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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.1 by dl, Tue Jan 6 14:30:31 2009 UTC vs.
Revision 1.16 by jsr166, Fri Jul 24 23:47:01 2009 UTC

#	Line 9 | Line 9 | import java.io.Serializable;
9		import java.util.*;
10		import java.util.concurrent.*;
11		import java.util.concurrent.atomic.*;
12	–	import sun.misc.Unsafe;
13	–	import java.lang.reflect.*;
12
13		/**
14	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
15	<	* ForkJoinTask is a thread-like entity that is much lighter weight
16	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
17	<	* hosted by a small number of actual threads in a ForkJoinPool,
18	<	* at the price of some usage limitations.
14	>	* Abstract base class for tasks that run within a {@link
15	>	* ForkJoinPool}.  A ForkJoinTask is a thread-like entity that is much
16	>	* lighter weight than a normal thread.  Huge numbers of tasks and
17	>	* subtasks may be hosted by a small number of actual threads in a
18	>	* ForkJoinPool, at the price of some usage limitations.
19		*
20	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
21	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
22	<	* set of restrictions (that are only partially statically
23	<	* enforceable) reflecting their intended use as computational tasks
24	<	* calculating pure functions or operating on purely isolated objects.
25	<	* The primary coordination mechanisms supported for ForkJoinTasks are
26	<	* <tt>fork</tt>, that arranges asynchronous execution, and
27	<	* <tt>join</tt>, that doesn't proceed until the task's result has
28	<	* been computed. (Cancellation is also supported).  The computation
29	<	* defined in the <tt>compute</tt> method should avoid
30	<	* <tt>synchronized</tt> methods or blocks, and should minimize
31	<	* blocking synchronization apart from joining other tasks or using
20	>	* <p> A "main" ForkJoinTask begins execution when submitted to a
21	>	* {@link ForkJoinPool}. Once started, it will usually in turn start
22	>	* other subtasks.  As indicated by the name of this class, many
23	>	* programs using ForkJoinTasks employ only methods {@code fork}
24	>	* and {@code join}, or derivatives such as
25	>	* {@code invokeAll}.  However, this class also provides a number
26	>	* of other methods that can come into play in advanced usages, as
27	>	* well as extension mechanics that allow support of new forms of
28	>	* fork/join processing.
29	>	*
30	>	* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
31	>	* efficiency of ForkJoinTasks stems from a set of restrictions (that
32	>	* are only partially statically enforceable) reflecting their
33	>	* intended use as computational tasks calculating pure functions or
34	>	* operating on purely isolated objects.  The primary coordination
35	>	* mechanisms are {@link #fork}, that arranges asynchronous execution,
36	>	* and {@link #join}, that doesn't proceed until the task's result has
37	>	* been computed.  Computations should avoid {@code synchronized}
38	>	* methods or blocks, and should minimize other blocking
39	>	* synchronization apart from joining other tasks or using
40		* synchronizers such as Phasers that are advertised to cooperate with
41		* fork/join scheduling. Tasks should also not perform blocking IO,
42		* and should ideally access variables that are completely independent
#	Line 38 | Line 44 | import java.lang.reflect.*;
44		* restrictions, for example using shared output streams, may be
45		* tolerable in practice, but frequent use may result in poor
46		* performance, and the potential to indefinitely stall if the number
47	<	* of threads not waiting for external synchronization becomes
48	<	* exhausted. This usage restriction is in part enforced by not
49	<	* permitting checked exceptions such as IOExceptions to be
50	<	* thrown. However, computations may still encounter unchecked
47	>	* of threads not waiting for IO or other external synchronization
48	>	* becomes exhausted. This usage restriction is in part enforced by
49	>	* not permitting checked exceptions such as {@code IOExceptions}
50	>	* to be thrown. However, computations may still encounter unchecked
51		* exceptions, that are rethrown to callers attempting join
52		* them. These exceptions may additionally include
53		* RejectedExecutionExceptions stemming from internal resource
54		* exhaustion such as failure to allocate internal task queues.
55		*
56	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
57	<	* subclassed.  Instead, you subclass one of the abstract classes that
58	<	* support different styles of fork/join processing.  Normally, a
59	<	* concrete ForkJoinTask subclass declares fields comprising its
60	<	* parameters, established in a constructor, and then defines a
61	<	* <tt>compute</tt> method that somehow uses the control methods
62	<	* supplied by this base class. While these methods have
63	<	* <tt>public</tt> access, some of them may only be called from within
64	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
65	<	* result in exceptions or errors including ClassCastException.  The
66	<	* only way to invoke a "main" driver task is to submit it to a
67	<	* ForkJoinPool. Once started, this will usually in turn start other
68	<	* subtasks.
56	>	* <p>The primary method for awaiting completion and extracting
57	>	* results of a task is {@link #join}, but there are several variants:
58	>	* The {@link Future#get} methods support interruptible and/or timed
59	>	* waits for completion and report results using {@code Future}
60	>	* conventions. Method {@link #helpJoin} enables callers to actively
61	>	* execute other tasks while awaiting joins, which is sometimes more
62	>	* efficient but only applies when all subtasks are known to be
63	>	* strictly tree-structured. Method {@link #invoke} is semantically
64	>	* equivalent to {@code fork(); join()} but always attempts to
65	>	* begin execution in the current thread. The "<em>quiet</em>" forms
66	>	* of these methods do not extract results or report exceptions. These
67	>	* may be useful when a set of tasks are being executed, and you need
68	>	* to delay processing of results or exceptions until all complete.
69	>	* Method {@code invokeAll} (available in multiple versions)
70	>	* performs the most common form of parallel invocation: forking a set
71	>	* of tasks and joining them all.
72	>	*
73	>	* <p> The ForkJoinTask class is not usually directly subclassed.
74	>	* Instead, you subclass one of the abstract classes that support a
75	>	* particular style of fork/join processing.  Normally, a concrete
76	>	* ForkJoinTask subclass declares fields comprising its parameters,
77	>	* established in a constructor, and then defines a {@code compute}
78	>	* method that somehow uses the control methods supplied by this base
79	>	* class. While these methods have {@code public} access (to allow
80	>	* instances of different task subclasses to call each others
81	>	* methods), some of them may only be called from within other
82	>	* ForkJoinTasks (as may be determined using method {@link
83	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
84	>	* result in exceptions or errors, possibly including
85	>	* ClassCastException.
86		*
87	<	* <p>Most base support methods are <tt>final</tt> because their
87	>	* <p>Most base support methods are {@code final} because their
88		* implementations are intrinsically tied to the underlying
89		* lightweight task scheduling framework, and so cannot be overridden.
90		* Developers creating new basic styles of fork/join processing should
91	<	* minimally implement protected methods <tt>exec</tt>,
92	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
93	<	* introducing an abstract computational method that can be
94	<	* implemented in its subclasses. To support such extensions,
95	<	* instances of ForkJoinTasks maintain an atomically updated
96	<	* <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.
91	>	* minimally implement {@code protected} methods
92	>	* {@code exec}, {@code setRawResult}, and
93	>	* {@code getRawResult}, while also introducing an abstract
94	>	* computational method that can be implemented in its subclasses,
95	>	* possibly relying on other {@code protected} methods provided
96	>	* by this class.
97		*
98		* <p>ForkJoinTasks should perform relatively small amounts of
99	<	* computations, othewise splitting into smaller tasks. As a very
99	>	* computations, otherwise splitting into smaller tasks. As a very
100		* rough rule of thumb, a task should perform more than 100 and less
101		* than 10000 basic computational steps. If tasks are too big, then
102	<	* parellelism cannot improve throughput. If too small, then memory
102	>	* parallelism cannot improve throughput. If too small, then memory
103		* and internal task maintenance overhead may overwhelm processing.
104		*
105	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
106	<	* be used in extensions such as remote execution frameworks. However,
107	<	* it is in general safe to serialize tasks only before or after, but
105	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
106	>	* to be used in extensions such as remote execution frameworks. It is
107	>	* in general sensible to serialize tasks only before or after, but
108		* not during execution. Serialization is not relied on during
109		* execution itself.
110	+	*
111	+	* @since 1.7
112	+	* @author Doug Lea
113		*/
114		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
115	+
116		/**
117	<	* Status field holding all run status. We pack this into a single
118	<	* int both to minimize footprint overhead and to ensure atomicity
119	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
117	>	* Run control status bits packed into a single int to minimize
118	>	* footprint and to ensure atomicity (via CAS).  Status is
119	>	* initially zero, and takes on nonnegative values until
120		* completed, upon which status holds COMPLETED. CANCELLED, or
121		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
122		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 131 | public abstract class ForkJoinTask<V> im
131		* currently unused. Also value 0x80000000 is available as spare
132		* completion value.
133		*/
134	<	volatile int status; // accessed directy by pool and workers
134	>	volatile int status; // accessed directly by pool and workers
135
136		static final int COMPLETION_MASK      = 0xe0000000;
137		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 144 | public abstract class ForkJoinTask<V> im
144		/**
145		* Table of exceptions thrown by tasks, to enable reporting by
146		* callers. Because exceptions are rare, we don't directly keep
147	<	* them with task objects, but instead us a weak ref table.  Note
147	>	* them with task objects, but instead use a weak ref table.  Note
148		* that cancellation exceptions don't appear in the table, but are
149		* instead recorded as status values.
150	<	* Todo: Use ConcurrentReferenceHashMap
150	>	* TODO: Use ConcurrentReferenceHashMap
151		*/
152		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
153		Collections.synchronizedMap
#	Line 136 | Line 156 | public abstract class ForkJoinTask<V> im
156		// within-package utilities
157
158		/**
159	<	* Get current worker thread, or null if not a worker thread
159	>	* Gets current worker thread, or null if not a worker thread.
160		*/
161		static ForkJoinWorkerThread getWorker() {
162		Thread t = Thread.currentThread();
163	<	return ((t instanceof ForkJoinWorkerThread)?
164	<	(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);
163	>	return ((t instanceof ForkJoinWorkerThread) ?
164	>	(ForkJoinWorkerThread) t : null);
165		}
166
167		final boolean casStatus(int cmp, int val) {
168	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
168	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
169		}
170
171		/**
#	Line 162 | Line 173 | public abstract class ForkJoinTask<V> im
173		*/
174		static void rethrowException(Throwable ex) {
175		if (ex != null)
176	<	_unsafe.throwException(ex);
176	>	UNSAFE.throwException(ex);
177		}
178
179		// Setting completion status
180
181		/**
182	<	* Mark completion and wake up threads waiting to join this task.
182	>	* Marks completion and wakes up threads waiting to join this task.
183	>	*
184		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
185		*/
186		final void setCompletion(int completion) {
187	<	ForkJoinPool pool = getWorkerPool();
187	>	ForkJoinPool pool = getPool();
188		if (pool != null) {
189		int s; // Clear signal bits while setting completion status
190	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
190	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
191
192		if ((s & SIGNAL_MASK) != 0) {
193		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
194		pool.updateRunningCount(s);
195	<	synchronized(this) { notifyAll(); }
195	>	synchronized (this) { notifyAll(); }
196		}
197		}
198		else
#	Line 193 | Line 205 | public abstract class ForkJoinTask<V> im
205		*/
206		private void externallySetCompletion(int completion) {
207		int s;
208	<	do;while ((s = status) >= 0 &&
209	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
210	<	synchronized(this) { notifyAll(); }
208	>	do {} while ((s = status) >= 0 &&
209	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
210	>	synchronized (this) { notifyAll(); }
211		}
212
213		/**
214	<	* Sets status to indicate normal completion
214	>	* Sets status to indicate normal completion.
215		*/
216		final void setNormalCompletion() {
217		// Try typical fast case -- single CAS, no signal, not already done.
218		// Manually expand casStatus to improve chances of inlining it
219	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
219	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
220		setCompletion(NORMAL);
221		}
222
223		// internal waiting and notification
224
225		/**
226	<	* Performs the actual monitor wait for awaitDone
226	>	* Performs the actual monitor wait for awaitDone.
227		*/
228		private void doAwaitDone() {
229		// Minimize lock bias and in/de-flation effects by maximizing
230		// chances of waiting inside sync
231		try {
232		while (status >= 0)
233	<	synchronized(this) { if (status >= 0) wait(); }
233	>	synchronized (this) { if (status >= 0) wait(); }
234		} catch (InterruptedException ie) {
235		onInterruptedWait();
236		}
237		}
238
239		/**
240	<	* Performs the actual monitor wait for awaitDone
240	>	* Performs the actual timed monitor wait for awaitDone.
241		*/
242		private void doAwaitDone(long startTime, long nanos) {
243	<	synchronized(this) {
243	>	synchronized (this) {
244		try {
245		while (status >= 0) {
246		long nt = nanos - System.nanoTime() - startTime;
247		if (nt <= 0)
248		break;
249	<	wait(nt / 1000000, (int)(nt % 1000000));
249	>	wait(nt / 1000000, (int) (nt % 1000000));
250		}
251		} catch (InterruptedException ie) {
252		onInterruptedWait();
#	Line 247 | Line 259 | public abstract class ForkJoinTask<V> im
259		/**
260		* Sets status to indicate there is joiner, then waits for join,
261		* surrounded with pool notifications.
262	+	*
263		* @return status upon exit
264		*/
265	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
266	<	ForkJoinPool pool = w == null? null : w.pool;
265	>	private int awaitDone(ForkJoinWorkerThread w,
266	>	boolean maintainParallelism) {
267	>	ForkJoinPool pool = (w == null) ? null : w.pool;
268		int s;
269		while ((s = status) >= 0) {
270	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
270	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
271		if (pool == null || !pool.preJoin(this, maintainParallelism))
272		doAwaitDone();
273		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 280 | public abstract class ForkJoinTask<V> im
280
281		/**
282		* Timed version of awaitDone
283	+	*
284		* @return status upon exit
285		*/
286	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
287	<	ForkJoinPool pool = w == null? null : w.pool;
286	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
287	>	ForkJoinPool pool = (w == null) ? null : w.pool;
288		int s;
289		while ((s = status) >= 0) {
290	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
290	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
291		long startTime = System.nanoTime();
292		if (pool == null || !pool.preJoin(this, false))
293		doAwaitDone(startTime, nanos);
#	Line 289 | Line 304 | public abstract class ForkJoinTask<V> im
304		}
305
306		/**
307	<	* Notify pool that thread is unblocked. Called by signalled
307	>	* Notifies pool that thread is unblocked. Called by signalled
308		* threads when woken by non-FJ threads (which is atypical).
309		*/
310		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
311		int s;
312	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
312	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
313		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
314		pool.updateRunningCount(s);
315		}
316
317		/**
318	<	* Notify pool to adjust counts on cancelled or timed out wait
318	>	* Notifies pool to adjust counts on cancelled or timed out wait.
319		*/
320		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
321		if (pool != null) {
#	Line 314 | Line 329 | public abstract class ForkJoinTask<V> im
329		}
330		}
331
332	+	/**
333	+	* Handles interruptions during waits.
334	+	*/
335		private void onInterruptedWait() {
336	<	Thread t = Thread.currentThread();
337	<	if (t instanceof ForkJoinWorkerThread) {
338	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
339	<	if (w.isTerminating())
340	<	cancelIgnoreExceptions();
341	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
336	>	ForkJoinWorkerThread w = getWorker();
337	>	if (w == null)
338	>	Thread.currentThread().interrupt(); // re-interrupt
339	>	else if (w.isTerminating())
340	>	cancelIgnoringExceptions();
341	>	// else if FJworker, ignore interrupt
342		}
343
344		// Recording and reporting exceptions
#	Line 337 | Line 349 | public abstract class ForkJoinTask<V> im
349		}
350
351		/**
352	<	* Throws the exception associated with status s;
352	>	* Throws the exception associated with status s.
353	>	*
354		* @throws the exception
355		*/
356		private void reportException(int s) {
#	Line 350 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Returns result or throws exception using j.u.c.Future conventions
367	<	* Only call when isDone known to be true.
366	>	* Returns result or throws exception using j.u.c.Future conventions.
367	>	* Only call when {@code isDone} known to be true.
368		*/
369		private V reportFutureResult()
370		throws ExecutionException, InterruptedException {
#	Line 370 | Line 383 | public abstract class ForkJoinTask<V> im
383
384		/**
385		* Returns result or throws exception using j.u.c.Future conventions
386	<	* with timeouts
386	>	* with timeouts.
387		*/
388		private V reportTimedFutureResult()
389		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 391 | Line 404 | public abstract class ForkJoinTask<V> im
404
405		/**
406		* Calls exec, recording completion, and rethrowing exception if
407	<	* encountered. Caller should normally check status before calling
407	>	* encountered. Caller should normally check status before calling.
408	>	*
409		* @return true if completed normally
410		*/
411		private boolean tryExec() {
#	Line 409 | Line 423 | public abstract class ForkJoinTask<V> im
423
424		/**
425		* Main execution method used by worker threads. Invokes
426	<	* base computation unless already complete
426	>	* base computation unless already complete.
427		*/
428		final void quietlyExec() {
429		if (status >= 0) {
430		try {
431		if (!exec())
432		return;
433	<	} catch(Throwable rex) {
433	>	} catch (Throwable rex) {
434		setDoneExceptionally(rex);
435		return;
436		}
#	Line 425 | Line 439 | public abstract class ForkJoinTask<V> im
439		}
440
441		/**
442	<	* Calls exec, recording but not rethrowing exception
443	<	* Caller should normally check status before calling
442	>	* Calls exec(), recording but not rethrowing exception.
443	>	* Caller should normally check status before calling.
444	>	*
445		* @return true if completed normally
446		*/
447		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 457 | public abstract class ForkJoinTask<V> im
457		}
458
459		/**
460	<	* Cancel, ignoring any exceptions it throws
460	>	* Cancels, ignoring any exceptions it throws.
461		*/
462	<	final void cancelIgnoreExceptions() {
462	>	final void cancelIgnoringExceptions() {
463		try {
464		cancel(false);
465	<	} catch(Throwable ignore) {
465	>	} catch (Throwable ignore) {
466		}
467		}
468
469	+	/**
470	+	* Main implementation of helpJoin
471	+	*/
472	+	private int busyJoin(ForkJoinWorkerThread w) {
473	+	int s;
474	+	ForkJoinTask<?> t;
475	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
476	+	t.quietlyExec();
477	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
478	+	}
479	+
480		// public methods
481
482		/**
483		* Arranges to asynchronously execute this task.  While it is not
484		* necessarily enforced, it is a usage error to fork a task more
485		* than once unless it has completed and been reinitialized.  This
486	<	* method may be invoked only from within other ForkJoinTask
487	<	* computations. Attempts to invoke in other contexts result in
488	<	* exceptions or errors including ClassCastException.
486	>	* method may be invoked only from within ForkJoinTask
487	>	* computations (as may be determined using method {@link
488	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
489	>	* in exceptions or errors, possibly including ClassCastException.
490		*/
491		public final void fork() {
492	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
492	>	((ForkJoinWorkerThread) Thread.currentThread())
493	>	.pushTask(this);
494		}
495
496		/**
497		* Returns the result of the computation when it is ready.
498	<	* This method differs from <tt>get</tt> in that abnormal
498	>	* This method differs from {@code get} in that abnormal
499		* completion results in RuntimeExceptions or Errors, not
500		* ExecutionExceptions.
501		*
#	Line 480 | Line 508 | public abstract class ForkJoinTask<V> im
508		return getRawResult();
509		}
510
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	–
511		/**
512	<	* Possibly executes other tasks until this task is ready, then
513	<	* returns the result of the computation.  This method may be more
514	<	* 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.
512	>	* Commences performing this task, awaits its completion if
513	>	* necessary, and return its result.
514	>	*
515		* @throws Throwable (a RuntimeException, Error, or unchecked
516	<	* exception) if the underlying computation did so.
516	>	* exception) if the underlying computation did so
517		* @return the computed result
518		*/
519		public final V invoke() {
#	Line 527 | Line 524 | public abstract class ForkJoinTask<V> im
524		}
525
526		/**
527	<	* Joins this task, without returning its result or throwing an
528	<	* exception. This method may be useful when processing
529	<	* collections of tasks when some have been cancelled or otherwise
530	<	* known to have aborted.
527	>	* Forks both tasks, returning when {@code isDone} holds for
528	>	* both of them or an exception is encountered. This method may be
529	>	* invoked only from within ForkJoinTask computations (as may be
530	>	* determined using method {@link #inForkJoinPool}). Attempts to
531	>	* invoke in other contexts result in exceptions or errors,
532	>	* possibly including ClassCastException.
533	>	*
534	>	* @param t1 one task
535	>	* @param t2 the other task
536	>	* @throws NullPointerException if t1 or t2 are null
537	>	* @throws RuntimeException or Error if either task did so
538		*/
539	<	public final void quietlyJoin() {
540	<	if (status >= 0) {
541	<	ForkJoinWorkerThread w = getWorker();
542	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
539	>	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
540	>	t2.fork();
541	>	t1.invoke();
542	>	t2.join();
543		}
544
545		/**
546	<	* Possibly executes other tasks until this task is ready.
546	>	* Forks the given tasks, returning when {@code isDone} holds
547	>	* for all of them. If any task encounters an exception, others
548	>	* may be cancelled.  This method may be invoked only from within
549	>	* ForkJoinTask computations (as may be determined using method
550	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
551	>	* result in exceptions or errors, possibly including
552	>	* ClassCastException.
553	>	*
554	>	* @param tasks the array of tasks
555	>	* @throws NullPointerException if tasks or any element are null
556	>	* @throws RuntimeException or Error if any task did so
557		*/
558	<	public final void quietlyHelpJoin() {
559	<	if (status >= 0) {
560	<	ForkJoinWorkerThread w =
561	<	(ForkJoinWorkerThread)(Thread.currentThread());
562	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
563	<	w.helpJoinTask(this);
558	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
559	>	Throwable ex = null;
560	>	int last = tasks.length - 1;
561	>	for (int i = last; i >= 0; --i) {
562	>	ForkJoinTask<?> t = tasks[i];
563	>	if (t == null) {
564	>	if (ex == null)
565	>	ex = new NullPointerException();
566	>	}
567	>	else if (i != 0)
568	>	t.fork();
569	>	else {
570	>	t.quietlyInvoke();
571	>	if (ex == null)
572	>	ex = t.getException();
573	>	}
574		}
575	+	for (int i = 1; i <= last; ++i) {
576	+	ForkJoinTask<?> t = tasks[i];
577	+	if (t != null) {
578	+	if (ex != null)
579	+	t.cancel(false);
580	+	else {
581	+	t.quietlyJoin();
582	+	if (ex == null)
583	+	ex = t.getException();
584	+	}
585	+	}
586	+	}
587	+	if (ex != null)
588	+	rethrowException(ex);
589		}
590
591		/**
592	<	* Performs this task and awaits its completion if necessary,
593	<	* without returning its result or throwing an exception. This
594	<	* method may be useful when processing collections of tasks when
595	<	* some have been cancelled or otherwise known to have aborted.
592	>	* Forks all tasks in the collection, returning when
593	>	* {@code isDone} holds for all of them. If any task
594	>	* encounters an exception, others may be cancelled.  This method
595	>	* may be invoked only from within ForkJoinTask computations (as
596	>	* may be determined using method {@link
597	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
598	>	* in exceptions or errors, possibly including ClassCastException.
599	>	*
600	>	* @param tasks the collection of tasks
601	>	* @throws NullPointerException if tasks or any element are null
602	>	* @throws RuntimeException or Error if any task did so
603		*/
604	<	public final void quietlyInvoke() {
605	<	if (status >= 0 && !tryQuietlyInvoke())
606	<	quietlyJoin();
604	>	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
605	>	if (!(tasks instanceof List<?>)) {
606	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
607	>	return;
608	>	}
609	>	@SuppressWarnings("unchecked")
610	>	List<? extends ForkJoinTask<?>> ts =
611	>	(List<? extends ForkJoinTask<?>>) tasks;
612	>	Throwable ex = null;
613	>	int last = ts.size() - 1;
614	>	for (int i = last; i >= 0; --i) {
615	>	ForkJoinTask<?> t = ts.get(i);
616	>	if (t == null) {
617	>	if (ex == null)
618	>	ex = new NullPointerException();
619	>	}
620	>	else if (i != 0)
621	>	t.fork();
622	>	else {
623	>	t.quietlyInvoke();
624	>	if (ex == null)
625	>	ex = t.getException();
626	>	}
627	>	}
628	>	for (int i = 1; i <= last; ++i) {
629	>	ForkJoinTask<?> t = ts.get(i);
630	>	if (t != null) {
631	>	if (ex != null)
632	>	t.cancel(false);
633	>	else {
634	>	t.quietlyJoin();
635	>	if (ex == null)
636	>	ex = t.getException();
637	>	}
638	>	}
639	>	}
640	>	if (ex != null)
641	>	rethrowException(ex);
642		}
643
644		/**
645		* Returns true if the computation performed by this task has
646		* completed (or has been cancelled).
647	+	*
648		* @return true if this computation has completed
649		*/
650		public final boolean isDone() {
#	Line 574 | Line 653 | public abstract class ForkJoinTask<V> im
653
654		/**
655		* Returns true if this task was cancelled.
656	+	*
657		* @return true if this task was cancelled
658		*/
659		public final boolean isCancelled() {
#	Line 581 | Line 661 | public abstract class ForkJoinTask<V> im
661		}
662
663		/**
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	–	/**
664		* Asserts that the results of this task's computation will not be
665	<	* used. If a cancellation occurs before this task is processed,
666	<	* then its <tt>compute</tt> method will not be executed,
667	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
668	<	* result in a CancellationException being thrown. Otherwise, when
665	>	* used. If a cancellation occurs before attempting to execute this
666	>	* task, then execution will be suppressed, {@code isCancelled}
667	>	* will report true, and {@code join} will result in a
668	>	* {@code CancellationException} being thrown. Otherwise, when
669		* cancellation races with completion, there are no guarantees
670	<	* about whether <tt>isCancelled</tt> will report true, whether
671	<	* <tt>join</tt> will return normally or via an exception, or
670	>	* about whether {@code isCancelled} will report true, whether
671	>	* {@code join} will return normally or via an exception, or
672		* whether these behaviors will remain consistent upon repeated
673		* invocation.
674		*
#	Line 622 | Line 679 | public abstract class ForkJoinTask<V> im
679		* <p> This method is designed to be invoked by <em>other</em>
680		* tasks. To terminate the current task, you can just return or
681		* throw an unchecked exception from its computation method, or
682	<	* invoke <tt>completeExceptionally(someException)</tt>.
682	>	* invoke {@code completeExceptionally}.
683		*
684		* @param mayInterruptIfRunning this value is ignored in the
685		* default implementation because tasks are not in general
686	<	* cancelled via interruption.
686	>	* cancelled via interruption
687		*
688		* @return true if this task is now cancelled
689		*/
#	Line 636 | Line 693 | public abstract class ForkJoinTask<V> im
693		}
694
695		/**
696	+	* Returns true if this task threw an exception or was cancelled.
697	+	*
698	+	* @return true if this task threw an exception or was cancelled
699	+	*/
700	+	public final boolean isCompletedAbnormally() {
701	+	return (status & COMPLETION_MASK) < NORMAL;
702	+	}
703	+
704	+	/**
705	+	* Returns the exception thrown by the base computation, or a
706	+	* CancellationException if cancelled, or null if none or if the
707	+	* method has not yet completed.
708	+	*
709	+	* @return the exception, or null if none
710	+	*/
711	+	public final Throwable getException() {
712	+	int s = status & COMPLETION_MASK;
713	+	if (s >= NORMAL)
714	+	return null;
715	+	if (s == CANCELLED)
716	+	return new CancellationException();
717	+	return exceptionMap.get(this);
718	+	}
719	+
720	+	/**
721		* Completes this task abnormally, and if not already aborted or
722		* cancelled, causes it to throw the given exception upon
723	<	* <tt>join</tt> and related operations. This method may be used
723	>	* {@code join} and related operations. This method may be used
724		* to induce exceptions in asynchronous tasks, or to force
725	<	* completion of tasks that would not otherwise complete.  This
726	<	* method is overridable, but overridden versions must invoke
727	<	* <tt>super</tt> implementation to maintain guarantees.
725	>	* completion of tasks that would not otherwise complete.  Its use
726	>	* in other situations is likely to be wrong.  This method is
727	>	* overridable, but overridden versions must invoke {@code super}
728	>	* implementation to maintain guarantees.
729	>	*
730		* @param ex the exception to throw. If this exception is
731		* not a RuntimeException or Error, the actual exception thrown
732		* will be a RuntimeException with cause ex.
733		*/
734		public void completeExceptionally(Throwable ex) {
735		setDoneExceptionally((ex instanceof RuntimeException) ||
736	<	(ex instanceof Error)? ex :
736	>	(ex instanceof Error) ? ex :
737		new RuntimeException(ex));
738		}
739
740		/**
741		* Completes this task, and if not already aborted or cancelled,
742	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
742	>	* returning a {@code null} result upon {@code join} and related
743		* operations. This method may be used to provide results for
744		* asynchronous tasks, or to provide alternative handling for
745	<	* tasks that would not otherwise complete normally.
745	>	* tasks that would not otherwise complete normally. Its use in
746	>	* other situations is likely to be wrong. This method is
747	>	* overridable, but overridden versions must invoke {@code super}
748	>	* implementation to maintain guarantees.
749		*
750	<	* @param value the result value for this task.
750	>	* @param value the result value for this task
751		*/
752		public void complete(V value) {
753		try {
754		setRawResult(value);
755	<	} catch(Throwable rex) {
755	>	} catch (Throwable rex) {
756		setDoneExceptionally(rex);
757		return;
758		}
759		setNormalCompletion();
760		}
761
762	+	public final V get() throws InterruptedException, ExecutionException {
763	+	ForkJoinWorkerThread w = getWorker();
764	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
765	+	awaitDone(w, true);
766	+	return reportFutureResult();
767	+	}
768	+
769	+	public final V get(long timeout, TimeUnit unit)
770	+	throws InterruptedException, ExecutionException, TimeoutException {
771	+	ForkJoinWorkerThread w = getWorker();
772	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
773	+	awaitDone(w, unit.toNanos(timeout));
774	+	return reportTimedFutureResult();
775	+	}
776	+
777	+	/**
778	+	* Possibly executes other tasks until this task is ready, then
779	+	* returns the result of the computation.  This method may be more
780	+	* efficient than {@code join}, but is only applicable when
781	+	* there are no potential dependencies between continuation of the
782	+	* current task and that of any other task that might be executed
783	+	* while helping. (This usually holds for pure divide-and-conquer
784	+	* tasks). This method may be invoked only from within
785	+	* ForkJoinTask computations (as may be determined using method
786	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
787	+	* result in exceptions or errors, possibly including
788	+	* ClassCastException.
789	+	*
790	+	* @return the computed result
791	+	*/
792	+	public final V helpJoin() {
793	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
794	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
795	+	reportException(busyJoin(w));
796	+	return getRawResult();
797	+	}
798	+
799	+	/**
800	+	* Possibly executes other tasks until this task is ready.  This
801	+	* method may be invoked only from within ForkJoinTask
802	+	* computations (as may be determined using method {@link
803	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
804	+	* in exceptions or errors, possibly including ClassCastException.
805	+	*/
806	+	public final void quietlyHelpJoin() {
807	+	if (status >= 0) {
808	+	ForkJoinWorkerThread w =
809	+	(ForkJoinWorkerThread) Thread.currentThread();
810	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
811	+	busyJoin(w);
812	+	}
813	+	}
814	+
815	+	/**
816	+	* Joins this task, without returning its result or throwing an
817	+	* exception. This method may be useful when processing
818	+	* collections of tasks when some have been cancelled or otherwise
819	+	* known to have aborted.
820	+	*/
821	+	public final void quietlyJoin() {
822	+	if (status >= 0) {
823	+	ForkJoinWorkerThread w = getWorker();
824	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
825	+	awaitDone(w, true);
826	+	}
827	+	}
828	+
829	+	/**
830	+	* Commences performing this task and awaits its completion if
831	+	* necessary, without returning its result or throwing an
832	+	* exception. This method may be useful when processing
833	+	* collections of tasks when some have been cancelled or otherwise
834	+	* known to have aborted.
835	+	*/
836	+	public final void quietlyInvoke() {
837	+	if (status >= 0 && !tryQuietlyInvoke())
838	+	quietlyJoin();
839	+	}
840	+
841	+	/**
842	+	* Possibly executes tasks until the pool hosting the current task
843	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
844	+	* designs in which many tasks are forked, but none are explicitly
845	+	* joined, instead executing them until all are processed.
846	+	*/
847	+	public static void helpQuiesce() {
848	+	((ForkJoinWorkerThread) Thread.currentThread())
849	+	.helpQuiescePool();
850	+	}
851	+
852		/**
853		* Resets the internal bookkeeping state of this task, allowing a
854	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
854	>	* subsequent {@code fork}. This method allows repeated reuse of
855		* this task, but only if reuse occurs when this task has either
856		* never been forked, or has been forked, then completed and all
857		* outstanding joins of this task have also completed. Effects
#	Line 689 | Line 866 | public abstract class ForkJoinTask<V> im
866		}
867
868		/**
869	<	* Tries to unschedule this task for execution. This method will
870	<	* typically succeed if this task is the next task that would be
871	<	* executed by the current thread, and will typically fail (return
872	<	* 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.
869	>	* Returns the pool hosting the current task execution, or null
870	>	* if this task is executing outside of any ForkJoinPool.
871	>	*
872	>	* @return the pool, or null if none
873		*/
874	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
875	<	t2.fork();
876	<	t1.invoke();
877	<	t2.join();
874	>	public static ForkJoinPool getPool() {
875	>	Thread t = Thread.currentThread();
876	>	return (t instanceof ForkJoinWorkerThread) ?
877	>	((ForkJoinWorkerThread) t).pool : null;
878		}
879
880		/**
881	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
882	<	* all of them. If any task encounters an exception, others may be
883	<	* cancelled.  This method may be invoked only from within other
884	<	* ForkJoinTask computations. Attempts to invoke in other contexts
885	<	* 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.
881	>	* Returns {@code true} if the current thread is executing as a
882	>	* ForkJoinPool computation.
883	>	*
884	>	* @return {@code true} if the current thread is executing as a
885	>	* ForkJoinPool computation, or false otherwise
886		*/
887	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
888	<	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);
887	>	public static boolean inForkJoinPool() {
888	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
889		}
890
891		/**
892	<	* Forks all tasks in the collection, returning when
893	<	* <tt>isDone</tt> holds for all of them. If any task encounters
894	<	* an exception, others may be cancelled.  This method may be
895	<	* invoked only from within other ForkJoinTask
896	<	* computations. Attempts to invoke in other contexts result in
897	<	* exceptions or errors including ClassCastException.
898	<	* @param tasks the collection of tasks
899	<	* @throws NullPointerException if tasks or any element are null.
900	<	* @throws RuntimeException or Error if any task did so.
892	>	* Tries to unschedule this task for execution. This method will
893	>	* typically succeed if this task is the most recently forked task
894	>	* by the current thread, and has not commenced executing in
895	>	* another thread.  This method may be useful when arranging
896	>	* alternative local processing of tasks that could have been, but
897	>	* were not, stolen. This method may be invoked only from within
898	>	* ForkJoinTask computations (as may be determined using method
899	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
900	>	* result in exceptions or errors, possibly including
901	>	* ClassCastException.
902	>	*
903	>	* @return true if unforked
904		*/
905	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
906	<	if (!(tasks instanceof List)) {
907	<	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);
905	>	public boolean tryUnfork() {
906	>	return ((ForkJoinWorkerThread) Thread.currentThread())
907	>	.unpushTask(this);
908		}
909
910		/**
911	<	* Possibly executes tasks until the pool hosting the current task
912	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
913	<	* designs in which many tasks are forked, but none are explicitly
914	<	* joined, instead executing them until all are processed.
911	>	* Returns an estimate of the number of tasks that have been
912	>	* forked by the current worker thread but not yet executed. This
913	>	* value may be useful for heuristic decisions about whether to
914	>	* fork other tasks.
915	>	*
916	>	* @return the number of tasks
917		*/
918	<	public static void helpQuiesce() {
919	<	((ForkJoinWorkerThread)(Thread.currentThread())).
920	<	helpQuiescePool();
918	>	public static int getQueuedTaskCount() {
919	>	return ((ForkJoinWorkerThread) Thread.currentThread())
920	>	.getQueueSize();
921		}
922
923		/**
924	<	* Returns a estimate of how many more locally queued tasks are
924	>	* Returns an estimate of how many more locally queued tasks are
925		* held by the current worker thread than there are other worker
926	<	* threads that might want to steal them.  This value may be
927	<	* useful for heuristic decisions about whether to fork other
928	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
929	<	* worker should aim to maintain a small constant surplus (for
930	<	* example, 3) of tasks, and to process computations locally if
931	<	* this threshold is exceeded.
926	>	* threads that might steal them.  This value may be useful for
927	>	* heuristic decisions about whether to fork other tasks. In many
928	>	* usages of ForkJoinTasks, at steady state, each worker should
929	>	* aim to maintain a small constant surplus (for example, 3) of
930	>	* tasks, and to process computations locally if this threshold is
931	>	* exceeded.
932	>	*
933		* @return the surplus number of tasks, which may be negative
934		*/
935	<	public static int surplus() {
936	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
935	>	public static int getSurplusQueuedTaskCount() {
936	>	return ((ForkJoinWorkerThread) Thread.currentThread())
937		.getEstimatedSurplusTaskCount();
938		}
939
940	<	// Extension kit
940	>	// Extension methods
941
942		/**
943	<	* Returns the result that would be returned by <tt>join</tt>, or
944	<	* null if this task is not known to have been completed.  This
945	<	* method is designed to aid debugging, as well as to support
946	<	* extensions. Its use in any other context is discouraged.
943	>	* Returns the result that would be returned by {@code join},
944	>	* even if this task completed abnormally, or null if this task is
945	>	* not known to have been completed.  This method is designed to
946	>	* aid debugging, as well as to support extensions. Its use in any
947	>	* other context is discouraged.
948		*
949	<	* @return the result, or null if not completed.
949	>	* @return the result, or null if not completed
950		*/
951		public abstract V getRawResult();
952
#	Line 865 | Line 965 | public abstract class ForkJoinTask<V> im
965		* called otherwise. The return value controls whether this task
966		* is considered to be done normally. It may return false in
967		* asynchronous actions that require explicit invocations of
968	<	* <tt>complete</tt> to become joinable. It may throw exceptions
968	>	* {@code complete} to become joinable. It may throw exceptions
969		* to indicate abnormal exit.
970	+	*
971		* @return true if completed normally
972		* @throws Error or RuntimeException if encountered during computation
973		*/
974		protected abstract boolean exec();
975
976	+	/**
977	+	* Returns, but does not unschedule or execute, the task queued by
978	+	* the current thread but not yet executed, if one is
979	+	* available. There is no guarantee that this task will actually
980	+	* be polled or executed next.  This method is designed primarily
981	+	* to support extensions, and is unlikely to be useful otherwise.
982	+	* This method may be invoked only from within ForkJoinTask
983	+	* computations (as may be determined using method {@link
984	+	* #inForkJoinPool}). Attempts to invoke in other contexts result
985	+	* in exceptions or errors, possibly including ClassCastException.
986	+	*
987	+	* @return the next task, or null if none are available
988	+	*/
989	+	protected static ForkJoinTask<?> peekNextLocalTask() {
990	+	return ((ForkJoinWorkerThread) Thread.currentThread())
991	+	.peekTask();
992	+	}
993	+
994	+	/**
995	+	* Unschedules and returns, without executing, the next task
996	+	* queued by the current thread but not yet executed.  This method
997	+	* is designed primarily to support extensions, and is unlikely to
998	+	* be useful otherwise.  This method may be invoked only from
999	+	* within ForkJoinTask computations (as may be determined using
1000	+	* method {@link #inForkJoinPool}). Attempts to invoke in other
1001	+	* contexts result in exceptions or errors, possibly including
1002	+	* ClassCastException.
1003	+	*
1004	+	* @return the next task, or null if none are available
1005	+	*/
1006	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1007	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1008	+	.pollLocalTask();
1009	+	}
1010	+
1011	+	/**
1012	+	* Unschedules and returns, without executing, the next task
1013	+	* queued by the current thread but not yet executed, if one is
1014	+	* available, or if not available, a task that was forked by some
1015	+	* other thread, if available. Availability may be transient, so a
1016	+	* {@code null} result does not necessarily imply quiescence
1017	+	* of the pool this task is operating in.  This method is designed
1018	+	* primarily to support extensions, and is unlikely to be useful
1019	+	* otherwise.  This method may be invoked only from within
1020	+	* ForkJoinTask computations (as may be determined using method
1021	+	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1022	+	* result in exceptions or errors, possibly including
1023	+	* ClassCastException.
1024	+	*
1025	+	* @return a task, or null if none are available
1026	+	*/
1027	+	protected static ForkJoinTask<?> pollTask() {
1028	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1029	+	.pollTask();
1030	+	}
1031	+
1032		// Serialization support
1033
1034		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1037 | public abstract class ForkJoinTask<V> im
1037		* Save the state to a stream.
1038		*
1039		* @serialData the current run status and the exception thrown
1040	<	* during execution, or null if none.
1040	>	* during execution, or null if none
1041		* @param s the stream
1042		*/
1043		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1048 | public abstract class ForkJoinTask<V> im
1048
1049		/**
1050		* Reconstitute the instance from a stream.
1051	+	*
1052		* @param s the stream
1053		*/
1054		private void readObject(java.io.ObjectInputStream s)
1055		throws java.io.IOException, ClassNotFoundException {
1056		s.defaultReadObject();
1057	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1057	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1058	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1059		Object ex = s.readObject();
1060		if (ex != null)
1061	<	setDoneExceptionally((Throwable)ex);
1061	>	setDoneExceptionally((Throwable) ex);
1062		}
1063
1064	<	// Temporary Unsafe mechanics for preliminary release
1064	>	// Unsafe mechanics for jsr166y 3rd party package.
1065	>	private static sun.misc.Unsafe getUnsafe() {
1066	>	try {
1067	>	return sun.misc.Unsafe.getUnsafe();
1068	>	} catch (SecurityException se) {
1069	>	try {
1070	>	return java.security.AccessController.doPrivileged
1071	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1072	>	public sun.misc.Unsafe run() throws Exception {
1073	>	return getUnsafeByReflection();
1074	>	}});
1075	>	} catch (java.security.PrivilegedActionException e) {
1076	>	throw new RuntimeException("Could not initialize intrinsics",
1077	>	e.getCause());
1078	>	}
1079	>	}
1080	>	}
1081
1082	<	static final Unsafe _unsafe;
1083	<	static final long statusOffset;
1082	>	private static sun.misc.Unsafe getUnsafeByReflection()
1083	>	throws NoSuchFieldException, IllegalAccessException {
1084	>	java.lang.reflect.Field f =
1085	>	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
1086	>	f.setAccessible(true);
1087	>	return (sun.misc.Unsafe) f.get(null);
1088	>	}
1089
1090	<	static {
1090	>	private static long fieldOffset(String fieldName, Class<?> klazz) {
1091		try {
1092	<	if (ForkJoinTask.class.getClassLoader() != null) {
1093	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1094	<	f.setAccessible(true);
1095	<	_unsafe = (Unsafe)f.get(null);
1096	<	}
1097	<	else
1098	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1092	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
1093	>	} catch (NoSuchFieldException e) {
1094	>	// Convert Exception to Error
1095	>	NoSuchFieldError error = new NoSuchFieldError(fieldName);
1096	>	error.initCause(e);
1097	>	throw error;
1098	>	}
1099		}
1100
1101	+	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1102	+	static final long statusOffset =
1103	+	fieldOffset("status", ForkJoinTask.class);
1104	+
1105		}

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