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Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.20 by jsr166, Sun Jul 26 05:55:34 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.Map;
16	>	import java.util.WeakHashMap;
17
18		/**
19	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
20	<	* ForkJoinTask is a thread-like entity that is much lighter weight
21	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
22	<	* hosted by a small number of actual threads in a ForkJoinPool,
23	<	* at the price of some usage limitations.
19	>	* Abstract base class for tasks that run within a {@link
20	>	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
21	>	* lighter weight than a normal thread.  Huge numbers of tasks and
22	>	* subtasks may be hosted by a small number of actual threads in a
23	>	* ForkJoinPool, at the price of some usage limitations.
24		*
25	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
26	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
27	<	* set of restrictions (that are only partially statically
28	<	* enforceable) reflecting their intended use as computational tasks
29	<	* calculating pure functions or operating on purely isolated objects.
30	<	* The primary coordination mechanisms supported for ForkJoinTasks are
31	<	* <tt>fork</tt>, that arranges asynchronous execution, and
32	<	* <tt>join</tt>, that doesn't proceed until the task's result has
33	<	* been computed. (Cancellation is also supported).  The computation
34	<	* defined in the <tt>compute</tt> method should avoid
35	<	* <tt>synchronized</tt> methods or blocks, and should minimize
36	<	* blocking synchronization apart from joining other tasks or using
25	>	* <p> A "main" ForkJoinTask begins execution when submitted to a
26	>	* {@link ForkJoinPool}. Once started, it will usually in turn start
27	>	* other subtasks.  As indicated by the name of this class, many
28	>	* programs using ForkJoinTasks employ only methods {@code fork}
29	>	* and {@code join}, or derivatives such as
30	>	* {@code invokeAll}.  However, this class also provides a number
31	>	* of other methods that can come into play in advanced usages, as
32	>	* well as extension mechanics that allow support of new forms of
33	>	* fork/join processing.
34	>	*
35	>	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
36	>	* efficiency of ForkJoinTasks stems from a set of restrictions (that
37	>	* are only partially statically enforceable) reflecting their
38	>	* intended use as computational tasks calculating pure functions or
39	>	* operating on purely isolated objects.  The primary coordination
40	>	* mechanisms are {@link #fork}, that arranges asynchronous execution,
41	>	* and {@link #join}, that doesn't proceed until the task's result has
42	>	* been computed.  Computations should avoid {@code synchronized}
43	>	* methods or blocks, and should minimize other blocking
44	>	* synchronization apart from joining other tasks or using
45		* synchronizers such as Phasers that are advertised to cooperate with
46		* fork/join scheduling. Tasks should also not perform blocking IO,
47		* and should ideally access variables that are completely independent
#	Line 38 | Line 49 | import java.lang.reflect.*;
49		* restrictions, for example using shared output streams, may be
50		* tolerable in practice, but frequent use may result in poor
51		* performance, and the potential to indefinitely stall if the number
52	<	* of threads not waiting for external synchronization becomes
53	<	* exhausted. This usage restriction is in part enforced by not
54	<	* permitting checked exceptions such as IOExceptions to be
55	<	* thrown. However, computations may still encounter unchecked
52	>	* of threads not waiting for IO or other external synchronization
53	>	* becomes exhausted. This usage restriction is in part enforced by
54	>	* not permitting checked exceptions such as {@code IOExceptions}
55	>	* to be thrown. However, computations may still encounter unchecked
56		* exceptions, that are rethrown to callers attempting join
57		* them. These exceptions may additionally include
58		* RejectedExecutionExceptions stemming from internal resource
59		* exhaustion such as failure to allocate internal task queues.
60		*
61	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
62	<	* subclassed.  Instead, you subclass one of the abstract classes that
63	<	* support different styles of fork/join processing.  Normally, a
64	<	* concrete ForkJoinTask subclass declares fields comprising its
65	<	* parameters, established in a constructor, and then defines a
66	<	* <tt>compute</tt> method that somehow uses the control methods
67	<	* supplied by this base class. While these methods have
68	<	* <tt>public</tt> access, some of them may only be called from within
69	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
70	<	* result in exceptions or errors including ClassCastException.  The
71	<	* only way to invoke a "main" driver task is to submit it to a
72	<	* ForkJoinPool. Once started, this will usually in turn start other
73	<	* subtasks.
61	>	* <p>The primary method for awaiting completion and extracting
62	>	* results of a task is {@link #join}, but there are several variants:
63	>	* The {@link Future#get} methods support interruptible and/or timed
64	>	* waits for completion and report results using {@code Future}
65	>	* conventions. Method {@link #helpJoin} enables callers to actively
66	>	* execute other tasks while awaiting joins, which is sometimes more
67	>	* efficient but only applies when all subtasks are known to be
68	>	* strictly tree-structured. Method {@link #invoke} is semantically
69	>	* equivalent to {@code fork(); join()} but always attempts to
70	>	* begin execution in the current thread. The "<em>quiet</em>" forms
71	>	* of these methods do not extract results or report exceptions. These
72	>	* may be useful when a set of tasks are being executed, and you need
73	>	* to delay processing of results or exceptions until all complete.
74	>	* Method {@code invokeAll} (available in multiple versions)
75	>	* performs the most common form of parallel invocation: forking a set
76	>	* of tasks and joining them all.
77	>	*
78	>	* <p> The ForkJoinTask class is not usually directly subclassed.
79	>	* Instead, you subclass one of the abstract classes that support a
80	>	* particular style of fork/join processing.  Normally, a concrete
81	>	* ForkJoinTask subclass declares fields comprising its parameters,
82	>	* established in a constructor, and then defines a {@code compute}
83	>	* method that somehow uses the control methods supplied by this base
84	>	* class. While these methods have {@code public} access (to allow
85	>	* instances of different task subclasses to call each others
86	>	* methods), some of them may only be called from within other
87	>	* ForkJoinTasks (as may be determined using method {@link
88	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
89	>	* result in exceptions or errors, possibly including
90	>	* ClassCastException.
91		*
92	<	* <p>Most base support methods are <tt>final</tt> because their
92	>	* <p>Most base support methods are {@code final} because their
93		* implementations are intrinsically tied to the underlying
94		* lightweight task scheduling framework, and so cannot be overridden.
95		* Developers creating new basic styles of fork/join processing should
96	<	* minimally implement protected methods <tt>exec</tt>,
97	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
98	<	* introducing an abstract computational method that can be
99	<	* implemented in its subclasses. To support such extensions,
100	<	* instances of ForkJoinTasks maintain an atomically updated
101	<	* <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.
96	>	* minimally implement {@code protected} methods
97	>	* {@code exec}, {@code setRawResult}, and
98	>	* {@code getRawResult}, while also introducing an abstract
99	>	* computational method that can be implemented in its subclasses,
100	>	* possibly relying on other {@code protected} methods provided
101	>	* by this class.
102		*
103		* <p>ForkJoinTasks should perform relatively small amounts of
104	<	* computations, othewise splitting into smaller tasks. As a very
104	>	* computations, otherwise splitting into smaller tasks. As a very
105		* rough rule of thumb, a task should perform more than 100 and less
106		* than 10000 basic computational steps. If tasks are too big, then
107	<	* parellelism cannot improve throughput. If too small, then memory
107	>	* parallelism cannot improve throughput. If too small, then memory
108		* and internal task maintenance overhead may overwhelm processing.
109		*
110	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
111	<	* be used in extensions such as remote execution frameworks. However,
112	<	* it is in general safe to serialize tasks only before or after, but
110	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
111	>	* to be used in extensions such as remote execution frameworks. It is
112	>	* in general sensible to serialize tasks only before or after, but
113		* not during execution. Serialization is not relied on during
114		* execution itself.
115	+	*
116	+	* @since 1.7
117	+	* @author Doug Lea
118		*/
119		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
120	+
121		/**
122	<	* Status field holding all run status. We pack this into a single
123	<	* int both to minimize footprint overhead and to ensure atomicity
124	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
122	>	* Run control status bits packed into a single int to minimize
123	>	* footprint and to ensure atomicity (via CAS).  Status is
124	>	* initially zero, and takes on nonnegative values until
125		* completed, upon which status holds COMPLETED. CANCELLED, or
126		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
127		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 136 | public abstract class ForkJoinTask<V> im
136		* currently unused. Also value 0x80000000 is available as spare
137		* completion value.
138		*/
139	<	volatile int status; // accessed directy by pool and workers
139	>	volatile int status; // accessed directly by pool and workers
140
141		static final int COMPLETION_MASK      = 0xe0000000;
142		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 149 | public abstract class ForkJoinTask<V> im
149		/**
150		* Table of exceptions thrown by tasks, to enable reporting by
151		* callers. Because exceptions are rare, we don't directly keep
152	<	* them with task objects, but instead us a weak ref table.  Note
152	>	* them with task objects, but instead use a weak ref table.  Note
153		* that cancellation exceptions don't appear in the table, but are
154		* instead recorded as status values.
155	<	* Todo: Use ConcurrentReferenceHashMap
155	>	* TODO: Use ConcurrentReferenceHashMap
156		*/
157		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
158		Collections.synchronizedMap
#	Line 136 | Line 161 | public abstract class ForkJoinTask<V> im
161		// within-package utilities
162
163		/**
164	<	* Get current worker thread, or null if not a worker thread
164	>	* Gets current worker thread, or null if not a worker thread.
165		*/
166		static ForkJoinWorkerThread getWorker() {
167		Thread t = Thread.currentThread();
168	<	return ((t instanceof ForkJoinWorkerThread)?
169	<	(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);
168	>	return ((t instanceof ForkJoinWorkerThread) ?
169	>	(ForkJoinWorkerThread) t : null);
170		}
171
172		final boolean casStatus(int cmp, int val) {
173	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
173	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
174		}
175
176		/**
#	Line 162 | Line 178 | public abstract class ForkJoinTask<V> im
178		*/
179		static void rethrowException(Throwable ex) {
180		if (ex != null)
181	<	_unsafe.throwException(ex);
181	>	UNSAFE.throwException(ex);
182		}
183
184		// Setting completion status
185
186		/**
187	<	* Mark completion and wake up threads waiting to join this task.
187	>	* Marks completion and wakes up threads waiting to join this task.
188	>	*
189		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
190		*/
191		final void setCompletion(int completion) {
192	<	ForkJoinPool pool = getWorkerPool();
192	>	ForkJoinPool pool = getPool();
193		if (pool != null) {
194		int s; // Clear signal bits while setting completion status
195	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
195	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
196
197		if ((s & SIGNAL_MASK) != 0) {
198		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
199		pool.updateRunningCount(s);
200	<	synchronized(this) { notifyAll(); }
200	>	synchronized (this) { notifyAll(); }
201		}
202		}
203		else
#	Line 193 | Line 210 | public abstract class ForkJoinTask<V> im
210		*/
211		private void externallySetCompletion(int completion) {
212		int s;
213	<	do;while ((s = status) >= 0 &&
214	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
215	<	synchronized(this) { notifyAll(); }
213	>	do {} while ((s = status) >= 0 &&
214	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
215	>	synchronized (this) { notifyAll(); }
216		}
217
218		/**
219	<	* Sets status to indicate normal completion
219	>	* Sets status to indicate normal completion.
220		*/
221		final void setNormalCompletion() {
222		// Try typical fast case -- single CAS, no signal, not already done.
223		// Manually expand casStatus to improve chances of inlining it
224	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
224	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
225		setCompletion(NORMAL);
226		}
227
228		// internal waiting and notification
229
230		/**
231	<	* Performs the actual monitor wait for awaitDone
231	>	* Performs the actual monitor wait for awaitDone.
232		*/
233		private void doAwaitDone() {
234		// Minimize lock bias and in/de-flation effects by maximizing
235		// chances of waiting inside sync
236		try {
237		while (status >= 0)
238	<	synchronized(this) { if (status >= 0) wait(); }
238	>	synchronized (this) { if (status >= 0) wait(); }
239		} catch (InterruptedException ie) {
240		onInterruptedWait();
241		}
242		}
243
244		/**
245	<	* Performs the actual monitor wait for awaitDone
245	>	* Performs the actual timed monitor wait for awaitDone.
246		*/
247		private void doAwaitDone(long startTime, long nanos) {
248	<	synchronized(this) {
248	>	synchronized (this) {
249		try {
250		while (status >= 0) {
251		long nt = nanos - System.nanoTime() - startTime;
252		if (nt <= 0)
253		break;
254	<	wait(nt / 1000000, (int)(nt % 1000000));
254	>	wait(nt / 1000000, (int) (nt % 1000000));
255		}
256		} catch (InterruptedException ie) {
257		onInterruptedWait();
#	Line 247 | Line 264 | public abstract class ForkJoinTask<V> im
264		/**
265		* Sets status to indicate there is joiner, then waits for join,
266		* surrounded with pool notifications.
267	+	*
268		* @return status upon exit
269		*/
270	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
271	<	ForkJoinPool pool = w == null? null : w.pool;
270	>	private int awaitDone(ForkJoinWorkerThread w,
271	>	boolean maintainParallelism) {
272	>	ForkJoinPool pool = (w == null) ? null : w.pool;
273		int s;
274		while ((s = status) >= 0) {
275	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
275	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
276		if (pool == null || !pool.preJoin(this, maintainParallelism))
277		doAwaitDone();
278		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 285 | public abstract class ForkJoinTask<V> im
285
286		/**
287		* Timed version of awaitDone
288	+	*
289		* @return status upon exit
290		*/
291	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
292	<	ForkJoinPool pool = w == null? null : w.pool;
291	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
292	>	ForkJoinPool pool = (w == null) ? null : w.pool;
293		int s;
294		while ((s = status) >= 0) {
295	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
295	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
296		long startTime = System.nanoTime();
297		if (pool == null || !pool.preJoin(this, false))
298		doAwaitDone(startTime, nanos);
#	Line 289 | Line 309 | public abstract class ForkJoinTask<V> im
309		}
310
311		/**
312	<	* Notify pool that thread is unblocked. Called by signalled
312	>	* Notifies pool that thread is unblocked. Called by signalled
313		* threads when woken by non-FJ threads (which is atypical).
314		*/
315		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
316		int s;
317	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
317	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
318		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
319		pool.updateRunningCount(s);
320		}
321
322		/**
323	<	* Notify pool to adjust counts on cancelled or timed out wait
323	>	* Notifies pool to adjust counts on cancelled or timed out wait.
324		*/
325		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
326		if (pool != null) {
#	Line 314 | Line 334 | public abstract class ForkJoinTask<V> im
334		}
335		}
336
337	+	/**
338	+	* Handles interruptions during waits.
339	+	*/
340		private void onInterruptedWait() {
341	<	Thread t = Thread.currentThread();
342	<	if (t instanceof ForkJoinWorkerThread) {
343	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
344	<	if (w.isTerminating())
345	<	cancelIgnoreExceptions();
346	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
341	>	ForkJoinWorkerThread w = getWorker();
342	>	if (w == null)
343	>	Thread.currentThread().interrupt(); // re-interrupt
344	>	else if (w.isTerminating())
345	>	cancelIgnoringExceptions();
346	>	// else if FJworker, ignore interrupt
347		}
348
349		// Recording and reporting exceptions
#	Line 337 | Line 354 | public abstract class ForkJoinTask<V> im
354		}
355
356		/**
357	<	* Throws the exception associated with status s;
357	>	* Throws the exception associated with status s.
358	>	*
359		* @throws the exception
360		*/
361		private void reportException(int s) {
#	Line 350 | Line 368 | public abstract class ForkJoinTask<V> im
368		}
369
370		/**
371	<	* Returns result or throws exception using j.u.c.Future conventions
372	<	* Only call when isDone known to be true.
371	>	* Returns result or throws exception using j.u.c.Future conventions.
372	>	* Only call when {@code isDone} known to be true.
373		*/
374		private V reportFutureResult()
375		throws ExecutionException, InterruptedException {
#	Line 370 | Line 388 | public abstract class ForkJoinTask<V> im
388
389		/**
390		* Returns result or throws exception using j.u.c.Future conventions
391	<	* with timeouts
391	>	* with timeouts.
392		*/
393		private V reportTimedFutureResult()
394		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 391 | Line 409 | public abstract class ForkJoinTask<V> im
409
410		/**
411		* Calls exec, recording completion, and rethrowing exception if
412	<	* encountered. Caller should normally check status before calling
412	>	* encountered. Caller should normally check status before calling.
413	>	*
414		* @return true if completed normally
415		*/
416		private boolean tryExec() {
#	Line 409 | Line 428 | public abstract class ForkJoinTask<V> im
428
429		/**
430		* Main execution method used by worker threads. Invokes
431	<	* base computation unless already complete
431	>	* base computation unless already complete.
432		*/
433		final void quietlyExec() {
434		if (status >= 0) {
435		try {
436		if (!exec())
437		return;
438	<	} catch(Throwable rex) {
438	>	} catch (Throwable rex) {
439		setDoneExceptionally(rex);
440		return;
441		}
#	Line 425 | Line 444 | public abstract class ForkJoinTask<V> im
444		}
445
446		/**
447	<	* Calls exec, recording but not rethrowing exception
448	<	* Caller should normally check status before calling
447	>	* Calls exec(), recording but not rethrowing exception.
448	>	* Caller should normally check status before calling.
449	>	*
450		* @return true if completed normally
451		*/
452		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 462 | public abstract class ForkJoinTask<V> im
462		}
463
464		/**
465	<	* Cancel, ignoring any exceptions it throws
465	>	* Cancels, ignoring any exceptions it throws.
466		*/
467	<	final void cancelIgnoreExceptions() {
467	>	final void cancelIgnoringExceptions() {
468		try {
469		cancel(false);
470	<	} catch(Throwable ignore) {
470	>	} catch (Throwable ignore) {
471		}
472		}
473
474	+	/**
475	+	* Main implementation of helpJoin
476	+	*/
477	+	private int busyJoin(ForkJoinWorkerThread w) {
478	+	int s;
479	+	ForkJoinTask<?> t;
480	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
481	+	t.quietlyExec();
482	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
483	+	}
484	+
485		// public methods
486
487		/**
488		* Arranges to asynchronously execute this task.  While it is not
489		* necessarily enforced, it is a usage error to fork a task more
490		* than once unless it has completed and been reinitialized.  This
491	<	* method may be invoked only from within other ForkJoinTask
492	<	* computations. Attempts to invoke in other contexts result in
493	<	* exceptions or errors including ClassCastException.
491	>	* method may be invoked only from within ForkJoinTask
492	>	* computations (as may be determined using method {@link
493	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
494	>	* in exceptions or errors, possibly including ClassCastException.
495	>	*
496	>	* @return <code>this</code>, to simplify usage.
497		*/
498	<	public final void fork() {
499	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
498	>	public final ForkJoinTask<V> fork() {
499	>	((ForkJoinWorkerThread) Thread.currentThread())
500	>	.pushTask(this);
501	>	return this;
502		}
503
504		/**
505		* Returns the result of the computation when it is ready.
506	<	* This method differs from <tt>get</tt> in that abnormal
506	>	* This method differs from {@code get} in that abnormal
507		* completion results in RuntimeExceptions or Errors, not
508		* ExecutionExceptions.
509		*
#	Line 480 | Line 516 | public abstract class ForkJoinTask<V> im
516		return getRawResult();
517		}
518
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	–
519		/**
520	<	* Possibly executes other tasks until this task is ready, then
521	<	* returns the result of the computation.  This method may be more
522	<	* efficient than <tt>join</tt>, but is only applicable when there
502	<	* are no potemtial dependencies between continuation of the
503	<	* current task and that of any other task that might be executed
504	<	* while helping. (This usually holds for pure divide-and-conquer
505	<	* tasks).
506	<	* @return the computed result
507	<	*/
508	<	public final V helpJoin() {
509	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
510	<	if (status < 0 || !w.unpushTask(this) || !tryExec())
511	<	reportException(w.helpJoinTask(this));
512	<	return getRawResult();
513	<	}
514	<
515	<	/**
516	<	* Performs this task, awaits its completion if necessary, and
517	<	* return its result.
520	>	* Commences performing this task, awaits its completion if
521	>	* necessary, and return its result.
522	>	*
523		* @throws Throwable (a RuntimeException, Error, or unchecked
524	<	* exception) if the underlying computation did so.
524	>	* exception) if the underlying computation did so
525		* @return the computed result
526		*/
527		public final V invoke() {
#	Line 527 | Line 532 | public abstract class ForkJoinTask<V> im
532		}
533
534		/**
535	<	* Joins this task, without returning its result or throwing an
536	<	* exception. This method may be useful when processing
537	<	* collections of tasks when some have been cancelled or otherwise
538	<	* known to have aborted.
535	>	* Forks both tasks, returning when {@code isDone} holds for
536	>	* both of them or an exception is encountered. This method may be
537	>	* invoked only from within ForkJoinTask computations (as may be
538	>	* determined using method {@link #inForkJoinPool}). Attempts to
539	>	* invoke in other contexts result in exceptions or errors,
540	>	* possibly including ClassCastException.
541	>	*
542	>	* @param t1 one task
543	>	* @param t2 the other task
544	>	* @throws NullPointerException if t1 or t2 are null
545	>	* @throws RuntimeException or Error if either task did so
546		*/
547	<	public final void quietlyJoin() {
548	<	if (status >= 0) {
549	<	ForkJoinWorkerThread w = getWorker();
550	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
547	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
548	>	t2.fork();
549	>	t1.invoke();
550	>	t2.join();
551		}
552
553		/**
554	<	* Possibly executes other tasks until this task is ready.
554	>	* Forks the given tasks, returning when {@code isDone} holds
555	>	* for all of them. If any task encounters an exception, others
556	>	* may be cancelled.  This method may be invoked only from within
557	>	* ForkJoinTask computations (as may be determined using method
558	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
559	>	* result in exceptions or errors, possibly including
560	>	* ClassCastException.
561	>	*
562	>	* @param tasks the array of tasks
563	>	* @throws NullPointerException if tasks or any element are null
564	>	* @throws RuntimeException or Error if any task did so
565		*/
566	<	public final void quietlyHelpJoin() {
567	<	if (status >= 0) {
568	<	ForkJoinWorkerThread w =
569	<	(ForkJoinWorkerThread)(Thread.currentThread());
570	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
571	<	w.helpJoinTask(this);
566	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
567	>	Throwable ex = null;
568	>	int last = tasks.length - 1;
569	>	for (int i = last; i >= 0; --i) {
570	>	ForkJoinTask<?> t = tasks[i];
571	>	if (t == null) {
572	>	if (ex == null)
573	>	ex = new NullPointerException();
574	>	}
575	>	else if (i != 0)
576	>	t.fork();
577	>	else {
578	>	t.quietlyInvoke();
579	>	if (ex == null)
580	>	ex = t.getException();
581	>	}
582		}
583	+	for (int i = 1; i <= last; ++i) {
584	+	ForkJoinTask<?> t = tasks[i];
585	+	if (t != null) {
586	+	if (ex != null)
587	+	t.cancel(false);
588	+	else {
589	+	t.quietlyJoin();
590	+	if (ex == null)
591	+	ex = t.getException();
592	+	}
593	+	}
594	+	}
595	+	if (ex != null)
596	+	rethrowException(ex);
597		}
598
599		/**
600	<	* Performs this task and awaits its completion if necessary,
601	<	* without returning its result or throwing an exception. This
602	<	* method may be useful when processing collections of tasks when
603	<	* some have been cancelled or otherwise known to have aborted.
604	<	*/
605	<	public final void quietlyInvoke() {
606	<	if (status >= 0 && !tryQuietlyInvoke())
607	<	quietlyJoin();
600	>	* Forks all tasks in the collection, returning when
601	>	* {@code isDone} holds for all of them. If any task
602	>	* encounters an exception, others may be cancelled.  This method
603	>	* may be invoked only from within ForkJoinTask computations (as
604	>	* may be determined using method {@link
605	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
606	>	* in exceptions or errors, possibly including ClassCastException.
607	>	*
608	>	* @param tasks the collection of tasks
609	>	* @return the tasks argument, to simplify usage
610	>	* @throws NullPointerException if tasks or any element are null
611	>	* @throws RuntimeException or Error if any task did so
612	>	*/
613	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
614	>	if (!(tasks instanceof List<?>)) {
615	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
616	>	return tasks;
617	>	}
618	>	@SuppressWarnings("unchecked")
619	>	List<? extends ForkJoinTask<?>> ts =
620	>	(List<? extends ForkJoinTask<?>>) tasks;
621	>	Throwable ex = null;
622	>	int last = ts.size() - 1;
623	>	for (int i = last; i >= 0; --i) {
624	>	ForkJoinTask<?> t = ts.get(i);
625	>	if (t == null) {
626	>	if (ex == null)
627	>	ex = new NullPointerException();
628	>	}
629	>	else if (i != 0)
630	>	t.fork();
631	>	else {
632	>	t.quietlyInvoke();
633	>	if (ex == null)
634	>	ex = t.getException();
635	>	}
636	>	}
637	>	for (int i = 1; i <= last; ++i) {
638	>	ForkJoinTask<?> t = ts.get(i);
639	>	if (t != null) {
640	>	if (ex != null)
641	>	t.cancel(false);
642	>	else {
643	>	t.quietlyJoin();
644	>	if (ex == null)
645	>	ex = t.getException();
646	>	}
647	>	}
648	>	}
649	>	if (ex != null)
650	>	rethrowException(ex);
651	>	return tasks;
652		}
653
654		/**
655		* Returns true if the computation performed by this task has
656		* completed (or has been cancelled).
657	+	*
658		* @return true if this computation has completed
659		*/
660		public final boolean isDone() {
#	Line 574 | Line 663 | public abstract class ForkJoinTask<V> im
663
664		/**
665		* Returns true if this task was cancelled.
666	+	*
667		* @return true if this task was cancelled
668		*/
669		public final boolean isCancelled() {
#	Line 581 | Line 671 | public abstract class ForkJoinTask<V> im
671		}
672
673		/**
584	–	* Returns true if this task threw an exception or was cancelled
585	–	* @return true if this task threw an exception or was cancelled
586	–	*/
587	–	public final boolean completedAbnormally() {
588	–	return (status & COMPLETION_MASK) < NORMAL;
589	–	}
590	–
591	–	/**
592	–	* Returns the exception thrown by the base computation, or a
593	–	* CancellationException if cancelled, or null if none or if the
594	–	* method has not yet completed.
595	–	* @return the exception, or null if none
596	–	*/
597	–	public final Throwable getException() {
598	–	int s = status & COMPLETION_MASK;
599	–	if (s >= NORMAL)
600	–	return null;
601	–	if (s == CANCELLED)
602	–	return new CancellationException();
603	–	return exceptionMap.get(this);
604	–	}
605	–
606	–	/**
674		* Asserts that the results of this task's computation will not be
675	<	* used. If a cancellation occurs before this task is processed,
676	<	* then its <tt>compute</tt> method will not be executed,
677	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
678	<	* result in a CancellationException being thrown. Otherwise, when
675	>	* used. If a cancellation occurs before attempting to execute this
676	>	* task, then execution will be suppressed, {@code isCancelled}
677	>	* will report true, and {@code join} will result in a
678	>	* {@code CancellationException} being thrown. Otherwise, when
679		* cancellation races with completion, there are no guarantees
680	<	* about whether <tt>isCancelled</tt> will report true, whether
681	<	* <tt>join</tt> will return normally or via an exception, or
680	>	* about whether {@code isCancelled} will report true, whether
681	>	* {@code join} will return normally or via an exception, or
682		* whether these behaviors will remain consistent upon repeated
683		* invocation.
684		*
#	Line 622 | Line 689 | public abstract class ForkJoinTask<V> im
689		* <p> This method is designed to be invoked by <em>other</em>
690		* tasks. To terminate the current task, you can just return or
691		* throw an unchecked exception from its computation method, or
692	<	* invoke <tt>completeExceptionally(someException)</tt>.
692	>	* invoke {@code completeExceptionally}.
693		*
694		* @param mayInterruptIfRunning this value is ignored in the
695		* default implementation because tasks are not in general
696	<	* cancelled via interruption.
696	>	* cancelled via interruption
697		*
698		* @return true if this task is now cancelled
699		*/
#	Line 636 | Line 703 | public abstract class ForkJoinTask<V> im
703		}
704
705		/**
706	+	* Returns true if this task threw an exception or was cancelled.
707	+	*
708	+	* @return true if this task threw an exception or was cancelled
709	+	*/
710	+	public final boolean isCompletedAbnormally() {
711	+	return (status & COMPLETION_MASK) < NORMAL;
712	+	}
713	+
714	+	/**
715	+	* Returns the exception thrown by the base computation, or a
716	+	* CancellationException if cancelled, or null if none or if the
717	+	* method has not yet completed.
718	+	*
719	+	* @return the exception, or null if none
720	+	*/
721	+	public final Throwable getException() {
722	+	int s = status & COMPLETION_MASK;
723	+	if (s >= NORMAL)
724	+	return null;
725	+	if (s == CANCELLED)
726	+	return new CancellationException();
727	+	return exceptionMap.get(this);
728	+	}
729	+
730	+	/**
731		* Completes this task abnormally, and if not already aborted or
732		* cancelled, causes it to throw the given exception upon
733	<	* <tt>join</tt> and related operations. This method may be used
733	>	* {@code join} and related operations. This method may be used
734		* to induce exceptions in asynchronous tasks, or to force
735	<	* completion of tasks that would not otherwise complete.  This
736	<	* method is overridable, but overridden versions must invoke
737	<	* <tt>super</tt> implementation to maintain guarantees.
735	>	* completion of tasks that would not otherwise complete.  Its use
736	>	* in other situations is likely to be wrong.  This method is
737	>	* overridable, but overridden versions must invoke {@code super}
738	>	* implementation to maintain guarantees.
739	>	*
740		* @param ex the exception to throw. If this exception is
741		* not a RuntimeException or Error, the actual exception thrown
742		* will be a RuntimeException with cause ex.
743		*/
744		public void completeExceptionally(Throwable ex) {
745		setDoneExceptionally((ex instanceof RuntimeException) ||
746	<	(ex instanceof Error)? ex :
746	>	(ex instanceof Error) ? ex :
747		new RuntimeException(ex));
748		}
749
750		/**
751		* Completes this task, and if not already aborted or cancelled,
752	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
752	>	* returning a {@code null} result upon {@code join} and related
753		* operations. This method may be used to provide results for
754		* asynchronous tasks, or to provide alternative handling for
755	<	* tasks that would not otherwise complete normally.
755	>	* tasks that would not otherwise complete normally. Its use in
756	>	* other situations is likely to be wrong. This method is
757	>	* overridable, but overridden versions must invoke {@code super}
758	>	* implementation to maintain guarantees.
759		*
760	<	* @param value the result value for this task.
760	>	* @param value the result value for this task
761		*/
762		public void complete(V value) {
763		try {
764		setRawResult(value);
765	<	} catch(Throwable rex) {
765	>	} catch (Throwable rex) {
766		setDoneExceptionally(rex);
767		return;
768		}
769		setNormalCompletion();
770		}
771
772	+	public final V get() throws InterruptedException, ExecutionException {
773	+	ForkJoinWorkerThread w = getWorker();
774	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
775	+	awaitDone(w, true);
776	+	return reportFutureResult();
777	+	}
778	+
779	+	public final V get(long timeout, TimeUnit unit)
780	+	throws InterruptedException, ExecutionException, TimeoutException {
781	+	ForkJoinWorkerThread w = getWorker();
782	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
783	+	awaitDone(w, unit.toNanos(timeout));
784	+	return reportTimedFutureResult();
785	+	}
786	+
787	+	/**
788	+	* Possibly executes other tasks until this task is ready, then
789	+	* returns the result of the computation.  This method may be more
790	+	* efficient than {@code join}, but is only applicable when
791	+	* there are no potential dependencies between continuation of the
792	+	* current task and that of any other task that might be executed
793	+	* while helping. (This usually holds for pure divide-and-conquer
794	+	* tasks). This method may be invoked only from within
795	+	* ForkJoinTask computations (as may be determined using method
796	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
797	+	* result in exceptions or errors, possibly including
798	+	* ClassCastException.
799	+	*
800	+	* @return the computed result
801	+	*/
802	+	public final V helpJoin() {
803	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
804	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
805	+	reportException(busyJoin(w));
806	+	return getRawResult();
807	+	}
808	+
809	+	/**
810	+	* Possibly executes other tasks until this task is ready.  This
811	+	* method may be invoked only from within ForkJoinTask
812	+	* computations (as may be determined using method {@link
813	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
814	+	* in exceptions or errors, possibly including ClassCastException.
815	+	*/
816	+	public final void quietlyHelpJoin() {
817	+	if (status >= 0) {
818	+	ForkJoinWorkerThread w =
819	+	(ForkJoinWorkerThread) Thread.currentThread();
820	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
821	+	busyJoin(w);
822	+	}
823	+	}
824	+
825	+	/**
826	+	* Joins this task, without returning its result or throwing an
827	+	* exception. This method may be useful when processing
828	+	* collections of tasks when some have been cancelled or otherwise
829	+	* known to have aborted.
830	+	*/
831	+	public final void quietlyJoin() {
832	+	if (status >= 0) {
833	+	ForkJoinWorkerThread w = getWorker();
834	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
835	+	awaitDone(w, true);
836	+	}
837	+	}
838	+
839	+	/**
840	+	* Commences performing this task and awaits its completion if
841	+	* necessary, without returning its result or throwing an
842	+	* exception. This method may be useful when processing
843	+	* collections of tasks when some have been cancelled or otherwise
844	+	* known to have aborted.
845	+	*/
846	+	public final void quietlyInvoke() {
847	+	if (status >= 0 && !tryQuietlyInvoke())
848	+	quietlyJoin();
849	+	}
850	+
851	+	/**
852	+	* Possibly executes tasks until the pool hosting the current task
853	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
854	+	* designs in which many tasks are forked, but none are explicitly
855	+	* joined, instead executing them until all are processed.
856	+	*/
857	+	public static void helpQuiesce() {
858	+	((ForkJoinWorkerThread) Thread.currentThread())
859	+	.helpQuiescePool();
860	+	}
861	+
862		/**
863		* Resets the internal bookkeeping state of this task, allowing a
864	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
864	>	* subsequent {@code fork}. This method allows repeated reuse of
865		* this task, but only if reuse occurs when this task has either
866		* never been forked, or has been forked, then completed and all
867		* outstanding joins of this task have also completed. Effects
#	Line 689 | Line 876 | public abstract class ForkJoinTask<V> im
876		}
877
878		/**
879	<	* Tries to unschedule this task for execution. This method will
880	<	* typically succeed if this task is the next task that would be
881	<	* executed by the current thread, and will typically fail (return
882	<	* false) otherwise. This method may be useful when arranging
696	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
699	<	*/
700	<	public boolean tryUnfork() {
701	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
702	<	}
703	<
704	<	/**
705	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
706	<	* of them or an exception is encountered. This method may be
707	<	* invoked only from within other ForkJoinTask
708	<	* computations. Attempts to invoke in other contexts result in
709	<	* exceptions or errors including ClassCastException.
710	<	* @param t1 one task
711	<	* @param t2 the other task
712	<	* @throws NullPointerException if t1 or t2 are null
713	<	* @throws RuntimeException or Error if either task did so.
879	>	* Returns the pool hosting the current task execution, or null
880	>	* if this task is executing outside of any ForkJoinPool.
881	>	*
882	>	* @return the pool, or null if none
883		*/
884	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
885	<	t2.fork();
886	<	t1.invoke();
887	<	t2.join();
884	>	public static ForkJoinPool getPool() {
885	>	Thread t = Thread.currentThread();
886	>	return (t instanceof ForkJoinWorkerThread) ?
887	>	((ForkJoinWorkerThread) t).pool : null;
888		}
889
890		/**
891	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
892	<	* all of them. If any task encounters an exception, others may be
893	<	* cancelled.  This method may be invoked only from within other
894	<	* ForkJoinTask computations. Attempts to invoke in other contexts
895	<	* result in exceptions or errors including ClassCastException.
727	<	* @param tasks the array of tasks
728	<	* @throws NullPointerException if tasks or any element are null.
729	<	* @throws RuntimeException or Error if any task did so.
891	>	* Returns {@code true} if the current thread is executing as a
892	>	* ForkJoinPool computation.
893	>	*
894	>	* @return {@code true} if the current thread is executing as a
895	>	* ForkJoinPool computation, or false otherwise
896		*/
897	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
898	<	Throwable ex = null;
733	<	int last = tasks.length - 1;
734	<	for (int i = last; i >= 0; --i) {
735	<	ForkJoinTask<?> t = tasks[i];
736	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
759	<	}
760	<	if (ex != null)
761	<	rethrowException(ex);
897	>	public static boolean inForkJoinPool() {
898	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
899		}
900
901		/**
902	<	* Forks all tasks in the collection, returning when
903	<	* <tt>isDone</tt> holds for all of them. If any task encounters
904	<	* an exception, others may be cancelled.  This method may be
905	<	* invoked only from within other ForkJoinTask
906	<	* computations. Attempts to invoke in other contexts result in
907	<	* exceptions or errors including ClassCastException.
908	<	* @param tasks the collection of tasks
909	<	* @throws NullPointerException if tasks or any element are null.
910	<	* @throws RuntimeException or Error if any task did so.
902	>	* Tries to unschedule this task for execution. This method will
903	>	* typically succeed if this task is the most recently forked task
904	>	* by the current thread, and has not commenced executing in
905	>	* another thread.  This method may be useful when arranging
906	>	* alternative local processing of tasks that could have been, but
907	>	* were not, stolen. This method may be invoked only from within
908	>	* ForkJoinTask computations (as may be determined using method
909	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
910	>	* result in exceptions or errors, possibly including
911	>	* ClassCastException.
912	>	*
913	>	* @return true if unforked
914		*/
915	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
916	<	if (!(tasks instanceof List)) {
917	<	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);
915	>	public boolean tryUnfork() {
916	>	return ((ForkJoinWorkerThread) Thread.currentThread())
917	>	.unpushTask(this);
918		}
919
920		/**
921	<	* Possibly executes tasks until the pool hosting the current task
922	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
923	<	* designs in which many tasks are forked, but none are explicitly
924	<	* joined, instead executing them until all are processed.
921	>	* Returns an estimate of the number of tasks that have been
922	>	* forked by the current worker thread but not yet executed. This
923	>	* value may be useful for heuristic decisions about whether to
924	>	* fork other tasks.
925	>	*
926	>	* @return the number of tasks
927		*/
928	<	public static void helpQuiesce() {
929	<	((ForkJoinWorkerThread)(Thread.currentThread())).
930	<	helpQuiescePool();
928	>	public static int getQueuedTaskCount() {
929	>	return ((ForkJoinWorkerThread) Thread.currentThread())
930	>	.getQueueSize();
931		}
932
933		/**
934	<	* Returns a estimate of how many more locally queued tasks are
934	>	* Returns an estimate of how many more locally queued tasks are
935		* held by the current worker thread than there are other worker
936	<	* threads that might want to steal them.  This value may be
937	<	* useful for heuristic decisions about whether to fork other
938	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
939	<	* worker should aim to maintain a small constant surplus (for
940	<	* example, 3) of tasks, and to process computations locally if
941	<	* this threshold is exceeded.
936	>	* threads that might steal them.  This value may be useful for
937	>	* heuristic decisions about whether to fork other tasks. In many
938	>	* usages of ForkJoinTasks, at steady state, each worker should
939	>	* aim to maintain a small constant surplus (for example, 3) of
940	>	* tasks, and to process computations locally if this threshold is
941	>	* exceeded.
942	>	*
943		* @return the surplus number of tasks, which may be negative
944		*/
945	<	public static int surplus() {
946	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
945	>	public static int getSurplusQueuedTaskCount() {
946	>	return ((ForkJoinWorkerThread) Thread.currentThread())
947		.getEstimatedSurplusTaskCount();
948		}
949
950	<	// Extension kit
950	>	// Extension methods
951
952		/**
953	<	* Returns the result that would be returned by <tt>join</tt>, or
954	<	* null if this task is not known to have been completed.  This
955	<	* method is designed to aid debugging, as well as to support
956	<	* extensions. Its use in any other context is discouraged.
953	>	* Returns the result that would be returned by {@code join},
954	>	* even if this task completed abnormally, or null if this task is
955	>	* not known to have been completed.  This method is designed to
956	>	* aid debugging, as well as to support extensions. Its use in any
957	>	* other context is discouraged.
958		*
959	<	* @return the result, or null if not completed.
959	>	* @return the result, or null if not completed
960		*/
961		public abstract V getRawResult();
962
#	Line 865 | Line 975 | public abstract class ForkJoinTask<V> im
975		* called otherwise. The return value controls whether this task
976		* is considered to be done normally. It may return false in
977		* asynchronous actions that require explicit invocations of
978	<	* <tt>complete</tt> to become joinable. It may throw exceptions
978	>	* {@code complete} to become joinable. It may throw exceptions
979		* to indicate abnormal exit.
980	+	*
981		* @return true if completed normally
982		* @throws Error or RuntimeException if encountered during computation
983		*/
984		protected abstract boolean exec();
985
986	+	/**
987	+	* Returns, but does not unschedule or execute, the task queued by
988	+	* the current thread but not yet executed, if one is
989	+	* available. There is no guarantee that this task will actually
990	+	* be polled or executed next.  This method is designed primarily
991	+	* to support extensions, and is unlikely to be useful otherwise.
992	+	* This method may be invoked only from within ForkJoinTask
993	+	* computations (as may be determined using method {@link
994	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
995	+	* in exceptions or errors, possibly including ClassCastException.
996	+	*
997	+	* @return the next task, or null if none are available
998	+	*/
999	+	protected static ForkJoinTask<?> peekNextLocalTask() {
1000	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1001	+	.peekTask();
1002	+	}
1003	+
1004	+	/**
1005	+	* Unschedules and returns, without executing, the next task
1006	+	* queued by the current thread but not yet executed.  This method
1007	+	* is designed primarily to support extensions, and is unlikely to
1008	+	* be useful otherwise.  This method may be invoked only from
1009	+	* within ForkJoinTask computations (as may be determined using
1010	+	* method {@link #inForkJoinPool}). Attempts to invoke in other
1011	+	* contexts result in exceptions or errors, possibly including
1012	+	* ClassCastException.
1013	+	*
1014	+	* @return the next task, or null if none are available
1015	+	*/
1016	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1017	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1018	+	.pollLocalTask();
1019	+	}
1020	+
1021	+	/**
1022	+	* Unschedules and returns, without executing, the next task
1023	+	* queued by the current thread but not yet executed, if one is
1024	+	* available, or if not available, a task that was forked by some
1025	+	* other thread, if available. Availability may be transient, so a
1026	+	* {@code null} result does not necessarily imply quiescence
1027	+	* of the pool this task is operating in.  This method is designed
1028	+	* primarily to support extensions, and is unlikely to be useful
1029	+	* otherwise.  This method may be invoked only from within
1030	+	* ForkJoinTask computations (as may be determined using method
1031	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1032	+	* result in exceptions or errors, possibly including
1033	+	* ClassCastException.
1034	+	*
1035	+	* @return a task, or null if none are available
1036	+	*/
1037	+	protected static ForkJoinTask<?> pollTask() {
1038	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1039	+	.pollTask();
1040	+	}
1041	+
1042	+	// adaptors
1043	+
1044	+	/**
1045	+	* Returns a new ForkJoinTask that performs the <code>run</code>
1046	+	* method of the given Runnable as its action, and returns a null
1047	+	* result upon <code>join</code>.
1048	+	*
1049	+	* @param runnable the runnable action
1050	+	* @return the task
1051	+	*/
1052	+	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1053	+	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1054	+	}
1055	+
1056	+	/**
1057	+	* Returns a new ForkJoinTask that performs the <code>run</code>
1058	+	* method of the given Runnable as its action, and returns the
1059	+	* given result upon <code>join</code>.
1060	+	*
1061	+	* @param runnable the runnable action
1062	+	* @param result the result upon completion
1063	+	* @return the task
1064	+	*/
1065	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1066	+	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1067	+	}
1068	+
1069	+	/**
1070	+	* Returns a new ForkJoinTask that performs the <code>call</code>
1071	+	* method of the given Callable as its action, and returns its
1072	+	* result upon <code>join</code>, translating any checked
1073	+	* exceptions encountered into <code>RuntimeException<code>.
1074	+	*
1075	+	* @param callable the callable action
1076	+	* @return the task
1077	+	*/
1078	+	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1079	+	return new ForkJoinPool.AdaptedCallable<T>(callable);
1080	+	}
1081	+
1082		// Serialization support
1083
1084		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1087 | public abstract class ForkJoinTask<V> im
1087		* Save the state to a stream.
1088		*
1089		* @serialData the current run status and the exception thrown
1090	<	* during execution, or null if none.
1090	>	* during execution, or null if none
1091		* @param s the stream
1092		*/
1093		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1098 | public abstract class ForkJoinTask<V> im
1098
1099		/**
1100		* Reconstitute the instance from a stream.
1101	+	*
1102		* @param s the stream
1103		*/
1104		private void readObject(java.io.ObjectInputStream s)
1105		throws java.io.IOException, ClassNotFoundException {
1106		s.defaultReadObject();
1107	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1107	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1108	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1109		Object ex = s.readObject();
1110		if (ex != null)
1111	<	setDoneExceptionally((Throwable)ex);
1111	>	setDoneExceptionally((Throwable) ex);
1112		}
1113
1114	<	// Temporary Unsafe mechanics for preliminary release
1114	>	// Unsafe mechanics for jsr166y 3rd party package.
1115	>	private static sun.misc.Unsafe getUnsafe() {
1116	>	try {
1117	>	return sun.misc.Unsafe.getUnsafe();
1118	>	} catch (SecurityException se) {
1119	>	try {
1120	>	return java.security.AccessController.doPrivileged
1121	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1122	>	public sun.misc.Unsafe run() throws Exception {
1123	>	return getUnsafeByReflection();
1124	>	}});
1125	>	} catch (java.security.PrivilegedActionException e) {
1126	>	throw new RuntimeException("Could not initialize intrinsics",
1127	>	e.getCause());
1128	>	}
1129	>	}
1130	>	}
1131
1132	<	static final Unsafe _unsafe;
1133	<	static final long statusOffset;
1132	>	private static sun.misc.Unsafe getUnsafeByReflection()
1133	>	throws NoSuchFieldException, IllegalAccessException {
1134	>	java.lang.reflect.Field f =
1135	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1136	>	f.setAccessible(true);
1137	>	return (sun.misc.Unsafe) f.get(null);
1138	>	}
1139
1140	<	static {
1140	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
1141		try {
1142	<	if (ForkJoinTask.class.getClassLoader() != null) {
1143	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1144	<	f.setAccessible(true);
1145	<	_unsafe = (Unsafe)f.get(null);
1146	<	}
1147	<	else
1148	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1142	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1143	>	} catch (NoSuchFieldException e) {
1144	>	// Convert Exception to Error
1145	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1146	>	error.initCause(e);
1147	>	throw error;
1148	>	}
1149		}
1150
1151	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1152	+	private static final long statusOffset =
1153	+	fieldOffset("status", ForkJoinTask.class);
1154	+
1155		}

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