked
977		*/
978	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
979	<	if (!(tasks instanceof List)) {
980	<	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);
978	>	public boolean tryUnfork() {
979	>	return ((ForkJoinWorkerThread) Thread.currentThread())
980	>	.unpushTask(this);
981		}
982
983		/**
984	<	* Possibly executes tasks until the pool hosting the current task
985	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
986	<	* designs in which many tasks are forked, but none are explicitly
987	<	* joined, instead executing them until all are processed.
984	>	* Returns an estimate of the number of tasks that have been
985	>	* forked by the current worker thread but not yet executed. This
986	>	* value may be useful for heuristic decisions about whether to
987	>	* fork other tasks.
988	>	*
989	>	* <p>This method may be invoked only from within {@code
990	>	* ForkJoinTask} computations (as may be determined using method
991	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
992	>	* result in exceptions or errors, possibly including {@code
993	>	* ClassCastException}.
994	>	*
995	>	* @return the number of tasks
996		*/
997	<	public static void helpQuiesce() {
998	<	((ForkJoinWorkerThread)(Thread.currentThread())).
999	<	helpQuiescePool();
997	>	public static int getQueuedTaskCount() {
998	>	return ((ForkJoinWorkerThread) Thread.currentThread())
999	>	.getQueueSize();
1000		}
1001
1002		/**
1003	<	* Returns a estimate of how many more locally queued tasks are
1003	>	* Returns an estimate of how many more locally queued tasks are
1004		* held by the current worker thread than there are other worker
1005	<	* threads that might want to steal them.  This value may be
1006	<	* useful for heuristic decisions about whether to fork other
1007	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
1008	<	* worker should aim to maintain a small constant surplus (for
1009	<	* example, 3) of tasks, and to process computations locally if
1010	<	* this threshold is exceeded.
1005	>	* threads that might steal them.  This value may be useful for
1006	>	* heuristic decisions about whether to fork other tasks. In many
1007	>	* usages of ForkJoinTasks, at steady state, each worker should
1008	>	* aim to maintain a small constant surplus (for example, 3) of
1009	>	* tasks, and to process computations locally if this threshold is
1010	>	* exceeded.
1011	>	*
1012	>	* <p>This method may be invoked only from within {@code
1013	>	* ForkJoinTask} computations (as may be determined using method
1014	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1015	>	* result in exceptions or errors, possibly including {@code
1016	>	* ClassCastException}.
1017	>	*
1018		* @return the surplus number of tasks, which may be negative
1019		*/
1020	<	public static int surplus() {
1021	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
1020	>	public static int getSurplusQueuedTaskCount() {
1021	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1022		.getEstimatedSurplusTaskCount();
1023		}
1024
1025	<	// Extension kit
1025	>	// Extension methods
1026
1027		/**
1028	<	* Returns the result that would be returned by <tt>join</tt>, or
1029	<	* null if this task is not known to have been completed.  This
1030	<	* method is designed to aid debugging, as well as to support
1031	<	* extensions. Its use in any other context is discouraged.
1028	>	* Returns the result that would be returned by {@link #join}, even
1029	>	* if this task completed abnormally, or {@code null} if this task
1030	>	* is not known to have been completed.  This method is designed
1031	>	* to aid debugging, as well as to support extensions. Its use in
1032	>	* any other context is discouraged.
1033		*
1034	<	* @return the result, or null if not completed.
1034	>	* @return the result, or {@code null} if not completed
1035		*/
1036		public abstract V getRawResult();
1037
#	Line 865 | Line 1050 | public abstract class ForkJoinTask<V> im
1050		* called otherwise. The return value controls whether this task
1051		* is considered to be done normally. It may return false in
1052		* asynchronous actions that require explicit invocations of
1053	<	* <tt>complete</tt> to become joinable. It may throw exceptions
1054	<	* to indicate abnormal exit.
1055	<	* @return true if completed normally
1056	<	* @throws Error or RuntimeException if encountered during computation
1053	>	* {@link #complete} to become joinable. It may also throw an
1054	>	* (unchecked) exception to indicate abnormal exit.
1055	>	*
1056	>	* @return {@code true} if completed normally
1057		*/
1058		protected abstract boolean exec();
1059
1060	+	/**
1061	+	* Returns, but does not unschedule or execute, a task queued by
1062	+	* the current thread but not yet executed, if one is immediately
1063	+	* available. There is no guarantee that this task will actually
1064	+	* be polled or executed next. Conversely, this method may return
1065	+	* null even if a task exists but cannot be accessed without
1066	+	* contention with other threads.  This method is designed
1067	+	* primarily to support extensions, and is unlikely to be useful
1068	+	* otherwise.
1069	+	*
1070	+	* <p>This method may be invoked only from within {@code
1071	+	* ForkJoinTask} computations (as may be determined using method
1072	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1073	+	* result in exceptions or errors, possibly including {@code
1074	+	* ClassCastException}.
1075	+	*
1076	+	* @return the next task, or {@code null} if none are available
1077	+	*/
1078	+	protected static ForkJoinTask<?> peekNextLocalTask() {
1079	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1080	+	.peekTask();
1081	+	}
1082	+
1083	+	/**
1084	+	* Unschedules and returns, without executing, the next task
1085	+	* queued by the current thread but not yet executed.  This method
1086	+	* is designed primarily to support extensions, and is unlikely to
1087	+	* be useful otherwise.
1088	+	*
1089	+	* <p>This method may be invoked only from within {@code
1090	+	* ForkJoinTask} computations (as may be determined using method
1091	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1092	+	* result in exceptions or errors, possibly including {@code
1093	+	* ClassCastException}.
1094	+	*
1095	+	* @return the next task, or {@code null} if none are available
1096	+	*/
1097	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1098	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1099	+	.pollLocalTask();
1100	+	}
1101	+
1102	+	/**
1103	+	* Unschedules and returns, without executing, the next task
1104	+	* queued by the current thread but not yet executed, if one is
1105	+	* available, or if not available, a task that was forked by some
1106	+	* other thread, if available. Availability may be transient, so a
1107	+	* {@code null} result does not necessarily imply quiescence
1108	+	* of the pool this task is operating in.  This method is designed
1109	+	* primarily to support extensions, and is unlikely to be useful
1110	+	* otherwise.
1111	+	*
1112	+	* <p>This method may be invoked only from within {@code
1113	+	* ForkJoinTask} computations (as may be determined using method
1114	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1115	+	* result in exceptions or errors, possibly including {@code
1116	+	* ClassCastException}.
1117	+	*
1118	+	* @return a task, or {@code null} if none are available
1119	+	*/
1120	+	protected static ForkJoinTask<?> pollTask() {
1121	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1122	+	.pollTask();
1123	+	}
1124	+
1125	+	/**
1126	+	* Adaptor for Runnables. This implements RunnableFuture
1127	+	* to be compliant with AbstractExecutorService constraints
1128	+	* when used in ForkJoinPool.
1129	+	*/
1130	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1131	+	implements RunnableFuture<T> {
1132	+	final Runnable runnable;
1133	+	final T resultOnCompletion;
1134	+	T result;
1135	+	AdaptedRunnable(Runnable runnable, T result) {
1136	+	if (runnable == null) throw new NullPointerException();
1137	+	this.runnable = runnable;
1138	+	this.resultOnCompletion = result;
1139	+	}
1140	+	public T getRawResult() { return result; }
1141	+	public void setRawResult(T v) { result = v; }
1142	+	public boolean exec() {
1143	+	runnable.run();
1144	+	result = resultOnCompletion;
1145	+	return true;
1146	+	}
1147	+	public void run() { invoke(); }
1148	+	private static final long serialVersionUID = 5232453952276885070L;
1149	+	}
1150	+
1151	+	/**
1152	+	* Adaptor for Callables
1153	+	*/
1154	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1155	+	implements RunnableFuture<T> {
1156	+	final Callable<? extends T> callable;
1157	+	T result;
1158	+	AdaptedCallable(Callable<? extends T> callable) {
1159	+	if (callable == null) throw new NullPointerException();
1160	+	this.callable = callable;
1161	+	}
1162	+	public T getRawResult() { return result; }
1163	+	public void setRawResult(T v) { result = v; }
1164	+	public boolean exec() {
1165	+	try {
1166	+	result = callable.call();
1167	+	return true;
1168	+	} catch (Error err) {
1169	+	throw err;
1170	+	} catch (RuntimeException rex) {
1171	+	throw rex;
1172	+	} catch (Exception ex) {
1173	+	throw new RuntimeException(ex);
1174	+	}
1175	+	}
1176	+	public void run() { invoke(); }
1177	+	private static final long serialVersionUID = 2838392045355241008L;
1178	+	}
1179	+
1180	+	/**
1181	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1182	+	* method of the given {@code Runnable} as its action, and returns
1183	+	* a null result upon {@link #join}.
1184	+	*
1185	+	* @param runnable the runnable action
1186	+	* @return the task
1187	+	*/
1188	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1189	+	return new AdaptedRunnable<Void>(runnable, null);
1190	+	}
1191	+
1192	+	/**
1193	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1194	+	* method of the given {@code Runnable} as its action, and returns
1195	+	* the given result upon {@link #join}.
1196	+	*
1197	+	* @param runnable the runnable action
1198	+	* @param result the result upon completion
1199	+	* @return the task
1200	+	*/
1201	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1202	+	return new AdaptedRunnable<T>(runnable, result);
1203	+	}
1204	+
1205	+	/**
1206	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1207	+	* method of the given {@code Callable} as its action, and returns
1208	+	* its result upon {@link #join}, translating any checked exceptions
1209	+	* encountered into {@code RuntimeException}.
1210	+	*
1211	+	* @param callable the callable action
1212	+	* @return the task
1213	+	*/
1214	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1215	+	return new AdaptedCallable<T>(callable);
1216	+	}
1217	+
1218		// Serialization support
1219
1220		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1223 | public abstract class ForkJoinTask<V> im
1223		* Save the state to a stream.
1224		*
1225		* @serialData the current run status and the exception thrown
1226	<	* during execution, or null if none.
1226	>	* during execution, or {@code null} if none
1227		* @param s the stream
1228		*/
1229		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1234 | public abstract class ForkJoinTask<V> im
1234
1235		/**
1236		* Reconstitute the instance from a stream.
1237	+	*
1238		* @param s the stream
1239		*/
1240		private void readObject(java.io.ObjectInputStream s)
1241		throws java.io.IOException, ClassNotFoundException {
1242		s.defaultReadObject();
1243	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1243	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1244	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1245		Object ex = s.readObject();
1246		if (ex != null)
1247	<	setDoneExceptionally((Throwable)ex);
1247	>	setDoneExceptionally((Throwable) ex);
1248		}
1249
1250	<	// Temporary Unsafe mechanics for preliminary release
1250	>	// Unsafe mechanics
1251
1252	<	static final Unsafe _unsafe;
1253	<	static final long statusOffset;
1252	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1253	>	private static final long statusOffset =
1254	>	objectFieldOffset("status", ForkJoinTask.class);
1255
1256	<	static {
1256	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1257		try {
1258	<	if (ForkJoinTask.class.getClassLoader() != null) {
1259	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1260	<	f.setAccessible(true);
1261	<	_unsafe = (Unsafe)f.get(null);
1262	<	}
1263	<	else
1264	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1258	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1259	>	} catch (NoSuchFieldException e) {
1260	>	// Convert Exception to corresponding Error
1261	>	NoSuchFieldError error = new NoSuchFieldError(field);
1262	>	error.initCause(e);
1263	>	throw error;
1264	>	}
1265		}
1266
1267	+	/**
1268	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1269	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1270	+	* into a jdk.
1271	+	*
1272	+	* @return a sun.misc.Unsafe
1273	+	*/
1274	+	private static sun.misc.Unsafe getUnsafe() {
1275	+	try {
1276	+	return sun.misc.Unsafe.getUnsafe();
1277	+	} catch (SecurityException se) {
1278	+	try {
1279	+	return java.security.AccessController.doPrivileged
1280	+	(new java.security
1281	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1282	+	public sun.misc.Unsafe run() throws Exception {
1283	+	java.lang.reflect.Field f = sun.misc
1284	+	.Unsafe.class.getDeclaredField("theUnsafe");
1285	+	f.setAccessible(true);
1286	+	return (sun.misc.Unsafe) f.get(null);
1287	+	}});
1288	+	} catch (java.security.PrivilegedActionException e) {
1289	+	throw new RuntimeException("Could not initialize intrinsics",
1290	+	e.getCause());
1291	+	}
1292	+	}
1293	+	}
1294		}

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