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

Comparing jsr166/src/jsr166y/ForkJoinTask.java (file contents):
Revision 1.34 by dl, Tue Aug 4 11:44:33 2009 UTC vs.
Revision 1.43 by dl, Wed Aug 19 11:24:58 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 #isCompletedNormally} is true if a task completed without
84	+	* cancellation or encountering an exception; {@link #isCancelled} is
85	+	* true if the task was cancelled (in which case {@link #getException}
86	+	* returns a {@link java.util.concurrent.CancellationException}); and
87	+	* {@link #isCompletedAbnormally} is true if a task was either
88	+	* cancelled or encountered an exception, in which case {@link
89	+	* #getException} will return either the encountered exception or
90	+	* {@link java.util.concurrent.CancellationException}.
91	+	*
92		* <p>The ForkJoinTask class is not usually directly subclassed.
93		* Instead, you subclass one of the abstract classes that support a
94		* particular style of fork/join processing, typically {@link
#	Line 111 | Line 123 | import java.util.WeakHashMap;
123		* improve throughput. If too small, then memory and internal task
124		* maintenance overhead may overwhelm processing.
125		*
126	<	* <p>This class provides {@code adapt} methods for {@link
127	<	* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that
128	<	* may be of use when mixing execution of ForkJoinTasks with other
129	<	* kinds of tasks. When all tasks are of this form, consider using a
130	<	* pool in {@link ForkJoinPool#setAsyncMode async mode}.
126	>	* <p>This class provides {@code adapt} methods for {@link Runnable}
127	>	* and {@link Callable}, that may be of use when mixing execution of
128	>	* {@code ForkJoinTasks} with other kinds of tasks. When all tasks
129	>	* are of this form, consider using a pool in
130	>	* {@linkplain ForkJoinPool#setAsyncMode async mode}.
131		*
132		* <p>ForkJoinTasks are {@code Serializable}, which enables them to be
133		* used in extensions such as remote execution frameworks. It is
#	Line 378 | Line 390 | public abstract class ForkJoinTask<V> im
390
391		/**
392		* Returns result or throws exception using j.u.c.Future conventions.
393	<	* Only call when {@code isDone} known to be true.
393	>	* Only call when {@code isDone} known to be true or thread known
394	>	* to be interrupted.
395		*/
396		private V reportFutureResult()
397	<	throws ExecutionException, InterruptedException {
397	>	throws InterruptedException, ExecutionException {
398		if (Thread.interrupted())
399		throw new InterruptedException();
400		int s = status & COMPLETION_MASK;
#	Line 407 | Line 420 | public abstract class ForkJoinTask<V> im
420		int s = status & COMPLETION_MASK;
421		if (s == NORMAL)
422		return getRawResult();
423	<	if (s == CANCELLED)
423	>	else if (s == CANCELLED)
424		throw new CancellationException();
425	<	if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
425	>	else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null)
426		throw new ExecutionException(ex);
427	<	throw new TimeoutException();
427	>	else
428	>	throw new TimeoutException();
429		}
430
431		// internal execution methods
#	Line 497 | Line 511 | public abstract class ForkJoinTask<V> im
511		* Arranges to asynchronously execute this task.  While it is not
512		* necessarily enforced, it is a usage error to fork a task more
513		* than once unless it has completed and been reinitialized.
514	+	* Subsequent modifications to the state of this task or any data
515	+	* it operates on are not necessarily consistently observable by
516	+	* any thread other than the one executing it unless preceded by a
517	+	* call to {@link #join} or related methods, or a call to {@link
518	+	* #isDone} returning {@code true}.
519		*
520		* <p>This method may be invoked only from within {@code
521		* ForkJoinTask} computations (as may be determined using method
#	Line 513 | Line 532 | public abstract class ForkJoinTask<V> im
532		}
533
534		/**
535	<	* Returns the result of the computation when it is ready.
535	>	* Returns the result of the computation when it {@link #isDone is done}.
536		* This method differs from {@link #get()} in that
537		* abnormal completion results in {@code RuntimeException} or
538		* {@code Error}, not {@code ExecutionException}.
#	Line 544 | Line 563 | public abstract class ForkJoinTask<V> im
563		/**
564		* Forks the given tasks, returning when {@code isDone} holds for
565		* each task or an (unchecked) exception is encountered, in which
566	<	* case the exception is rethrown.  If more than one task
567	<	* encounters an exception, then this method throws any one of
568	<	* these exceptions.  The individual status of each task may be
566	>	* case the exception is rethrown.  If either task encounters an
567	>	* exception, the other one may be, but is not guaranteed to be,
568	>	* cancelled.  If both tasks throw an exception, then this method
569	>	* throws one of them.  The individual status of each task may be
570		* checked using {@link #getException()} and related methods.
571		*
572		* <p>This method may be invoked only from within {@code
#	Line 709 | Line 729 | public abstract class ForkJoinTask<V> im
729		return (status & COMPLETION_MASK) == CANCELLED;
730		}
731
712	–	/**
713	–	* Returns {@code true} if the computation performed by this task
714	–	* has completed (or has been cancelled).
715	–	*
716	–	* @return {@code true} if this computation has completed
717	–	*/
732		public final boolean isDone() {
733		return status < 0;
734		}
735
722	–	/**
723	–	* Returns {@code true} if this task was cancelled.
724	–	*
725	–	* @return {@code true} if this task was cancelled
726	–	*/
736		public final boolean isCancelled() {
737		return (status & COMPLETION_MASK) == CANCELLED;
738		}
#	Line 749 | Line 758 | public abstract class ForkJoinTask<V> im
758		}
759
760		/**
752	–	* Returns {@code true} if this task threw an exception.
753	–	*
754	–	* @return {@code true} if this task threw an exception
755	–	*/
756	–	public final boolean isCompletedExceptionally() {
757	–	return (status & COMPLETION_MASK) == EXCEPTIONAL;
758	–	}
759	–
760	–	/**
761		* Returns the exception thrown by the base computation, or a
762		* {@code CancellationException} if cancelled, or {@code null} if
763		* none or if the method has not yet completed.
#	Line 766 | Line 766 | public abstract class ForkJoinTask<V> im
766		*/
767		public final Throwable getException() {
768		int s = status & COMPLETION_MASK;
769	<	if (s >= NORMAL)
770	<	return null;
771	<	if (s == CANCELLED)
772	<	return new CancellationException();
773	<	return exceptionMap.get(this);
769	>	return ((s >= NORMAL)    ? null :
770	>	(s == CANCELLED) ? new CancellationException() :
771	>	exceptionMap.get(this));
772		}
773
774		/**
#	Line 832 | Line 830 | public abstract class ForkJoinTask<V> im
830		}
831
832		/**
833	<	* Possibly executes other tasks until this task is ready, then
834	<	* returns the result of the computation.  This method may be more
835	<	* efficient than {@code join}, but is only applicable when
836	<	* there are no potential dependencies between continuation of the
837	<	* current task and that of any other task that might be executed
838	<	* while helping. (This usually holds for pure divide-and-conquer
839	<	* tasks).
833	>	* Possibly executes other tasks until this task {@link #isDone is
834	>	* done}, then returns the result of the computation.  This method
835	>	* may be more efficient than {@code join}, but is only applicable
836	>	* when there are no potential dependencies between continuation
837	>	* of the current task and that of any other task that might be
838	>	* executed while helping. (This usually holds for pure
839	>	* divide-and-conquer tasks).
840		*
841		* <p>This method may be invoked only from within {@code
842		* ForkJoinTask} computations (as may be determined using method
#	Line 856 | Line 854 | public abstract class ForkJoinTask<V> im
854		}
855
856		/**
857	<	* Possibly executes other tasks until this task is ready.  This
858	<	* method may be useful when processing collections of tasks when
859	<	* some have been cancelled or otherwise known to have aborted.
857	>	* Possibly executes other tasks until this task {@link #isDone is
858	>	* done}.  This method may be useful when processing collections
859	>	* of tasks when some have been cancelled or otherwise known to
860	>	* have aborted.
861		*
862		* <p>This method may be invoked only from within {@code
863		* ForkJoinTask} computations (as may be determined using method

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