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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 1.24 by jsr166, Mon Jul 27 21:41:53 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} and
29	>	* {@code join}, or derivatives such as {@code invokeAll}.  However,
30	>	* this class also provides a number of other methods that can come
31	>	* into play in advanced usages, as well as extension mechanics that
32	>	* allow support of new forms of fork/join processing.
33	>	*
34	>	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
35	>	* efficiency of ForkJoinTasks stems from a set of restrictions (that
36	>	* are only partially statically enforceable) reflecting their
37	>	* intended use as computational tasks calculating pure functions or
38	>	* operating on purely isolated objects.  The primary coordination
39	>	* mechanisms are {@link #fork}, that arranges asynchronous execution,
40	>	* and {@link #join}, that doesn't proceed until the task's result has
41	>	* been computed.  Computations should avoid {@code synchronized}
42	>	* methods or blocks, and should minimize other blocking
43	>	* synchronization apart from joining other tasks or using
44		* synchronizers such as Phasers that are advertised to cooperate with
45		* fork/join scheduling. Tasks should also not perform blocking IO,
46		* and should ideally access variables that are completely independent
#	Line 38 | Line 48 | import java.lang.reflect.*;
48		* restrictions, for example using shared output streams, may be
49		* tolerable in practice, but frequent use may result in poor
50		* performance, and the potential to indefinitely stall if the number
51	<	* of threads not waiting for external synchronization becomes
52	<	* exhausted. This usage restriction is in part enforced by not
53	<	* permitting checked exceptions such as IOExceptions to be
54	<	* thrown. However, computations may still encounter unchecked
51	>	* of threads not waiting for IO or other external synchronization
52	>	* becomes exhausted. This usage restriction is in part enforced by
53	>	* not permitting checked exceptions such as {@code IOExceptions}
54	>	* to be thrown. However, computations may still encounter unchecked
55		* exceptions, that are rethrown to callers attempting join
56		* them. These exceptions may additionally include
57		* RejectedExecutionExceptions stemming from internal resource
58		* exhaustion such as failure to allocate internal task queues.
59		*
60	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
61	<	* subclassed.  Instead, you subclass one of the abstract classes that
62	<	* support different styles of fork/join processing.  Normally, a
63	<	* concrete ForkJoinTask subclass declares fields comprising its
64	<	* parameters, established in a constructor, and then defines a
65	<	* <tt>compute</tt> method that somehow uses the control methods
66	<	* supplied by this base class. While these methods have
67	<	* <tt>public</tt> access, some of them may only be called from within
68	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
69	<	* result in exceptions or errors including ClassCastException.  The
70	<	* only way to invoke a "main" driver task is to submit it to a
71	<	* ForkJoinPool. Once started, this will usually in turn start other
72	<	* subtasks.
60	>	* <p>The primary method for awaiting completion and extracting
61	>	* results of a task is {@link #join}, but there are several variants:
62	>	* The {@link Future#get} methods support interruptible and/or timed
63	>	* waits for completion and report results using {@code Future}
64	>	* conventions. Method {@link #helpJoin} enables callers to actively
65	>	* execute other tasks while awaiting joins, which is sometimes more
66	>	* efficient but only applies when all subtasks are known to be
67	>	* strictly tree-structured. Method {@link #invoke} is semantically
68	>	* equivalent to {@code fork(); join()} but always attempts to
69	>	* begin execution in the current thread. The "<em>quiet</em>" forms
70	>	* of these methods do not extract results or report exceptions. These
71	>	* may be useful when a set of tasks are being executed, and you need
72	>	* to delay processing of results or exceptions until all complete.
73	>	* Method {@code invokeAll} (available in multiple versions)
74	>	* performs the most common form of parallel invocation: forking a set
75	>	* of tasks and joining them all.
76	>	*
77	>	* <p> The ForkJoinTask class is not usually directly subclassed.
78	>	* Instead, you subclass one of the abstract classes that support a
79	>	* particular style of fork/join processing.  Normally, a concrete
80	>	* ForkJoinTask subclass declares fields comprising its parameters,
81	>	* established in a constructor, and then defines a {@code compute}
82	>	* method that somehow uses the control methods supplied by this base
83	>	* class. While these methods have {@code public} access (to allow
84	>	* instances of different task subclasses to call each others
85	>	* methods), some of them may only be called from within other
86	>	* ForkJoinTasks (as may be determined using method {@link
87	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
88	>	* result in exceptions or errors, possibly including
89	>	* ClassCastException.
90		*
91	<	* <p>Most base support methods are <tt>final</tt> because their
91	>	* <p>Most base support methods are {@code final} because their
92		* implementations are intrinsically tied to the underlying
93		* lightweight task scheduling framework, and so cannot be overridden.
94		* Developers creating new basic styles of fork/join processing should
95	<	* minimally implement protected methods <tt>exec</tt>,
96	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
97	<	* introducing an abstract computational method that can be
98	<	* implemented in its subclasses. To support such extensions,
99	<	* instances of ForkJoinTasks maintain an atomically updated
100	<	* <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.
95	>	* minimally implement {@code protected} methods
96	>	* {@link #exec}, {@link #setRawResult}, and
97	>	* {@link #getRawResult}, while also introducing an abstract
98	>	* computational method that can be implemented in its subclasses,
99	>	* possibly relying on other {@code protected} methods provided
100	>	* by this class.
101		*
102		* <p>ForkJoinTasks should perform relatively small amounts of
103	<	* computations, othewise splitting into smaller tasks. As a very
103	>	* computations, otherwise splitting into smaller tasks. As a very
104		* rough rule of thumb, a task should perform more than 100 and less
105		* than 10000 basic computational steps. If tasks are too big, then
106	<	* parellelism cannot improve throughput. If too small, then memory
106	>	* parallelism cannot improve throughput. If too small, then memory
107		* and internal task maintenance overhead may overwhelm processing.
108		*
109	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
110	<	* be used in extensions such as remote execution frameworks. However,
111	<	* it is in general safe to serialize tasks only before or after, but
109	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
110	>	* to be used in extensions such as remote execution frameworks. It is
111	>	* in general sensible to serialize tasks only before or after, but
112		* not during execution. Serialization is not relied on during
113		* execution itself.
114	+	*
115	+	* @since 1.7
116	+	* @author Doug Lea
117		*/
118		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
119	+
120		/**
121	<	* Status field holding all run status. We pack this into a single
122	<	* int both to minimize footprint overhead and to ensure atomicity
123	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
121	>	* Run control status bits packed into a single int to minimize
122	>	* footprint and to ensure atomicity (via CAS).  Status is
123	>	* initially zero, and takes on nonnegative values until
124		* completed, upon which status holds COMPLETED. CANCELLED, or
125		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
126		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 135 | public abstract class ForkJoinTask<V> im
135		* currently unused. Also value 0x80000000 is available as spare
136		* completion value.
137		*/
138	<	volatile int status; // accessed directy by pool and workers
138	>	volatile int status; // accessed directly by pool and workers
139
140		static final int COMPLETION_MASK      = 0xe0000000;
141		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 148 | public abstract class ForkJoinTask<V> im
148		/**
149		* Table of exceptions thrown by tasks, to enable reporting by
150		* callers. Because exceptions are rare, we don't directly keep
151	<	* them with task objects, but instead us a weak ref table.  Note
151	>	* them with task objects, but instead use a weak ref table.  Note
152		* that cancellation exceptions don't appear in the table, but are
153		* instead recorded as status values.
154	<	* Todo: Use ConcurrentReferenceHashMap
154	>	* TODO: Use ConcurrentReferenceHashMap
155		*/
156		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
157		Collections.synchronizedMap
#	Line 136 | Line 160 | public abstract class ForkJoinTask<V> im
160		// within-package utilities
161
162		/**
163	<	* Get current worker thread, or null if not a worker thread
163	>	* Gets current worker thread, or null if not a worker thread.
164		*/
165		static ForkJoinWorkerThread getWorker() {
166		Thread t = Thread.currentThread();
167	<	return ((t instanceof ForkJoinWorkerThread)?
168	<	(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);
167	>	return ((t instanceof ForkJoinWorkerThread) ?
168	>	(ForkJoinWorkerThread) t : null);
169		}
170
171		final boolean casStatus(int cmp, int val) {
172	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
172	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
173		}
174
175		/**
#	Line 162 | Line 177 | public abstract class ForkJoinTask<V> im
177		*/
178		static void rethrowException(Throwable ex) {
179		if (ex != null)
180	<	_unsafe.throwException(ex);
180	>	UNSAFE.throwException(ex);
181		}
182
183		// Setting completion status
184
185		/**
186	<	* Mark completion and wake up threads waiting to join this task.
186	>	* Marks completion and wakes up threads waiting to join this task.
187	>	*
188		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
189		*/
190		final void setCompletion(int completion) {
191	<	ForkJoinPool pool = getWorkerPool();
191	>	ForkJoinPool pool = getPool();
192		if (pool != null) {
193		int s; // Clear signal bits while setting completion status
194	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
194	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
195
196		if ((s & SIGNAL_MASK) != 0) {
197		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
198		pool.updateRunningCount(s);
199	<	synchronized(this) { notifyAll(); }
199	>	synchronized (this) { notifyAll(); }
200		}
201		}
202		else
#	Line 193 | Line 209 | public abstract class ForkJoinTask<V> im
209		*/
210		private void externallySetCompletion(int completion) {
211		int s;
212	<	do;while ((s = status) >= 0 &&
213	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
214	<	synchronized(this) { notifyAll(); }
212	>	do {} while ((s = status) >= 0 &&
213	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
214	>	synchronized (this) { notifyAll(); }
215		}
216
217		/**
218	<	* Sets status to indicate normal completion
218	>	* Sets status to indicate normal completion.
219		*/
220		final void setNormalCompletion() {
221		// Try typical fast case -- single CAS, no signal, not already done.
222		// Manually expand casStatus to improve chances of inlining it
223	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
223	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
224		setCompletion(NORMAL);
225		}
226
227		// internal waiting and notification
228
229		/**
230	<	* Performs the actual monitor wait for awaitDone
230	>	* Performs the actual monitor wait for awaitDone.
231		*/
232		private void doAwaitDone() {
233		// Minimize lock bias and in/de-flation effects by maximizing
234		// chances of waiting inside sync
235		try {
236		while (status >= 0)
237	<	synchronized(this) { if (status >= 0) wait(); }
237	>	synchronized (this) { if (status >= 0) wait(); }
238		} catch (InterruptedException ie) {
239		onInterruptedWait();
240		}
241		}
242
243		/**
244	<	* Performs the actual monitor wait for awaitDone
244	>	* Performs the actual timed monitor wait for awaitDone.
245		*/
246		private void doAwaitDone(long startTime, long nanos) {
247	<	synchronized(this) {
247	>	synchronized (this) {
248		try {
249		while (status >= 0) {
250		long nt = nanos - System.nanoTime() - startTime;
251		if (nt <= 0)
252		break;
253	<	wait(nt / 1000000, (int)(nt % 1000000));
253	>	wait(nt / 1000000, (int) (nt % 1000000));
254		}
255		} catch (InterruptedException ie) {
256		onInterruptedWait();
#	Line 247 | Line 263 | public abstract class ForkJoinTask<V> im
263		/**
264		* Sets status to indicate there is joiner, then waits for join,
265		* surrounded with pool notifications.
266	+	*
267		* @return status upon exit
268		*/
269	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
270	<	ForkJoinPool pool = w == null? null : w.pool;
269	>	private int awaitDone(ForkJoinWorkerThread w,
270	>	boolean maintainParallelism) {
271	>	ForkJoinPool pool = (w == null) ? null : w.pool;
272		int s;
273		while ((s = status) >= 0) {
274	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
274	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
275		if (pool == null || !pool.preJoin(this, maintainParallelism))
276		doAwaitDone();
277		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 284 | public abstract class ForkJoinTask<V> im
284
285		/**
286		* Timed version of awaitDone
287	+	*
288		* @return status upon exit
289		*/
290	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
291	<	ForkJoinPool pool = w == null? null : w.pool;
290	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
291	>	ForkJoinPool pool = (w == null) ? null : w.pool;
292		int s;
293		while ((s = status) >= 0) {
294	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
294	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
295		long startTime = System.nanoTime();
296		if (pool == null || !pool.preJoin(this, false))
297		doAwaitDone(startTime, nanos);
#	Line 289 | Line 308 | public abstract class ForkJoinTask<V> im
308		}
309
310		/**
311	<	* Notify pool that thread is unblocked. Called by signalled
311	>	* Notifies pool that thread is unblocked. Called by signalled
312		* threads when woken by non-FJ threads (which is atypical).
313		*/
314		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
315		int s;
316	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
316	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
317		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
318		pool.updateRunningCount(s);
319		}
320
321		/**
322	<	* Notify pool to adjust counts on cancelled or timed out wait
322	>	* Notifies pool to adjust counts on cancelled or timed out wait.
323		*/
324		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
325		if (pool != null) {
#	Line 314 | Line 333 | public abstract class ForkJoinTask<V> im
333		}
334		}
335
336	+	/**
337	+	* Handles interruptions during waits.
338	+	*/
339		private void onInterruptedWait() {
340	<	Thread t = Thread.currentThread();
341	<	if (t instanceof ForkJoinWorkerThread) {
342	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
343	<	if (w.isTerminating())
344	<	cancelIgnoreExceptions();
345	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
340	>	ForkJoinWorkerThread w = getWorker();
341	>	if (w == null)
342	>	Thread.currentThread().interrupt(); // re-interrupt
343	>	else if (w.isTerminating())
344	>	cancelIgnoringExceptions();
345	>	// else if FJworker, ignore interrupt
346		}
347
348		// Recording and reporting exceptions
#	Line 337 | Line 353 | public abstract class ForkJoinTask<V> im
353		}
354
355		/**
356	<	* Throws the exception associated with status s;
356	>	* Throws the exception associated with status s.
357	>	*
358		* @throws the exception
359		*/
360		private void reportException(int s) {
#	Line 350 | Line 367 | public abstract class ForkJoinTask<V> im
367		}
368
369		/**
370	<	* Returns result or throws exception using j.u.c.Future conventions
371	<	* Only call when isDone known to be true.
370	>	* Returns result or throws exception using j.u.c.Future conventions.
371	>	* Only call when {@code isDone} known to be true.
372		*/
373		private V reportFutureResult()
374		throws ExecutionException, InterruptedException {
#	Line 370 | Line 387 | public abstract class ForkJoinTask<V> im
387
388		/**
389		* Returns result or throws exception using j.u.c.Future conventions
390	<	* with timeouts
390	>	* with timeouts.
391		*/
392		private V reportTimedFutureResult()
393		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 391 | Line 408 | public abstract class ForkJoinTask<V> im
408
409		/**
410		* Calls exec, recording completion, and rethrowing exception if
411	<	* encountered. Caller should normally check status before calling
411	>	* encountered. Caller should normally check status before calling.
412	>	*
413		* @return true if completed normally
414		*/
415		private boolean tryExec() {
#	Line 409 | Line 427 | public abstract class ForkJoinTask<V> im
427
428		/**
429		* Main execution method used by worker threads. Invokes
430	<	* base computation unless already complete
430	>	* base computation unless already complete.
431		*/
432		final void quietlyExec() {
433		if (status >= 0) {
434		try {
435		if (!exec())
436		return;
437	<	} catch(Throwable rex) {
437	>	} catch (Throwable rex) {
438		setDoneExceptionally(rex);
439		return;
440		}
#	Line 425 | Line 443 | public abstract class ForkJoinTask<V> im
443		}
444
445		/**
446	<	* Calls exec, recording but not rethrowing exception
447	<	* Caller should normally check status before calling
446	>	* Calls exec(), recording but not rethrowing exception.
447	>	* Caller should normally check status before calling.
448	>	*
449		* @return true if completed normally
450		*/
451		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 461 | public abstract class ForkJoinTask<V> im
461		}
462
463		/**
464	<	* Cancel, ignoring any exceptions it throws
464	>	* Cancels, ignoring any exceptions it throws.
465		*/
466	<	final void cancelIgnoreExceptions() {
466	>	final void cancelIgnoringExceptions() {
467		try {
468		cancel(false);
469	<	} catch(Throwable ignore) {
469	>	} catch (Throwable ignore) {
470		}
471		}
472
473	+	/**
474	+	* Main implementation of helpJoin
475	+	*/
476	+	private int busyJoin(ForkJoinWorkerThread w) {
477	+	int s;
478	+	ForkJoinTask<?> t;
479	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
480	+	t.quietlyExec();
481	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
482	+	}
483	+
484		// public methods
485
486		/**
487		* Arranges to asynchronously execute this task.  While it is not
488		* necessarily enforced, it is a usage error to fork a task more
489		* than once unless it has completed and been reinitialized.  This
490	<	* method may be invoked only from within other ForkJoinTask
491	<	* computations. Attempts to invoke in other contexts result in
492	<	* exceptions or errors including ClassCastException.
490	>	* method may be invoked only from within ForkJoinTask
491	>	* computations (as may be determined using method {@link
492	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
493	>	* in exceptions or errors, possibly including ClassCastException.
494	>	*
495	>	* @return {@code this}, to simplify usage.
496		*/
497	<	public final void fork() {
498	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
497	>	public final ForkJoinTask<V> fork() {
498	>	((ForkJoinWorkerThread) Thread.currentThread())
499	>	.pushTask(this);
500	>	return this;
501		}
502
503		/**
504		* Returns the result of the computation when it is ready.
505	<	* This method differs from <tt>get</tt> in that abnormal
505	>	* This method differs from {@code get} in that abnormal
506		* completion results in RuntimeExceptions or Errors, not
507		* ExecutionExceptions.
508		*
#	Line 480 | Line 515 | public abstract class ForkJoinTask<V> im
515		return getRawResult();
516		}
517
483	–	public final V get() throws InterruptedException, ExecutionException {
484	–	ForkJoinWorkerThread w = getWorker();
485	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
486	–	awaitDone(w, true);
487	–	return reportFutureResult();
488	–	}
489	–
490	–	public final V get(long timeout, TimeUnit unit)
491	–	throws InterruptedException, ExecutionException, TimeoutException {
492	–	ForkJoinWorkerThread w = getWorker();
493	–	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
494	–	awaitDone(w, unit.toNanos(timeout));
495	–	return reportTimedFutureResult();
496	–	}
497	–
498	–	/**
499	–	* Possibly executes other tasks until this task is ready, then
500	–	* returns the result of the computation.  This method may be more
501	–	* efficient than <tt>join</tt>, but is only applicable when there
502	–	* are no potemtial dependencies between continuation of the
503	–	* current task and that of any other task that might be executed
504	–	* while helping. (This usually holds for pure divide-and-conquer
505	–	* tasks).
506	–	* @return the computed result
507	–	*/
508	–	public final V helpJoin() {
509	–	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
510	–	if (status < 0 || !w.unpushTask(this) || !tryExec())
511	–	reportException(w.helpJoinTask(this));
512	–	return getRawResult();
513	–	}
514	–
518		/**
519	<	* Performs this task, awaits its completion if necessary, and
520	<	* return its result.
519	>	* Commences performing this task, awaits its completion if
520	>	* necessary, and return its result.
521	>	*
522		* @throws Throwable (a RuntimeException, Error, or unchecked
523	<	* exception) if the underlying computation did so.
523	>	* exception) if the underlying computation did so
524		* @return the computed result
525		*/
526		public final V invoke() {
#	Line 527 | Line 531 | public abstract class ForkJoinTask<V> im
531		}
532
533		/**
534	<	* Joins this task, without returning its result or throwing an
535	<	* exception. This method may be useful when processing
536	<	* collections of tasks when some have been cancelled or otherwise
537	<	* known to have aborted.
534	>	* Forks both tasks, returning when {@code isDone} holds for
535	>	* both of them or an exception is encountered. This method may be
536	>	* invoked only from within ForkJoinTask computations (as may be
537	>	* determined using method {@link #inForkJoinPool}). Attempts to
538	>	* invoke in other contexts result in exceptions or errors,
539	>	* possibly including ClassCastException.
540	>	*
541	>	* @param t1 one task
542	>	* @param t2 the other task
543	>	* @throws NullPointerException if t1 or t2 are null
544	>	* @throws RuntimeException or Error if either task did so
545		*/
546	<	public final void quietlyJoin() {
547	<	if (status >= 0) {
548	<	ForkJoinWorkerThread w = getWorker();
549	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
546	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
547	>	t2.fork();
548	>	t1.invoke();
549	>	t2.join();
550		}
551
552		/**
553	<	* Possibly executes other tasks until this task is ready.
553	>	* Forks the given tasks, returning when {@code isDone} holds
554	>	* for all of them. If any task encounters an exception, others
555	>	* may be cancelled.  This method may be invoked only from within
556	>	* ForkJoinTask computations (as may be determined using method
557	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
558	>	* result in exceptions or errors, possibly including
559	>	* ClassCastException.
560	>	*
561	>	* @param tasks the array of tasks
562	>	* @throws NullPointerException if tasks or any element are null
563	>	* @throws RuntimeException or Error if any task did so
564		*/
565	<	public final void quietlyHelpJoin() {
566	<	if (status >= 0) {
567	<	ForkJoinWorkerThread w =
568	<	(ForkJoinWorkerThread)(Thread.currentThread());
569	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
570	<	w.helpJoinTask(this);
565	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
566	>	Throwable ex = null;
567	>	int last = tasks.length - 1;
568	>	for (int i = last; i >= 0; --i) {
569	>	ForkJoinTask<?> t = tasks[i];
570	>	if (t == null) {
571	>	if (ex == null)
572	>	ex = new NullPointerException();
573	>	}
574	>	else if (i != 0)
575	>	t.fork();
576	>	else {
577	>	t.quietlyInvoke();
578	>	if (ex == null)
579	>	ex = t.getException();
580	>	}
581	>	}
582	>	for (int i = 1; i <= last; ++i) {
583	>	ForkJoinTask<?> t = tasks[i];
584	>	if (t != null) {
585	>	if (ex != null)
586	>	t.cancel(false);
587	>	else {
588	>	t.quietlyJoin();
589	>	if (ex == null)
590	>	ex = t.getException();
591	>	}
592	>	}
593		}
594	+	if (ex != null)
595	+	rethrowException(ex);
596		}
597
598		/**
599	<	* Performs this task and awaits its completion if necessary,
600	<	* without returning its result or throwing an exception. This
601	<	* method may be useful when processing collections of tasks when
602	<	* some have been cancelled or otherwise known to have aborted.
603	<	*/
604	<	public final void quietlyInvoke() {
605	<	if (status >= 0 && !tryQuietlyInvoke())
606	<	quietlyJoin();
599	>	* Forks all tasks in the collection, returning when
600	>	* {@code isDone} holds for all of them. If any task
601	>	* encounters an exception, others may be cancelled.  This method
602	>	* may be invoked only from within ForkJoinTask computations (as
603	>	* may be determined using method {@link
604	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
605	>	* in exceptions or errors, possibly including ClassCastException.
606	>	*
607	>	* @param tasks the collection of tasks
608	>	* @return the tasks argument, to simplify usage
609	>	* @throws NullPointerException if tasks or any element are null
610	>	* @throws RuntimeException or Error if any task did so
611	>	*/
612	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
613	>	if (!(tasks instanceof List<?>)) {
614	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
615	>	return tasks;
616	>	}
617	>	@SuppressWarnings("unchecked")
618	>	List<? extends ForkJoinTask<?>> ts =
619	>	(List<? extends ForkJoinTask<?>>) tasks;
620	>	Throwable ex = null;
621	>	int last = ts.size() - 1;
622	>	for (int i = last; i >= 0; --i) {
623	>	ForkJoinTask<?> t = ts.get(i);
624	>	if (t == null) {
625	>	if (ex == null)
626	>	ex = new NullPointerException();
627	>	}
628	>	else if (i != 0)
629	>	t.fork();
630	>	else {
631	>	t.quietlyInvoke();
632	>	if (ex == null)
633	>	ex = t.getException();
634	>	}
635	>	}
636	>	for (int i = 1; i <= last; ++i) {
637	>	ForkJoinTask<?> t = ts.get(i);
638	>	if (t != null) {
639	>	if (ex != null)
640	>	t.cancel(false);
641	>	else {
642	>	t.quietlyJoin();
643	>	if (ex == null)
644	>	ex = t.getException();
645	>	}
646	>	}
647	>	}
648	>	if (ex != null)
649	>	rethrowException(ex);
650	>	return tasks;
651		}
652
653		/**
654	<	* Returns true if the computation performed by this task has
655	<	* completed (or has been cancelled).
656	<	* @return true if this computation has completed
654	>	* Returns {@code true} if the computation performed by this task
655	>	* has completed (or has been cancelled).
656	>	*
657	>	* @return {@code true} if this computation has completed
658		*/
659		public final boolean isDone() {
660		return status < 0;
661		}
662
663		/**
664	<	* Returns true if this task was cancelled.
665	<	* @return true if this task was cancelled
664	>	* Returns {@code true} if this task was cancelled.
665	>	*
666	>	* @return {@code true} if this task was cancelled
667		*/
668		public final boolean isCancelled() {
669		return (status & COMPLETION_MASK) == CANCELLED;
670		}
671
672		/**
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	–	/**
673		* Asserts that the results of this task's computation will not be
674	<	* used. If a cancellation occurs before this task is processed,
675	<	* then its <tt>compute</tt> method will not be executed,
676	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
677	<	* result in a CancellationException being thrown. Otherwise, when
674	>	* used. If a cancellation occurs before attempting to execute this
675	>	* task, execution will be suppressed, {@link #isCancelled}
676	>	* will report true, and {@link #join} will result in a
677	>	* {@code CancellationException} being thrown. Otherwise, when
678		* cancellation races with completion, there are no guarantees
679	<	* about whether <tt>isCancelled</tt> will report true, whether
680	<	* <tt>join</tt> will return normally or via an exception, or
681	<	* whether these behaviors will remain consistent upon repeated
679	>	* about whether {@code isCancelled} will report {@code true},
680	>	* whether {@code join} will return normally or via an exception,
681	>	* or whether these behaviors will remain consistent upon repeated
682		* invocation.
683		*
684		* <p>This method may be overridden in subclasses, but if so, must
#	Line 622 | Line 688 | public abstract class ForkJoinTask<V> im
688		* <p> This method is designed to be invoked by <em>other</em>
689		* tasks. To terminate the current task, you can just return or
690		* throw an unchecked exception from its computation method, or
691	<	* invoke <tt>completeExceptionally(someException)</tt>.
691	>	* invoke {@link #completeExceptionally}.
692		*
693		* @param mayInterruptIfRunning this value is ignored in the
694		* default implementation because tasks are not in general
695	<	* cancelled via interruption.
695	>	* cancelled via interruption
696		*
697	<	* @return true if this task is now cancelled
697	>	* @return {@code true} if this task is now cancelled
698		*/
699		public boolean cancel(boolean mayInterruptIfRunning) {
700		setCompletion(CANCELLED);
#	Line 636 | Line 702 | public abstract class ForkJoinTask<V> im
702		}
703
704		/**
705	+	* Returns {@code true} if this task threw an exception or was cancelled.
706	+	*
707	+	* @return {@code true} if this task threw an exception or was cancelled
708	+	*/
709	+	public final boolean isCompletedAbnormally() {
710	+	return (status & COMPLETION_MASK) < NORMAL;
711	+	}
712	+
713	+	/**
714	+	* Returns the exception thrown by the base computation, or a
715	+	* CancellationException if cancelled, or null if none or if the
716	+	* method has not yet completed.
717	+	*
718	+	* @return the exception, or {@code null} if none
719	+	*/
720	+	public final Throwable getException() {
721	+	int s = status & COMPLETION_MASK;
722	+	if (s >= NORMAL)
723	+	return null;
724	+	if (s == CANCELLED)
725	+	return new CancellationException();
726	+	return exceptionMap.get(this);
727	+	}
728	+
729	+	/**
730		* Completes this task abnormally, and if not already aborted or
731		* cancelled, causes it to throw the given exception upon
732	<	* <tt>join</tt> and related operations. This method may be used
732	>	* {@code join} and related operations. This method may be used
733		* to induce exceptions in asynchronous tasks, or to force
734	<	* completion of tasks that would not otherwise complete.  This
735	<	* method is overridable, but overridden versions must invoke
736	<	* <tt>super</tt> implementation to maintain guarantees.
734	>	* completion of tasks that would not otherwise complete.  Its use
735	>	* in other situations is likely to be wrong.  This method is
736	>	* overridable, but overridden versions must invoke {@code super}
737	>	* implementation to maintain guarantees.
738	>	*
739		* @param ex the exception to throw. If this exception is
740		* not a RuntimeException or Error, the actual exception thrown
741		* will be a RuntimeException with cause ex.
742		*/
743		public void completeExceptionally(Throwable ex) {
744		setDoneExceptionally((ex instanceof RuntimeException) ||
745	<	(ex instanceof Error)? ex :
745	>	(ex instanceof Error) ? ex :
746		new RuntimeException(ex));
747		}
748
749		/**
750		* Completes this task, and if not already aborted or cancelled,
751	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
751	>	* returning a {@code null} result upon {@code join} and related
752		* operations. This method may be used to provide results for
753		* asynchronous tasks, or to provide alternative handling for
754	<	* tasks that would not otherwise complete normally.
754	>	* tasks that would not otherwise complete normally. Its use in
755	>	* other situations is likely to be wrong. This method is
756	>	* overridable, but overridden versions must invoke {@code super}
757	>	* implementation to maintain guarantees.
758		*
759	<	* @param value the result value for this task.
759	>	* @param value the result value for this task
760		*/
761		public void complete(V value) {
762		try {
763		setRawResult(value);
764	<	} catch(Throwable rex) {
764	>	} catch (Throwable rex) {
765		setDoneExceptionally(rex);
766		return;
767		}
768		setNormalCompletion();
769		}
770
771	+	public final V get() throws InterruptedException, ExecutionException {
772	+	ForkJoinWorkerThread w = getWorker();
773	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
774	+	awaitDone(w, true);
775	+	return reportFutureResult();
776	+	}
777	+
778	+	public final V get(long timeout, TimeUnit unit)
779	+	throws InterruptedException, ExecutionException, TimeoutException {
780	+	ForkJoinWorkerThread w = getWorker();
781	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
782	+	awaitDone(w, unit.toNanos(timeout));
783	+	return reportTimedFutureResult();
784	+	}
785	+
786	+	/**
787	+	* Possibly executes other tasks until this task is ready, then
788	+	* returns the result of the computation.  This method may be more
789	+	* efficient than {@code join}, but is only applicable when
790	+	* there are no potential dependencies between continuation of the
791	+	* current task and that of any other task that might be executed
792	+	* while helping. (This usually holds for pure divide-and-conquer
793	+	* tasks). This method may be invoked only from within
794	+	* ForkJoinTask computations (as may be determined using method
795	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
796	+	* result in exceptions or errors, possibly including
797	+	* ClassCastException.
798	+	*
799	+	* @return the computed result
800	+	*/
801	+	public final V helpJoin() {
802	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
803	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
804	+	reportException(busyJoin(w));
805	+	return getRawResult();
806	+	}
807	+
808	+	/**
809	+	* Possibly executes other tasks until this task is ready.  This
810	+	* method may be invoked only from within ForkJoinTask
811	+	* computations (as may be determined using method {@link
812	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
813	+	* in exceptions or errors, possibly including ClassCastException.
814	+	*/
815	+	public final void quietlyHelpJoin() {
816	+	if (status >= 0) {
817	+	ForkJoinWorkerThread w =
818	+	(ForkJoinWorkerThread) Thread.currentThread();
819	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
820	+	busyJoin(w);
821	+	}
822	+	}
823	+
824	+	/**
825	+	* Joins this task, without returning its result or throwing an
826	+	* exception. This method may be useful when processing
827	+	* collections of tasks when some have been cancelled or otherwise
828	+	* known to have aborted.
829	+	*/
830	+	public final void quietlyJoin() {
831	+	if (status >= 0) {
832	+	ForkJoinWorkerThread w = getWorker();
833	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
834	+	awaitDone(w, true);
835	+	}
836	+	}
837	+
838	+	/**
839	+	* Commences performing this task and awaits its completion if
840	+	* necessary, without returning its result or throwing an
841	+	* exception. This method may be useful when processing
842	+	* collections of tasks when some have been cancelled or otherwise
843	+	* known to have aborted.
844	+	*/
845	+	public final void quietlyInvoke() {
846	+	if (status >= 0 && !tryQuietlyInvoke())
847	+	quietlyJoin();
848	+	}
849	+
850	+	/**
851	+	* Possibly executes tasks until the pool hosting the current task
852	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
853	+	* designs in which many tasks are forked, but none are explicitly
854	+	* joined, instead executing them until all are processed.
855	+	*/
856	+	public static void helpQuiesce() {
857	+	((ForkJoinWorkerThread) Thread.currentThread())
858	+	.helpQuiescePool();
859	+	}
860	+
861		/**
862		* Resets the internal bookkeeping state of this task, allowing a
863	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
863	>	* subsequent {@code fork}. This method allows repeated reuse of
864		* this task, but only if reuse occurs when this task has either
865		* never been forked, or has been forked, then completed and all
866		* outstanding joins of this task have also completed. Effects
#	Line 689 | Line 875 | public abstract class ForkJoinTask<V> im
875		}
876
877		/**
878	<	* Tries to unschedule this task for execution. This method will
879	<	* typically succeed if this task is the next task that would be
880	<	* executed by the current thread, and will typically fail (return
881	<	* 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.
878	>	* Returns the pool hosting the current task execution, or null
879	>	* if this task is executing outside of any ForkJoinPool.
880	>	*
881	>	* @return the pool, or {@code null} if none
882		*/
883	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
884	<	t2.fork();
885	<	t1.invoke();
886	<	t2.join();
883	>	public static ForkJoinPool getPool() {
884	>	Thread t = Thread.currentThread();
885	>	return (t instanceof ForkJoinWorkerThread) ?
886	>	((ForkJoinWorkerThread) t).pool : null;
887		}
888
889		/**
890	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
891	<	* all of them. If any task encounters an exception, others may be
892	<	* cancelled.  This method may be invoked only from within other
893	<	* ForkJoinTask computations. Attempts to invoke in other contexts
894	<	* 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.
890	>	* Returns {@code true} if the current thread is executing as a
891	>	* ForkJoinPool computation.
892	>	*
893	>	* @return {@code true} if the current thread is executing as a
894	>	* ForkJoinPool computation, or false otherwise
895		*/
896	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
897	<	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);
896	>	public static boolean inForkJoinPool() {
897	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
898		}
899
900		/**
901	<	* Forks all tasks in the collection, returning when
902	<	* <tt>isDone</tt> holds for all of them. If any task encounters
903	<	* an exception, others may be cancelled.  This method may be
904	<	* invoked only from within other ForkJoinTask
905	<	* computations. Attempts to invoke in other contexts result in
906	<	* exceptions or errors including ClassCastException.
907	<	* @param tasks the collection of tasks
908	<	* @throws NullPointerException if tasks or any element are null.
909	<	* @throws RuntimeException or Error if any task did so.
901	>	* Tries to unschedule this task for execution. This method will
902	>	* typically succeed if this task is the most recently forked task
903	>	* by the current thread, and has not commenced executing in
904	>	* another thread.  This method may be useful when arranging
905	>	* alternative local processing of tasks that could have been, but
906	>	* were not, stolen. This method may be invoked only from within
907	>	* ForkJoinTask computations (as may be determined using method
908	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
909	>	* result in exceptions or errors, possibly including
910	>	* ClassCastException.
911	>	*
912	>	* @return {@code true} if unforked
913		*/
914	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
915	<	if (!(tasks instanceof List)) {
916	<	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);
914	>	public boolean tryUnfork() {
915	>	return ((ForkJoinWorkerThread) Thread.currentThread())
916	>	.unpushTask(this);
917		}
918
919		/**
920	<	* Possibly executes tasks until the pool hosting the current task
921	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
922	<	* designs in which many tasks are forked, but none are explicitly
923	<	* joined, instead executing them until all are processed.
920	>	* Returns an estimate of the number of tasks that have been
921	>	* forked by the current worker thread but not yet executed. This
922	>	* value may be useful for heuristic decisions about whether to
923	>	* fork other tasks.
924	>	*
925	>	* @return the number of tasks
926		*/
927	<	public static void helpQuiesce() {
928	<	((ForkJoinWorkerThread)(Thread.currentThread())).
929	<	helpQuiescePool();
927	>	public static int getQueuedTaskCount() {
928	>	return ((ForkJoinWorkerThread) Thread.currentThread())
929	>	.getQueueSize();
930		}
931
932		/**
933	<	* Returns a estimate of how many more locally queued tasks are
933	>	* Returns an estimate of how many more locally queued tasks are
934		* held by the current worker thread than there are other worker
935	<	* threads that might want to steal them.  This value may be
936	<	* useful for heuristic decisions about whether to fork other
937	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
938	<	* worker should aim to maintain a small constant surplus (for
939	<	* example, 3) of tasks, and to process computations locally if
940	<	* this threshold is exceeded.
935	>	* threads that might steal them.  This value may be useful for
936	>	* heuristic decisions about whether to fork other tasks. In many
937	>	* usages of ForkJoinTasks, at steady state, each worker should
938	>	* aim to maintain a small constant surplus (for example, 3) of
939	>	* tasks, and to process computations locally if this threshold is
940	>	* exceeded.
941	>	*
942		* @return the surplus number of tasks, which may be negative
943		*/
944	<	public static int surplus() {
945	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
944	>	public static int getSurplusQueuedTaskCount() {
945	>	return ((ForkJoinWorkerThread) Thread.currentThread())
946		.getEstimatedSurplusTaskCount();
947		}
948
949	<	// Extension kit
949	>	// Extension methods
950
951		/**
952	<	* Returns the result that would be returned by <tt>join</tt>, or
953	<	* null if this task is not known to have been completed.  This
954	<	* method is designed to aid debugging, as well as to support
955	<	* extensions. Its use in any other context is discouraged.
952	>	* Returns the result that would be returned by {@link #join}, even
953	>	* if this task completed abnormally, or {@code null} if this task
954	>	* is not known to have been completed.  This method is designed
955	>	* to aid debugging, as well as to support extensions. Its use in
956	>	* any other context is discouraged.
957		*
958	<	* @return the result, or null if not completed.
958	>	* @return the result, or {@code null} if not completed
959		*/
960		public abstract V getRawResult();
961
#	Line 865 | Line 974 | public abstract class ForkJoinTask<V> im
974		* called otherwise. The return value controls whether this task
975		* is considered to be done normally. It may return false in
976		* asynchronous actions that require explicit invocations of
977	<	* <tt>complete</tt> to become joinable. It may throw exceptions
977	>	* {@link #complete} to become joinable. It may throw exceptions
978		* to indicate abnormal exit.
979	<	* @return true if completed normally
979	>	*
980	>	* @return {@code true} if completed normally
981		* @throws Error or RuntimeException if encountered during computation
982		*/
983		protected abstract boolean exec();
984
985	+	/**
986	+	* Returns, but does not unschedule or execute, the task queued by
987	+	* the current thread but not yet executed, if one is
988	+	* available. There is no guarantee that this task will actually
989	+	* be polled or executed next.  This method is designed primarily
990	+	* to support extensions, and is unlikely to be useful otherwise.
991	+	* This method may be invoked only from within ForkJoinTask
992	+	* computations (as may be determined using method {@link
993	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
994	+	* in exceptions or errors, possibly including ClassCastException.
995	+	*
996	+	* @return the next task, or {@code null} if none are available
997	+	*/
998	+	protected static ForkJoinTask<?> peekNextLocalTask() {
999	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1000	+	.peekTask();
1001	+	}
1002	+
1003	+	/**
1004	+	* Unschedules and returns, without executing, the next task
1005	+	* queued by the current thread but not yet executed.  This method
1006	+	* is designed primarily to support extensions, and is unlikely to
1007	+	* be useful otherwise.  This method may be invoked only from
1008	+	* within ForkJoinTask computations (as may be determined using
1009	+	* method {@link #inForkJoinPool}). Attempts to invoke in other
1010	+	* contexts result in exceptions or errors, possibly including
1011	+	* ClassCastException.
1012	+	*
1013	+	* @return the next task, or {@code null} if none are available
1014	+	*/
1015	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1016	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1017	+	.pollLocalTask();
1018	+	}
1019	+
1020	+	/**
1021	+	* Unschedules and returns, without executing, the next task
1022	+	* queued by the current thread but not yet executed, if one is
1023	+	* available, or if not available, a task that was forked by some
1024	+	* other thread, if available. Availability may be transient, so a
1025	+	* {@code null} result does not necessarily imply quiescence
1026	+	* of the pool this task is operating in.  This method is designed
1027	+	* primarily to support extensions, and is unlikely to be useful
1028	+	* otherwise.  This method may be invoked only from within
1029	+	* ForkJoinTask computations (as may be determined using method
1030	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1031	+	* result in exceptions or errors, possibly including
1032	+	* ClassCastException.
1033	+	*
1034	+	* @return a task, or {@code null} if none are available
1035	+	*/
1036	+	protected static ForkJoinTask<?> pollTask() {
1037	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1038	+	.pollTask();
1039	+	}
1040	+
1041	+	// adaptors
1042	+
1043	+	/**
1044	+	* Returns a new ForkJoinTask that performs the {@code run}
1045	+	* method of the given Runnable as its action, and returns a null
1046	+	* result upon {@code join}.
1047	+	*
1048	+	* @param runnable the runnable action
1049	+	* @return the task
1050	+	*/
1051	+	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1052	+	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1053	+	}
1054	+
1055	+	/**
1056	+	* Returns a new ForkJoinTask that performs the {@code run}
1057	+	* method of the given Runnable as its action, and returns the
1058	+	* given result upon {@code join}.
1059	+	*
1060	+	* @param runnable the runnable action
1061	+	* @param result the result upon completion
1062	+	* @return the task
1063	+	*/
1064	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1065	+	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1066	+	}
1067	+
1068	+	/**
1069	+	* Returns a new ForkJoinTask that performs the {@code call}
1070	+	* method of the given Callable as its action, and returns its
1071	+	* result upon {@code join}, translating any checked
1072	+	* exceptions encountered into {@code RuntimeException}.
1073	+	*
1074	+	* @param callable the callable action
1075	+	* @return the task
1076	+	*/
1077	+	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1078	+	return new ForkJoinPool.AdaptedCallable<T>(callable);
1079	+	}
1080	+
1081		// Serialization support
1082
1083		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1086 | public abstract class ForkJoinTask<V> im
1086		* Save the state to a stream.
1087		*
1088		* @serialData the current run status and the exception thrown
1089	<	* during execution, or null if none.
1089	>	* during execution, or {@code null} if none
1090		* @param s the stream
1091		*/
1092		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1097 | public abstract class ForkJoinTask<V> im
1097
1098		/**
1099		* Reconstitute the instance from a stream.
1100	+	*
1101		* @param s the stream
1102		*/
1103		private void readObject(java.io.ObjectInputStream s)
1104		throws java.io.IOException, ClassNotFoundException {
1105		s.defaultReadObject();
1106	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1106	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1107	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1108		Object ex = s.readObject();
1109		if (ex != null)
1110	<	setDoneExceptionally((Throwable)ex);
1110	>	setDoneExceptionally((Throwable) ex);
1111		}
1112
1113	<	// Temporary Unsafe mechanics for preliminary release
1113	>	// Unsafe mechanics
1114
1115	<	static final Unsafe _unsafe;
1116	<	static final long statusOffset;
1115	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1116	>	private static final long statusOffset =
1117	>	objectFieldOffset("status", ForkJoinTask.class);
1118
1119	<	static {
1119	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1120		try {
1121	<	if (ForkJoinTask.class.getClassLoader() != null) {
1122	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1123	<	f.setAccessible(true);
1124	<	_unsafe = (Unsafe)f.get(null);
1125	<	}
1126	<	else
1127	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1121	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1122	>	} catch (NoSuchFieldException e) {
1123	>	// Convert Exception to corresponding Error
1124	>	NoSuchFieldError error = new NoSuchFieldError(field);
1125	>	error.initCause(e);
1126	>	throw error;
1127	>	}
1128		}
1129
1130	+	/**
1131	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1132	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1133	+	* into a jdk.
1134	+	*
1135	+	* @return a sun.misc.Unsafe
1136	+	*/
1137	+	private static sun.misc.Unsafe getUnsafe() {
1138	+	try {
1139	+	return sun.misc.Unsafe.getUnsafe();
1140	+	} catch (SecurityException se) {
1141	+	try {
1142	+	return java.security.AccessController.doPrivileged
1143	+	(new java.security
1144	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1145	+	public sun.misc.Unsafe run() throws Exception {
1146	+	java.lang.reflect.Field f = sun.misc
1147	+	.Unsafe.class.getDeclaredField("theUnsafe");
1148	+	f.setAccessible(true);
1149	+	return (sun.misc.Unsafe) f.get(null);
1150	+	}});
1151	+	} catch (java.security.PrivilegedActionException e) {
1152	+	throw new RuntimeException("Could not initialize intrinsics",
1153	+	e.getCause());
1154	+	}
1155	+	}
1156	+	}
1157		}

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