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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.5 by jsr166, Thu Mar 19 05:10:42 2009 UTC vs.
Revision 1.35 by dl, Tue Aug 4 12:41:27 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.RandomAccess;
16	>	import java.util.Map;
17	>	import java.util.WeakHashMap;
18
19		/**
20	<	* Abstract base class for tasks that run within a {@link
21	<	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22		* lighter weight than a normal thread.  Huge numbers of tasks and
23		* subtasks may be hosted by a small number of actual threads in a
24		* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> A "main" ForkJoinTask begins execution when submitted to a
27	<	* {@link ForkJoinPool}. Once started, it will usually in turn start
28	<	* other subtasks.  As indicated by the name of this class, many
29	<	* programs using ForkJoinTasks employ only methods <code>fork</code>
30	<	* and <code>join</code>, or derivatives such as
31	<	* <code>invokeAll</code>.  However, this class also provides a number
32	<	* of other methods that can come into play in advanced usages, as
33	<	* well as extension mechanics that allow support of new forms of
34	<	* fork/join processing.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
37	<	* efficiency of ForkJoinTasks stems from a set of restrictions (that
38	<	* are only partially statically enforceable) reflecting their
39	<	* intended use as computational tasks calculating pure functions or
40	<	* operating on purely isolated objects.  The primary coordination
41	<	* mechanisms are {@link #fork}, that arranges asynchronous execution,
42	<	* and {@link #join}, that doesn't proceed until the task's result has
43	<	* been computed.  Computations should avoid <code>synchronized</code>
44	<	* methods or blocks, and should minimize other blocking
45	<	* synchronization apart from joining other tasks or using
46	<	* synchronizers such as Phasers that are advertised to cooperate with
47	<	* fork/join scheduling. Tasks should also not perform blocking IO,
48	<	* and should ideally access variables that are completely independent
49	<	* of those accessed by other running tasks. Minor breaches of these
50	<	* restrictions, for example using shared output streams, may be
51	<	* tolerable in practice, but frequent use may result in poor
52	<	* performance, and the potential to indefinitely stall if the number
53	<	* of threads not waiting for IO or other external synchronization
54	<	* becomes exhausted. This usage restriction is in part enforced by
55	<	* not permitting checked exceptions such as <code>IOExceptions</code>
56	<	* to be thrown. However, computations may still encounter unchecked
57	<	* exceptions, that are rethrown to callers attempting join
58	<	* them. These exceptions may additionally include
59	<	* RejectedExecutionExceptions stemming from internal resource
60	<	* exhaustion such as failure to allocate internal task queues.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include RejectedExecutionExceptions stemming from
60	>	* internal resource exhaustion such as failure to allocate internal
61	>	* task queues.
62		*
63		* <p>The primary method for awaiting completion and extracting
64		* results of a task is {@link #join}, but there are several variants:
65		* The {@link Future#get} methods support interruptible and/or timed
66	<	* waits for completion and report results using <code>Future</code>
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()</code> but always attempts to
72	<	* begin execution in the current thread. The "<em>quiet</em>" forms
73	<	* of these methods do not extract results or report exceptions. These
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* these methods do not extract results or report exceptions. These
74		* may be useful when a set of tasks are being executed, and you need
75		* to delay processing of results or exceptions until all complete.
76	<	* Method <code>invokeAll</code> (available in multiple versions)
76	>	* Method {@code invokeAll} (available in multiple versions)
77		* performs the most common form of parallel invocation: forking a set
78		* of tasks and joining them all.
79		*
80	<	* <p> The ForkJoinTask class is not usually directly subclassed.
80	>	* <p>The execution status of tasks may be queried at several levels
81	>	* of detail: {@link #isDone} is true if a task completed in any way
82	>	* (including the case where a task was cancelled without executing);
83	>	* {@link #isCancelled} is true if completion was due to cancellation;
84	>	* {@link #isCompletedNormally} is true if a task completed without
85	>	* cancellation or encountering an exception; {@link
86	>	* #isCompletedExceptionally} is true if if the task encountered an
87	>	* exception (in which case {@link #getException} returns the
88	>	* exception); {@link #isCancelled} is true if the task was cancelled
89	>	* (in which case {@link #getException} returns a {@link
90	>	* java.util.concurrent.CancellationException}; and {@link
91	>	* #isCompletedAbnormally} is true if a task was either cancelled or
92	>	* encountered an exception.
93	>	*
94	>	* <p>The ForkJoinTask class is not usually directly subclassed.
95		* Instead, you subclass one of the abstract classes that support a
96	<	* particular style of fork/join processing.  Normally, a concrete
96	>	* particular style of fork/join processing, typically {@link
97	>	* RecursiveAction} for computations that do not return results, or
98	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
99		* ForkJoinTask subclass declares fields comprising its parameters,
100	<	* established in a constructor, and then defines a <code>compute</code>
100	>	* established in a constructor, and then defines a {@code compute}
101		* method that somehow uses the control methods supplied by this base
102	<	* class. While these methods have <code>public</code> access (to allow
103	<	* instances of different task subclasses to call each others
102	>	* class. While these methods have {@code public} access (to allow
103	>	* instances of different task subclasses to call each other's
104		* methods), some of them may only be called from within other
105	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
106	<	* exceptions or errors possibly including ClassCastException.
105	>	* ForkJoinTasks (as may be determined using method {@link
106	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
107	>	* result in exceptions or errors, possibly including
108	>	* ClassCastException.
109		*
110	<	* <p>Most base support methods are <code>final</code> because their
111	<	* implementations are intrinsically tied to the underlying
112	<	* lightweight task scheduling framework, and so cannot be overridden.
113	<	* Developers creating new basic styles of fork/join processing should
114	<	* minimally implement <code>protected</code> methods
115	<	* <code>exec</code>, <code>setRawResult</code>, and
116	<	* <code>getRawResult</code>, while also introducing an abstract
117	<	* computational method that can be implemented in its subclasses,
118	<	* possibly relying on other <code>protected</code> methods provided
96	<	* by this class.
110	>	* <p>Most base support methods are {@code final}, to prevent
111	>	* overriding of implementations that are intrinsically tied to the
112	>	* underlying lightweight task scheduling framework.  Developers
113	>	* creating new basic styles of fork/join processing should minimally
114	>	* implement {@code protected} methods {@link #exec}, {@link
115	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
116	>	* an abstract computational method that can be implemented in its
117	>	* subclasses, possibly relying on other {@code protected} methods
118	>	* provided by this class.
119		*
120		* <p>ForkJoinTasks should perform relatively small amounts of
121	<	* computations, othewise splitting into smaller tasks. As a very
122	<	* rough rule of thumb, a task should perform more than 100 and less
123	<	* than 10000 basic computational steps. If tasks are too big, then
124	<	* parellelism cannot improve throughput. If too small, then memory
125	<	* and internal task maintenance overhead may overwhelm processing.
121	>	* computation. Large tasks should be split into smaller subtasks,
122	>	* usually via recursive decomposition. As a very rough rule of thumb,
123	>	* a task should perform more than 100 and less than 10000 basic
124	>	* computational steps. If tasks are too big, then parallelism cannot
125	>	* improve throughput. If too small, then memory and internal task
126	>	* maintenance overhead may overwhelm processing.
127		*
128	<	* <p>ForkJoinTasks are <code>Serializable</code>, which enables them
129	<	* to be used in extensions such as remote execution frameworks. It is
130	<	* in general sensible to serialize tasks only before or after, but
131	<	* not during execution. Serialization is not relied on during
132	<	* execution itself.
128	>	* <p>This class provides {@code adapt} methods for {@link
129	>	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
130	>	* may be of use when mixing execution of ForkJoinTasks with other
131	>	* kinds of tasks. When all tasks are of this form, consider using a
132	>	* pool in {@link ForkJoinPool#setAsyncMode async mode}.
133	>	*
134	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
135	>	* used in extensions such as remote execution frameworks. It is
136	>	* sensible to serialize tasks only before or after, but not during,
137	>	* execution. Serialization is not relied on during execution itself.
138	>	*
139	>	* @since 1.7
140	>	* @author Doug Lea
141		*/
142		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
143
#	Line 128 | Line 159 | public abstract class ForkJoinTask<V> im
159		* currently unused. Also value 0x80000000 is available as spare
160		* completion value.
161		*/
162	<	volatile int status; // accessed directy by pool and workers
162	>	volatile int status; // accessed directly by pool and workers
163
164		static final int COMPLETION_MASK      = 0xe0000000;
165		static final int NORMAL               = 0xe0000000; // == mask
#	Line 141 | Line 172 | public abstract class ForkJoinTask<V> im
172		/**
173		* Table of exceptions thrown by tasks, to enable reporting by
174		* callers. Because exceptions are rare, we don't directly keep
175	<	* them with task objects, but instead us a weak ref table.  Note
175	>	* them with task objects, but instead use a weak ref table.  Note
176		* that cancellation exceptions don't appear in the table, but are
177		* instead recorded as status values.
178	<	* Todo: Use ConcurrentReferenceHashMap
178	>	* TODO: Use ConcurrentReferenceHashMap
179		*/
180		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
181		Collections.synchronizedMap
#	Line 153 | Line 184 | public abstract class ForkJoinTask<V> im
184		// within-package utilities
185
186		/**
187	<	* Get current worker thread, or null if not a worker thread
187	>	* Gets current worker thread, or null if not a worker thread.
188		*/
189		static ForkJoinWorkerThread getWorker() {
190		Thread t = Thread.currentThread();
191	<	return ((t instanceof ForkJoinWorkerThread)?
192	<	(ForkJoinWorkerThread)t : null);
191	>	return ((t instanceof ForkJoinWorkerThread) ?
192	>	(ForkJoinWorkerThread) t : null);
193		}
194
195		final boolean casStatus(int cmp, int val) {
196	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
196	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
197		}
198
199		/**
#	Line 170 | Line 201 | public abstract class ForkJoinTask<V> im
201		*/
202		static void rethrowException(Throwable ex) {
203		if (ex != null)
204	<	_unsafe.throwException(ex);
204	>	UNSAFE.throwException(ex);
205		}
206
207		// Setting completion status
208
209		/**
210	<	* Mark completion and wake up threads waiting to join this task.
210	>	* Marks completion and wakes up threads waiting to join this task.
211	>	*
212		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
213		*/
214		final void setCompletion(int completion) {
215		ForkJoinPool pool = getPool();
216		if (pool != null) {
217		int s; // Clear signal bits while setting completion status
218	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
218	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
219
220		if ((s & SIGNAL_MASK) != 0) {
221		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
222		pool.updateRunningCount(s);
223	<	synchronized(this) { notifyAll(); }
223	>	synchronized (this) { notifyAll(); }
224		}
225		}
226		else
#	Line 201 | Line 233 | public abstract class ForkJoinTask<V> im
233		*/
234		private void externallySetCompletion(int completion) {
235		int s;
236	<	do;while ((s = status) >= 0 &&
237	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
238	<	synchronized(this) { notifyAll(); }
236	>	do {} while ((s = status) >= 0 &&
237	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
238	>	synchronized (this) { notifyAll(); }
239		}
240
241		/**
242	<	* Sets status to indicate normal completion
242	>	* Sets status to indicate normal completion.
243		*/
244		final void setNormalCompletion() {
245		// Try typical fast case -- single CAS, no signal, not already done.
246		// Manually expand casStatus to improve chances of inlining it
247	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
247	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
248		setCompletion(NORMAL);
249		}
250
251		// internal waiting and notification
252
253		/**
254	<	* Performs the actual monitor wait for awaitDone
254	>	* Performs the actual monitor wait for awaitDone.
255		*/
256		private void doAwaitDone() {
257		// Minimize lock bias and in/de-flation effects by maximizing
258		// chances of waiting inside sync
259		try {
260		while (status >= 0)
261	<	synchronized(this) { if (status >= 0) wait(); }
261	>	synchronized (this) { if (status >= 0) wait(); }
262		} catch (InterruptedException ie) {
263		onInterruptedWait();
264		}
265		}
266
267		/**
268	<	* Performs the actual monitor wait for awaitDone
268	>	* Performs the actual timed monitor wait for awaitDone.
269		*/
270		private void doAwaitDone(long startTime, long nanos) {
271	<	synchronized(this) {
271	>	synchronized (this) {
272		try {
273		while (status >= 0) {
274	<	long nt = nanos - System.nanoTime() - startTime;
274	>	long nt = nanos - (System.nanoTime() - startTime);
275		if (nt <= 0)
276		break;
277	<	wait(nt / 1000000, (int)(nt % 1000000));
277	>	wait(nt / 1000000, (int) (nt % 1000000));
278		}
279		} catch (InterruptedException ie) {
280		onInterruptedWait();
#	Line 255 | Line 287 | public abstract class ForkJoinTask<V> im
287		/**
288		* Sets status to indicate there is joiner, then waits for join,
289		* surrounded with pool notifications.
290	+	*
291		* @return status upon exit
292		*/
293	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
294	<	ForkJoinPool pool = w == null? null : w.pool;
293	>	private int awaitDone(ForkJoinWorkerThread w,
294	>	boolean maintainParallelism) {
295	>	ForkJoinPool pool = (w == null) ? null : w.pool;
296		int s;
297		while ((s = status) >= 0) {
298	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
298	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
299		if (pool == null || !pool.preJoin(this, maintainParallelism))
300		doAwaitDone();
301		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 308 | public abstract class ForkJoinTask<V> im
308
309		/**
310		* Timed version of awaitDone
311	+	*
312		* @return status upon exit
313		*/
314		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
315	<	ForkJoinPool pool = w == null? null : w.pool;
315	>	ForkJoinPool pool = (w == null) ? null : w.pool;
316		int s;
317		while ((s = status) >= 0) {
318	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
318	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
319		long startTime = System.nanoTime();
320		if (pool == null || !pool.preJoin(this, false))
321		doAwaitDone(startTime, nanos);
#	Line 297 | Line 332 | public abstract class ForkJoinTask<V> im
332		}
333
334		/**
335	<	* Notify pool that thread is unblocked. Called by signalled
335	>	* Notifies pool that thread is unblocked. Called by signalled
336		* threads when woken by non-FJ threads (which is atypical).
337		*/
338		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
339		int s;
340	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
340	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
341		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
342		pool.updateRunningCount(s);
343		}
344
345		/**
346	<	* Notify pool to adjust counts on cancelled or timed out wait
346	>	* Notifies pool to adjust counts on cancelled or timed out wait.
347		*/
348		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
349		if (pool != null) {
#	Line 323 | Line 358 | public abstract class ForkJoinTask<V> im
358		}
359
360		/**
361	<	* Handle interruptions during waits.
361	>	* Handles interruptions during waits.
362		*/
363		private void onInterruptedWait() {
364		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 377 | public abstract class ForkJoinTask<V> im
377		}
378
379		/**
380	<	* Throws the exception associated with status s;
380	>	* Throws the exception associated with status s.
381	>	*
382		* @throws the exception
383		*/
384		private void reportException(int s) {
#	Line 355 | Line 391 | public abstract class ForkJoinTask<V> im
391		}
392
393		/**
394	<	* Returns result or throws exception using j.u.c.Future conventions
395	<	* Only call when isDone known to be true.
394	>	* Returns result or throws exception using j.u.c.Future conventions.
395	>	* Only call when {@code isDone} known to be true.
396		*/
397		private V reportFutureResult()
398		throws ExecutionException, InterruptedException {
399	+	if (Thread.interrupted())
400	+	throw new InterruptedException();
401		int s = status & COMPLETION_MASK;
402		if (s < NORMAL) {
403		Throwable ex;
#	Line 367 | Line 405 | public abstract class ForkJoinTask<V> im
405		throw new CancellationException();
406		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
407		throw new ExecutionException(ex);
370	–	if (Thread.interrupted())
371	–	throw new InterruptedException();
408		}
409		return getRawResult();
410		}
411
412		/**
413		* Returns result or throws exception using j.u.c.Future conventions
414	<	* with timeouts
414	>	* with timeouts.
415		*/
416		private V reportTimedFutureResult()
417		throws InterruptedException, ExecutionException, TimeoutException {
418	+	if (Thread.interrupted())
419	+	throw new InterruptedException();
420		Throwable ex;
421		int s = status & COMPLETION_MASK;
422		if (s == NORMAL)
#	Line 387 | Line 425 | public abstract class ForkJoinTask<V> im
425		throw new CancellationException();
426		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427		throw new ExecutionException(ex);
390	–	if (Thread.interrupted())
391	–	throw new InterruptedException();
428		throw new TimeoutException();
429		}
430
#	Line 396 | Line 432 | public abstract class ForkJoinTask<V> im
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 414 | 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 430 | 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 447 | 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 cancelIgnoringExceptions() {
491		try {
492		cancel(false);
493	<	} catch(Throwable ignore) {
493	>	} catch (Throwable ignore) {
494		}
495		}
496
#	Line 464 | Line 502 | public abstract class ForkJoinTask<V> im
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
505	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
506		}
507
508		// public methods
#	Line 472 | Line 510 | public abstract class ForkJoinTask<V> im
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 ForkJoinTask
515	<	* computations. Attempts to invoke in other contexts result in
516	<	* exceptions or errors possibly 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 <code>get</code> in that abnormal
532	<	* completion results in RuntimeExceptions or Errors, not
533	<	* ExecutionExceptions.
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 498 | Line 543 | public abstract class ForkJoinTask<V> im
543
544		/**
545		* Commences performing this task, awaits its completion if
546	<	* necessary, and return its result.
547	<	* @throws Throwable (a RuntimeException, Error, or unchecked
548	<	* exception) if the underlying computation did so.
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 511 | Line 556 | public abstract class ForkJoinTask<V> im
556		}
557
558		/**
559	<	* Forks both tasks, returning when <code>isDone</code> holds for
560	<	* both of them or an exception is encountered. This method may be
561	<	* invoked only from within ForkJoinTask computations. Attempts to
562	<	* invoke in other contexts result in exceptions or errors
563	<	* possibly including ClassCastException.
564	<	* @param t1 one task
565	<	* @param t2 the other task
566	<	* @throws NullPointerException if t1 or t2 are null
567	<	* @throws RuntimeException or Error if either task did so.
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 more than one task
562	>	* encounters an exception, then this method throws any one of
563	>	* these exceptions.  The individual status of each task may be
564	>	* checked using {@link #getException()} and related methods.
565	>	*
566	>	* <p>This method may be invoked only from within {@code
567	>	* ForkJoinTask} computations (as may be determined using method
568	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
569	>	* result in exceptions or errors, possibly including {@code
570	>	* ClassCastException}.
571	>	*
572	>	* @param t1 the first task
573	>	* @param t2 the second task
574	>	* @throws NullPointerException if any task is null
575		*/
576	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
576	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
577		t2.fork();
578		t1.invoke();
579		t2.join();
580		}
581
582		/**
583	<	* Forks the given tasks, returning when <code>isDone</code> holds
584	<	* for all of them. If any task encounters an exception, others
585	<	* may be cancelled.  This method may be invoked only from within
586	<	* ForkJoinTask computations. Attempts to invoke in other contexts
587	<	* result in exceptions or errors possibly including ClassCastException.
588	<	* @param tasks the array of tasks
589	<	* @throws NullPointerException if tasks or any element are null.
590	<	* @throws RuntimeException or Error if any task did so.
583	>	* Forks the given tasks, returning when {@code isDone} holds for
584	>	* each task or an (unchecked) exception is encountered, in which
585	>	* case the exception is rethrown. If any task encounters an
586	>	* exception, others may be, but are not guaranteed to be,
587	>	* cancelled.  If more than one task encounters an exception, then
588	>	* this method throws any one of these exceptions.  The individual
589	>	* status of each task may be checked using {@link #getException()}
590	>	* and related methods.
591	>	*
592	>	* <p>This method may be invoked only from within {@code
593	>	* ForkJoinTask} computations (as may be determined using method
594	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
595	>	* result in exceptions or errors, possibly including {@code
596	>	* ClassCastException}.
597	>	*
598	>	* @param tasks the tasks
599	>	* @throws NullPointerException if any task is null
600		*/
601		public static void invokeAll(ForkJoinTask<?>... tasks) {
602		Throwable ex = null;
#	Line 571 | Line 632 | public abstract class ForkJoinTask<V> im
632		}
633
634		/**
635	<	* Forks all tasks in the collection, returning when
636	<	* <code>isDone</code> holds for all of them. If any task
637	<	* encounters an exception, others may be cancelled.  This method
638	<	* may be invoked only from within ForkJoinTask
639	<	* computations. Attempts to invoke in other contexts resul!t in
640	<	* exceptions or errors possibly including ClassCastException.
635	>	* Forks all tasks in the specified collection, returning when
636	>	* {@code isDone} holds for each task or an (unchecked) exception
637	>	* is encountered.  If any task encounters an exception, others
638	>	* may be, but are not guaranteed to be, cancelled.  If more than
639	>	* one task encounters an exception, then this method throws any
640	>	* one of these exceptions.  The individual status of each task
641	>	* may be checked using {@link #getException()} and related
642	>	* methods.  The behavior of this operation is undefined if the
643	>	* specified collection is modified while the operation is in
644	>	* progress.
645	>	*
646	>	* <p>This method may be invoked only from within {@code
647	>	* ForkJoinTask} computations (as may be determined using method
648	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
649	>	* result in exceptions or errors, possibly including {@code
650	>	* ClassCastException}.
651	>	*
652		* @param tasks the collection of tasks
653	<	* @throws NullPointerException if tasks or any element are null.
654	<	* @throws RuntimeException or Error if any task did so.
653	>	* @return the tasks argument, to simplify usage
654	>	* @throws NullPointerException if tasks or any element are null
655		*/
656	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
657	<	if (!(tasks instanceof List)) {
658	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
659	<	return;
656	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
657	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
658	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
659	>	return tasks;
660		}
661	+	@SuppressWarnings("unchecked")
662		List<? extends ForkJoinTask<?>> ts =
663	<	(List<? extends ForkJoinTask<?>>)tasks;
663	>	(List<? extends ForkJoinTask<?>>) tasks;
664		Throwable ex = null;
665		int last = ts.size() - 1;
666		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 691 | public abstract class ForkJoinTask<V> im
691		}
692		if (ex != null)
693		rethrowException(ex);
694	+	return tasks;
695		}
696
697		/**
698	<	* Returns true if the computation performed by this task has
699	<	* completed (or has been cancelled).
700	<	* @return true if this computation has completed
701	<	*/
702	<	public final boolean isDone() {
703	<	return status < 0;
704	<	}
631	<
632	<	/**
633	<	* Returns true if this task was cancelled.
634	<	* @return true if this task was cancelled
635	<	*/
636	<	public final boolean isCancelled() {
637	<	return (status & COMPLETION_MASK) == CANCELLED;
638	<	}
639	<
640	<	/**
641	<	* Asserts that the results of this task's computation will not be
642	<	* used. If a cancellation occurs before atempting to execute this
643	<	* task, then execution will be suppressed, <code>isCancelled</code>
644	<	* will report true, and <code>join</code> will result in a
645	<	* <code>CancellationException</code> being thrown. Otherwise, when
646	<	* cancellation races with completion, there are no guarantees
647	<	* about whether <code>isCancelled</code> will report true, whether
648	<	* <code>join</code> will return normally or via an exception, or
649	<	* whether these behaviors will remain consistent upon repeated
650	<	* invocation.
698	>	* Attempts to cancel execution of this task. This attempt will
699	>	* fail if the task has already completed, has already been
700	>	* cancelled, or could not be cancelled for some other reason. If
701	>	* successful, and this task has not started when cancel is
702	>	* called, execution of this task is suppressed, {@link
703	>	* #isCancelled} will report true, and {@link #join} will result
704	>	* in a {@code CancellationException} being thrown.
705		*
706		* <p>This method may be overridden in subclasses, but if so, must
707		* still ensure that these minimal properties hold. In particular,
708	<	* the cancel method itself must not throw exceptions.
708	>	* the {@code cancel} method itself must not throw exceptions.
709		*
710	<	* <p> This method is designed to be invoked by <em>other</em>
710	>	* <p>This method is designed to be invoked by <em>other</em>
711		* tasks. To terminate the current task, you can just return or
712		* throw an unchecked exception from its computation method, or
713	<	* invoke <code>completeExceptionally</code>.
713	>	* invoke {@link #completeExceptionally}.
714		*
715		* @param mayInterruptIfRunning this value is ignored in the
716	<	* default implementation because tasks are not in general
717	<	* cancelled via interruption.
716	>	* default implementation because tasks are not
717	>	* cancelled via interruption
718		*
719	<	* @return true if this task is now cancelled
719	>	* @return {@code true} if this task is now cancelled
720		*/
721		public boolean cancel(boolean mayInterruptIfRunning) {
722		setCompletion(CANCELLED);
#	Line 670 | Line 724 | public abstract class ForkJoinTask<V> im
724		}
725
726		/**
727	<	* Returns true if this task threw an exception or was cancelled
728	<	* @return true if this task threw an exception or was cancelled
727	>	* Returns {@code true} if the computation performed by this task
728	>	* has completed (or has been cancelled).
729	>	*
730	>	* @return {@code true} if this computation has completed
731	>	*/
732	>	public final boolean isDone() {
733	>	return status < 0;
734	>	}
735	>
736	>	/**
737	>	* Returns {@code true} if this task was cancelled.
738	>	*
739	>	* @return {@code true} if this task was cancelled
740	>	*/
741	>	public final boolean isCancelled() {
742	>	return (status & COMPLETION_MASK) == CANCELLED;
743	>	}
744	>
745	>	/**
746	>	* Returns {@code true} if this task threw an exception or was cancelled.
747	>	*
748	>	* @return {@code true} if this task threw an exception or was cancelled
749		*/
750		public final boolean isCompletedAbnormally() {
751		return (status & COMPLETION_MASK) < NORMAL;
752		}
753
754		/**
755	+	* Returns {@code true} if this task completed without throwing an
756	+	* exception and was not cancelled.
757	+	*
758	+	* @return {@code true} if this task completed without throwing an
759	+	* exception and was not cancelled
760	+	*/
761	+	public final boolean isCompletedNormally() {
762	+	return (status & COMPLETION_MASK) == NORMAL;
763	+	}
764	+
765	+	/**
766	+	* Returns {@code true} if this task threw an exception.
767	+	*
768	+	* @return {@code true} if this task threw an exception
769	+	*/
770	+	public final boolean isCompletedExceptionally() {
771	+	return (status & COMPLETION_MASK) == EXCEPTIONAL;
772	+	}
773	+
774	+	/**
775		* Returns the exception thrown by the base computation, or a
776	<	* CancellationException if cancelled, or null if none or if the
777	<	* method has not yet completed.
778	<	* @return the exception, or null if none
776	>	* {@code CancellationException} if cancelled, or {@code null} if
777	>	* none or if the method has not yet completed.
778	>	*
779	>	* @return the exception, or {@code null} if none
780		*/
781		public final Throwable getException() {
782		int s = status & COMPLETION_MASK;
#	Line 695 | Line 790 | public abstract class ForkJoinTask<V> im
790		/**
791		* Completes this task abnormally, and if not already aborted or
792		* cancelled, causes it to throw the given exception upon
793	<	* <code>join</code> and related operations. This method may be used
793	>	* {@code join} and related operations. This method may be used
794		* to induce exceptions in asynchronous tasks, or to force
795		* completion of tasks that would not otherwise complete.  Its use
796	<	* in other situations is likely to be wrong.  This method is
797	<	* overridable, but overridden versions must invoke <code>super</code>
796	>	* in other situations is discouraged.  This method is
797	>	* overridable, but overridden versions must invoke {@code super}
798		* implementation to maintain guarantees.
799		*
800		* @param ex the exception to throw. If this exception is
#	Line 708 | Line 803 | public abstract class ForkJoinTask<V> im
803		*/
804		public void completeExceptionally(Throwable ex) {
805		setDoneExceptionally((ex instanceof RuntimeException) ||
806	<	(ex instanceof Error)? ex :
806	>	(ex instanceof Error) ? ex :
807		new RuntimeException(ex));
808		}
809
810		/**
811		* Completes this task, and if not already aborted or cancelled,
812	<	* returning a <code>null</code> result upon <code>join</code> and related
812	>	* returning a {@code null} result upon {@code join} and related
813		* operations. This method may be used to provide results for
814		* asynchronous tasks, or to provide alternative handling for
815		* tasks that would not otherwise complete normally. Its use in
816	<	* other situations is likely to be wrong. This method is
817	<	* overridable, but overridden versions must invoke <code>super</code>
816	>	* other situations is discouraged. This method is
817	>	* overridable, but overridden versions must invoke {@code super}
818		* implementation to maintain guarantees.
819		*
820	<	* @param value the result value for this task.
820	>	* @param value the result value for this task
821		*/
822		public void complete(V value) {
823		try {
824		setRawResult(value);
825	<	} catch(Throwable rex) {
825	>	} catch (Throwable rex) {
826		setDoneExceptionally(rex);
827		return;
828		}
#	Line 743 | Line 838 | public abstract class ForkJoinTask<V> im
838
839		public final V get(long timeout, TimeUnit unit)
840		throws InterruptedException, ExecutionException, TimeoutException {
841	+	long nanos = unit.toNanos(timeout);
842		ForkJoinWorkerThread w = getWorker();
843		if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
844	<	awaitDone(w, unit.toNanos(timeout));
844	>	awaitDone(w, nanos);
845		return reportTimedFutureResult();
846		}
847
848		/**
849		* Possibly executes other tasks until this task is ready, then
850		* returns the result of the computation.  This method may be more
851	<	* efficient than <code>join</code>, but is only applicable when
852	<	* there are no potemtial dependencies between continuation of the
851	>	* efficient than {@code join}, but is only applicable when
852	>	* there are no potential dependencies between continuation of the
853		* current task and that of any other task that might be executed
854		* while helping. (This usually holds for pure divide-and-conquer
855	<	* tasks). This method may be invoked only from within
856	<	* ForkJoinTask computations. Attempts to invoke in other contexts
857	<	* resul!t in exceptions or errors possibly including ClassCastException.
855	>	* tasks).
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		* @return the computed result
864		*/
865		public final V helpJoin() {
866	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
866	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
867		if (status < 0 || !w.unpushTask(this) || !tryExec())
868		reportException(busyJoin(w));
869		return getRawResult();
#	Line 770 | Line 871 | public abstract class ForkJoinTask<V> im
871
872		/**
873		* Possibly executes other tasks until this task is ready.  This
874	<	* method may be invoked only from within ForkJoinTask
875	<	* computations. Attempts to invoke in other contexts resul!t in
876	<	* exceptions or errors possibly including ClassCastException.
874	>	* method may be useful when processing collections of tasks when
875	>	* some have been cancelled or otherwise known to have aborted.
876	>	*
877	>	* <p>This method may be invoked only from within {@code
878	>	* ForkJoinTask} computations (as may be determined using method
879	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
880	>	* result in exceptions or errors, possibly including {@code
881	>	* ClassCastException}.
882		*/
883		public final void quietlyHelpJoin() {
884		if (status >= 0) {
885		ForkJoinWorkerThread w =
886	<	(ForkJoinWorkerThread)(Thread.currentThread());
886	>	(ForkJoinWorkerThread) Thread.currentThread();
887		if (!w.unpushTask(this) || !tryQuietlyInvoke())
888		busyJoin(w);
889		}
#	Line 811 | Line 917 | public abstract class ForkJoinTask<V> im
917
918		/**
919		* Possibly executes tasks until the pool hosting the current task
920	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
921	<	* designs in which many tasks are forked, but none are explicitly
922	<	* joined, instead executing them until all are processed.
920	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
921	>	* be of use in designs in which many tasks are forked, but none
922	>	* are explicitly joined, instead executing them until all are
923	>	* processed.
924	>	*
925	>	* <p>This method may be invoked only from within {@code
926	>	* ForkJoinTask} computations (as may be determined using method
927	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
928	>	* result in exceptions or errors, possibly including {@code
929	>	* ClassCastException}.
930		*/
931		public static void helpQuiesce() {
932	<	((ForkJoinWorkerThread)(Thread.currentThread())).
933	<	helpQuiescePool();
932	>	((ForkJoinWorkerThread) Thread.currentThread())
933	>	.helpQuiescePool();
934		}
935
936		/**
937		* Resets the internal bookkeeping state of this task, allowing a
938	<	* subsequent <code>fork</code>. This method allows repeated reuse of
938	>	* subsequent {@code fork}. This method allows repeated reuse of
939		* this task, but only if reuse occurs when this task has either
940		* never been forked, or has been forked, then completed and all
941		* outstanding joins of this task have also completed. Effects
942	<	* under any other usage conditions are not guaranteed, and are
943	<	* almost surely wrong. This method may be useful when executing
942	>	* under any other usage conditions are not guaranteed.
943	>	* This method may be useful when executing
944		* pre-constructed trees of subtasks in loops.
945		*/
946		public void reinitialize() {
#	Line 838 | Line 951 | public abstract class ForkJoinTask<V> im
951
952		/**
953		* Returns the pool hosting the current task execution, or null
954	<	* if this task is executing outside of any pool.
955	<	* @return the pool, or null if none.
954	>	* if this task is executing outside of any ForkJoinPool.
955	>	*
956	>	* @see #inForkJoinPool
957	>	* @return the pool, or {@code null} if none
958		*/
959		public static ForkJoinPool getPool() {
960		Thread t = Thread.currentThread();
961	<	return ((t instanceof ForkJoinWorkerThread)?
962	<	((ForkJoinWorkerThread)t).pool : null);
961	>	return (t instanceof ForkJoinWorkerThread) ?
962	>	((ForkJoinWorkerThread) t).pool : null;
963	>	}
964	>
965	>	/**
966	>	* Returns {@code true} if the current thread is executing as a
967	>	* ForkJoinPool computation.
968	>	*
969	>	* @return {@code true} if the current thread is executing as a
970	>	* ForkJoinPool computation, or false otherwise
971	>	*/
972	>	public static boolean inForkJoinPool() {
973	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
974		}
975
976		/**
#	Line 853 | Line 979 | public abstract class ForkJoinTask<V> im
979		* by the current thread, and has not commenced executing in
980		* another thread.  This method may be useful when arranging
981		* alternative local processing of tasks that could have been, but
982	<	* were not, stolen. This method may be invoked only from within
983	<	* ForkJoinTask computations. Attempts to invoke in other contexts
984	<	* result in exceptions or errors possibly including ClassCastException.
985	<	* @return true if unforked
982	>	* were not, stolen.
983	>	*
984	>	* <p>This method may be invoked only from within {@code
985	>	* ForkJoinTask} computations (as may be determined using method
986	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
987	>	* result in exceptions or errors, possibly including {@code
988	>	* ClassCastException}.
989	>	*
990	>	* @return {@code true} if unforked
991		*/
992		public boolean tryUnfork() {
993	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
993	>	return ((ForkJoinWorkerThread) Thread.currentThread())
994	>	.unpushTask(this);
995		}
996
997		/**
#	Line 867 | Line 999 | public abstract class ForkJoinTask<V> im
999		* forked by the current worker thread but not yet executed. This
1000		* value may be useful for heuristic decisions about whether to
1001		* fork other tasks.
1002	+	*
1003	+	* <p>This method may be invoked only from within {@code
1004	+	* ForkJoinTask} computations (as may be determined using method
1005	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1006	+	* result in exceptions or errors, possibly including {@code
1007	+	* ClassCastException}.
1008	+	*
1009		* @return the number of tasks
1010		*/
1011		public static int getQueuedTaskCount() {
1012	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1013	<	getQueueSize();
1012	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1013	>	.getQueueSize();
1014		}
1015
1016		/**
1017	<	* Returns a estimate of how many more locally queued tasks are
1017	>	* Returns an estimate of how many more locally queued tasks are
1018		* held by the current worker thread than there are other worker
1019		* threads that might steal them.  This value may be useful for
1020		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 1022 | public abstract class ForkJoinTask<V> im
1022		* aim to maintain a small constant surplus (for example, 3) of
1023		* tasks, and to process computations locally if this threshold is
1024		* exceeded.
1025	+	*
1026	+	* <p>This method may be invoked only from within {@code
1027	+	* ForkJoinTask} computations (as may be determined using method
1028	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1029	+	* result in exceptions or errors, possibly including {@code
1030	+	* ClassCastException}.
1031	+	*
1032		* @return the surplus number of tasks, which may be negative
1033		*/
1034		public static int getSurplusQueuedTaskCount() {
1035	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
1035	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1036		.getEstimatedSurplusTaskCount();
1037		}
1038
1039		// Extension methods
1040
1041		/**
1042	<	* Returns the result that would be returned by <code>join</code>,
1043	<	* even if this task completed abnormally, or null if this task is
1044	<	* not known to have been completed.  This method is designed to
1045	<	* aid debugging, as well as to support extensions. Its use in any
1046	<	* other context is discouraged.
1042	>	* Returns the result that would be returned by {@link #join}, even
1043	>	* if this task completed abnormally, or {@code null} if this task
1044	>	* is not known to have been completed.  This method is designed
1045	>	* to aid debugging, as well as to support extensions. Its use in
1046	>	* any other context is discouraged.
1047		*
1048	<	* @return the result, or null if not completed.
1048	>	* @return the result, or {@code null} if not completed
1049		*/
1050		public abstract V getRawResult();
1051
#	Line 918 | Line 1064 | public abstract class ForkJoinTask<V> im
1064		* called otherwise. The return value controls whether this task
1065		* is considered to be done normally. It may return false in
1066		* asynchronous actions that require explicit invocations of
1067	<	* <code>complete</code> to become joinable. It may throw exceptions
1068	<	* to indicate abnormal exit.
1069	<	* @return true if completed normally
1070	<	* @throws Error or RuntimeException if encountered during computation
1067	>	* {@link #complete} to become joinable. It may also throw an
1068	>	* (unchecked) exception to indicate abnormal exit.
1069	>	*
1070	>	* @return {@code true} if completed normally
1071		*/
1072		protected abstract boolean exec();
1073
1074		/**
1075	<	* Returns, but does not unschedule or execute, the task most
1076	<	* recently forked by the current thread but not yet executed, if
1077	<	* one is available. There is no guarantee that this task will
1078	<	* actually be polled or executed next.
1079	<	* This method is designed primarily to support extensions,
1080	<	* and is unlikely to be useful otherwise.
1081	<	* This method may be invoked only from within
1082	<	* ForkJoinTask computations. Attempts to invoke in other contexts
937	<	* result in exceptions or errors possibly including ClassCastException.
1075	>	* Returns, but does not unschedule or execute, a task queued by
1076	>	* the current thread but not yet executed, if one is immediately
1077	>	* available. There is no guarantee that this task will actually
1078	>	* be polled or executed next. Conversely, this method may return
1079	>	* null even if a task exists but cannot be accessed without
1080	>	* contention with other threads.  This method is designed
1081	>	* primarily to support extensions, and is unlikely to be useful
1082	>	* otherwise.
1083		*
1084	<	* @return the next task, or null if none are available
1084	>	* <p>This method may be invoked only from within {@code
1085	>	* ForkJoinTask} computations (as may be determined using method
1086	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1087	>	* result in exceptions or errors, possibly including {@code
1088	>	* ClassCastException}.
1089	>	*
1090	>	* @return the next task, or {@code null} if none are available
1091		*/
1092		protected static ForkJoinTask<?> peekNextLocalTask() {
1093	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
1093	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1094	>	.peekTask();
1095		}
1096
1097		/**
1098	<	* Unschedules and returns, without executing, the task most
1099	<	* recently forked by the current thread but not yet executed.
1100	<	* This method is designed primarily to support extensions,
1101	<	* and is unlikely to be useful otherwise.
1102	<	* This method may be invoked only from within
1103	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1104	<	* result in exceptions or errors possibly including ClassCastException.
1098	>	* Unschedules and returns, without executing, the next task
1099	>	* queued by the current thread but not yet executed.  This method
1100	>	* is designed primarily to support extensions, and is unlikely to
1101	>	* be useful otherwise.
1102	>	*
1103	>	* <p>This method may be invoked only from within {@code
1104	>	* ForkJoinTask} computations (as may be determined using method
1105	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1106	>	* result in exceptions or errors, possibly including {@code
1107	>	* ClassCastException}.
1108		*
1109	<	* @return the next task, or null if none are available
1109	>	* @return the next task, or {@code null} if none are available
1110		*/
1111		protected static ForkJoinTask<?> pollNextLocalTask() {
1112	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask();
1112	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1113	>	.pollLocalTask();
1114		}
1115
1116		/**
1117	<	* Unschedules and returns, without executing, the task most
1118	<	* recently forked by the current thread but not yet executed, if
1119	<	* one is available, or if not available, a task that was forked
1120	<	* by some other thread, if available. Availability may be
1121	<	* transient, so a <code>null</code> result does not necessarily
1122	<	* imply quiecence of the pool this task is operating in.
1123	<	* This method is designed primarily to support extensions,
1124	<	* and is unlikely to be useful otherwise.
969	<	* This method may be invoked only from within
970	<	* ForkJoinTask computations. Attempts to invoke in other contexts
971	<	* result in exceptions or errors possibly including ClassCastException.
1117	>	* Unschedules and returns, without executing, the next task
1118	>	* queued by the current thread but not yet executed, if one is
1119	>	* available, or if not available, a task that was forked by some
1120	>	* other thread, if available. Availability may be transient, so a
1121	>	* {@code null} result does not necessarily imply quiescence
1122	>	* of the pool this task is operating in.  This method is designed
1123	>	* primarily to support extensions, and is unlikely to be useful
1124	>	* otherwise.
1125		*
1126	<	* @return a task, or null if none are available
1126	>	* <p>This method may be invoked only from within {@code
1127	>	* ForkJoinTask} computations (as may be determined using method
1128	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1129	>	* result in exceptions or errors, possibly including {@code
1130	>	* ClassCastException}.
1131	>	*
1132	>	* @return a task, or {@code null} if none are available
1133		*/
1134		protected static ForkJoinTask<?> pollTask() {
1135	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1136	<	pollTask();
1135	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1136	>	.pollTask();
1137	>	}
1138	>
1139	>	/**
1140	>	* Adaptor for Runnables. This implements RunnableFuture
1141	>	* to be compliant with AbstractExecutorService constraints
1142	>	* when used in ForkJoinPool.
1143	>	*/
1144	>	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1145	>	implements RunnableFuture<T> {
1146	>	final Runnable runnable;
1147	>	final T resultOnCompletion;
1148	>	T result;
1149	>	AdaptedRunnable(Runnable runnable, T result) {
1150	>	if (runnable == null) throw new NullPointerException();
1151	>	this.runnable = runnable;
1152	>	this.resultOnCompletion = result;
1153	>	}
1154	>	public T getRawResult() { return result; }
1155	>	public void setRawResult(T v) { result = v; }
1156	>	public boolean exec() {
1157	>	runnable.run();
1158	>	result = resultOnCompletion;
1159	>	return true;
1160	>	}
1161	>	public void run() { invoke(); }
1162	>	private static final long serialVersionUID = 5232453952276885070L;
1163	>	}
1164	>
1165	>	/**
1166	>	* Adaptor for Callables
1167	>	*/
1168	>	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1169	>	implements RunnableFuture<T> {
1170	>	final Callable<? extends T> callable;
1171	>	T result;
1172	>	AdaptedCallable(Callable<? extends T> callable) {
1173	>	if (callable == null) throw new NullPointerException();
1174	>	this.callable = callable;
1175	>	}
1176	>	public T getRawResult() { return result; }
1177	>	public void setRawResult(T v) { result = v; }
1178	>	public boolean exec() {
1179	>	try {
1180	>	result = callable.call();
1181	>	return true;
1182	>	} catch (Error err) {
1183	>	throw err;
1184	>	} catch (RuntimeException rex) {
1185	>	throw rex;
1186	>	} catch (Exception ex) {
1187	>	throw new RuntimeException(ex);
1188	>	}
1189	>	}
1190	>	public void run() { invoke(); }
1191	>	private static final long serialVersionUID = 2838392045355241008L;
1192	>	}
1193	>
1194	>	/**
1195	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1196	>	* method of the given {@code Runnable} as its action, and returns
1197	>	* a null result upon {@link #join}.
1198	>	*
1199	>	* @param runnable the runnable action
1200	>	* @return the task
1201	>	*/
1202	>	public static ForkJoinTask<?> adapt(Runnable runnable) {
1203	>	return new AdaptedRunnable<Void>(runnable, null);
1204	>	}
1205	>
1206	>	/**
1207	>	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1208	>	* method of the given {@code Runnable} as its action, and returns
1209	>	* the given result upon {@link #join}.
1210	>	*
1211	>	* @param runnable the runnable action
1212	>	* @param result the result upon completion
1213	>	* @return the task
1214	>	*/
1215	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1216	>	return new AdaptedRunnable<T>(runnable, result);
1217	>	}
1218	>
1219	>	/**
1220	>	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1221	>	* method of the given {@code Callable} as its action, and returns
1222	>	* its result upon {@link #join}, translating any checked exceptions
1223	>	* encountered into {@code RuntimeException}.
1224	>	*
1225	>	* @param callable the callable action
1226	>	* @return the task
1227	>	*/
1228	>	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1229	>	return new AdaptedCallable<T>(callable);
1230		}
1231
1232		// Serialization support
#	Line 985 | Line 1237 | public abstract class ForkJoinTask<V> im
1237		* Save the state to a stream.
1238		*
1239		* @serialData the current run status and the exception thrown
1240	<	* during execution, or null if none.
1240	>	* during execution, or {@code null} if none
1241		* @param s the stream
1242		*/
1243		private void writeObject(java.io.ObjectOutputStream s)
#	Line 996 | Line 1248 | public abstract class ForkJoinTask<V> im
1248
1249		/**
1250		* Reconstitute the instance from a stream.
1251	+	*
1252		* @param s the stream
1253		*/
1254		private void readObject(java.io.ObjectInputStream s)
#	Line 1005 | Line 1258 | public abstract class ForkJoinTask<V> im
1258		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1259		Object ex = s.readObject();
1260		if (ex != null)
1261	<	setDoneExceptionally((Throwable)ex);
1261	>	setDoneExceptionally((Throwable) ex);
1262		}
1263
1264	<	// Temporary Unsafe mechanics for preliminary release
1265	<	private static Unsafe getUnsafe() throws Throwable {
1264	>	// Unsafe mechanics
1265	>
1266	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1267	>	private static final long statusOffset =
1268	>	objectFieldOffset("status", ForkJoinTask.class);
1269	>
1270	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1271		try {
1272	<	return Unsafe.getUnsafe();
1272	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1273	>	} catch (NoSuchFieldException e) {
1274	>	// Convert Exception to corresponding Error
1275	>	NoSuchFieldError error = new NoSuchFieldError(field);
1276	>	error.initCause(e);
1277	>	throw error;
1278	>	}
1279	>	}
1280	>
1281	>	/**
1282	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1283	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1284	>	* into a jdk.
1285	>	*
1286	>	* @return a sun.misc.Unsafe
1287	>	*/
1288	>	private static sun.misc.Unsafe getUnsafe() {
1289	>	try {
1290	>	return sun.misc.Unsafe.getUnsafe();
1291		} catch (SecurityException se) {
1292		try {
1293		return java.security.AccessController.doPrivileged
1294	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1295	<	public Unsafe run() throws Exception {
1296	<	return getUnsafePrivileged();
1294	>	(new java.security
1295	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1296	>	public sun.misc.Unsafe run() throws Exception {
1297	>	java.lang.reflect.Field f = sun.misc
1298	>	.Unsafe.class.getDeclaredField("theUnsafe");
1299	>	f.setAccessible(true);
1300	>	return (sun.misc.Unsafe) f.get(null);
1301		}});
1302		} catch (java.security.PrivilegedActionException e) {
1303	<	throw e.getCause();
1303	>	throw new RuntimeException("Could not initialize intrinsics",
1304	>	e.getCause());
1305		}
1306		}
1307		}
1027	–
1028	–	private static Unsafe getUnsafePrivileged()
1029	–	throws NoSuchFieldException, IllegalAccessException {
1030	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1031	–	f.setAccessible(true);
1032	–	return (Unsafe) f.get(null);
1033	–	}
1034	–
1035	–	private static long fieldOffset(String fieldName)
1036	–	throws NoSuchFieldException {
1037	–	return _unsafe.objectFieldOffset
1038	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1039	–	}
1040	–
1041	–	static final Unsafe _unsafe;
1042	–	static final long statusOffset;
1043	–
1044	–	static {
1045	–	try {
1046	–	_unsafe = getUnsafe();
1047	–	statusOffset = fieldOffset("status");
1048	–	} catch (Throwable e) {
1049	–	throw new RuntimeException("Could not initialize intrinsics", e);
1050	–	}
1051	–	}
1052	–
1308		}

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