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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 1.32 by dl, Mon Aug 3 13:01:15 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.RandomAccess;
16	>	import java.util.Map;
17	>	import java.util.WeakHashMap;
18
19		/**
20	<	* Abstract base class for tasks that run within a ForkJoinPool.  A
21	<	* ForkJoinTask is a thread-like entity that is much lighter weight
22	<	* than a normal thread.  Huge numbers of tasks and subtasks may be
23	<	* hosted by a small number of actual threads in a ForkJoinPool,
24	<	* at the price of some usage limitations.
20	>	* Abstract base class for tasks that run within a {@link ForkJoinPool}.
21	>	* A {@code ForkJoinTask} is a thread-like entity that is much
22	>	* lighter weight than a normal thread.  Huge numbers of tasks and
23	>	* subtasks may be hosted by a small number of actual threads in a
24	>	* ForkJoinPool, at the price of some usage limitations.
25		*
26	<	* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a
27	<	* limited range of use.  The "lightness" of ForkJoinTasks is due to a
28	<	* set of restrictions (that are only partially statically
29	<	* enforceable) reflecting their intended use as computational tasks
30	<	* calculating pure functions or operating on purely isolated objects.
31	<	* The primary coordination mechanisms supported for ForkJoinTasks are
32	<	* <tt>fork</tt>, that arranges asynchronous execution, and
33	<	* <tt>join</tt>, that doesn't proceed until the task's result has
34	<	* been computed. (Cancellation is also supported).  The computation
31	<	* defined in the <tt>compute</tt> method should avoid
32	<	* <tt>synchronized</tt> methods or blocks, and should minimize
33	<	* blocking synchronization apart from joining other tasks or using
34	<	* synchronizers such as Phasers that are advertised to cooperate with
35	<	* fork/join scheduling. Tasks should also not perform blocking IO,
36	<	* and should ideally access variables that are completely independent
37	<	* of those accessed by other running tasks. Minor breaches of these
38	<	* restrictions, for example using shared output streams, may be
39	<	* tolerable in practice, but frequent use may result in poor
40	<	* performance, and the potential to indefinitely stall if the number
41	<	* of threads not waiting for external synchronization becomes
42	<	* exhausted. This usage restriction is in part enforced by not
43	<	* permitting checked exceptions such as IOExceptions to be
44	<	* thrown. However, computations may still encounter unchecked
45	<	* exceptions, that are rethrown to callers attempting join
46	<	* them. These exceptions may additionally include
47	<	* RejectedExecutionExceptions stemming from internal resource
48	<	* exhaustion such as failure to allocate internal task queues.
26	>	* <p>A "main" {@code ForkJoinTask} begins execution when submitted
27	>	* to a {@link ForkJoinPool}.  Once started, it will usually in turn
28	>	* start other subtasks.  As indicated by the name of this class,
29	>	* many programs using {@code ForkJoinTask} employ only methods
30	>	* {@link #fork} and {@link #join}, or derivatives such as {@link
31	>	* #invokeAll}.  However, this class also provides a number of other
32	>	* methods that can come into play in advanced usages, as well as
33	>	* extension mechanics that allow support of new forms of fork/join
34	>	* processing.
35		*
36	<	* <p> The <tt>ForkJoinTask</tt> class is not usually directly
37	<	* subclassed.  Instead, you subclass one of the abstract classes that
38	<	* support different styles of fork/join processing.  Normally, a
39	<	* concrete ForkJoinTask subclass declares fields comprising its
40	<	* parameters, established in a constructor, and then defines a
41	<	* <tt>compute</tt> method that somehow uses the control methods
42	<	* supplied by this base class. While these methods have
43	<	* <tt>public</tt> access, some of them may only be called from within
44	<	* other ForkJoinTasks. Attempts to invoke them in other contexts
45	<	* result in exceptions or errors including ClassCastException.  The
46	<	* only way to invoke a "main" driver task is to submit it to a
47	<	* ForkJoinPool. Once started, this will usually in turn start other
48	<	* subtasks.
36	>	* <p>A {@code ForkJoinTask} is a lightweight form of {@link Future}.
37	>	* The efficiency of {@code ForkJoinTask}s stems from a set of
38	>	* restrictions (that are only partially statically enforceable)
39	>	* reflecting their intended use as computational tasks calculating
40	>	* pure functions or operating on purely isolated objects.  The
41	>	* primary coordination mechanisms are {@link #fork}, that arranges
42	>	* asynchronous execution, and {@link #join}, that doesn't proceed
43	>	* until the task's result has been computed.  Computations should
44	>	* avoid {@code synchronized} methods or blocks, and should minimize
45	>	* other blocking synchronization apart from joining other tasks or
46	>	* using synchronizers such as Phasers that are advertised to
47	>	* cooperate with fork/join scheduling. Tasks should also not perform
48	>	* blocking IO, and should ideally access variables that are
49	>	* completely independent of those accessed by other running
50	>	* tasks. Minor breaches of these restrictions, for example using
51	>	* shared output streams, may be tolerable in practice, but frequent
52	>	* use may result in poor performance, and the potential to
53	>	* indefinitely stall if the number of threads not waiting for IO or
54	>	* other external synchronization becomes exhausted. This usage
55	>	* restriction is in part enforced by not permitting checked
56	>	* exceptions such as {@code IOExceptions} to be thrown. However,
57	>	* computations may still encounter unchecked exceptions, that are
58	>	* rethrown to callers attempting to join them. These exceptions may
59	>	* additionally include RejectedExecutionExceptions stemming from
60	>	* internal resource exhaustion such as failure to allocate internal
61	>	* task queues.
62		*
63	<	* <p>Most base support methods are <tt>final</tt> because their
64	<	* implementations are intrinsically tied to the underlying
65	<	* lightweight task scheduling framework, and so cannot be overridden.
66	<	* Developers creating new basic styles of fork/join processing should
67	<	* minimally implement protected methods <tt>exec</tt>,
68	<	* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also
69	<	* introducing an abstract computational method that can be
70	<	* implemented in its subclasses. To support such extensions,
71	<	* instances of ForkJoinTasks maintain an atomically updated
72	<	* <tt>short</tt> representing user-defined control state.  Control
73	<	* state is guaranteed initially to be zero, and to be negative upon
74	<	* completion, but may otherwise be used for any other control
75	<	* purposes, such as maintaining join counts.  The {@link
76	<	* ForkJoinWorkerThread} class supports additional inspection and
77	<	* tuning methods that can be useful when developing extensions.
63	>	* <p>The primary method for awaiting completion and extracting
64	>	* results of a task is {@link #join}, but there are several variants:
65	>	* The {@link Future#get} methods support interruptible and/or timed
66	>	* waits for completion and report results using {@code Future}
67	>	* conventions. Method {@link #helpJoin} enables callers to actively
68	>	* execute other tasks while awaiting joins, which is sometimes more
69	>	* efficient but only applies when all subtasks are known to be
70	>	* strictly tree-structured. Method {@link #invoke} is semantically
71	>	* equivalent to {@code fork(); join()} but always attempts to
72	>	* begin execution in the current thread. The "<em>quiet</em>" forms
73	>	* of these methods do not extract results or report exceptions. These
74	>	* may be useful when a set of tasks are being executed, and you need
75	>	* to delay processing of results or exceptions until all complete.
76	>	* Method {@code invokeAll} (available in multiple versions)
77	>	* performs the most common form of parallel invocation: forking a set
78	>	* of tasks and joining them all.
79	>	*
80	>	* <p>The ForkJoinTask class is not usually directly subclassed.
81	>	* Instead, you subclass one of the abstract classes that support a
82	>	* particular style of fork/join processing, typically {@link
83	>	* RecursiveAction} for computations that do not return results, or
84	>	* {@link RecursiveTask} for those that do.  Normally, a concrete
85	>	* ForkJoinTask subclass declares fields comprising its parameters,
86	>	* established in a constructor, and then defines a {@code compute}
87	>	* method that somehow uses the control methods supplied by this base
88	>	* class. While these methods have {@code public} access (to allow
89	>	* instances of different task subclasses to call each other's
90	>	* methods), some of them may only be called from within other
91	>	* ForkJoinTasks (as may be determined using method {@link
92	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
93	>	* result in exceptions or errors, possibly including
94	>	* ClassCastException.
95	>	*
96	>	* <p>Most base support methods are {@code final}, to prevent
97	>	* overriding of implementations that are intrinsically tied to the
98	>	* underlying lightweight task scheduling framework.  Developers
99	>	* creating new basic styles of fork/join processing should minimally
100	>	* implement {@code protected} methods {@link #exec}, {@link
101	>	* #setRawResult}, and {@link #getRawResult}, while also introducing
102	>	* an abstract computational method that can be implemented in its
103	>	* subclasses, possibly relying on other {@code protected} methods
104	>	* provided by this class.
105		*
106		* <p>ForkJoinTasks should perform relatively small amounts of
107	<	* computations, othewise splitting into smaller tasks. As a very
108	<	* rough rule of thumb, a task should perform more than 100 and less
109	<	* than 10000 basic computational steps. If tasks are too big, then
110	<	* parellelism cannot improve throughput. If too small, then memory
111	<	* and internal task maintenance overhead may overwhelm processing.
107	>	* computation. Large tasks should be split into smaller subtasks,
108	>	* usually via recursive decomposition. As a very rough rule of thumb,
109	>	* a task should perform more than 100 and less than 10000 basic
110	>	* computational steps. If tasks are too big, then parallelism cannot
111	>	* improve throughput. If too small, then memory and internal task
112	>	* maintenance overhead may overwhelm processing.
113	>	*
114	>	* <p>This class provides {@code adapt} methods for {@link
115	>	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
116	>	* may be of use when mixing execution of ForkJoinTasks with other
117	>	* kinds of tasks. When all tasks are of this form, consider using a
118	>	* pool in {@link ForkJoinPool#setAsyncMode}.
119		*
120	<	* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to
121	<	* be used in extensions such as remote execution frameworks. However,
122	<	* it is in general safe to serialize tasks only before or after, but
123	<	* not during execution. Serialization is not relied on during
124	<	* execution itself.
120	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
121	>	* used in extensions such as remote execution frameworks. It is
122	>	* sensible to serialize tasks only before or after, but not during,
123	>	* execution. Serialization is not relied on during execution itself.
124	>	*
125	>	* @since 1.7
126	>	* @author Doug Lea
127		*/
128		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
129	+
130		/**
131	<	* Status field holding all run status. We pack this into a single
132	<	* int both to minimize footprint overhead and to ensure atomicity
133	<	* (updates are via CAS).
98	<	*
99	<	* Status is initially zero, and takes on nonnegative values until
131	>	* Run control status bits packed into a single int to minimize
132	>	* footprint and to ensure atomicity (via CAS).  Status is
133	>	* initially zero, and takes on nonnegative values until
134		* completed, upon which status holds COMPLETED. CANCELLED, or
135		* EXCEPTIONAL, which use the top 3 bits.  Tasks undergoing
136		* blocking waits by other threads have SIGNAL_MASK bits set --
#	Line 111 | Line 145 | public abstract class ForkJoinTask<V> im
145		* currently unused. Also value 0x80000000 is available as spare
146		* completion value.
147		*/
148	<	volatile int status; // accessed directy by pool and workers
148	>	volatile int status; // accessed directly by pool and workers
149
150		static final int COMPLETION_MASK      = 0xe0000000;
151		static final int NORMAL               = 0xe0000000; // == mask
#	Line 124 | Line 158 | public abstract class ForkJoinTask<V> im
158		/**
159		* Table of exceptions thrown by tasks, to enable reporting by
160		* callers. Because exceptions are rare, we don't directly keep
161	<	* them with task objects, but instead us a weak ref table.  Note
161	>	* them with task objects, but instead use a weak ref table.  Note
162		* that cancellation exceptions don't appear in the table, but are
163		* instead recorded as status values.
164	<	* Todo: Use ConcurrentReferenceHashMap
164	>	* TODO: Use ConcurrentReferenceHashMap
165		*/
166		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
167		Collections.synchronizedMap
#	Line 136 | Line 170 | public abstract class ForkJoinTask<V> im
170		// within-package utilities
171
172		/**
173	<	* Get current worker thread, or null if not a worker thread
173	>	* Gets current worker thread, or null if not a worker thread.
174		*/
175		static ForkJoinWorkerThread getWorker() {
176		Thread t = Thread.currentThread();
177	<	return ((t instanceof ForkJoinWorkerThread)?
178	<	(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);
177	>	return ((t instanceof ForkJoinWorkerThread) ?
178	>	(ForkJoinWorkerThread) t : null);
179		}
180
181		final boolean casStatus(int cmp, int val) {
182	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
182	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
183		}
184
185		/**
#	Line 162 | Line 187 | public abstract class ForkJoinTask<V> im
187		*/
188		static void rethrowException(Throwable ex) {
189		if (ex != null)
190	<	_unsafe.throwException(ex);
190	>	UNSAFE.throwException(ex);
191		}
192
193		// Setting completion status
194
195		/**
196	<	* Mark completion and wake up threads waiting to join this task.
196	>	* Marks completion and wakes up threads waiting to join this task.
197	>	*
198		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
199		*/
200		final void setCompletion(int completion) {
201	<	ForkJoinPool pool = getWorkerPool();
201	>	ForkJoinPool pool = getPool();
202		if (pool != null) {
203		int s; // Clear signal bits while setting completion status
204	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
204	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
205
206		if ((s & SIGNAL_MASK) != 0) {
207		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
208		pool.updateRunningCount(s);
209	<	synchronized(this) { notifyAll(); }
209	>	synchronized (this) { notifyAll(); }
210		}
211		}
212		else
#	Line 193 | Line 219 | public abstract class ForkJoinTask<V> im
219		*/
220		private void externallySetCompletion(int completion) {
221		int s;
222	<	do;while ((s = status) >= 0 &&
223	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	<	synchronized(this) { notifyAll(); }
222	>	do {} while ((s = status) >= 0 &&
223	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
224	>	synchronized (this) { notifyAll(); }
225		}
226
227		/**
228	<	* Sets status to indicate normal completion
228	>	* Sets status to indicate normal completion.
229		*/
230		final void setNormalCompletion() {
231		// Try typical fast case -- single CAS, no signal, not already done.
232		// Manually expand casStatus to improve chances of inlining it
233	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
233	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
234		setCompletion(NORMAL);
235		}
236
237		// internal waiting and notification
238
239		/**
240	<	* Performs the actual monitor wait for awaitDone
240	>	* Performs the actual monitor wait for awaitDone.
241		*/
242		private void doAwaitDone() {
243		// Minimize lock bias and in/de-flation effects by maximizing
244		// chances of waiting inside sync
245		try {
246		while (status >= 0)
247	<	synchronized(this) { if (status >= 0) wait(); }
247	>	synchronized (this) { if (status >= 0) wait(); }
248		} catch (InterruptedException ie) {
249		onInterruptedWait();
250		}
251		}
252
253		/**
254	<	* Performs the actual monitor wait for awaitDone
254	>	* Performs the actual timed monitor wait for awaitDone.
255		*/
256		private void doAwaitDone(long startTime, long nanos) {
257	<	synchronized(this) {
257	>	synchronized (this) {
258		try {
259		while (status >= 0) {
260	<	long nt = nanos - System.nanoTime() - startTime;
260	>	long nt = nanos - (System.nanoTime() - startTime);
261		if (nt <= 0)
262		break;
263	<	wait(nt / 1000000, (int)(nt % 1000000));
263	>	wait(nt / 1000000, (int) (nt % 1000000));
264		}
265		} catch (InterruptedException ie) {
266		onInterruptedWait();
#	Line 247 | Line 273 | public abstract class ForkJoinTask<V> im
273		/**
274		* Sets status to indicate there is joiner, then waits for join,
275		* surrounded with pool notifications.
276	+	*
277		* @return status upon exit
278		*/
279	<	final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
280	<	ForkJoinPool pool = w == null? null : w.pool;
279	>	private int awaitDone(ForkJoinWorkerThread w,
280	>	boolean maintainParallelism) {
281	>	ForkJoinPool pool = (w == null) ? null : w.pool;
282		int s;
283		while ((s = status) >= 0) {
284	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
284	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
285		if (pool == null || !pool.preJoin(this, maintainParallelism))
286		doAwaitDone();
287		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 266 | Line 294 | public abstract class ForkJoinTask<V> im
294
295		/**
296		* Timed version of awaitDone
297	+	*
298		* @return status upon exit
299		*/
300	<	final int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	<	ForkJoinPool pool = w == null? null : w.pool;
300	>	private int awaitDone(ForkJoinWorkerThread w, long nanos) {
301	>	ForkJoinPool pool = (w == null) ? null : w.pool;
302		int s;
303		while ((s = status) >= 0) {
304	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
304	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
305		long startTime = System.nanoTime();
306		if (pool == null || !pool.preJoin(this, false))
307		doAwaitDone(startTime, nanos);
#	Line 289 | Line 318 | public abstract class ForkJoinTask<V> im
318		}
319
320		/**
321	<	* Notify pool that thread is unblocked. Called by signalled
321	>	* Notifies pool that thread is unblocked. Called by signalled
322		* threads when woken by non-FJ threads (which is atypical).
323		*/
324		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
325		int s;
326	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
326	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
327		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
328		pool.updateRunningCount(s);
329		}
330
331		/**
332	<	* Notify pool to adjust counts on cancelled or timed out wait
332	>	* Notifies pool to adjust counts on cancelled or timed out wait.
333		*/
334		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
335		if (pool != null) {
#	Line 314 | Line 343 | public abstract class ForkJoinTask<V> im
343		}
344		}
345
346	+	/**
347	+	* Handles interruptions during waits.
348	+	*/
349		private void onInterruptedWait() {
350	<	Thread t = Thread.currentThread();
351	<	if (t instanceof ForkJoinWorkerThread) {
352	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)t;
353	<	if (w.isTerminating())
354	<	cancelIgnoreExceptions();
355	<	}
324	<	else { // re-interrupt
325	<	try {
326	<	t.interrupt();
327	<	} catch (SecurityException ignore) {
328	<	}
329	<	}
350	>	ForkJoinWorkerThread w = getWorker();
351	>	if (w == null)
352	>	Thread.currentThread().interrupt(); // re-interrupt
353	>	else if (w.isTerminating())
354	>	cancelIgnoringExceptions();
355	>	// else if FJworker, ignore interrupt
356		}
357
358		// Recording and reporting exceptions
#	Line 337 | Line 363 | public abstract class ForkJoinTask<V> im
363		}
364
365		/**
366	<	* Throws the exception associated with status s;
366	>	* Throws the exception associated with status s.
367	>	*
368		* @throws the exception
369		*/
370		private void reportException(int s) {
#	Line 350 | Line 377 | public abstract class ForkJoinTask<V> im
377		}
378
379		/**
380	<	* Returns result or throws exception using j.u.c.Future conventions
381	<	* Only call when isDone known to be true.
380	>	* Returns result or throws exception using j.u.c.Future conventions.
381	>	* Only call when {@code isDone} known to be true.
382		*/
383		private V reportFutureResult()
384		throws ExecutionException, InterruptedException {
#	Line 370 | Line 397 | public abstract class ForkJoinTask<V> im
397
398		/**
399		* Returns result or throws exception using j.u.c.Future conventions
400	<	* with timeouts
400	>	* with timeouts.
401		*/
402		private V reportTimedFutureResult()
403		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 391 | Line 418 | public abstract class ForkJoinTask<V> im
418
419		/**
420		* Calls exec, recording completion, and rethrowing exception if
421	<	* encountered. Caller should normally check status before calling
421	>	* encountered. Caller should normally check status before calling.
422	>	*
423		* @return true if completed normally
424		*/
425		private boolean tryExec() {
#	Line 409 | Line 437 | public abstract class ForkJoinTask<V> im
437
438		/**
439		* Main execution method used by worker threads. Invokes
440	<	* base computation unless already complete
440	>	* base computation unless already complete.
441		*/
442		final void quietlyExec() {
443		if (status >= 0) {
444		try {
445		if (!exec())
446		return;
447	<	} catch(Throwable rex) {
447	>	} catch (Throwable rex) {
448		setDoneExceptionally(rex);
449		return;
450		}
#	Line 425 | Line 453 | public abstract class ForkJoinTask<V> im
453		}
454
455		/**
456	<	* Calls exec, recording but not rethrowing exception
457	<	* Caller should normally check status before calling
456	>	* Calls exec(), recording but not rethrowing exception.
457	>	* Caller should normally check status before calling.
458	>	*
459		* @return true if completed normally
460		*/
461		private boolean tryQuietlyInvoke() {
#	Line 442 | Line 471 | public abstract class ForkJoinTask<V> im
471		}
472
473		/**
474	<	* Cancel, ignoring any exceptions it throws
474	>	* Cancels, ignoring any exceptions it throws.
475		*/
476	<	final void cancelIgnoreExceptions() {
476	>	final void cancelIgnoringExceptions() {
477		try {
478		cancel(false);
479	<	} catch(Throwable ignore) {
479	>	} catch (Throwable ignore) {
480		}
481		}
482
483	+	/**
484	+	* Main implementation of helpJoin
485	+	*/
486	+	private int busyJoin(ForkJoinWorkerThread w) {
487	+	int s;
488	+	ForkJoinTask<?> t;
489	+	while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
490	+	t.quietlyExec();
491	+	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
492	+	}
493	+
494		// public methods
495
496		/**
497		* Arranges to asynchronously execute this task.  While it is not
498		* necessarily enforced, it is a usage error to fork a task more
499	<	* than once unless it has completed and been reinitialized.  This
500	<	* method may be invoked only from within other ForkJoinTask
501	<	* computations. Attempts to invoke in other contexts result in
502	<	* exceptions or errors including ClassCastException.
499	>	* than once unless it has completed and been reinitialized.
500	>	*
501	>	* <p>This method may be invoked only from within {@code
502	>	* ForkJoinTask} computations (as may be determined using method
503	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
504	>	* result in exceptions or errors, possibly including {@code
505	>	* ClassCastException}.
506	>	*
507	>	* @return {@code this}, to simplify usage
508		*/
509	<	public final void fork() {
510	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
509	>	public final ForkJoinTask<V> fork() {
510	>	((ForkJoinWorkerThread) Thread.currentThread())
511	>	.pushTask(this);
512	>	return this;
513		}
514
515		/**
516		* Returns the result of the computation when it is ready.
517	<	* This method differs from <tt>get</tt> in that abnormal
518	<	* completion results in RuntimeExceptions or Errors, not
519	<	* ExecutionExceptions.
517	>	* This method differs from {@link #get()} in that
518	>	* abnormal completion results in {@code RuntimeException} or
519	>	* {@code Error}, not {@code ExecutionException}.
520		*
521		* @return the computed result
522		*/
#	Line 480 | Line 527 | public abstract class ForkJoinTask<V> im
527		return getRawResult();
528		}
529
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	–
530		/**
531	<	* Performs this task, awaits its completion if necessary, and
532	<	* return its result.
531	>	* Commences performing this task, awaits its completion if
532	>	* necessary, and return its result.
533	>	*
534		* @throws Throwable (a RuntimeException, Error, or unchecked
535	<	* exception) if the underlying computation did so.
535	>	* exception) if the underlying computation did so
536		* @return the computed result
537		*/
538		public final V invoke() {
#	Line 527 | Line 543 | public abstract class ForkJoinTask<V> im
543		}
544
545		/**
546	<	* Joins this task, without returning its result or throwing an
547	<	* exception. This method may be useful when processing
548	<	* collections of tasks when some have been cancelled or otherwise
549	<	* known to have aborted.
546	>	* Forks the given tasks, returning when {@code isDone} holds
547	>	* for each task or an exception is encountered.
548	>	*
549	>	* <p>This method may be invoked only from within {@code
550	>	* ForkJoinTask} computations (as may be determined using method
551	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
552	>	* result in exceptions or errors, possibly including {@code
553	>	* ClassCastException}.
554	>	*
555	>	* @param t1 the first task
556	>	* @param t2 the second task
557	>	* @throws NullPointerException if any task is null
558	>	* @throws RuntimeException or Error if a task did so
559		*/
560	<	public final void quietlyJoin() {
561	<	if (status >= 0) {
562	<	ForkJoinWorkerThread w = getWorker();
563	<	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
539	<	awaitDone(w, true);
540	<	}
560	>	public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
561	>	t2.fork();
562	>	t1.invoke();
563	>	t2.join();
564		}
565
566		/**
567	<	* Possibly executes other tasks until this task is ready.
567	>	* Forks the given tasks, returning when {@code isDone} holds for
568	>	* each task or an exception is encountered. If any task
569	>	* encounters an exception, others may be, but are not guaranteed
570	>	* to be, cancelled.
571	>	*
572	>	* <p>This method may be invoked only from within {@code
573	>	* ForkJoinTask} computations (as may be determined using method
574	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
575	>	* result in exceptions or errors, possibly including {@code
576	>	* ClassCastException}.
577	>	*
578	>	* @param tasks the tasks
579	>	* @throws NullPointerException if tasks or any element are null
580	>	* @throws RuntimeException or Error if any task did so
581		*/
582	<	public final void quietlyHelpJoin() {
583	<	if (status >= 0) {
584	<	ForkJoinWorkerThread w =
585	<	(ForkJoinWorkerThread)(Thread.currentThread());
586	<	if (!w.unpushTask(this) || !tryQuietlyInvoke())
587	<	w.helpJoinTask(this);
582	>	public static void invokeAll(ForkJoinTask<?>... tasks) {
583	>	Throwable ex = null;
584	>	int last = tasks.length - 1;
585	>	for (int i = last; i >= 0; --i) {
586	>	ForkJoinTask<?> t = tasks[i];
587	>	if (t == null) {
588	>	if (ex == null)
589	>	ex = new NullPointerException();
590	>	}
591	>	else if (i != 0)
592	>	t.fork();
593	>	else {
594	>	t.quietlyInvoke();
595	>	if (ex == null)
596	>	ex = t.getException();
597	>	}
598	>	}
599	>	for (int i = 1; i <= last; ++i) {
600	>	ForkJoinTask<?> t = tasks[i];
601	>	if (t != null) {
602	>	if (ex != null)
603	>	t.cancel(false);
604	>	else {
605	>	t.quietlyJoin();
606	>	if (ex == null)
607	>	ex = t.getException();
608	>	}
609	>	}
610		}
611	+	if (ex != null)
612	+	rethrowException(ex);
613		}
614
615		/**
616	<	* Performs this task and awaits its completion if necessary,
617	<	* without returning its result or throwing an exception. This
618	<	* method may be useful when processing collections of tasks when
619	<	* some have been cancelled or otherwise known to have aborted.
620	<	*/
621	<	public final void quietlyInvoke() {
622	<	if (status >= 0 && !tryQuietlyInvoke())
623	<	quietlyJoin();
616	>	* Forks all tasks in the specified collection, returning when
617	>	* {@code isDone} holds for each task or an exception is
618	>	* encountered.  If any task encounters an exception, others may
619	>	* be, but are not guaranteed to be, cancelled. The behavior of
620	>	* this operation is undefined if the specified collection is
621	>	* modified while the operation is in progress.
622	>	*
623	>	* <p>This method may be invoked only from within {@code
624	>	* ForkJoinTask} computations (as may be determined using method
625	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
626	>	* result in exceptions or errors, possibly including {@code
627	>	* ClassCastException}.
628	>	*
629	>	* @param tasks the collection of tasks
630	>	* @return the tasks argument, to simplify usage
631	>	* @throws NullPointerException if tasks or any element are null
632	>	* @throws RuntimeException or Error if any task did so
633	>	*/
634	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
635	>	if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
636	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
637	>	return tasks;
638	>	}
639	>	@SuppressWarnings("unchecked")
640	>	List<? extends ForkJoinTask<?>> ts =
641	>	(List<? extends ForkJoinTask<?>>) tasks;
642	>	Throwable ex = null;
643	>	int last = ts.size() - 1;
644	>	for (int i = last; i >= 0; --i) {
645	>	ForkJoinTask<?> t = ts.get(i);
646	>	if (t == null) {
647	>	if (ex == null)
648	>	ex = new NullPointerException();
649	>	}
650	>	else if (i != 0)
651	>	t.fork();
652	>	else {
653	>	t.quietlyInvoke();
654	>	if (ex == null)
655	>	ex = t.getException();
656	>	}
657	>	}
658	>	for (int i = 1; i <= last; ++i) {
659	>	ForkJoinTask<?> t = ts.get(i);
660	>	if (t != null) {
661	>	if (ex != null)
662	>	t.cancel(false);
663	>	else {
664	>	t.quietlyJoin();
665	>	if (ex == null)
666	>	ex = t.getException();
667	>	}
668	>	}
669	>	}
670	>	if (ex != null)
671	>	rethrowException(ex);
672	>	return tasks;
673		}
674
675		/**
676	<	* Returns true if the computation performed by this task has
677	<	* completed (or has been cancelled).
678	<	* @return true if this computation has completed
676	>	* Returns {@code true} if the computation performed by this task
677	>	* has completed (or has been cancelled).
678	>	*
679	>	* @return {@code true} if this computation has completed
680		*/
681		public final boolean isDone() {
682		return status < 0;
683		}
684
685		/**
686	<	* Returns true if this task was cancelled.
687	<	* @return true if this task was cancelled
686	>	* Returns {@code true} if this task was cancelled.
687	>	*
688	>	* @return {@code true} if this task was cancelled
689		*/
690		public final boolean isCancelled() {
691		return (status & COMPLETION_MASK) == CANCELLED;
692		}
693
694		/**
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	–	/**
695		* Asserts that the results of this task's computation will not be
696	<	* used. If a cancellation occurs before this task is processed,
697	<	* then its <tt>compute</tt> method will not be executed,
698	<	* <tt>isCancelled</tt> will report true, and <tt>join</tt> will
699	<	* result in a CancellationException being thrown. Otherwise, when
696	>	* used. If a cancellation occurs before attempting to execute this
697	>	* task, execution will be suppressed, {@link #isCancelled}
698	>	* will report true, and {@link #join} will result in a
699	>	* {@code CancellationException} being thrown. Otherwise, when
700		* cancellation races with completion, there are no guarantees
701	<	* about whether <tt>isCancelled</tt> will report true, whether
702	<	* <tt>join</tt> will return normally or via an exception, or
703	<	* whether these behaviors will remain consistent upon repeated
701	>	* about whether {@code isCancelled} will report {@code true},
702	>	* whether {@code join} will return normally or via an exception,
703	>	* or whether these behaviors will remain consistent upon repeated
704		* invocation.
705		*
706		* <p>This method may be overridden in subclasses, but if so, must
707		* still ensure that these minimal properties hold. In particular,
708	<	* the cancel method itself must not throw exceptions.
708	>	* the {@code cancel} method itself must not throw exceptions.
709		*
710	<	* <p> This method is designed to be invoked by <em>other</em>
710	>	* <p>This method is designed to be invoked by <em>other</em>
711		* tasks. To terminate the current task, you can just return or
712		* throw an unchecked exception from its computation method, or
713	<	* invoke <tt>completeExceptionally(someException)</tt>.
713	>	* invoke {@link #completeExceptionally}.
714		*
715		* @param mayInterruptIfRunning this value is ignored in the
716		* default implementation because tasks are not in general
717	<	* cancelled via interruption.
717	>	* cancelled via interruption
718		*
719	<	* @return true if this task is now cancelled
719	>	* @return {@code true} if this task is now cancelled
720		*/
721		public boolean cancel(boolean mayInterruptIfRunning) {
722		setCompletion(CANCELLED);
#	Line 636 | Line 724 | public abstract class ForkJoinTask<V> im
724		}
725
726		/**
727	+	* Returns {@code true} if this task threw an exception or was cancelled.
728	+	*
729	+	* @return {@code true} if this task threw an exception or was cancelled
730	+	*/
731	+	public final boolean isCompletedAbnormally() {
732	+	return (status & COMPLETION_MASK) < NORMAL;
733	+	}
734	+
735	+	/**
736	+	* Returns the exception thrown by the base computation, or a
737	+	* {@code CancellationException} if cancelled, or {@code null} if
738	+	* none or if the method has not yet completed.
739	+	*
740	+	* @return the exception, or {@code null} if none
741	+	*/
742	+	public final Throwable getException() {
743	+	int s = status & COMPLETION_MASK;
744	+	if (s >= NORMAL)
745	+	return null;
746	+	if (s == CANCELLED)
747	+	return new CancellationException();
748	+	return exceptionMap.get(this);
749	+	}
750	+
751	+	/**
752		* Completes this task abnormally, and if not already aborted or
753		* cancelled, causes it to throw the given exception upon
754	<	* <tt>join</tt> and related operations. This method may be used
754	>	* {@code join} and related operations. This method may be used
755		* to induce exceptions in asynchronous tasks, or to force
756	<	* completion of tasks that would not otherwise complete.  This
757	<	* method is overridable, but overridden versions must invoke
758	<	* <tt>super</tt> implementation to maintain guarantees.
756	>	* completion of tasks that would not otherwise complete.  Its use
757	>	* in other situations is discouraged.  This method is
758	>	* overridable, but overridden versions must invoke {@code super}
759	>	* implementation to maintain guarantees.
760	>	*
761		* @param ex the exception to throw. If this exception is
762		* not a RuntimeException or Error, the actual exception thrown
763		* will be a RuntimeException with cause ex.
764		*/
765		public void completeExceptionally(Throwable ex) {
766		setDoneExceptionally((ex instanceof RuntimeException) ||
767	<	(ex instanceof Error)? ex :
767	>	(ex instanceof Error) ? ex :
768		new RuntimeException(ex));
769		}
770
771		/**
772		* Completes this task, and if not already aborted or cancelled,
773	<	* returning a <tt>null</tt> result upon <tt>join</tt> and related
773	>	* returning a {@code null} result upon {@code join} and related
774		* operations. This method may be used to provide results for
775		* asynchronous tasks, or to provide alternative handling for
776	<	* tasks that would not otherwise complete normally.
776	>	* tasks that would not otherwise complete normally. Its use in
777	>	* other situations is discouraged. This method is
778	>	* overridable, but overridden versions must invoke {@code super}
779	>	* implementation to maintain guarantees.
780		*
781	<	* @param value the result value for this task.
781	>	* @param value the result value for this task
782		*/
783		public void complete(V value) {
784		try {
785		setRawResult(value);
786	<	} catch(Throwable rex) {
786	>	} catch (Throwable rex) {
787		setDoneExceptionally(rex);
788		return;
789		}
790		setNormalCompletion();
791		}
792
793	+	public final V get() throws InterruptedException, ExecutionException {
794	+	ForkJoinWorkerThread w = getWorker();
795	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
796	+	awaitDone(w, true);
797	+	return reportFutureResult();
798	+	}
799	+
800	+	public final V get(long timeout, TimeUnit unit)
801	+	throws InterruptedException, ExecutionException, TimeoutException {
802	+	long nanos = unit.toNanos(timeout);
803	+	ForkJoinWorkerThread w = getWorker();
804	+	if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke())
805	+	awaitDone(w, nanos);
806	+	return reportTimedFutureResult();
807	+	}
808	+
809	+	/**
810	+	* Possibly executes other tasks until this task is ready, then
811	+	* returns the result of the computation.  This method may be more
812	+	* efficient than {@code join}, but is only applicable when
813	+	* there are no potential dependencies between continuation of the
814	+	* current task and that of any other task that might be executed
815	+	* while helping. (This usually holds for pure divide-and-conquer
816	+	* tasks).
817	+	*
818	+	* <p>This method may be invoked only from within {@code
819	+	* ForkJoinTask} computations (as may be determined using method
820	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
821	+	* result in exceptions or errors, possibly including {@code
822	+	* ClassCastException}.
823	+	*
824	+	* @return the computed result
825	+	*/
826	+	public final V helpJoin() {
827	+	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
828	+	if (status < 0 || !w.unpushTask(this) || !tryExec())
829	+	reportException(busyJoin(w));
830	+	return getRawResult();
831	+	}
832	+
833	+	/**
834	+	* Possibly executes other tasks until this task is ready.  This
835	+	* method may be useful when processing collections of tasks when
836	+	* some have been cancelled or otherwise known to have aborted.
837	+	*
838	+	* <p>This method may be invoked only from within {@code
839	+	* ForkJoinTask} computations (as may be determined using method
840	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
841	+	* result in exceptions or errors, possibly including {@code
842	+	* ClassCastException}.
843	+	*/
844	+	public final void quietlyHelpJoin() {
845	+	if (status >= 0) {
846	+	ForkJoinWorkerThread w =
847	+	(ForkJoinWorkerThread) Thread.currentThread();
848	+	if (!w.unpushTask(this) || !tryQuietlyInvoke())
849	+	busyJoin(w);
850	+	}
851	+	}
852	+
853	+	/**
854	+	* Joins this task, without returning its result or throwing an
855	+	* exception. This method may be useful when processing
856	+	* collections of tasks when some have been cancelled or otherwise
857	+	* known to have aborted.
858	+	*/
859	+	public final void quietlyJoin() {
860	+	if (status >= 0) {
861	+	ForkJoinWorkerThread w = getWorker();
862	+	if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke())
863	+	awaitDone(w, true);
864	+	}
865	+	}
866	+
867	+	/**
868	+	* Commences performing this task and awaits its completion if
869	+	* necessary, without returning its result or throwing an
870	+	* exception. This method may be useful when processing
871	+	* collections of tasks when some have been cancelled or otherwise
872	+	* known to have aborted.
873	+	*/
874	+	public final void quietlyInvoke() {
875	+	if (status >= 0 && !tryQuietlyInvoke())
876	+	quietlyJoin();
877	+	}
878	+
879	+	/**
880	+	* Possibly executes tasks until the pool hosting the current task
881	+	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
882	+	* designs in which many tasks are forked, but none are explicitly
883	+	* joined, instead executing them until all are processed.
884	+	*
885	+	* <p>This method may be invoked only from within {@code
886	+	* ForkJoinTask} computations (as may be determined using method
887	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
888	+	* result in exceptions or errors, possibly including {@code
889	+	* ClassCastException}.
890	+	*/
891	+	public static void helpQuiesce() {
892	+	((ForkJoinWorkerThread) Thread.currentThread())
893	+	.helpQuiescePool();
894	+	}
895	+
896		/**
897		* Resets the internal bookkeeping state of this task, allowing a
898	<	* subsequent <tt>fork</tt>. This method allows repeated reuse of
898	>	* subsequent {@code fork}. This method allows repeated reuse of
899		* this task, but only if reuse occurs when this task has either
900		* never been forked, or has been forked, then completed and all
901		* outstanding joins of this task have also completed. Effects
902	<	* under any other usage conditions are not guaranteed, and are
903	<	* almost surely wrong. This method may be useful when executing
902	>	* under any other usage conditions are not guaranteed.
903	>	* This method may be useful when executing
904		* pre-constructed trees of subtasks in loops.
905		*/
906		public void reinitialize() {
#	Line 689 | Line 910 | public abstract class ForkJoinTask<V> im
910		}
911
912		/**
913	<	* Tries to unschedule this task for execution. This method will
914	<	* typically succeed if this task is the next task that would be
915	<	* executed by the current thread, and will typically fail (return
916	<	* false) otherwise. This method may be useful when arranging
917	<	* faster local processing of tasks that could have been, but were
697	<	* not, stolen.
698	<	* @return true if unforked
913	>	* Returns the pool hosting the current task execution, or null
914	>	* if this task is executing outside of any ForkJoinPool.
915	>	*
916	>	* @see #inForkJoinPool
917	>	* @return the pool, or {@code null} if none
918		*/
919	<	public boolean tryUnfork() {
920	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
919	>	public static ForkJoinPool getPool() {
920	>	Thread t = Thread.currentThread();
921	>	return (t instanceof ForkJoinWorkerThread) ?
922	>	((ForkJoinWorkerThread) t).pool : null;
923		}
924
925		/**
926	<	* Forks both tasks, returning when <tt>isDone</tt> holds for both
927	<	* of them or an exception is encountered. This method may be
928	<	* invoked only from within other ForkJoinTask
929	<	* computations. Attempts to invoke in other contexts result in
930	<	* 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.
926	>	* Returns {@code true} if the current thread is executing as a
927	>	* ForkJoinPool computation.
928	>	*
929	>	* @return {@code true} if the current thread is executing as a
930	>	* ForkJoinPool computation, or false otherwise
931		*/
932	<	public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
933	<	t2.fork();
717	<	t1.invoke();
718	<	t2.join();
932	>	public static boolean inForkJoinPool() {
933	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
934		}
935
936		/**
937	<	* Forks the given tasks, returning when <tt>isDone</tt> holds for
938	<	* all of them. If any task encounters an exception, others may be
939	<	* cancelled.  This method may be invoked only from within other
940	<	* ForkJoinTask computations. Attempts to invoke in other contexts
941	<	* result in exceptions or errors including ClassCastException.
942	<	* @param tasks the array of tasks
943	<	* @throws NullPointerException if tasks or any element are null.
944	<	* @throws RuntimeException or Error if any task did so.
945	<	*/
946	<	public static void invokeAll(ForkJoinTask<?>... tasks) {
947	<	Throwable ex = null;
948	<	int last = tasks.length - 1;
949	<	for (int i = last; i >= 0; --i) {
950	<	ForkJoinTask<?> t = tasks[i];
736	<	if (t == null) {
737	<	if (ex == null)
738	<	ex = new NullPointerException();
739	<	}
740	<	else if (i != 0)
741	<	t.fork();
742	<	else {
743	<	t.quietlyInvoke();
744	<	if (ex == null)
745	<	ex = t.getException();
746	<	}
747	<	}
748	<	for (int i = 1; i <= last; ++i) {
749	<	ForkJoinTask<?> t = tasks[i];
750	<	if (t != null) {
751	<	if (ex != null)
752	<	t.cancel(false);
753	<	else {
754	<	t.quietlyJoin();
755	<	if (ex == null)
756	<	ex = t.getException();
757	<	}
758	<	}
759	<	}
760	<	if (ex != null)
761	<	rethrowException(ex);
762	<	}
763	<
764	<	/**
765	<	* Forks all tasks in the collection, returning when
766	<	* <tt>isDone</tt> holds for all of them. If any task encounters
767	<	* an exception, others may be cancelled.  This method may be
768	<	* invoked only from within other ForkJoinTask
769	<	* computations. Attempts to invoke in other contexts result in
770	<	* exceptions or errors including ClassCastException.
771	<	* @param tasks the collection of tasks
772	<	* @throws NullPointerException if tasks or any element are null.
773	<	* @throws RuntimeException or Error if any task did so.
937	>	* Tries to unschedule this task for execution. This method will
938	>	* typically succeed if this task is the most recently forked task
939	>	* by the current thread, and has not commenced executing in
940	>	* another thread.  This method may be useful when arranging
941	>	* alternative local processing of tasks that could have been, but
942	>	* were not, stolen.
943	>	*
944	>	* <p>This method may be invoked only from within {@code
945	>	* ForkJoinTask} computations (as may be determined using method
946	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
947	>	* result in exceptions or errors, possibly including {@code
948	>	* ClassCastException}.
949	>	*
950	>	* @return {@code true} if unforked
951		*/
952	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
953	<	if (!(tasks instanceof List)) {
954	<	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);
952	>	public boolean tryUnfork() {
953	>	return ((ForkJoinWorkerThread) Thread.currentThread())
954	>	.unpushTask(this);
955		}
956
957		/**
958	<	* Possibly executes tasks until the pool hosting the current task
959	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
960	<	* designs in which many tasks are forked, but none are explicitly
961	<	* joined, instead executing them until all are processed.
958	>	* Returns an estimate of the number of tasks that have been
959	>	* forked by the current worker thread but not yet executed. This
960	>	* value may be useful for heuristic decisions about whether to
961	>	* fork other tasks.
962	>	*
963	>	* <p>This method may be invoked only from within {@code
964	>	* ForkJoinTask} computations (as may be determined using method
965	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
966	>	* result in exceptions or errors, possibly including {@code
967	>	* ClassCastException}.
968	>	*
969	>	* @return the number of tasks
970		*/
971	<	public static void helpQuiesce() {
972	<	((ForkJoinWorkerThread)(Thread.currentThread())).
973	<	helpQuiescePool();
971	>	public static int getQueuedTaskCount() {
972	>	return ((ForkJoinWorkerThread) Thread.currentThread())
973	>	.getQueueSize();
974		}
975
976		/**
977	<	* Returns a estimate of how many more locally queued tasks are
977	>	* Returns an estimate of how many more locally queued tasks are
978		* held by the current worker thread than there are other worker
979	<	* threads that might want to steal them.  This value may be
980	<	* useful for heuristic decisions about whether to fork other
981	<	* tasks. In many usages of ForkJoinTasks, at steady state, each
982	<	* worker should aim to maintain a small constant surplus (for
983	<	* example, 3) of tasks, and to process computations locally if
984	<	* this threshold is exceeded.
979	>	* threads that might steal them.  This value may be useful for
980	>	* heuristic decisions about whether to fork other tasks. In many
981	>	* usages of ForkJoinTasks, at steady state, each worker should
982	>	* aim to maintain a small constant surplus (for example, 3) of
983	>	* tasks, and to process computations locally if this threshold is
984	>	* exceeded.
985	>	*
986	>	* <p>This method may be invoked only from within {@code
987	>	* ForkJoinTask} computations (as may be determined using method
988	>	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
989	>	* result in exceptions or errors, possibly including {@code
990	>	* ClassCastException}.
991	>	*
992		* @return the surplus number of tasks, which may be negative
993		*/
994	<	public static int surplus() {
995	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
994	>	public static int getSurplusQueuedTaskCount() {
995	>	return ((ForkJoinWorkerThread) Thread.currentThread())
996		.getEstimatedSurplusTaskCount();
997		}
998
999	<	// Extension kit
999	>	// Extension methods
1000
1001		/**
1002	<	* Returns the result that would be returned by <tt>join</tt>, or
1003	<	* null if this task is not known to have been completed.  This
1004	<	* method is designed to aid debugging, as well as to support
1005	<	* extensions. Its use in any other context is discouraged.
1002	>	* Returns the result that would be returned by {@link #join}, even
1003	>	* if this task completed abnormally, or {@code null} if this task
1004	>	* is not known to have been completed.  This method is designed
1005	>	* to aid debugging, as well as to support extensions. Its use in
1006	>	* any other context is discouraged.
1007		*
1008	<	* @return the result, or null if not completed.
1008	>	* @return the result, or {@code null} if not completed
1009		*/
1010		public abstract V getRawResult();
1011
#	Line 865 | Line 1024 | public abstract class ForkJoinTask<V> im
1024		* called otherwise. The return value controls whether this task
1025		* is considered to be done normally. It may return false in
1026		* asynchronous actions that require explicit invocations of
1027	<	* <tt>complete</tt> to become joinable. It may throw exceptions
1027	>	* {@link #complete} to become joinable. It may throw exceptions
1028		* to indicate abnormal exit.
1029	<	* @return true if completed normally
1029	>	*
1030	>	* @return {@code true} if completed normally
1031		* @throws Error or RuntimeException if encountered during computation
1032		*/
1033		protected abstract boolean exec();
1034
1035	+	/**
1036	+	* Returns, but does not unschedule or execute, a task queued by
1037	+	* the current thread but not yet executed, if one is immediately
1038	+	* available. There is no guarantee that this task will actually
1039	+	* be polled or executed next. Conversely, this method may return
1040	+	* null even if a task exists but cannot be accessed without
1041	+	* contention with other threads.  This method is designed
1042	+	* primarily to support extensions, and is unlikely to be useful
1043	+	* otherwise.
1044	+	*
1045	+	* <p>This method may be invoked only from within {@code
1046	+	* ForkJoinTask} computations (as may be determined using method
1047	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1048	+	* result in exceptions or errors, possibly including {@code
1049	+	* ClassCastException}.
1050	+	*
1051	+	* @return the next task, or {@code null} if none are available
1052	+	*/
1053	+	protected static ForkJoinTask<?> peekNextLocalTask() {
1054	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1055	+	.peekTask();
1056	+	}
1057	+
1058	+	/**
1059	+	* Unschedules and returns, without executing, the next task
1060	+	* queued by the current thread but not yet executed.  This method
1061	+	* is designed primarily to support extensions, and is unlikely to
1062	+	* be useful otherwise.
1063	+	*
1064	+	* <p>This method may be invoked only from within {@code
1065	+	* ForkJoinTask} computations (as may be determined using method
1066	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1067	+	* result in exceptions or errors, possibly including {@code
1068	+	* ClassCastException}.
1069	+	*
1070	+	* @return the next task, or {@code null} if none are available
1071	+	*/
1072	+	protected static ForkJoinTask<?> pollNextLocalTask() {
1073	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1074	+	.pollLocalTask();
1075	+	}
1076	+
1077	+	/**
1078	+	* Unschedules and returns, without executing, the next task
1079	+	* queued by the current thread but not yet executed, if one is
1080	+	* available, or if not available, a task that was forked by some
1081	+	* other thread, if available. Availability may be transient, so a
1082	+	* {@code null} result does not necessarily imply quiescence
1083	+	* of the pool this task is operating in.  This method is designed
1084	+	* primarily to support extensions, and is unlikely to be useful
1085	+	* otherwise.
1086	+	*
1087	+	* <p>This method may be invoked only from within {@code
1088	+	* ForkJoinTask} computations (as may be determined using method
1089	+	* {@link #inForkJoinPool}).  Attempts to invoke in other contexts
1090	+	* result in exceptions or errors, possibly including {@code
1091	+	* ClassCastException}.
1092	+	*
1093	+	* @return a task, or {@code null} if none are available
1094	+	*/
1095	+	protected static ForkJoinTask<?> pollTask() {
1096	+	return ((ForkJoinWorkerThread) Thread.currentThread())
1097	+	.pollTask();
1098	+	}
1099	+
1100	+	/**
1101	+	* Adaptor for Runnables. This implements RunnableFuture
1102	+	* to be compliant with AbstractExecutorService constraints
1103	+	* when used in ForkJoinPool.
1104	+	*/
1105	+	static final class AdaptedRunnable<T> extends ForkJoinTask<T>
1106	+	implements RunnableFuture<T> {
1107	+	final Runnable runnable;
1108	+	final T resultOnCompletion;
1109	+	T result;
1110	+	AdaptedRunnable(Runnable runnable, T result) {
1111	+	if (runnable == null) throw new NullPointerException();
1112	+	this.runnable = runnable;
1113	+	this.resultOnCompletion = result;
1114	+	}
1115	+	public T getRawResult() { return result; }
1116	+	public void setRawResult(T v) { result = v; }
1117	+	public boolean exec() {
1118	+	runnable.run();
1119	+	result = resultOnCompletion;
1120	+	return true;
1121	+	}
1122	+	public void run() { invoke(); }
1123	+	private static final long serialVersionUID = 5232453952276885070L;
1124	+	}
1125	+
1126	+	/**
1127	+	* Adaptor for Callables
1128	+	*/
1129	+	static final class AdaptedCallable<T> extends ForkJoinTask<T>
1130	+	implements RunnableFuture<T> {
1131	+	final Callable<? extends T> callable;
1132	+	T result;
1133	+	AdaptedCallable(Callable<? extends T> callable) {
1134	+	if (callable == null) throw new NullPointerException();
1135	+	this.callable = callable;
1136	+	}
1137	+	public T getRawResult() { return result; }
1138	+	public void setRawResult(T v) { result = v; }
1139	+	public boolean exec() {
1140	+	try {
1141	+	result = callable.call();
1142	+	return true;
1143	+	} catch (Error err) {
1144	+	throw err;
1145	+	} catch (RuntimeException rex) {
1146	+	throw rex;
1147	+	} catch (Exception ex) {
1148	+	throw new RuntimeException(ex);
1149	+	}
1150	+	}
1151	+	public void run() { invoke(); }
1152	+	private static final long serialVersionUID = 2838392045355241008L;
1153	+	}
1154	+
1155	+	/**
1156	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1157	+	* method of the given {@code Runnable} as its action, and returns
1158	+	* a null result upon {@link #join}.
1159	+	*
1160	+	* @param runnable the runnable action
1161	+	* @return the task
1162	+	*/
1163	+	public static ForkJoinTask<?> adapt(Runnable runnable) {
1164	+	return new AdaptedRunnable<Void>(runnable, null);
1165	+	}
1166	+
1167	+	/**
1168	+	* Returns a new {@code ForkJoinTask} that performs the {@code run}
1169	+	* method of the given {@code Runnable} as its action, and returns
1170	+	* the given result upon {@link #join}.
1171	+	*
1172	+	* @param runnable the runnable action
1173	+	* @param result the result upon completion
1174	+	* @return the task
1175	+	*/
1176	+	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1177	+	return new AdaptedRunnable<T>(runnable, result);
1178	+	}
1179	+
1180	+	/**
1181	+	* Returns a new {@code ForkJoinTask} that performs the {@code call}
1182	+	* method of the given {@code Callable} as its action, and returns
1183	+	* its result upon {@link #join}, translating any checked exceptions
1184	+	* encountered into {@code RuntimeException}.
1185	+	*
1186	+	* @param callable the callable action
1187	+	* @return the task
1188	+	*/
1189	+	public static <T> ForkJoinTask<T> adapt(Callable<? extends T> callable) {
1190	+	return new AdaptedCallable<T>(callable);
1191	+	}
1192	+
1193		// Serialization support
1194
1195		private static final long serialVersionUID = -7721805057305804111L;
#	Line 880 | Line 1198 | public abstract class ForkJoinTask<V> im
1198		* Save the state to a stream.
1199		*
1200		* @serialData the current run status and the exception thrown
1201	<	* during execution, or null if none.
1201	>	* during execution, or {@code null} if none
1202		* @param s the stream
1203		*/
1204		private void writeObject(java.io.ObjectOutputStream s)
#	Line 891 | Line 1209 | public abstract class ForkJoinTask<V> im
1209
1210		/**
1211		* Reconstitute the instance from a stream.
1212	+	*
1213		* @param s the stream
1214		*/
1215		private void readObject(java.io.ObjectInputStream s)
1216		throws java.io.IOException, ClassNotFoundException {
1217		s.defaultReadObject();
1218	<	//        status &= ~INTERNAL_SIGNAL_MASK; //  todo: define policy
1218	>	status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts
1219	>	status |= EXTERNAL_SIGNAL; // conservatively set external signal
1220		Object ex = s.readObject();
1221		if (ex != null)
1222	<	setDoneExceptionally((Throwable)ex);
1222	>	setDoneExceptionally((Throwable) ex);
1223		}
1224
1225	<	// Temporary Unsafe mechanics for preliminary release
1225	>	// Unsafe mechanics
1226
1227	<	static final Unsafe _unsafe;
1228	<	static final long statusOffset;
1227	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1228	>	private static final long statusOffset =
1229	>	objectFieldOffset("status", ForkJoinTask.class);
1230
1231	<	static {
1231	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1232		try {
1233	<	if (ForkJoinTask.class.getClassLoader() != null) {
1234	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1235	<	f.setAccessible(true);
1236	<	_unsafe = (Unsafe)f.get(null);
1237	<	}
1238	<	else
1239	<	_unsafe = Unsafe.getUnsafe();
919	<	statusOffset = _unsafe.objectFieldOffset
920	<	(ForkJoinTask.class.getDeclaredField("status"));
921	<	} catch (Exception ex) { throw new Error(ex); }
1233	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1234	>	} catch (NoSuchFieldException e) {
1235	>	// Convert Exception to corresponding Error
1236	>	NoSuchFieldError error = new NoSuchFieldError(field);
1237	>	error.initCause(e);
1238	>	throw error;
1239	>	}
1240		}
1241
1242	+	/**
1243	+	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1244	+	* Replace with a simple call to Unsafe.getUnsafe when integrating
1245	+	* into a jdk.
1246	+	*
1247	+	* @return a sun.misc.Unsafe
1248	+	*/
1249	+	private static sun.misc.Unsafe getUnsafe() {
1250	+	try {
1251	+	return sun.misc.Unsafe.getUnsafe();
1252	+	} catch (SecurityException se) {
1253	+	try {
1254	+	return java.security.AccessController.doPrivileged
1255	+	(new java.security
1256	+	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1257	+	public sun.misc.Unsafe run() throws Exception {
1258	+	java.lang.reflect.Field f = sun.misc
1259	+	.Unsafe.class.getDeclaredField("theUnsafe");
1260	+	f.setAccessible(true);
1261	+	return (sun.misc.Unsafe) f.get(null);
1262	+	}});
1263	+	} catch (java.security.PrivilegedActionException e) {
1264	+	throw new RuntimeException("Could not initialize intrinsics",
1265	+	e.getCause());
1266	+	}
1267	+	}
1268	+	}
1269		}

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