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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 1.42 by dl, Thu Aug 6 23:08:50 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>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35	>	*
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include RejectedExecutionExceptions stemming from
60	>	* internal resource exhaustion such as failure to allocate internal
61	>	* task queues.
62	>	*
63	>	* <p>The primary method for awaiting completion and extracting
64	>	* results of a task is {@link #join}, but there are several variants:
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 begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74	>	* may be useful when a set of tasks are being executed, and you need
75	>	* to delay processing of results or exceptions until all complete.
76	>	* Method {@code invokeAll} (available in multiple versions)
77	>	* performs the most common form of parallel invocation: forking a set
78	>	* of tasks and joining them all.
79		*
80	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
81	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
82	<	* set of restrictions (that are only partially statically
83	<	* enforceable) reflecting their intended use as computational tasks
84	<	* calculating pure functions or operating on purely isolated objects.
85	<	* The primary coordination mechanisms supported for ForkJoinTasks are
86	<	* <tt>fork</tt>, that arranges asynchronous execution, and
87	<	* <tt>join</tt>, that doesn't proceed until the task's result has
88	<	* been computed. (Cancellation is also supported).  The computation
89	<	* defined in the <tt>compute</tt> method should avoid
90	<	* <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.
80	>	* <p>The execution status of tasks may be queried at several levels
81	>	* of detail: {@link #isDone} is true if a task completed in any way
82	>	* (including the case where a task was cancelled without executing);
83	>	* {@link #isCompletedNormally} is true if a task completed without
84	>	* cancellation or encountering an exception; {@link #isCancelled} is
85	>	* true if the task was cancelled (in which case {@link #getException}
86	>	* returns a {@link java.util.concurrent.CancellationException}); and
87	>	* {@link #isCompletedAbnormally} is true if a task was either
88	>	* cancelled or encountered an exception, in which case {@link
89	>	* #getException} will return either the encountered exception or
90	>	* {@link java.util.concurrent.CancellationException}.
91		*
92	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
93	<	* subclassed.  Instead, you subclass one of the abstract classes that
94	<	* support different styles of fork/join processing.  Normally, a
95	<	* concrete ForkJoinTask subclass declares fields comprising its
96	<	* parameters, established in a constructor, and then defines a
97	<	* <tt>compute</tt> method that somehow uses the control methods
98	<	* supplied by this base class. While these methods have
99	<	* <tt>public</tt> access, some of them may only be called from within
100	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
101	<	* result in exceptions or errors including ClassCastException.  The
102	<	* only way to invoke a "main" driver task is to submit it to a
103	<	* ForkJoinPool. Once started, this will usually in turn start other
104	<	* subtasks.
92	>	* <p>The ForkJoinTask class is not usually directly subclassed.
93	>	* Instead, you subclass one of the abstract classes that support a
94	>	* particular style of fork/join processing, typically {@link
95	>	* RecursiveAction} for computations that do not return results, or
96	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
97	>	* ForkJoinTask subclass declares fields comprising its parameters,
98	>	* established in a constructor, and then defines a {@code compute}
99	>	* method that somehow uses the control methods supplied by this base
100	>	* class. While these methods have {@code public} access (to allow
101	>	* instances of different task subclasses to call each other's
102	>	* methods), some of them may only be called from within other
103	>	* ForkJoinTasks (as may be determined using method {@link
104	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
105	>	* result in exceptions or errors, possibly including
106	>	* ClassCastException.
107		*
108	<	* <p>Most base support methods are <tt>final</tt> because their
109	<	* implementations are intrinsically tied to the underlying
110	<	* lightweight task scheduling framework, and so cannot be overridden.
111	<	* Developers creating new basic styles of fork/join processing should
112	<	* minimally implement protected methods <tt>exec</tt>,
113	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
114	<	* introducing an abstract computational method that can be
115	<	* implemented in its subclasses. To support such extensions,
116	<	* instances of ForkJoinTasks maintain an atomically updated
73	<	* <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.
108	>	* <p>Most base support methods are {@code final}, to prevent
109	>	* overriding of implementations that are intrinsically tied to the
110	>	* underlying lightweight task scheduling framework.  Developers
111	>	* creating new basic styles of fork/join processing should minimally
112	>	* implement {@code protected} methods {@link #exec}, {@link
113	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
114	>	* an abstract computational method that can be implemented in its
115	>	* subclasses, possibly relying on other {@code protected} methods
116	>	* provided by this class.
117		*
118		* <p>ForkJoinTasks should perform relatively small amounts of
119	<	* computations, othewise splitting into smaller tasks. As a very
120	<	* rough rule of thumb, a task should perform more than 100 and less
121	<	* than 10000 basic computational steps. If tasks are too big, then
122	<	* parellelism cannot improve throughput. If too small, then memory
123	<	* and internal task maintenance overhead may overwhelm processing.
119	>	* computation. Large tasks should be split into smaller subtasks,
120	>	* usually via recursive decomposition. As a very rough rule of thumb,
121	>	* a task should perform more than 100 and less than 10000 basic
122	>	* computational steps. If tasks are too big, then parallelism cannot
123	>	* improve throughput. If too small, then memory and internal task
124	>	* maintenance overhead may overwhelm processing.
125		*
126	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
127	<	* be used in extensions such as remote execution frameworks. However,
128	<	* it is in general safe to serialize tasks only before or after, but
129	<	* not during execution. Serialization is not relied on during
130	<	* execution itself.
126	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
127	>	* and {@link Callable}, that may be of use when mixing execution of
128	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
129	>	* are of this form, consider using a pool in
130	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
131	>	*
132	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
133	>	* used in extensions such as remote execution frameworks. It is
134	>	* sensible to serialize tasks only before or after, but not during,
135	>	* execution. Serialization is not relied on during execution itself.
136	>	*
137	>	* @since 1.7
138	>	* @author Doug Lea
139		*/
140		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
141	+
142		/**
143	<	* Status field holding all run status. We pack this into a single
144	<	* int both to minimize footprint overhead and to ensure atomicity
145	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
143	>	* Run control status bits packed into a single int to minimize
144	>	* footprint and to ensure atomicity (via CAS).  Status is
145	>	* initially zero, and takes on nonnegative values until
146		* completed, upon which status holds COMPLETED. CANCELLED, or
147		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
148		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 157 | public abstract class ForkJoinTask<V> im
157		* currently unused. Also value 0x80000000 is available as spare
158		* completion value.
159		*/
160	<	volatile int status; // accessed directy by pool and workers
160	>	volatile int status; // accessed directly by pool and workers
161
162		static final int COMPLETION_MASK      = 0xe0000000;
163		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 170 | public abstract class ForkJoinTask<V> im
170		/**
171		* Table of exceptions thrown by tasks, to enable reporting by
172		* callers. Because exceptions are rare, we don't directly keep
173	<	* them with task objects, but instead us a weak ref table.  Note
173	>	* them with task objects, but instead use a weak ref table.  Note
174		* that cancellation exceptions don't appear in the table, but are
175		* instead recorded as status values.
176	<	* Todo: Use ConcurrentReferenceHashMap
176	>	* TODO: Use ConcurrentReferenceHashMap
177		*/
178		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
179		Collections.synchronizedMap
#	Line 136 | Line 182 | public abstract class ForkJoinTask<V> im
182		// within-package utilities
183
184		/**
185	<	* Get current worker thread, or null if not a worker thread
185	>	* Gets current worker thread, or null if not a worker thread.
186		*/
187		static ForkJoinWorkerThread getWorker() {
188		Thread t = Thread.currentThread();
189	<	return ((t instanceof ForkJoinWorkerThread)?
190	<	(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);
189	>	return ((t instanceof ForkJoinWorkerThread) ?
190	>	(ForkJoinWorkerThread) t : null);
191		}
192
193		final boolean casStatus(int cmp, int val) {
194	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
194	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
195		}
196
197		/**
#	Line 162 | Line 199 | public abstract class ForkJoinTask<V> im
199		*/
200		static void rethrowException(Throwable ex) {
201		if (ex != null)
202	<	_unsafe.throwException(ex);
202	>	UNSAFE.throwException(ex);
203		}
204
205		// Setting completion status
206
207		/**
208	<	* Mark completion and wake up threads waiting to join this task.
208	>	* Marks completion and wakes up threads waiting to join this task.
209	>	*
210		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
211		*/
212		final void setCompletion(int completion) {
213	<	ForkJoinPool pool = getWorkerPool();
213	>	ForkJoinPool pool = getPool();
214		if (pool != null) {
215		int s; // Clear signal bits while setting completion status
216	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
216	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
217
218		if ((s & SIGNAL_MASK) != 0) {
219		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
220		pool.updateRunningCount(s);
221	<	synchronized(this) { notifyAll(); }
221	>	synchronized (this) { notifyAll(); }
222		}
223		}
224		else
#	Line 193 | Line 231 | public abstract class ForkJoinTask<V> im
231		*/
232		private void externallySetCompletion(int completion) {
233		int s;
234	<	do;while ((s = status) >= 0 &&
235	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
236	<	synchronized(this) { notifyAll(); }
234	>	do {} while ((s = status) >= 0 &&
235	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
236	>	synchronized (this) { notifyAll(); }
237		}
238
239		/**
240	<	* Sets status to indicate normal completion
240	>	* Sets status to indicate normal completion.
241		*/
242		final void setNormalCompletion() {
243		// Try typical fast case -- single CAS, no signal, not already done.
244		// Manually expand casStatus to improve chances of inlining it
245	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
245	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
246		setCompletion(NORMAL);
247		}
248
249		// internal waiting and notification
250
251		/**
252	<	* Performs the actual monitor wait for awaitDone
252	>	* Performs the actual monitor wait for awaitDone.
253		*/
254		private void doAwaitDone() {
255		// Minimize lock bias and in/de-flation effects by maximizing
256		// chances of waiting inside sync
257		try {
258		while (status >= 0)
259	<	synchronized(this) { if (status >= 0) wait(); }
259	>	synchronized (this) { if (status >= 0) wait(); }
260		} catch (InterruptedException ie) {
261		onInterruptedWait();
262		}
263		}
264
265		/**
266	<	* Performs the actual monitor wait for awaitDone
266	>	* Performs the actual timed monitor wait for awaitDone.
267		*/
268		private void doAwaitDone(long startTime, long nanos) {
269	<	synchronized(this) {
269	>	synchronized (this) {
270		try {
271		while (status >= 0) {
272	<	long nt = nanos - System.nanoTime() - startTime;
272	>	long nt = nanos - (System.nanoTime() - startTime);
273		if (nt <= 0)
274		break;
275	<	wait(nt / 1000000, (int)(nt % 1000000));
275	>	wait(nt / 1000000, (int) (nt % 1000000));
276		}
277		} catch (InterruptedException ie) {
278		onInterruptedWait();
#	Line 247 | Line 285 | public abstract class ForkJoinTask<V> im
285		/**
286		* Sets status to indicate there is joiner, then waits for join,
287		* surrounded with pool notifications.
288	+	*
289		* @return status upon exit
290		*/
291	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
292	<	ForkJoinPool pool = w == null? null : w.pool;
291	>	private int awaitDone(ForkJoinWorkerThread w,
292	>	boolean maintainParallelism) {
293	>	ForkJoinPool pool = (w == null) ? null : w.pool;
294		int s;
295		while ((s = status) >= 0) {
296	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
296	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
297		if (pool == null || !pool.preJoin(this, maintainParallelism))
298		doAwaitDone();
299		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 306 | public abstract class ForkJoinTask<V> im
306
307		/**
308		* Timed version of awaitDone
309	+	*
310		* @return status upon exit
311		*/
312	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
313	<	ForkJoinPool pool = w == null? null : w.pool;
312	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
313	>	ForkJoinPool pool = (w == null) ? null : w.pool;
314		int s;
315		while ((s = status) >= 0) {
316	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
316	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
317		long startTime = System.nanoTime();
318		if (pool == null || !pool.preJoin(this, false))
319		doAwaitDone(startTime, nanos);
#	Line 289 | Line 330 | public abstract class ForkJoinTask<V> im
330		}
331
332		/**
333	<	* Notify pool that thread is unblocked. Called by signalled
333	>	* Notifies pool that thread is unblocked. Called by signalled
334		* threads when woken by non-FJ threads (which is atypical).
335		*/
336		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
337		int s;
338	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
338	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
339		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
340		pool.updateRunningCount(s);
341		}
342
343		/**
344	<	* Notify pool to adjust counts on cancelled or timed out wait
344	>	* Notifies pool to adjust counts on cancelled or timed out wait.
345		*/
346		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
347		if (pool != null) {
#	Line 314 | Line 355 | public abstract class ForkJoinTask<V> im
355		}
356		}
357
358	+	/**
359	+	* Handles interruptions during waits.
360	+	*/
361		private void onInterruptedWait() {
362	<	Thread t = Thread.currentThread();
363	<	if (t instanceof ForkJoinWorkerThread) {
364	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
365	<	if (w.isTerminating())
366	<	cancelIgnoreExceptions();
367	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
362	>	ForkJoinWorkerThread w = getWorker();
363	>	if (w == null)
364	>	Thread.currentThread().interrupt(); // re-interrupt
365	>	else if (w.isTerminating())
366	>	cancelIgnoringExceptions();
367	>	// else if FJworker, ignore interrupt
368		}
369
370		// Recording and reporting exceptions
#	Line 337 | Line 375 | public abstract class ForkJoinTask<V> im
375		}
376
377		/**
378	<	* Throws the exception associated with status s;
378	>	* Throws the exception associated with status s.
379	>	*
380		* @throws the exception
381		*/
382		private void reportException(int s) {
#	Line 350 | Line 389 | public abstract class ForkJoinTask<V> im
389		}
390
391		/**
392	<	* Returns result or throws exception using j.u.c.Future conventions
393	<	* Only call when isDone known to be true.
392	>	* Returns result or throws exception using j.u.c.Future conventions.
393	>	* Only call when {@code isDone} known to be true or thread known
394	>	* to be interrupted.
395		*/
396		private V reportFutureResult()
397	<	throws ExecutionException, InterruptedException {
397	>	throws InterruptedException, ExecutionException {
398	>	if (Thread.interrupted())
399	>	throw new InterruptedException();
400		int s = status & COMPLETION_MASK;
401		if (s < NORMAL) {
402		Throwable ex;
#	Line 362 | Line 404 | public abstract class ForkJoinTask<V> im
404		throw new CancellationException();
405		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
406		throw new ExecutionException(ex);
365	–	if (Thread.interrupted())
366	–	throw new InterruptedException();
407		}
408		return getRawResult();
409		}
410
411		/**
412		* Returns result or throws exception using j.u.c.Future conventions
413	<	* with timeouts
413	>	* with timeouts.
414		*/
415		private V reportTimedFutureResult()
416		throws InterruptedException, ExecutionException, TimeoutException {
417	+	if (Thread.interrupted())
418	+	throw new InterruptedException();
419		Throwable ex;
420		int s = status & COMPLETION_MASK;
421		if (s == NORMAL)
422		return getRawResult();
423	<	if (s == CANCELLED)
423	>	else if (s == CANCELLED)
424		throw new CancellationException();
425	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
425	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
426		throw new ExecutionException(ex);
427	<	if (Thread.interrupted())
428	<	throw new InterruptedException();
387	<	throw new TimeoutException();
427	>	else
428	>	throw new TimeoutException();
429		}
430
431		// internal execution methods
432
433		/**
434		* Calls exec, recording completion, and rethrowing exception if
435	<	* encountered. Caller should normally check status before calling
435	>	* encountered. Caller should normally check status before calling.
436	>	*
437		* @return true if completed normally
438		*/
439		private boolean tryExec() {
#	Line 409 | Line 451 | public abstract class ForkJoinTask<V> im
451
452		/**
453		* Main execution method used by worker threads. Invokes
454	<	* base computation unless already complete
454	>	* base computation unless already complete.
455		*/
456		final void quietlyExec() {
457		if (status >= 0) {
458		try {
459		if (!exec())
460		return;
461	<	} catch(Throwable rex) {
461	>	} catch (Throwable rex) {
462		setDoneExceptionally(rex);
463		return;
464		}
#	Line 425 | Line 467 | public abstract class ForkJoinTask<V> im
467		}
468
469		/**
470	<	* Calls exec, recording but not rethrowing exception
471	<	* Caller should normally check status before calling
470	>	* Calls exec(), recording but not rethrowing exception.
471	>	* Caller should normally check status before calling.
472	>	*
473		* @return true if completed normally
474		*/
475		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 485 | public abstract class ForkJoinTask<V> im
485		}
486
487		/**
488	<	* Cancel, ignoring any exceptions it throws
488	>	* Cancels, ignoring any exceptions it throws.
489		*/
490	<	final void cancelIgnoreExceptions() {
490	>	final void cancelIgnoringExceptions() {
491		try {
492		cancel(false);
493	<	} catch(Throwable ignore) {
493	>	} catch (Throwable ignore) {
494		}
495		}
496
497	+	/**
498	+	* Main implementation of helpJoin
499	+	*/
500	+	private int busyJoin(ForkJoinWorkerThread w) {
501	+	int s;
502	+	ForkJoinTask<?> t;
503	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
504	+	t.quietlyExec();
505	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
506	+	}
507	+
508		// public methods
509
510		/**
511		* Arranges to asynchronously execute this task.  While it is not
512		* necessarily enforced, it is a usage error to fork a task more
513	<	* than once unless it has completed and been reinitialized.  This
514	<	* method may be invoked only from within other ForkJoinTask
515	<	* computations. Attempts to invoke in other contexts result in
516	<	* exceptions or errors including ClassCastException.
513	>	* than once unless it has completed and been reinitialized.
514	>	*
515	>	* <p>This method may be invoked only from within {@code
516	>	* ForkJoinTask} computations (as may be determined using method
517	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
518	>	* result in exceptions or errors, possibly including {@code
519	>	* ClassCastException}.
520	>	*
521	>	* @return {@code this}, to simplify usage
522		*/
523	<	public final void fork() {
524	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
523	>	public final ForkJoinTask<V> fork() {
524	>	((ForkJoinWorkerThread) Thread.currentThread())
525	>	.pushTask(this);
526	>	return this;
527		}
528
529		/**
530	<	* Returns the result of the computation when it is ready.
531	<	* This method differs from <tt>get</tt> in that abnormal
532	<	* completion results in RuntimeExceptions or Errors, not
533	<	* ExecutionExceptions.
530	>	* Returns the result of the computation when it {@link #isDone is done}.
531	>	* This method differs from {@link #get()} in that
532	>	* abnormal completion results in {@code RuntimeException} or
533	>	* {@code Error}, not {@code ExecutionException}.
534		*
535		* @return the computed result
536		*/
#	Line 480 | Line 541 | public abstract class ForkJoinTask<V> im
541		return getRawResult();
542		}
543
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	–
498	–	/**
499	–	* Possibly executes other tasks until this task is ready, then
500	–	* returns the result of the computation.  This method may be more
501	–	* 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	–
544		/**
545	<	* Performs this task, awaits its completion if necessary, and
546	<	* return its result.
547	<	* @throws Throwable (a RuntimeException, Error, or unchecked
548	<	* exception) if the underlying computation did so.
545	>	* Commences performing this task, awaits its completion if
546	>	* necessary, and return its result, or throws an (unchecked)
547	>	* exception if the underlying computation did so.
548	>	*
549		* @return the computed result
550		*/
551		public final V invoke() {
#	Line 527 | Line 556 | public abstract class ForkJoinTask<V> im
556		}
557
558		/**
559	<	* Joins this task, without returning its result or throwing an
560	<	* exception. This method may be useful when processing
561	<	* collections of tasks when some have been cancelled or otherwise
562	<	* known to have aborted.
559	>	* Forks the given tasks, returning when {@code isDone} holds for
560	>	* each task or an (unchecked) exception is encountered, in which
561	>	* case the exception is rethrown.  If either task encounters an
562	>	* exception, the other one may be, but is not guaranteed to be,
563	>	* cancelled.  If both tasks throw an exception, then this method
564	>	* throws one of them.  The individual status of each task may be
565	>	* checked using {@link #getException()} and related methods.
566	>	*
567	>	* <p>This method may be invoked only from within {@code
568	>	* ForkJoinTask} computations (as may be determined using method
569	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
570	>	* result in exceptions or errors, possibly including {@code
571	>	* ClassCastException}.
572	>	*
573	>	* @param t1 the first task
574	>	* @param t2 the second task
575	>	* @throws NullPointerException if any task is null
576		*/
577	<	public final void quietlyJoin() {
578	<	if (status >= 0) {
579	<	ForkJoinWorkerThread w = getWorker();
580	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
577	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
578	>	t2.fork();
579	>	t1.invoke();
580	>	t2.join();
581		}
582
583		/**
584	<	* Possibly executes other tasks until this task is ready.
584	>	* Forks the given tasks, returning when {@code isDone} holds for
585	>	* each task or an (unchecked) exception is encountered, in which
586	>	* case the exception is rethrown. If any task encounters an
587	>	* exception, others may be, but are not guaranteed to be,
588	>	* cancelled.  If more than one task encounters an exception, then
589	>	* this method throws any one of these exceptions.  The individual
590	>	* status of each task may be checked using {@link #getException()}
591	>	* and related methods.
592	>	*
593	>	* <p>This method may be invoked only from within {@code
594	>	* ForkJoinTask} computations (as may be determined using method
595	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
596	>	* result in exceptions or errors, possibly including {@code
597	>	* ClassCastException}.
598	>	*
599	>	* @param tasks the tasks
600	>	* @throws NullPointerException if any task is null
601		*/
602	<	public final void quietlyHelpJoin() {
603	<	if (status >= 0) {
604	<	ForkJoinWorkerThread w =
605	<	(ForkJoinWorkerThread)(Thread.currentThread());
606	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
607	<	w.helpJoinTask(this);
602	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
603	>	Throwable ex = null;
604	>	int last = tasks.length - 1;
605	>	for (int i = last; i >= 0; --i) {
606	>	ForkJoinTask<?> t = tasks[i];
607	>	if (t == null) {
608	>	if (ex == null)
609	>	ex = new NullPointerException();
610	>	}
611	>	else if (i != 0)
612	>	t.fork();
613	>	else {
614	>	t.quietlyInvoke();
615	>	if (ex == null)
616	>	ex = t.getException();
617	>	}
618	>	}
619	>	for (int i = 1; i <= last; ++i) {
620	>	ForkJoinTask<?> t = tasks[i];
621	>	if (t != null) {
622	>	if (ex != null)
623	>	t.cancel(false);
624	>	else {
625	>	t.quietlyJoin();
626	>	if (ex == null)
627	>	ex = t.getException();
628	>	}
629	>	}
630		}
631	+	if (ex != null)
632	+	rethrowException(ex);
633		}
634
635		/**
636	<	* Performs this task and awaits its completion if necessary,
637	<	* without returning its result or throwing an exception. This
638	<	* method may be useful when processing collections of tasks when
639	<	* some have been cancelled or otherwise known to have aborted.
636	>	* Forks all tasks in the specified collection, returning when
637	>	* {@code isDone} holds for each task or an (unchecked) exception
638	>	* is encountered.  If any task encounters an exception, others
639	>	* may be, but are not guaranteed to be, cancelled.  If more than
640	>	* one task encounters an exception, then this method throws any
641	>	* one of these exceptions.  The individual status of each task
642	>	* may be checked using {@link #getException()} and related
643	>	* methods.  The behavior of this operation is undefined if the
644	>	* specified collection is modified while the operation is in
645	>	* progress.
646	>	*
647	>	* <p>This method may be invoked only from within {@code
648	>	* ForkJoinTask} computations (as may be determined using method
649	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
650	>	* result in exceptions or errors, possibly including {@code
651	>	* ClassCastException}.
652	>	*
653	>	* @param tasks the collection of tasks
654	>	* @return the tasks argument, to simplify usage
655	>	* @throws NullPointerException if tasks or any element are null
656		*/
657	<	public final void quietlyInvoke() {
658	<	if (status >= 0 && !tryQuietlyInvoke())
659	<	quietlyJoin();
657	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
658	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
659	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
660	>	return tasks;
661	>	}
662	>	@SuppressWarnings("unchecked")
663	>	List<? extends ForkJoinTask<?>> ts =
664	>	(List<? extends ForkJoinTask<?>>) tasks;
665	>	Throwable ex = null;
666	>	int last = ts.size() - 1;
667	>	for (int i = last; i >= 0; --i) {
668	>	ForkJoinTask<?> t = ts.get(i);
669	>	if (t == null) {
670	>	if (ex == null)
671	>	ex = new NullPointerException();
672	>	}
673	>	else if (i != 0)
674	>	t.fork();
675	>	else {
676	>	t.quietlyInvoke();
677	>	if (ex == null)
678	>	ex = t.getException();
679	>	}
680	>	}
681	>	for (int i = 1; i <= last; ++i) {
682	>	ForkJoinTask<?> t = ts.get(i);
683	>	if (t != null) {
684	>	if (ex != null)
685	>	t.cancel(false);
686	>	else {
687	>	t.quietlyJoin();
688	>	if (ex == null)
689	>	ex = t.getException();
690	>	}
691	>	}
692	>	}
693	>	if (ex != null)
694	>	rethrowException(ex);
695	>	return tasks;
696		}
697
698		/**
699	<	* Returns true if the computation performed by this task has
700	<	* completed (or has been cancelled).
701	<	* @return true if this computation has completed
699	>	* Attempts to cancel execution of this task. This attempt will
700	>	* fail if the task has already completed, has already been
701	>	* cancelled, or could not be cancelled for some other reason. If
702	>	* successful, and this task has not started when cancel is
703	>	* called, execution of this task is suppressed, {@link
704	>	* #isCancelled} will report true, and {@link #join} will result
705	>	* in a {@code CancellationException} being thrown.
706	>	*
707	>	* <p>This method may be overridden in subclasses, but if so, must
708	>	* still ensure that these minimal properties hold. In particular,
709	>	* the {@code cancel} method itself must not throw exceptions.
710	>	*
711	>	* <p>This method is designed to be invoked by <em>other</em>
712	>	* tasks. To terminate the current task, you can just return or
713	>	* throw an unchecked exception from its computation method, or
714	>	* invoke {@link #completeExceptionally}.
715	>	*
716	>	* @param mayInterruptIfRunning this value is ignored in the
717	>	* default implementation because tasks are not
718	>	* cancelled via interruption
719	>	*
720	>	* @return {@code true} if this task is now cancelled
721		*/
722	+	public boolean cancel(boolean mayInterruptIfRunning) {
723	+	setCompletion(CANCELLED);
724	+	return (status & COMPLETION_MASK) == CANCELLED;
725	+	}
726	+
727		public final boolean isDone() {
728		return status < 0;
729		}
730
575	–	/**
576	–	* Returns true if this task was cancelled.
577	–	* @return true if this task was cancelled
578	–	*/
731		public final boolean isCancelled() {
732		return (status & COMPLETION_MASK) == CANCELLED;
733		}
734
735		/**
736	<	* Returns true if this task threw an exception or was cancelled
737	<	* @return true if this task threw an exception or was cancelled
736	>	* Returns {@code true} if this task threw an exception or was cancelled.
737	>	*
738	>	* @return {@code true} if this task threw an exception or was cancelled
739		*/
740	<	public final boolean completedAbnormally() {
740	>	public final boolean isCompletedAbnormally() {
741		return (status & COMPLETION_MASK) < NORMAL;
742		}
743
744		/**
745	<	* Returns the exception thrown by the base computation, or a
746	<	* CancellationException if cancelled, or null if none or if the
747	<	* method has not yet completed.
748	<	* @return the exception, or null if none
745	>	* Returns {@code true} if this task completed without throwing an
746	>	* exception and was not cancelled.
747	>	*
748	>	* @return {@code true} if this task completed without throwing an
749	>	* exception and was not cancelled
750		*/
751	<	public final Throwable getException() {
752	<	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);
751	>	public final boolean isCompletedNormally() {
752	>	return (status & COMPLETION_MASK) == NORMAL;
753		}
754
755		/**
756	<	* Asserts that the results of this task's computation will not be
757	<	* used. If a cancellation occurs before this task is processed,
758	<	* 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.
756	>	* Returns the exception thrown by the base computation, or a
757	>	* {@code CancellationException} if cancelled, or {@code null} if
758	>	* none or if the method has not yet completed.
759		*
760	<	* @return true if this task is now cancelled
760	>	* @return the exception, or {@code null} if none
761		*/
762	<	public boolean cancel(boolean mayInterruptIfRunning) {
763	<	setCompletion(CANCELLED);
764	<	return (status & COMPLETION_MASK) == CANCELLED;
762	>	public final Throwable getException() {
763	>	int s = status & COMPLETION_MASK;
764	>	return ((s >= NORMAL)    ? null :
765	>	(s == CANCELLED) ? new CancellationException() :
766	>	exceptionMap.get(this));
767		}
768
769		/**
770		* Completes this task abnormally, and if not already aborted or
771		* cancelled, causes it to throw the given exception upon
772	<	* <tt>join</tt> and related operations. This method may be used
772	>	* {@code join} and related operations. This method may be used
773		* to induce exceptions in asynchronous tasks, or to force
774	<	* completion of tasks that would not otherwise complete.  This
775	<	* method is overridable, but overridden versions must invoke
776	<	* <tt>super</tt> implementation to maintain guarantees.
774	>	* completion of tasks that would not otherwise complete.  Its use
775	>	* in other situations is discouraged.  This method is
776	>	* overridable, but overridden versions must invoke {@code super}
777	>	* implementation to maintain guarantees.
778	>	*
779		* @param ex the exception to throw. If this exception is
780		* not a RuntimeException or Error, the actual exception thrown
781		* will be a RuntimeException with cause ex.
782		*/
783		public void completeExceptionally(Throwable ex) {
784		setDoneExceptionally((ex instanceof RuntimeException) ||
785	<	(ex instanceof Error)? ex :
785	>	(ex instanceof Error) ? ex :
786		new RuntimeException(ex));
787		}
788
789		/**
790		* Completes this task, and if not already aborted or cancelled,
791	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
791	>	* returning a {@code null} result upon {@code join} and related
792		* operations. This method may be used to provide results for
793		* asynchronous tasks, or to provide alternative handling for
794	<	* tasks that would not otherwise complete normally.
794	>	* tasks that would not otherwise complete normally. Its use in
795	>	* other situations is discouraged. This method is
796	>	* overridable, but overridden versions must invoke {@code super}
797	>	* implementation to maintain guarantees.
798		*
799	<	* @param value the result value for this task.
799	>	* @param value the result value for this task
800		*/
801		public void complete(V value) {
802		try {
803		setRawResult(value);
804	<	} catch(Throwable rex) {
804	>	} catch (Throwable rex) {
805		setDoneExceptionally(rex);
806		return;
807		}
808		setNormalCompletion();
809		}
810
811	+	public final V get() throws InterruptedException, ExecutionException {
812	+	ForkJoinWorkerThread w = getWorker();
813	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
814	+	awaitDone(w, true);
815	+	return reportFutureResult();
816	+	}
817	+
818	+	public final V get(long timeout, TimeUnit unit)
819	+	throws InterruptedException, ExecutionException, TimeoutException {
820	+	long nanos = unit.toNanos(timeout);
821	+	ForkJoinWorkerThread w = getWorker();
822	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
823	+	awaitDone(w, nanos);
824	+	return reportTimedFutureResult();
825	+	}
826	+
827	+	/**
828	+	* Possibly executes other tasks until this task {@link #isDone is
829	+	* done}, then returns the result of the computation.  This method
830	+	* may be more efficient than {@code join}, but is only applicable
831	+	* when there are no potential dependencies between continuation
832	+	* of the current task and that of any other task that might be
833	+	* executed while helping. (This usually holds for pure
834	+	* divide-and-conquer tasks).
835	+	*
836	+	* <p>This method may be invoked only from within {@code
837	+	* ForkJoinTask} computations (as may be determined using method
838	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
839	+	* result in exceptions or errors, possibly including {@code
840	+	* ClassCastException}.
841	+	*
842	+	* @return the computed result
843	+	*/
844	+	public final V helpJoin() {
845	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
846	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
847	+	reportException(busyJoin(w));
848	+	return getRawResult();
849	+	}
850	+
851	+	/**
852	+	* Possibly executes other tasks until this task {@link #isDone is
853	+	* done}.  This method may be useful when processing collections
854	+	* of tasks when some have been cancelled or otherwise known to
855	+	* have aborted.
856	+	*
857	+	* <p>This method may be invoked only from within {@code
858	+	* ForkJoinTask} computations (as may be determined using method
859	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
860	+	* result in exceptions or errors, possibly including {@code
861	+	* ClassCastException}.
862	+	*/
863	+	public final void quietlyHelpJoin() {
864	+	if (status >= 0) {
865	+	ForkJoinWorkerThread w =
866	+	(ForkJoinWorkerThread) Thread.currentThread();
867	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
868	+	busyJoin(w);
869	+	}
870	+	}
871	+
872	+	/**
873	+	* Joins this task, without returning its result or throwing an
874	+	* exception. This method may be useful when processing
875	+	* collections of tasks when some have been cancelled or otherwise
876	+	* known to have aborted.
877	+	*/
878	+	public final void quietlyJoin() {
879	+	if (status >= 0) {
880	+	ForkJoinWorkerThread w = getWorker();
881	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
882	+	awaitDone(w, true);
883	+	}
884	+	}
885	+
886	+	/**
887	+	* Commences performing this task and awaits its completion if
888	+	* necessary, without returning its result or throwing an
889	+	* exception. This method may be useful when processing
890	+	* collections of tasks when some have been cancelled or otherwise
891	+	* known to have aborted.
892	+	*/
893	+	public final void quietlyInvoke() {
894	+	if (status >= 0 && !tryQuietlyInvoke())
895	+	quietlyJoin();
896	+	}
897	+
898	+	/**
899	+	* Possibly executes tasks until the pool hosting the current task
900	+	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
901	+	* be of use in designs in which many tasks are forked, but none
902	+	* are explicitly joined, instead executing them until all are
903	+	* processed.
904	+	*
905	+	* <p>This method may be invoked only from within {@code
906	+	* ForkJoinTask} computations (as may be determined using method
907	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
908	+	* result in exceptions or errors, possibly including {@code
909	+	* ClassCastException}.
910	+	*/
911	+	public static void helpQuiesce() {
912	+	((ForkJoinWorkerThread) Thread.currentThread())
913	+	.helpQuiescePool();
914	+	}
915	+
916		/**
917		* Resets the internal bookkeeping state of this task, allowing a
918	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
918	>	* subsequent {@code fork}. This method allows repeated reuse of
919		* this task, but only if reuse occurs when this task has either
920		* never been forked, or has been forked, then completed and all
921		* outstanding joins of this task have also completed. Effects
922	<	* under any other usage conditions are not guaranteed, and are
923	<	* almost surely wrong. This method may be useful when executing
922	>	* under any other usage conditions are not guaranteed.
923	>	* This method may be useful when executing
924		* pre-constructed trees of subtasks in loops.
925		*/
926		public void reinitialize() {
#	Line 689 | Line 930 | public abstract class ForkJoinTask<V> im
930		}
931
932		/**
933	<	* Tries to unschedule this task for execution. This method will
934	<	* typically succeed if this task is the next task that would be
935	<	* executed by the current thread, and will typically fail (return
936	<	* false) otherwise. This method may be useful when arranging
937	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
933	>	* Returns the pool hosting the current task execution, or null
934	>	* if this task is executing outside of any ForkJoinPool.
935	>	*
936	>	* @see #inForkJoinPool
937	>	* @return the pool, or {@code null} if none
938		*/
939	<	public boolean tryUnfork() {
940	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
939	>	public static ForkJoinPool getPool() {
940	>	Thread t = Thread.currentThread();
941	>	return (t instanceof ForkJoinWorkerThread) ?
942	>	((ForkJoinWorkerThread) t).pool : null;
943		}
944
945		/**
946	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
947	<	* of them or an exception is encountered. This method may be
948	<	* invoked only from within other ForkJoinTask
949	<	* computations. Attempts to invoke in other contexts result in
950	<	* 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.
946	>	* Returns {@code true} if the current thread is executing as a
947	>	* ForkJoinPool computation.
948	>	*
949	>	* @return {@code true} if the current thread is executing as a
950	>	* ForkJoinPool computation, or false otherwise
951		*/
952	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
953	<	t2.fork();
717	<	t1.invoke();
718	<	t2.join();
952	>	public static boolean inForkJoinPool() {
953	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
954		}
955
956		/**
957	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
958	<	* all of them. If any task encounters an exception, others may be
959	<	* cancelled.  This method may be invoked only from within other
960	<	* ForkJoinTask computations. Attempts to invoke in other contexts
961	<	* result in exceptions or errors including ClassCastException.
962	<	* @param tasks the array of tasks
963	<	* @throws NullPointerException if tasks or any element are null.
964	<	* @throws RuntimeException or Error if any task did so.
965	<	*/
966	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
967	<	Throwable ex = null;
968	<	int last = tasks.length - 1;
969	<	for (int i = last; i >= 0; --i) {
970	<	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.
957	>	* Tries to unschedule this task for execution. This method will
958	>	* typically succeed if this task is the most recently forked task
959	>	* by the current thread, and has not commenced executing in
960	>	* another thread.  This method may be useful when arranging
961	>	* alternative local processing of tasks that could have been, but
962	>	* were not, stolen.
963	>	*
964	>	* <p>This method may be invoked only from within {@code
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 {@code
968	>	* ClassCastException}.
969	>	*
970	>	* @return {@code true} if unforked
971		*/
972	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
973	<	if (!(tasks instanceof List)) {
974	<	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);
972	>	public boolean tryUnfork() {
973	>	return ((ForkJoinWorkerThread) Thread.currentThread())
974	>	.unpushTask(this);
975		}
976
977		/**
978	<	* Possibly executes tasks until the pool hosting the current task
979	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
980	<	* designs in which many tasks are forked, but none are explicitly
981	<	* joined, instead executing them until all are processed.
978	>	* Returns an estimate of the number of tasks that have been
979	>	* forked by the current worker thread but not yet executed. This
980	>	* value may be useful for heuristic decisions about whether to
981	>	* fork other tasks.
982	>	*
983	>	* <p>This method may be invoked only from within {@code
984	>	* ForkJoinTask} computations (as may be determined using method
985	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
986	>	* result in exceptions or errors, possibly including {@code
987	>	* ClassCastException}.
988	>	*
989	>	* @return the number of tasks
990		*/
991	<	public static void helpQuiesce() {
992	<	((ForkJoinWorkerThread)(Thread.currentThread())).
993	<	helpQuiescePool();
991	>	public static int getQueuedTaskCount() {
992	>	return ((ForkJoinWorkerThread) Thread.currentThread())
993	>	.getQueueSize();
994		}
995
996		/**
997	<	* Returns a estimate of how many more locally queued tasks are
997	>	* Returns an estimate of how many more locally queued tasks are
998		* held by the current worker thread than there are other worker
999	<	* threads that might want to steal them.  This value may be
1000	<	* useful for heuristic decisions about whether to fork other
1001	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
1002	<	* worker should aim to maintain a small constant surplus (for
1003	<	* example, 3) of tasks, and to process computations locally if
1004	<	* this threshold is exceeded.
999	>	* threads that might steal them.  This value may be useful for
1000	>	* heuristic decisions about whether to fork other tasks. In many
1001	>	* usages of ForkJoinTasks, at steady state, each worker should
1002	>	* aim to maintain a small constant surplus (for example, 3) of
1003	>	* tasks, and to process computations locally if this threshold is
1004	>	* exceeded.
1005	>	*
1006	>	* <p>This method may be invoked only from within {@code
1007	>	* ForkJoinTask} computations (as may be determined using method
1008	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1009	>	* result in exceptions or errors, possibly including {@code
1010	>	* ClassCastException}.
1011	>	*
1012		* @return the surplus number of tasks, which may be negative
1013		*/
1014	<	public static int surplus() {
1015	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
1014	>	public static int getSurplusQueuedTaskCount() {
1015	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1016		.getEstimatedSurplusTaskCount();
1017		}
1018
1019	<	// Extension kit
1019	>	// Extension methods
1020
1021		/**
1022	<	* Returns the result that would be returned by <tt>join</tt>, or
1023	<	* null if this task is not known to have been completed.  This
1024	<	* method is designed to aid debugging, as well as to support
1025	<	* extensions. Its use in any other context is discouraged.
1022	>	* Returns the result that would be returned by {@link #join}, even
1023	>	* if this task completed abnormally, or {@code null} if this task
1024	>	* is not known to have been completed.  This method is designed
1025	>	* to aid debugging, as well as to support extensions. Its use in
1026	>	* any other context is discouraged.
1027		*
1028	<	* @return the result, or null if not completed.
1028	>	* @return the result, or {@code null} if not completed
1029		*/
1030		public abstract V getRawResult();
1031
#	Line 865 | Line 1044 | public abstract class ForkJoinTask<V> im
1044		* called otherwise. The return value controls whether this task
1045		* is considered to be done normally. It may return false in
1046		* asynchronous actions that require explicit invocations of
1047	<	* <tt>complete</tt> to become joinable. It may throw exceptions
1048	<	* to indicate abnormal exit.
1049	<	* @return true if completed normally
1050	<	* @throws Error or RuntimeException if encountered during computation
1047	>	* {@link #complete} to become joinable. It may also throw an
1048	>	* (unchecked) exception to indicate abnormal exit.
1049	>	*
1050	>	* @return {@code true} if completed normally
1051		*/
1052		protected abstract boolean exec();
1053
1054	+	/**
1055	+	* Returns, but does not unschedule or execute, a task queued by
1056	+	* the current thread but not yet executed, if one is immediately
1057	+	* available. There is no guarantee that this task will actually
1058	+	* be polled or executed next. Conversely, this method may return
1059	+	* null even if a task exists but cannot be accessed without
1060	+	* contention with other threads.  This method is designed
1061	+	* primarily to support extensions, and is unlikely to be useful
1062	+	* otherwise.
1063	+	*
1064	+	* <p>This method may be invoked only from within {@code
1065	+	* ForkJoinTask} computations (as may be determined using method
1066	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1067	+	* result in exceptions or errors, possibly including {@code
1068	+	* ClassCastException}.
1069	+	*
1070	+	* @return the next task, or {@code null} if none are available
1071	+	*/
1072	+	protected static ForkJoinTask<?> peekNextLocalTask() {
1073	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1074	+	.peekTask();
1075	+	}
1076	+
1077	+	/**
1078	+	* Unschedules and returns, without executing, the next task
1079	+	* queued by the current thread but not yet executed.  This method
1080	+	* is designed primarily to support extensions, and is unlikely to
1081	+	* be useful otherwise.
1082	+	*
1083	+	* <p>This method may be invoked only from within {@code
1084	+	* ForkJoinTask} computations (as may be determined using method
1085	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1086	+	* result in exceptions or errors, possibly including {@code
1087	+	* ClassCastException}.
1088	+	*
1089	+	* @return the next task, or {@code null} if none are available
1090	+	*/
1091	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1092	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1093	+	.pollLocalTask();
1094	+	}
1095	+
1096	+	/**
1097	+	* Unschedules and returns, without executing, the next task
1098	+	* queued by the current thread but not yet executed, if one is
1099	+	* available, or if not available, a task that was forked by some
1100	+	* other thread, if available. Availability may be transient, so a
1101	+	* {@code null} result does not necessarily imply quiescence
1102	+	* of the pool this task is operating in.  This method is designed
1103	+	* primarily to support extensions, and is unlikely to be useful
1104	+	* otherwise.
1105	+	*
1106	+	* <p>This method may be invoked only from within {@code
1107	+	* ForkJoinTask} computations (as may be determined using method
1108	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1109	+	* result in exceptions or errors, possibly including {@code
1110	+	* ClassCastException}.
1111	+	*
1112	+	* @return a task, or {@code null} if none are available
1113	+	*/
1114	+	protected static ForkJoinTask<?> pollTask() {
1115	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1116	+	.pollTask();
1117	+	}
1118	+
1119	+	/**
1120	+	* Adaptor for Runnables. This implements RunnableFuture
1121	+	* to be compliant with AbstractExecutorService constraints
1122	+	* when used in ForkJoinPool.
1123	+	*/
1124	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1125	+	implements RunnableFuture<T> {
1126	+	final Runnable runnable;
1127	+	final T resultOnCompletion;
1128	+	T result;
1129	+	AdaptedRunnable(Runnable runnable, T result) {
1130	+	if (runnable == null) throw new NullPointerException();
1131	+	this.runnable = runnable;
1132	+	this.resultOnCompletion = result;
1133	+	}
1134	+	public T getRawResult() { return result; }
1135	+	public void setRawResult(T v) { result = v; }
1136	+	public boolean exec() {
1137	+	runnable.run();
1138	+	result = resultOnCompletion;
1139	+	return true;
1140	+	}
1141	+	public void run() { invoke(); }
1142	+	private static final long serialVersionUID = 5232453952276885070L;
1143	+	}
1144	+
1145	+	/**
1146	+	* Adaptor for Callables
1147	+	*/
1148	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1149	+	implements RunnableFuture<T> {
1150	+	final Callable<? extends T> callable;
1151	+	T result;
1152	+	AdaptedCallable(Callable<? extends T> callable) {
1153	+	if (callable == null) throw new NullPointerException();
1154	+	this.callable = callable;
1155	+	}
1156	+	public T getRawResult() { return result; }
1157	+	public void setRawResult(T v) { result = v; }
1158	+	public boolean exec() {
1159	+	try {
1160	+	result = callable.call();
1161	+	return true;
1162	+	} catch (Error err) {
1163	+	throw err;
1164	+	} catch (RuntimeException rex) {
1165	+	throw rex;
1166	+	} catch (Exception ex) {
1167	+	throw new RuntimeException(ex);
1168	+	}
1169	+	}
1170	+	public void run() { invoke(); }
1171	+	private static final long serialVersionUID = 2838392045355241008L;
1172	+	}
1173	+
1174	+	/**
1175	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1176	+	* method of the given {@code Runnable} as its action, and returns
1177	+	* a null result upon {@link #join}.
1178	+	*
1179	+	* @param runnable the runnable action
1180	+	* @return the task
1181	+	*/
1182	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1183	+	return new AdaptedRunnable<Void>(runnable, null);
1184	+	}
1185	+
1186	+	/**
1187	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1188	+	* method of the given {@code Runnable} as its action, and returns
1189	+	* the given result upon {@link #join}.
1190	+	*
1191	+	* @param runnable the runnable action
1192	+	* @param result the result upon completion
1193	+	* @return the task
1194	+	*/
1195	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1196	+	return new AdaptedRunnable<T>(runnable, result);
1197	+	}
1198	+
1199	+	/**
1200	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1201	+	* method of the given {@code Callable} as its action, and returns
1202	+	* its result upon {@link #join}, translating any checked exceptions
1203	+	* encountered into {@code RuntimeException}.
1204	+	*
1205	+	* @param callable the callable action
1206	+	* @return the task
1207	+	*/
1208	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1209	+	return new AdaptedCallable<T>(callable);
1210	+	}
1211	+
1212		// Serialization support
1213
1214		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1217 | public abstract class ForkJoinTask<V> im
1217		* Save the state to a stream.
1218		*
1219		* @serialData the current run status and the exception thrown
1220	<	* during execution, or null if none.
1220	>	* during execution, or {@code null} if none
1221		* @param s the stream
1222		*/
1223		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1228 | public abstract class ForkJoinTask<V> im
1228
1229		/**
1230		* Reconstitute the instance from a stream.
1231	+	*
1232		* @param s the stream
1233		*/
1234		private void readObject(java.io.ObjectInputStream s)
1235		throws java.io.IOException, ClassNotFoundException {
1236		s.defaultReadObject();
1237	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1237	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1238	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1239		Object ex = s.readObject();
1240		if (ex != null)
1241	<	setDoneExceptionally((Throwable)ex);
1241	>	setDoneExceptionally((Throwable) ex);
1242		}
1243
1244	<	// Temporary Unsafe mechanics for preliminary release
1244	>	// Unsafe mechanics
1245
1246	<	static final Unsafe _unsafe;
1247	<	static final long statusOffset;
1246	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1247	>	private static final long statusOffset =
1248	>	objectFieldOffset("status", ForkJoinTask.class);
1249
1250	<	static {
1250	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1251		try {
1252	<	if (ForkJoinTask.class.getClassLoader() != null) {
1253	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1254	<	f.setAccessible(true);
1255	<	_unsafe = (Unsafe)f.get(null);
1256	<	}
1257	<	else
1258	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1252	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1253	>	} catch (NoSuchFieldException e) {
1254	>	// Convert Exception to corresponding Error
1255	>	NoSuchFieldError error = new NoSuchFieldError(field);
1256	>	error.initCause(e);
1257	>	throw error;
1258	>	}
1259		}
1260
1261	+	/**
1262	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1263	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1264	+	* into a jdk.
1265	+	*
1266	+	* @return a sun.misc.Unsafe
1267	+	*/
1268	+	private static sun.misc.Unsafe getUnsafe() {
1269	+	try {
1270	+	return sun.misc.Unsafe.getUnsafe();
1271	+	} catch (SecurityException se) {
1272	+	try {
1273	+	return java.security.AccessController.doPrivileged
1274	+	(new java.security
1275	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1276	+	public sun.misc.Unsafe run() throws Exception {
1277	+	java.lang.reflect.Field f = sun.misc
1278	+	.Unsafe.class.getDeclaredField("theUnsafe");
1279	+	f.setAccessible(true);
1280	+	return (sun.misc.Unsafe) f.get(null);
1281	+	}});
1282	+	} catch (java.security.PrivilegedActionException e) {
1283	+	throw new RuntimeException("Could not initialize intrinsics",
1284	+	e.getCause());
1285	+	}
1286	+	}
1287	+	}
1288		}

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