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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.6 by dl, Thu Jul 16 15:32:34 2009 UTC vs.
Revision 1.24 by jsr166, Mon Jul 27 21:41:53 2009 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.io.Serializable;
9	<	import java.util.*;
8	>
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
11	<	import sun.misc.Unsafe;
12	<	import java.lang.reflect.*;
10	>
11	>	import java.io.Serializable;
12	>	import java.util.Collection;
13	>	import java.util.Collections;
14	>	import java.util.List;
15	>	import java.util.Map;
16	>	import java.util.WeakHashMap;
17
18		/**
19		* Abstract base class for tasks that run within a {@link
#	Line 22 | Line 25 | import java.lang.reflect.*;
25		* <p> A "main" ForkJoinTask begins execution when submitted to a
26		* {@link ForkJoinPool}. Once started, it will usually in turn start
27		* other subtasks.  As indicated by the name of this class, many
28	<	* programs using ForkJoinTasks employ only methods <code>fork</code>
29	<	* and <code>join</code>, or derivatives such as
30	<	* <code>invokeAll</code>.  However, this class also provides a number
31	<	* of other methods that can come into play in advanced usages, as
32	<	* well as extension mechanics that allow support of new forms of
30	<	* fork/join processing.
28	>	* programs using ForkJoinTasks employ only methods {@code fork} and
29	>	* {@code join}, or derivatives such as {@code invokeAll}.  However,
30	>	* this class also provides a number of other methods that can come
31	>	* into play in advanced usages, as well as extension mechanics that
32	>	* allow support of new forms of fork/join processing.
33		*
34		* <p>A ForkJoinTask is a lightweight form of {@link Future}.  The
35		* efficiency of ForkJoinTasks stems from a set of restrictions (that
#	Line 36 | Line 38 | import java.lang.reflect.*;
38		* operating on purely isolated objects.  The primary coordination
39		* mechanisms are {@link #fork}, that arranges asynchronous execution,
40		* and {@link #join}, that doesn't proceed until the task's result has
41	<	* been computed.  Computations should avoid <code>synchronized</code>
41	>	* been computed.  Computations should avoid {@code synchronized}
42		* methods or blocks, and should minimize other blocking
43		* synchronization apart from joining other tasks or using
44		* synchronizers such as Phasers that are advertised to cooperate with
#	Line 48 | Line 50 | import java.lang.reflect.*;
50		* performance, and the potential to indefinitely stall if the number
51		* of threads not waiting for IO or other external synchronization
52		* becomes exhausted. This usage restriction is in part enforced by
53	<	* not permitting checked exceptions such as <code>IOExceptions</code>
53	>	* not permitting checked exceptions such as {@code IOExceptions}
54		* to be thrown. However, computations may still encounter unchecked
55		* exceptions, that are rethrown to callers attempting join
56		* them. These exceptions may additionally include
#	Line 58 | Line 60 | import java.lang.reflect.*;
60		* <p>The primary method for awaiting completion and extracting
61		* results of a task is {@link #join}, but there are several variants:
62		* The {@link Future#get} methods support interruptible and/or timed
63	<	* waits for completion and report results using <code>Future</code>
63	>	* waits for completion and report results using {@code Future}
64		* conventions. Method {@link #helpJoin} enables callers to actively
65		* execute other tasks while awaiting joins, which is sometimes more
66		* efficient but only applies when all subtasks are known to be
67		* strictly tree-structured. Method {@link #invoke} is semantically
68	<	* equivalent to <code>fork(); join()</code> but always attempts to
68	>	* equivalent to {@code fork(); join()} but always attempts to
69		* begin execution in the current thread. The "<em>quiet</em>" forms
70		* of these methods do not extract results or report exceptions. These
71		* may be useful when a set of tasks are being executed, and you need
72		* to delay processing of results or exceptions until all complete.
73	<	* Method <code>invokeAll</code> (available in multiple versions)
73	>	* Method {@code invokeAll} (available in multiple versions)
74		* performs the most common form of parallel invocation: forking a set
75		* of tasks and joining them all.
76		*
#	Line 76 | Line 78 | import java.lang.reflect.*;
78		* Instead, you subclass one of the abstract classes that support a
79		* particular style of fork/join processing.  Normally, a concrete
80		* ForkJoinTask subclass declares fields comprising its parameters,
81	<	* established in a constructor, and then defines a <code>compute</code>
81	>	* established in a constructor, and then defines a {@code compute}
82		* method that somehow uses the control methods supplied by this base
83	<	* class. While these methods have <code>public</code> access (to allow
83	>	* class. While these methods have {@code public} access (to allow
84		* instances of different task subclasses to call each others
85		* methods), some of them may only be called from within other
86	<	* ForkJoinTasks. Attempts to invoke them in other contexts result in
87	<	* exceptions or errors possibly including ClassCastException.
86	>	* ForkJoinTasks (as may be determined using method {@link
87	>	* #inForkJoinPool}).  Attempts to invoke them in other contexts
88	>	* result in exceptions or errors, possibly including
89	>	* ClassCastException.
90		*
91	<	* <p>Most base support methods are <code>final</code> because their
91	>	* <p>Most base support methods are {@code final} because their
92		* implementations are intrinsically tied to the underlying
93		* lightweight task scheduling framework, and so cannot be overridden.
94		* Developers creating new basic styles of fork/join processing should
95	<	* minimally implement <code>protected</code> methods
96	<	* <code>exec</code>, <code>setRawResult</code>, and
97	<	* <code>getRawResult</code>, while also introducing an abstract
95	>	* minimally implement {@code protected} methods
96	>	* {@link #exec}, {@link #setRawResult}, and
97	>	* {@link #getRawResult}, while also introducing an abstract
98		* computational method that can be implemented in its subclasses,
99	<	* possibly relying on other <code>protected</code> methods provided
99	>	* possibly relying on other {@code protected} methods provided
100		* by this class.
101		*
102		* <p>ForkJoinTasks should perform relatively small amounts of
103	<	* computations, othewise splitting into smaller tasks. As a very
103	>	* computations, otherwise splitting into smaller tasks. As a very
104		* rough rule of thumb, a task should perform more than 100 and less
105		* than 10000 basic computational steps. If tasks are too big, then
106	<	* parellelism cannot improve throughput. If too small, then memory
106	>	* parallelism cannot improve throughput. If too small, then memory
107		* and internal task maintenance overhead may overwhelm processing.
108		*
109	<	* <p>ForkJoinTasks are <code>Serializable</code>, which enables them
109	>	* <p>ForkJoinTasks are {@code Serializable}, which enables them
110		* to be used in extensions such as remote execution frameworks. It is
111		* in general sensible to serialize tasks only before or after, but
112		* not during execution. Serialization is not relied on during
113		* execution itself.
114	+	*
115	+	* @since 1.7
116	+	* @author Doug Lea
117		*/
118		public abstract class ForkJoinTask<V> implements Future<V>, Serializable {
119
#	Line 128 | Line 135 | public abstract class ForkJoinTask<V> im
135		* currently unused. Also value 0x80000000 is available as spare
136		* completion value.
137		*/
138	<	volatile int status; // accessed directy by pool and workers
138	>	volatile int status; // accessed directly by pool and workers
139
140		static final int COMPLETION_MASK      = 0xe0000000;
141		static final int NORMAL               = 0xe0000000; // == mask
#	Line 141 | Line 148 | public abstract class ForkJoinTask<V> im
148		/**
149		* Table of exceptions thrown by tasks, to enable reporting by
150		* callers. Because exceptions are rare, we don't directly keep
151	<	* them with task objects, but instead us a weak ref table.  Note
151	>	* them with task objects, but instead use a weak ref table.  Note
152		* that cancellation exceptions don't appear in the table, but are
153		* instead recorded as status values.
154	<	* Todo: Use ConcurrentReferenceHashMap
154	>	* TODO: Use ConcurrentReferenceHashMap
155		*/
156		static final Map<ForkJoinTask<?>, Throwable> exceptionMap =
157		Collections.synchronizedMap
#	Line 153 | Line 160 | public abstract class ForkJoinTask<V> im
160		// within-package utilities
161
162		/**
163	<	* Get current worker thread, or null if not a worker thread
163	>	* Gets current worker thread, or null if not a worker thread.
164		*/
165		static ForkJoinWorkerThread getWorker() {
166		Thread t = Thread.currentThread();
167	<	return ((t instanceof ForkJoinWorkerThread)?
168	<	(ForkJoinWorkerThread)t : null);
167	>	return ((t instanceof ForkJoinWorkerThread) ?
168	>	(ForkJoinWorkerThread) t : null);
169		}
170
171		final boolean casStatus(int cmp, int val) {
172	<	return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val);
172	>	return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
173		}
174
175		/**
#	Line 170 | Line 177 | public abstract class ForkJoinTask<V> im
177		*/
178		static void rethrowException(Throwable ex) {
179		if (ex != null)
180	<	_unsafe.throwException(ex);
180	>	UNSAFE.throwException(ex);
181		}
182
183		// Setting completion status
184
185		/**
186	<	* Mark completion and wake up threads waiting to join this task.
186	>	* Marks completion and wakes up threads waiting to join this task.
187	>	*
188		* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
189		*/
190		final void setCompletion(int completion) {
191		ForkJoinPool pool = getPool();
192		if (pool != null) {
193		int s; // Clear signal bits while setting completion status
194	<	do;while ((s = status) >= 0 && !casStatus(s, completion));
194	>	do {} while ((s = status) >= 0 && !casStatus(s, completion));
195
196		if ((s & SIGNAL_MASK) != 0) {
197		if ((s &= INTERNAL_SIGNAL_MASK) != 0)
198		pool.updateRunningCount(s);
199	<	synchronized(this) { notifyAll(); }
199	>	synchronized (this) { notifyAll(); }
200		}
201		}
202		else
#	Line 201 | Line 209 | public abstract class ForkJoinTask<V> im
209		*/
210		private void externallySetCompletion(int completion) {
211		int s;
212	<	do;while ((s = status) >= 0 &&
213	<	!casStatus(s, (s & SIGNAL_MASK) | completion));
214	<	synchronized(this) { notifyAll(); }
212	>	do {} while ((s = status) >= 0 &&
213	>	!casStatus(s, (s & SIGNAL_MASK) | completion));
214	>	synchronized (this) { notifyAll(); }
215		}
216
217		/**
218	<	* Sets status to indicate normal completion
218	>	* Sets status to indicate normal completion.
219		*/
220		final void setNormalCompletion() {
221		// Try typical fast case -- single CAS, no signal, not already done.
222		// Manually expand casStatus to improve chances of inlining it
223	<	if (!_unsafe.compareAndSwapInt(this, statusOffset, 0, NORMAL))
223	>	if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
224		setCompletion(NORMAL);
225		}
226
227		// internal waiting and notification
228
229		/**
230	<	* Performs the actual monitor wait for awaitDone
230	>	* Performs the actual monitor wait for awaitDone.
231		*/
232		private void doAwaitDone() {
233		// Minimize lock bias and in/de-flation effects by maximizing
234		// chances of waiting inside sync
235		try {
236		while (status >= 0)
237	<	synchronized(this) { if (status >= 0) wait(); }
237	>	synchronized (this) { if (status >= 0) wait(); }
238		} catch (InterruptedException ie) {
239		onInterruptedWait();
240		}
241		}
242
243		/**
244	<	* Performs the actual monitor wait for awaitDone
244	>	* Performs the actual timed monitor wait for awaitDone.
245		*/
246		private void doAwaitDone(long startTime, long nanos) {
247	<	synchronized(this) {
247	>	synchronized (this) {
248		try {
249		while (status >= 0) {
250		long nt = nanos - System.nanoTime() - startTime;
251		if (nt <= 0)
252		break;
253	<	wait(nt / 1000000, (int)(nt % 1000000));
253	>	wait(nt / 1000000, (int) (nt % 1000000));
254		}
255		} catch (InterruptedException ie) {
256		onInterruptedWait();
#	Line 255 | Line 263 | public abstract class ForkJoinTask<V> im
263		/**
264		* Sets status to indicate there is joiner, then waits for join,
265		* surrounded with pool notifications.
266	+	*
267		* @return status upon exit
268		*/
269	<	private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
270	<	ForkJoinPool pool = w == null? null : w.pool;
269	>	private int awaitDone(ForkJoinWorkerThread w,
270	>	boolean maintainParallelism) {
271	>	ForkJoinPool pool = (w == null) ? null : w.pool;
272		int s;
273		while ((s = status) >= 0) {
274	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
274	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
275		if (pool == null || !pool.preJoin(this, maintainParallelism))
276		doAwaitDone();
277		if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
#	Line 274 | Line 284 | public abstract class ForkJoinTask<V> im
284
285		/**
286		* Timed version of awaitDone
287	+	*
288		* @return status upon exit
289		*/
290		private int awaitDone(ForkJoinWorkerThread w, long nanos) {
291	<	ForkJoinPool pool = w == null? null : w.pool;
291	>	ForkJoinPool pool = (w == null) ? null : w.pool;
292		int s;
293		while ((s = status) >= 0) {
294	<	if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
294	>	if (casStatus(s, (pool == null) ? s|EXTERNAL_SIGNAL : s+1)) {
295		long startTime = System.nanoTime();
296		if (pool == null || !pool.preJoin(this, false))
297		doAwaitDone(startTime, nanos);
#	Line 297 | Line 308 | public abstract class ForkJoinTask<V> im
308		}
309
310		/**
311	<	* Notify pool that thread is unblocked. Called by signalled
311	>	* Notifies pool that thread is unblocked. Called by signalled
312		* threads when woken by non-FJ threads (which is atypical).
313		*/
314		private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
315		int s;
316	<	do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
316	>	do {} while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
317		if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
318		pool.updateRunningCount(s);
319		}
320
321		/**
322	<	* Notify pool to adjust counts on cancelled or timed out wait
322	>	* Notifies pool to adjust counts on cancelled or timed out wait.
323		*/
324		private void adjustPoolCountsOnCancelledWait(ForkJoinPool pool) {
325		if (pool != null) {
#	Line 323 | Line 334 | public abstract class ForkJoinTask<V> im
334		}
335
336		/**
337	<	* Handle interruptions during waits.
337	>	* Handles interruptions during waits.
338		*/
339		private void onInterruptedWait() {
340		ForkJoinWorkerThread w = getWorker();
#	Line 342 | Line 353 | public abstract class ForkJoinTask<V> im
353		}
354
355		/**
356	<	* Throws the exception associated with status s;
356	>	* Throws the exception associated with status s.
357	>	*
358		* @throws the exception
359		*/
360		private void reportException(int s) {
#	Line 355 | Line 367 | public abstract class ForkJoinTask<V> im
367		}
368
369		/**
370	<	* Returns result or throws exception using j.u.c.Future conventions
371	<	* Only call when isDone known to be true.
370	>	* Returns result or throws exception using j.u.c.Future conventions.
371	>	* Only call when {@code isDone} known to be true.
372		*/
373		private V reportFutureResult()
374		throws ExecutionException, InterruptedException {
#	Line 375 | Line 387 | public abstract class ForkJoinTask<V> im
387
388		/**
389		* Returns result or throws exception using j.u.c.Future conventions
390	<	* with timeouts
390	>	* with timeouts.
391		*/
392		private V reportTimedFutureResult()
393		throws InterruptedException, ExecutionException, TimeoutException {
#	Line 396 | Line 408 | public abstract class ForkJoinTask<V> im
408
409		/**
410		* Calls exec, recording completion, and rethrowing exception if
411	<	* encountered. Caller should normally check status before calling
411	>	* encountered. Caller should normally check status before calling.
412	>	*
413		* @return true if completed normally
414		*/
415		private boolean tryExec() {
#	Line 414 | Line 427 | public abstract class ForkJoinTask<V> im
427
428		/**
429		* Main execution method used by worker threads. Invokes
430	<	* base computation unless already complete
430	>	* base computation unless already complete.
431		*/
432		final void quietlyExec() {
433		if (status >= 0) {
434		try {
435		if (!exec())
436		return;
437	<	} catch(Throwable rex) {
437	>	} catch (Throwable rex) {
438		setDoneExceptionally(rex);
439		return;
440		}
#	Line 430 | Line 443 | public abstract class ForkJoinTask<V> im
443		}
444
445		/**
446	<	* Calls exec, recording but not rethrowing exception
447	<	* Caller should normally check status before calling
446	>	* Calls exec(), recording but not rethrowing exception.
447	>	* Caller should normally check status before calling.
448	>	*
449		* @return true if completed normally
450		*/
451		private boolean tryQuietlyInvoke() {
#	Line 447 | Line 461 | public abstract class ForkJoinTask<V> im
461		}
462
463		/**
464	<	* Cancel, ignoring any exceptions it throws
464	>	* Cancels, ignoring any exceptions it throws.
465		*/
466		final void cancelIgnoringExceptions() {
467		try {
468		cancel(false);
469	<	} catch(Throwable ignore) {
469	>	} catch (Throwable ignore) {
470		}
471		}
472
#	Line 464 | Line 478 | public abstract class ForkJoinTask<V> im
478		ForkJoinTask<?> t;
479		while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null)
480		t.quietlyExec();
481	<	return (s >= 0)? awaitDone(w, false) : s; // block if no work
481	>	return (s >= 0) ? awaitDone(w, false) : s; // block if no work
482		}
483
484		// public methods
#	Line 474 | Line 488 | public abstract class ForkJoinTask<V> im
488		* necessarily enforced, it is a usage error to fork a task more
489		* than once unless it has completed and been reinitialized.  This
490		* method may be invoked only from within ForkJoinTask
491	<	* computations. Attempts to invoke in other contexts result in
492	<	* exceptions or errors possibly including ClassCastException.
491	>	* computations (as may be determined using method {@link
492	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
493	>	* in exceptions or errors, possibly including ClassCastException.
494	>	*
495	>	* @return {@code this}, to simplify usage.
496		*/
497	<	public final void fork() {
498	<	((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this);
497	>	public final ForkJoinTask<V> fork() {
498	>	((ForkJoinWorkerThread) Thread.currentThread())
499	>	.pushTask(this);
500	>	return this;
501		}
502
503		/**
504		* Returns the result of the computation when it is ready.
505	<	* This method differs from <code>get</code> in that abnormal
505	>	* This method differs from {@code get} in that abnormal
506		* completion results in RuntimeExceptions or Errors, not
507		* ExecutionExceptions.
508		*
#	Line 499 | Line 518 | public abstract class ForkJoinTask<V> im
518		/**
519		* Commences performing this task, awaits its completion if
520		* necessary, and return its result.
521	+	*
522		* @throws Throwable (a RuntimeException, Error, or unchecked
523	<	* exception) if the underlying computation did so.
523	>	* exception) if the underlying computation did so
524		* @return the computed result
525		*/
526		public final V invoke() {
#	Line 511 | Line 531 | public abstract class ForkJoinTask<V> im
531		}
532
533		/**
534	<	* Forks both tasks, returning when <code>isDone</code> holds for
534	>	* Forks both tasks, returning when {@code isDone} holds for
535		* both of them or an exception is encountered. This method may be
536	<	* invoked only from within ForkJoinTask computations. Attempts to
537	<	* invoke in other contexts result in exceptions or errors
536	>	* invoked only from within ForkJoinTask computations (as may be
537	>	* determined using method {@link #inForkJoinPool}). Attempts to
538	>	* invoke in other contexts result in exceptions or errors,
539		* possibly including ClassCastException.
540	+	*
541		* @param t1 one task
542		* @param t2 the other task
543		* @throws NullPointerException if t1 or t2 are null
544	<	* @throws RuntimeException or Error if either task did so.
544	>	* @throws RuntimeException or Error if either task did so
545		*/
546		public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) {
547		t2.fork();
#	Line 528 | Line 550 | public abstract class ForkJoinTask<V> im
550		}
551
552		/**
553	<	* Forks the given tasks, returning when <code>isDone</code> holds
553	>	* Forks the given tasks, returning when {@code isDone} holds
554		* for all of them. If any task encounters an exception, others
555		* may be cancelled.  This method may be invoked only from within
556	<	* ForkJoinTask computations. Attempts to invoke in other contexts
557	<	* result in exceptions or errors possibly including ClassCastException.
556	>	* ForkJoinTask computations (as may be determined using method
557	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
558	>	* result in exceptions or errors, possibly including
559	>	* ClassCastException.
560	>	*
561		* @param tasks the array of tasks
562	<	* @throws NullPointerException if tasks or any element are null.
563	<	* @throws RuntimeException or Error if any task did so.
562	>	* @throws NullPointerException if tasks or any element are null
563	>	* @throws RuntimeException or Error if any task did so
564		*/
565		public static void invokeAll(ForkJoinTask<?>... tasks) {
566		Throwable ex = null;
#	Line 572 | Line 597 | public abstract class ForkJoinTask<V> im
597
598		/**
599		* Forks all tasks in the collection, returning when
600	<	* <code>isDone</code> holds for all of them. If any task
600	>	* {@code isDone} holds for all of them. If any task
601		* encounters an exception, others may be cancelled.  This method
602	<	* may be invoked only from within ForkJoinTask
603	<	* computations. Attempts to invoke in other contexts resul!t in
604	<	* exceptions or errors possibly including ClassCastException.
602	>	* may be invoked only from within ForkJoinTask computations (as
603	>	* may be determined using method {@link
604	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
605	>	* in exceptions or errors, possibly including ClassCastException.
606	>	*
607		* @param tasks the collection of tasks
608	<	* @throws NullPointerException if tasks or any element are null.
609	<	* @throws RuntimeException or Error if any task did so.
610	<	*/
611	<	public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) {
612	<	if (!(tasks instanceof List)) {
613	<	invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()]));
614	<	return;
608	>	* @return the tasks argument, to simplify usage
609	>	* @throws NullPointerException if tasks or any element are null
610	>	* @throws RuntimeException or Error if any task did so
611	>	*/
612	>	public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
613	>	if (!(tasks instanceof List<?>)) {
614	>	invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()]));
615	>	return tasks;
616		}
617	+	@SuppressWarnings("unchecked")
618		List<? extends ForkJoinTask<?>> ts =
619	<	(List<? extends ForkJoinTask<?>>)tasks;
619	>	(List<? extends ForkJoinTask<?>>) tasks;
620		Throwable ex = null;
621		int last = ts.size() - 1;
622		for (int i = last; i >= 0; --i) {
#	Line 618 | Line 647 | public abstract class ForkJoinTask<V> im
647		}
648		if (ex != null)
649		rethrowException(ex);
650	+	return tasks;
651		}
652
653		/**
654	<	* Returns true if the computation performed by this task has
655	<	* completed (or has been cancelled).
656	<	* @return true if this computation has completed
654	>	* Returns {@code true} if the computation performed by this task
655	>	* has completed (or has been cancelled).
656	>	*
657	>	* @return {@code true} if this computation has completed
658		*/
659		public final boolean isDone() {
660		return status < 0;
661		}
662
663		/**
664	<	* Returns true if this task was cancelled.
665	<	* @return true if this task was cancelled
664	>	* Returns {@code true} if this task was cancelled.
665	>	*
666	>	* @return {@code true} if this task was cancelled
667		*/
668		public final boolean isCancelled() {
669		return (status & COMPLETION_MASK) == CANCELLED;
#	Line 639 | Line 671 | public abstract class ForkJoinTask<V> im
671
672		/**
673		* Asserts that the results of this task's computation will not be
674	<	* used. If a cancellation occurs before atempting to execute this
675	<	* task, then execution will be suppressed, <code>isCancelled</code>
676	<	* will report true, and <code>join</code> will result in a
677	<	* <code>CancellationException</code> being thrown. Otherwise, when
674	>	* used. If a cancellation occurs before attempting to execute this
675	>	* task, execution will be suppressed, {@link #isCancelled}
676	>	* will report true, and {@link #join} will result in a
677	>	* {@code CancellationException} being thrown. Otherwise, when
678		* cancellation races with completion, there are no guarantees
679	<	* about whether <code>isCancelled</code> will report true, whether
680	<	* <code>join</code> will return normally or via an exception, or
681	<	* whether these behaviors will remain consistent upon repeated
679	>	* about whether {@code isCancelled} will report {@code true},
680	>	* whether {@code join} will return normally or via an exception,
681	>	* or whether these behaviors will remain consistent upon repeated
682		* invocation.
683		*
684		* <p>This method may be overridden in subclasses, but if so, must
#	Line 656 | Line 688 | public abstract class ForkJoinTask<V> im
688		* <p> This method is designed to be invoked by <em>other</em>
689		* tasks. To terminate the current task, you can just return or
690		* throw an unchecked exception from its computation method, or
691	<	* invoke <code>completeExceptionally</code>.
691	>	* invoke {@link #completeExceptionally}.
692		*
693		* @param mayInterruptIfRunning this value is ignored in the
694		* default implementation because tasks are not in general
695	<	* cancelled via interruption.
695	>	* cancelled via interruption
696		*
697	<	* @return true if this task is now cancelled
697	>	* @return {@code true} if this task is now cancelled
698		*/
699		public boolean cancel(boolean mayInterruptIfRunning) {
700		setCompletion(CANCELLED);
#	Line 670 | Line 702 | public abstract class ForkJoinTask<V> im
702		}
703
704		/**
705	<	* Returns true if this task threw an exception or was cancelled
706	<	* @return true if this task threw an exception or was cancelled
705	>	* Returns {@code true} if this task threw an exception or was cancelled.
706	>	*
707	>	* @return {@code true} if this task threw an exception or was cancelled
708		*/
709		public final boolean isCompletedAbnormally() {
710		return (status & COMPLETION_MASK) < NORMAL;
#	Line 681 | Line 714 | public abstract class ForkJoinTask<V> im
714		* Returns the exception thrown by the base computation, or a
715		* CancellationException if cancelled, or null if none or if the
716		* method has not yet completed.
717	<	* @return the exception, or null if none
717	>	*
718	>	* @return the exception, or {@code null} if none
719		*/
720		public final Throwable getException() {
721		int s = status & COMPLETION_MASK;
#	Line 695 | Line 729 | public abstract class ForkJoinTask<V> im
729		/**
730		* Completes this task abnormally, and if not already aborted or
731		* cancelled, causes it to throw the given exception upon
732	<	* <code>join</code> and related operations. This method may be used
732	>	* {@code join} and related operations. This method may be used
733		* to induce exceptions in asynchronous tasks, or to force
734		* completion of tasks that would not otherwise complete.  Its use
735		* in other situations is likely to be wrong.  This method is
736	<	* overridable, but overridden versions must invoke <code>super</code>
736	>	* overridable, but overridden versions must invoke {@code super}
737		* implementation to maintain guarantees.
738		*
739		* @param ex the exception to throw. If this exception is
#	Line 708 | Line 742 | public abstract class ForkJoinTask<V> im
742		*/
743		public void completeExceptionally(Throwable ex) {
744		setDoneExceptionally((ex instanceof RuntimeException) ||
745	<	(ex instanceof Error)? ex :
745	>	(ex instanceof Error) ? ex :
746		new RuntimeException(ex));
747		}
748
749		/**
750		* Completes this task, and if not already aborted or cancelled,
751	<	* returning a <code>null</code> result upon <code>join</code> and related
751	>	* returning a {@code null} result upon {@code join} and related
752		* operations. This method may be used to provide results for
753		* asynchronous tasks, or to provide alternative handling for
754		* tasks that would not otherwise complete normally. Its use in
755		* other situations is likely to be wrong. This method is
756	<	* overridable, but overridden versions must invoke <code>super</code>
756	>	* overridable, but overridden versions must invoke {@code super}
757		* implementation to maintain guarantees.
758		*
759	<	* @param value the result value for this task.
759	>	* @param value the result value for this task
760		*/
761		public void complete(V value) {
762		try {
763		setRawResult(value);
764	<	} catch(Throwable rex) {
764	>	} catch (Throwable rex) {
765		setDoneExceptionally(rex);
766		return;
767		}
#	Line 752 | Line 786 | public abstract class ForkJoinTask<V> im
786		/**
787		* Possibly executes other tasks until this task is ready, then
788		* returns the result of the computation.  This method may be more
789	<	* efficient than <code>join</code>, but is only applicable when
790	<	* there are no potemtial dependencies between continuation of the
789	>	* efficient than {@code join}, but is only applicable when
790	>	* there are no potential dependencies between continuation of the
791		* current task and that of any other task that might be executed
792		* while helping. (This usually holds for pure divide-and-conquer
793		* tasks). This method may be invoked only from within
794	<	* ForkJoinTask computations. Attempts to invoke in other contexts
795	<	* resul!t in exceptions or errors possibly including ClassCastException.
794	>	* ForkJoinTask computations (as may be determined using method
795	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
796	>	* result in exceptions or errors, possibly including
797	>	* ClassCastException.
798	>	*
799		* @return the computed result
800		*/
801		public final V helpJoin() {
802	<	ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread());
802	>	ForkJoinWorkerThread w = (ForkJoinWorkerThread) Thread.currentThread();
803		if (status < 0 || !w.unpushTask(this) || !tryExec())
804		reportException(busyJoin(w));
805		return getRawResult();
#	Line 771 | Line 808 | public abstract class ForkJoinTask<V> im
808		/**
809		* Possibly executes other tasks until this task is ready.  This
810		* method may be invoked only from within ForkJoinTask
811	<	* computations. Attempts to invoke in other contexts resul!t in
812	<	* exceptions or errors possibly including ClassCastException.
811	>	* computations (as may be determined using method {@link
812	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
813	>	* in exceptions or errors, possibly including ClassCastException.
814		*/
815		public final void quietlyHelpJoin() {
816		if (status >= 0) {
817		ForkJoinWorkerThread w =
818	<	(ForkJoinWorkerThread)(Thread.currentThread());
818	>	(ForkJoinWorkerThread) Thread.currentThread();
819		if (!w.unpushTask(this) || !tryQuietlyInvoke())
820		busyJoin(w);
821		}
#	Line 816 | Line 854 | public abstract class ForkJoinTask<V> im
854		* joined, instead executing them until all are processed.
855		*/
856		public static void helpQuiesce() {
857	<	((ForkJoinWorkerThread)(Thread.currentThread())).
858	<	helpQuiescePool();
857	>	((ForkJoinWorkerThread) Thread.currentThread())
858	>	.helpQuiescePool();
859		}
860
861		/**
862		* Resets the internal bookkeeping state of this task, allowing a
863	<	* subsequent <code>fork</code>. This method allows repeated reuse of
863	>	* subsequent {@code fork}. This method allows repeated reuse of
864		* this task, but only if reuse occurs when this task has either
865		* never been forked, or has been forked, then completed and all
866		* outstanding joins of this task have also completed. Effects
#	Line 838 | Line 876 | public abstract class ForkJoinTask<V> im
876
877		/**
878		* Returns the pool hosting the current task execution, or null
879	<	* if this task is executing outside of any pool.
880	<	* @return the pool, or null if none.
879	>	* if this task is executing outside of any ForkJoinPool.
880	>	*
881	>	* @return the pool, or {@code null} if none
882		*/
883		public static ForkJoinPool getPool() {
884		Thread t = Thread.currentThread();
885	<	return ((t instanceof ForkJoinWorkerThread)?
886	<	((ForkJoinWorkerThread)t).pool : null);
885	>	return (t instanceof ForkJoinWorkerThread) ?
886	>	((ForkJoinWorkerThread) t).pool : null;
887	>	}
888	>
889	>	/**
890	>	* Returns {@code true} if the current thread is executing as a
891	>	* ForkJoinPool computation.
892	>	*
893	>	* @return {@code true} if the current thread is executing as a
894	>	* ForkJoinPool computation, or false otherwise
895	>	*/
896	>	public static boolean inForkJoinPool() {
897	>	return Thread.currentThread() instanceof ForkJoinWorkerThread;
898		}
899
900		/**
#	Line 854 | Line 904 | public abstract class ForkJoinTask<V> im
904		* another thread.  This method may be useful when arranging
905		* alternative local processing of tasks that could have been, but
906		* were not, stolen. This method may be invoked only from within
907	<	* ForkJoinTask computations. Attempts to invoke in other contexts
908	<	* result in exceptions or errors possibly including ClassCastException.
909	<	* @return true if unforked
907	>	* ForkJoinTask computations (as may be determined using method
908	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
909	>	* result in exceptions or errors, possibly including
910	>	* ClassCastException.
911	>	*
912	>	* @return {@code true} if unforked
913		*/
914		public boolean tryUnfork() {
915	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this);
915	>	return ((ForkJoinWorkerThread) Thread.currentThread())
916	>	.unpushTask(this);
917		}
918
919		/**
#	Line 867 | Line 921 | public abstract class ForkJoinTask<V> im
921		* forked by the current worker thread but not yet executed. This
922		* value may be useful for heuristic decisions about whether to
923		* fork other tasks.
924	+	*
925		* @return the number of tasks
926		*/
927		public static int getQueuedTaskCount() {
928	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
929	<	getQueueSize();
928	>	return ((ForkJoinWorkerThread) Thread.currentThread())
929	>	.getQueueSize();
930		}
931
932		/**
933	<	* Returns a estimate of how many more locally queued tasks are
933	>	* Returns an estimate of how many more locally queued tasks are
934		* held by the current worker thread than there are other worker
935		* threads that might steal them.  This value may be useful for
936		* heuristic decisions about whether to fork other tasks. In many
#	Line 883 | Line 938 | public abstract class ForkJoinTask<V> im
938		* aim to maintain a small constant surplus (for example, 3) of
939		* tasks, and to process computations locally if this threshold is
940		* exceeded.
941	+	*
942		* @return the surplus number of tasks, which may be negative
943		*/
944		public static int getSurplusQueuedTaskCount() {
945	<	return ((ForkJoinWorkerThread)(Thread.currentThread()))
945	>	return ((ForkJoinWorkerThread) Thread.currentThread())
946		.getEstimatedSurplusTaskCount();
947		}
948
949		// Extension methods
950
951		/**
952	<	* Returns the result that would be returned by <code>join</code>,
953	<	* even if this task completed abnormally, or null if this task is
954	<	* not known to have been completed.  This method is designed to
955	<	* aid debugging, as well as to support extensions. Its use in any
956	<	* other context is discouraged.
952	>	* Returns the result that would be returned by {@link #join}, even
953	>	* if this task completed abnormally, or {@code null} if this task
954	>	* is not known to have been completed.  This method is designed
955	>	* to aid debugging, as well as to support extensions. Its use in
956	>	* any other context is discouraged.
957		*
958	<	* @return the result, or null if not completed.
958	>	* @return the result, or {@code null} if not completed
959		*/
960		public abstract V getRawResult();
961
#	Line 918 | Line 974 | public abstract class ForkJoinTask<V> im
974		* called otherwise. The return value controls whether this task
975		* is considered to be done normally. It may return false in
976		* asynchronous actions that require explicit invocations of
977	<	* <code>complete</code> to become joinable. It may throw exceptions
977	>	* {@link #complete} to become joinable. It may throw exceptions
978		* to indicate abnormal exit.
979	<	* @return true if completed normally
979	>	*
980	>	* @return {@code true} if completed normally
981		* @throws Error or RuntimeException if encountered during computation
982		*/
983		protected abstract boolean exec();
#	Line 932 | Line 989 | public abstract class ForkJoinTask<V> im
989		* be polled or executed next.  This method is designed primarily
990		* to support extensions, and is unlikely to be useful otherwise.
991		* This method may be invoked only from within ForkJoinTask
992	<	* computations. Attempts to invoke in other contexts result in
993	<	* exceptions or errors possibly including ClassCastException.
992	>	* computations (as may be determined using method {@link
993	>	* #inForkJoinPool}). Attempts to invoke in other contexts result
994	>	* in exceptions or errors, possibly including ClassCastException.
995		*
996	<	* @return the next task, or null if none are available
996	>	* @return the next task, or {@code null} if none are available
997		*/
998		protected static ForkJoinTask<?> peekNextLocalTask() {
999	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask();
999	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1000	>	.peekTask();
1001		}
1002
1003		/**
#	Line 946 | Line 1005 | public abstract class ForkJoinTask<V> im
1005		* queued by the current thread but not yet executed.  This method
1006		* is designed primarily to support extensions, and is unlikely to
1007		* be useful otherwise.  This method may be invoked only from
1008	<	* within ForkJoinTask computations. Attempts to invoke in other
1009	<	* contexts result in exceptions or errors possibly including
1008	>	* within ForkJoinTask computations (as may be determined using
1009	>	* method {@link #inForkJoinPool}). Attempts to invoke in other
1010	>	* contexts result in exceptions or errors, possibly including
1011		* ClassCastException.
1012		*
1013	<	* @return the next task, or null if none are available
1013	>	* @return the next task, or {@code null} if none are available
1014		*/
1015		protected static ForkJoinTask<?> pollNextLocalTask() {
1016	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).pollLocalTask();
1016	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1017	>	.pollLocalTask();
1018		}
1019	<
1019	>
1020		/**
1021		* Unschedules and returns, without executing, the next task
1022		* queued by the current thread but not yet executed, if one is
1023		* available, or if not available, a task that was forked by some
1024		* other thread, if available. Availability may be transient, so a
1025	<	* <code>null</code> result does not necessarily imply quiecence
1025	>	* {@code null} result does not necessarily imply quiescence
1026		* of the pool this task is operating in.  This method is designed
1027		* primarily to support extensions, and is unlikely to be useful
1028		* otherwise.  This method may be invoked only from within
1029	<	* ForkJoinTask computations. Attempts to invoke in other contexts
1030	<	* result in exceptions or errors possibly including
1029	>	* ForkJoinTask computations (as may be determined using method
1030	>	* {@link #inForkJoinPool}). Attempts to invoke in other contexts
1031	>	* result in exceptions or errors, possibly including
1032		* ClassCastException.
1033		*
1034	<	* @return a task, or null if none are available
1034	>	* @return a task, or {@code null} if none are available
1035		*/
1036		protected static ForkJoinTask<?> pollTask() {
1037	<	return ((ForkJoinWorkerThread)(Thread.currentThread())).
1038	<	pollTask();
1037	>	return ((ForkJoinWorkerThread) Thread.currentThread())
1038	>	.pollTask();
1039	>	}
1040	>
1041	>	// adaptors
1042	>
1043	>	/**
1044	>	* Returns a new ForkJoinTask that performs the {@code run}
1045	>	* method of the given Runnable as its action, and returns a null
1046	>	* result upon {@code join}.
1047	>	*
1048	>	* @param runnable the runnable action
1049	>	* @return the task
1050	>	*/
1051	>	public static ForkJoinTask<Void> adapt(Runnable runnable) {
1052	>	return new ForkJoinPool.AdaptedRunnable<Void>(runnable, null);
1053	>	}
1054	>
1055	>	/**
1056	>	* Returns a new ForkJoinTask that performs the {@code run}
1057	>	* method of the given Runnable as its action, and returns the
1058	>	* given result upon {@code join}.
1059	>	*
1060	>	* @param runnable the runnable action
1061	>	* @param result the result upon completion
1062	>	* @return the task
1063	>	*/
1064	>	public static <T> ForkJoinTask<T> adapt(Runnable runnable, T result) {
1065	>	return new ForkJoinPool.AdaptedRunnable<T>(runnable, result);
1066	>	}
1067	>
1068	>	/**
1069	>	* Returns a new ForkJoinTask that performs the {@code call}
1070	>	* method of the given Callable as its action, and returns its
1071	>	* result upon {@code join}, translating any checked
1072	>	* exceptions encountered into {@code RuntimeException}.
1073	>	*
1074	>	* @param callable the callable action
1075	>	* @return the task
1076	>	*/
1077	>	public static <T> ForkJoinTask<T> adapt(Callable<T> callable) {
1078	>	return new ForkJoinPool.AdaptedCallable<T>(callable);
1079		}
1080
1081		// Serialization support
#	Line 984 | Line 1086 | public abstract class ForkJoinTask<V> im
1086		* Save the state to a stream.
1087		*
1088		* @serialData the current run status and the exception thrown
1089	<	* during execution, or null if none.
1089	>	* during execution, or {@code null} if none
1090		* @param s the stream
1091		*/
1092		private void writeObject(java.io.ObjectOutputStream s)
#	Line 995 | Line 1097 | public abstract class ForkJoinTask<V> im
1097
1098		/**
1099		* Reconstitute the instance from a stream.
1100	+	*
1101		* @param s the stream
1102		*/
1103		private void readObject(java.io.ObjectInputStream s)
#	Line 1004 | Line 1107 | public abstract class ForkJoinTask<V> im
1107		status |= EXTERNAL_SIGNAL; // conservatively set external signal
1108		Object ex = s.readObject();
1109		if (ex != null)
1110	<	setDoneExceptionally((Throwable)ex);
1110	>	setDoneExceptionally((Throwable) ex);
1111		}
1112
1113	<	// Temporary Unsafe mechanics for preliminary release
1114	<	private static Unsafe getUnsafe() throws Throwable {
1113	>	// Unsafe mechanics
1114	>
1115	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
1116	>	private static final long statusOffset =
1117	>	objectFieldOffset("status", ForkJoinTask.class);
1118	>
1119	>	private static long objectFieldOffset(String field, Class<?> klazz) {
1120	>	try {
1121	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
1122	>	} catch (NoSuchFieldException e) {
1123	>	// Convert Exception to corresponding Error
1124	>	NoSuchFieldError error = new NoSuchFieldError(field);
1125	>	error.initCause(e);
1126	>	throw error;
1127	>	}
1128	>	}
1129	>
1130	>	/**
1131	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1132	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1133	>	* into a jdk.
1134	>	*
1135	>	* @return a sun.misc.Unsafe
1136	>	*/
1137	>	private static sun.misc.Unsafe getUnsafe() {
1138		try {
1139	<	return Unsafe.getUnsafe();
1139	>	return sun.misc.Unsafe.getUnsafe();
1140		} catch (SecurityException se) {
1141		try {
1142		return java.security.AccessController.doPrivileged
1143	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1144	<	public Unsafe run() throws Exception {
1145	<	return getUnsafePrivileged();
1143	>	(new java.security
1144	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1145	>	public sun.misc.Unsafe run() throws Exception {
1146	>	java.lang.reflect.Field f = sun.misc
1147	>	.Unsafe.class.getDeclaredField("theUnsafe");
1148	>	f.setAccessible(true);
1149	>	return (sun.misc.Unsafe) f.get(null);
1150		}});
1151		} catch (java.security.PrivilegedActionException e) {
1152	<	throw e.getCause();
1152	>	throw new RuntimeException("Could not initialize intrinsics",
1153	>	e.getCause());
1154		}
1155		}
1156		}
1026	–
1027	–	private static Unsafe getUnsafePrivileged()
1028	–	throws NoSuchFieldException, IllegalAccessException {
1029	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
1030	–	f.setAccessible(true);
1031	–	return (Unsafe) f.get(null);
1032	–	}
1033	–
1034	–	private static long fieldOffset(String fieldName)
1035	–	throws NoSuchFieldException {
1036	–	return _unsafe.objectFieldOffset
1037	–	(ForkJoinTask.class.getDeclaredField(fieldName));
1038	–	}
1039	–
1040	–	static final Unsafe _unsafe;
1041	–	static final long statusOffset;
1042	–
1043	–	static {
1044	–	try {
1045	–	_unsafe = getUnsafe();
1046	–	statusOffset = fieldOffset("status");
1047	–	} catch (Throwable e) {
1048	–	throw new RuntimeException("Could not initialize intrinsics", e);
1049	–	}
1050	–	}
1051	–
1157		}

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