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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.32 by dl, Mon Aug 3 13:01:15 2009 UTC vs.
Revision 1.37 by jsr166, Tue Aug 4 20:24:54 2009 UTC

#	Line 68 | Line 68 | import java.util.WeakHashMap;
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
71	>	* equivalent to {@code fork(); join()} but always attempts to begin
72	>	* execution in the current thread. The "<em>quiet</em>" forms of
73	>	* 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 execution status of tasks may be queried at several levels
81	+	* of detail: {@link #isDone} is true if a task completed in any way
82	+	* (including the case where a task was cancelled without executing);
83	+	* {@link #isCancelled} is true if completion was due to cancellation;
84	+	* {@link #isCompletedNormally} is true if a task completed without
85	+	* cancellation or encountering an exception; {@link
86	+	* #isCompletedExceptionally} is true if if the task encountered an
87	+	* exception (in which case {@link #getException} returns the
88	+	* exception); {@link #isCancelled} is true if the task was cancelled
89	+	* (in which case {@link #getException} returns a {@link
90	+	* java.util.concurrent.CancellationException}); and {@link
91	+	* #isCompletedAbnormally} is true if a task was either cancelled or
92	+	* encountered an exception.
93	+	*
94		* <p>The ForkJoinTask class is not usually directly subclassed.
95		* Instead, you subclass one of the abstract classes that support a
96		* particular style of fork/join processing, typically {@link
#	Line 111 | Line 125 | import java.util.WeakHashMap;
125		* improve throughput. If too small, then memory and internal task
126		* maintenance overhead may overwhelm processing.
127		*
128	<	* <p>This class provides {@code adapt} methods for {@link
129	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
130	<	* may be of use when mixing execution of ForkJoinTasks with other
131	<	* kinds of tasks. When all tasks are of this form, consider using a
132	<	* pool in {@link ForkJoinPool#setAsyncMode}.
128	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
129	>	* and {@link Callable}, that may be of use when mixing execution of
130	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
131	>	* are of this form, consider using a pool in
132	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
133		*
134		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
135		* used in extensions such as remote execution frameworks. It is
#	Line 381 | Line 395 | public abstract class ForkJoinTask<V> im
395		* Only call when {@code isDone} known to be true.
396		*/
397		private V reportFutureResult()
398	<	throws ExecutionException, InterruptedException {
398	>	throws InterruptedException, ExecutionException {
399	>	if (Thread.interrupted())
400	>	throw new InterruptedException();
401		int s = status & COMPLETION_MASK;
402		if (s < NORMAL) {
403		Throwable ex;
#	Line 389 | Line 405 | public abstract class ForkJoinTask<V> im
405		throw new CancellationException();
406		if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
407		throw new ExecutionException(ex);
392	–	if (Thread.interrupted())
393	–	throw new InterruptedException();
408		}
409		return getRawResult();
410		}
#	Line 401 | Line 415 | public abstract class ForkJoinTask<V> im
415		*/
416		private V reportTimedFutureResult()
417		throws InterruptedException, ExecutionException, TimeoutException {
418	+	if (Thread.interrupted())
419	+	throw new InterruptedException();
420		Throwable ex;
421		int s = status & COMPLETION_MASK;
422		if (s == NORMAL)
423		return getRawResult();
424	<	if (s == CANCELLED)
424	>	else if (s == CANCELLED)
425		throw new CancellationException();
426	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
426	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
427		throw new ExecutionException(ex);
428	<	if (Thread.interrupted())
429	<	throw new InterruptedException();
414	<	throw new TimeoutException();
428	>	else
429	>	throw new TimeoutException();
430		}
431
432		// internal execution methods
#	Line 529 | Line 544 | public abstract class ForkJoinTask<V> im
544
545		/**
546		* Commences performing this task, awaits its completion if
547	<	* necessary, and return its result.
547	>	* necessary, and return its result, or throws an (unchecked)
548	>	* exception if the underlying computation did so.
549		*
534	–	* @throws Throwable (a RuntimeException, Error, or unchecked
535	–	* exception) if the underlying computation did so
550		* @return the computed result
551		*/
552		public final V invoke() {
#	Line 543 | Line 557 | public abstract class ForkJoinTask<V> im
557		}
558
559		/**
560	<	* Forks the given tasks, returning when {@code isDone} holds
561	<	* for each task or an exception is encountered.
560	>	* Forks the given tasks, returning when {@code isDone} holds for
561	>	* each task or an (unchecked) exception is encountered, in which
562	>	* case the exception is rethrown.  If more than one task
563	>	* encounters an exception, then this method throws any one of
564	>	* these exceptions.  The individual status of each task may be
565	>	* checked using {@link #getException()} and related methods.
566		*
567		* <p>This method may be invoked only from within {@code
568		* ForkJoinTask} computations (as may be determined using method
#	Line 555 | Line 573 | public abstract class ForkJoinTask<V> im
573		* @param t1 the first task
574		* @param t2 the second task
575		* @throws NullPointerException if any task is null
558	–	* @throws RuntimeException or Error if a task did so
576		*/
577		public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) {
578		t2.fork();
#	Line 565 | Line 582 | public abstract class ForkJoinTask<V> im
582
583		/**
584		* Forks the given tasks, returning when {@code isDone} holds for
585	<	* each task or an exception is encountered. If any task
586	<	* encounters an exception, others may be, but are not guaranteed
587	<	* to be, cancelled.
585	>	* each task or an (unchecked) exception is encountered, in which
586	>	* case the exception is rethrown. If any task encounters an
587	>	* exception, others may be, but are not guaranteed to be,
588	>	* cancelled.  If more than one task encounters an exception, then
589	>	* this method throws any one of these exceptions.  The individual
590	>	* status of each task may be checked using {@link #getException()}
591	>	* and related methods.
592		*
593		* <p>This method may be invoked only from within {@code
594		* ForkJoinTask} computations (as may be determined using method
#	Line 576 | Line 597 | public abstract class ForkJoinTask<V> im
597		* ClassCastException}.
598		*
599		* @param tasks the tasks
600	<	* @throws NullPointerException if tasks or any element are null
580	<	* @throws RuntimeException or Error if any task did so
600	>	* @throws NullPointerException if any task is null
601		*/
602		public static void invokeAll(ForkJoinTask<?>... tasks) {
603		Throwable ex = null;
#	Line 614 | Line 634 | public abstract class ForkJoinTask<V> im
634
635		/**
636		* Forks all tasks in the specified collection, returning when
637	<	* {@code isDone} holds for each task or an exception is
638	<	* encountered.  If any task encounters an exception, others may
639	<	* be, but are not guaranteed to be, cancelled. The behavior of
640	<	* this operation is undefined if the specified collection is
641	<	* modified while the operation is in progress.
637	>	* {@code isDone} holds for each task or an (unchecked) exception
638	>	* is encountered.  If any task encounters an exception, others
639	>	* may be, but are not guaranteed to be, cancelled.  If more than
640	>	* one task encounters an exception, then this method throws any
641	>	* one of these exceptions.  The individual status of each task
642	>	* may be checked using {@link #getException()} and related
643	>	* methods.  The behavior of this operation is undefined if the
644	>	* specified collection is modified while the operation is in
645	>	* progress.
646		*
647		* <p>This method may be invoked only from within {@code
648		* ForkJoinTask} computations (as may be determined using method
#	Line 629 | Line 653 | public abstract class ForkJoinTask<V> im
653		* @param tasks the collection of tasks
654		* @return the tasks argument, to simplify usage
655		* @throws NullPointerException if tasks or any element are null
632	–	* @throws RuntimeException or Error if any task did so
656		*/
657		public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) {
658		if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) {
#	Line 673 | Line 696 | public abstract class ForkJoinTask<V> im
696		}
697
698		/**
699	<	* Returns {@code true} if the computation performed by this task
700	<	* has completed (or has been cancelled).
701	<	*
702	<	* @return {@code true} if this computation has completed
703	<	*/
704	<	public final boolean isDone() {
705	<	return status < 0;
683	<	}
684	<
685	<	/**
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	<	/**
695	<	* Asserts that the results of this task's computation will not be
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 {@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.
699	>	* Attempts to cancel execution of this task. This attempt will
700	>	* fail if the task has already completed, has already been
701	>	* cancelled, or could not be cancelled for some other reason. If
702	>	* successful, and this task has not started when cancel is
703	>	* called, execution of this task is suppressed, {@link
704	>	* #isCancelled} will report true, and {@link #join} will result
705	>	* in a {@code CancellationException} being thrown.
706		*
707		* <p>This method may be overridden in subclasses, but if so, must
708		* still ensure that these minimal properties hold. In particular,
#	Line 713 | Line 714 | public abstract class ForkJoinTask<V> im
714		* invoke {@link #completeExceptionally}.
715		*
716		* @param mayInterruptIfRunning this value is ignored in the
717	<	* default implementation because tasks are not in general
717	>	* default implementation because tasks are not
718		* cancelled via interruption
719		*
720		* @return {@code true} if this task is now cancelled
#	Line 724 | Line 725 | public abstract class ForkJoinTask<V> im
725		}
726
727		/**
728	+	* Returns {@code true} if the computation performed by this task
729	+	* has completed (or has been cancelled).
730	+	*
731	+	* @return {@code true} if this computation has completed
732	+	*/
733	+	public final boolean isDone() {
734	+	return status < 0;
735	+	}
736	+
737	+	/**
738	+	* Returns {@code true} if this task was cancelled.
739	+	*
740	+	* @return {@code true} if this task was cancelled
741	+	*/
742	+	public final boolean isCancelled() {
743	+	return (status & COMPLETION_MASK) == CANCELLED;
744	+	}
745	+
746	+	/**
747		* Returns {@code true} if this task threw an exception or was cancelled.
748		*
749		* @return {@code true} if this task threw an exception or was cancelled
#	Line 733 | Line 753 | public abstract class ForkJoinTask<V> im
753		}
754
755		/**
756	+	* Returns {@code true} if this task completed without throwing an
757	+	* exception and was not cancelled.
758	+	*
759	+	* @return {@code true} if this task completed without throwing an
760	+	* exception and was not cancelled
761	+	*/
762	+	public final boolean isCompletedNormally() {
763	+	return (status & COMPLETION_MASK) == NORMAL;
764	+	}
765	+
766	+	/**
767	+	* Returns {@code true} if this task threw an exception.
768	+	*
769	+	* @return {@code true} if this task threw an exception
770	+	*/
771	+	public final boolean isCompletedExceptionally() {
772	+	return (status & COMPLETION_MASK) == EXCEPTIONAL;
773	+	}
774	+
775	+	/**
776		* Returns the exception thrown by the base computation, or a
777		* {@code CancellationException} if cancelled, or {@code null} if
778		* none or if the method has not yet completed.
#	Line 741 | Line 781 | public abstract class ForkJoinTask<V> im
781		*/
782		public final Throwable getException() {
783		int s = status & COMPLETION_MASK;
784	<	if (s >= NORMAL)
785	<	return null;
786	<	if (s == CANCELLED)
747	<	return new CancellationException();
748	<	return exceptionMap.get(this);
784	>	return ((s >= NORMAL)    ? null :
785	>	(s == CANCELLED) ? new CancellationException() :
786	>	exceptionMap.get(this));
787		}
788
789		/**
#	Line 878 | Line 916 | public abstract class ForkJoinTask<V> im
916
917		/**
918		* Possibly executes tasks until the pool hosting the current task
919	<	* {@link ForkJoinPool#isQuiescent}. This method may be of use in
920	<	* designs in which many tasks are forked, but none are explicitly
921	<	* joined, instead executing them until all are processed.
919	>	* {@link ForkJoinPool#isQuiescent is quiescent}. This method may
920	>	* be of use in designs in which many tasks are forked, but none
921	>	* are explicitly joined, instead executing them until all are
922	>	* processed.
923		*
924		* <p>This method may be invoked only from within {@code
925		* ForkJoinTask} computations (as may be determined using method
#	Line 1024 | Line 1063 | public abstract class ForkJoinTask<V> im
1063		* called otherwise. The return value controls whether this task
1064		* is considered to be done normally. It may return false in
1065		* asynchronous actions that require explicit invocations of
1066	<	* {@link #complete} to become joinable. It may throw exceptions
1067	<	* to indicate abnormal exit.
1066	>	* {@link #complete} to become joinable. It may also throw an
1067	>	* (unchecked) exception to indicate abnormal exit.
1068		*
1069		* @return {@code true} if completed normally
1031	–	* @throws Error or RuntimeException if encountered during computation
1070		*/
1071		protected abstract boolean exec();
1072

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