12 |
|
import java.util.Collection; |
13 |
|
import java.util.Collections; |
14 |
|
import java.util.List; |
15 |
+ |
import java.util.RandomAccess; |
16 |
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import java.util.Map; |
17 |
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import java.util.WeakHashMap; |
18 |
|
|
55 |
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* 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 join them. These exceptions may |
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. |
68 |
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* 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 |
98 |
|
* established in a constructor, and then defines a {@code compute} |
99 |
|
* method that somehow uses the control methods supplied by this base |
100 |
|
* class. While these methods have {@code public} access (to allow |
101 |
< |
* instances of different task subclasses to call each others |
101 |
> |
* instances of different task subclasses to call each other's |
102 |
|
* methods), some of them may only be called from within other |
103 |
|
* ForkJoinTasks (as may be determined using method {@link |
104 |
|
* #inForkJoinPool}). Attempts to invoke them in other contexts |
105 |
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* result in exceptions or errors, possibly including |
106 |
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* ClassCastException. |
107 |
|
* |
108 |
< |
* <p>Most base support methods are {@code final} because their |
109 |
< |
* implementations are intrinsically tied to the underlying |
110 |
< |
* lightweight task scheduling framework, and so cannot be overridden. |
111 |
< |
* Developers creating new basic styles of fork/join processing should |
112 |
< |
* minimally implement {@code protected} methods |
113 |
< |
* {@link #exec}, {@link #setRawResult}, and |
114 |
< |
* {@link #getRawResult}, while also introducing an abstract |
115 |
< |
* computational method that can be implemented in its subclasses, |
116 |
< |
* possibly relying on other {@code protected} methods provided |
104 |
< |
* by this class. |
108 |
> |
* <p>Most base support methods are {@code final}, to prevent |
109 |
> |
* overriding of implementations that are intrinsically tied to the |
110 |
> |
* underlying lightweight task scheduling framework. Developers |
111 |
> |
* creating new basic styles of fork/join processing should minimally |
112 |
> |
* implement {@code protected} methods {@link #exec}, {@link |
113 |
> |
* #setRawResult}, and {@link #getRawResult}, while also introducing |
114 |
> |
* an abstract computational method that can be implemented in its |
115 |
> |
* subclasses, possibly relying on other {@code protected} methods |
116 |
> |
* provided by this class. |
117 |
|
* |
118 |
|
* <p>ForkJoinTasks should perform relatively small amounts of |
119 |
< |
* computations, otherwise splitting into smaller tasks. As a very |
120 |
< |
* rough rule of thumb, a task should perform more than 100 and less |
121 |
< |
* than 10000 basic computational steps. If tasks are too big, then |
122 |
< |
* parallelism cannot improve throughput. If too small, then memory |
123 |
< |
* and internal task maintenance overhead may overwhelm processing. |
119 |
> |
* computation. Large tasks should be split into smaller subtasks, |
120 |
> |
* usually via recursive decomposition. As a very rough rule of thumb, |
121 |
> |
* a task should perform more than 100 and less than 10000 basic |
122 |
> |
* computational steps. If tasks are too big, then parallelism cannot |
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}. |
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 |
133 |
< |
* to be used in extensions such as remote execution frameworks. It is |
134 |
< |
* in general sensible to serialize tasks only before or after, but |
135 |
< |
* not during execution. Serialization is not relied on during |
123 |
< |
* execution itself. |
132 |
> |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
133 |
> |
* used in extensions such as remote execution frameworks. It is |
134 |
> |
* sensible to serialize tasks only before or after, but not during, |
135 |
> |
* execution. Serialization is not relied on during execution itself. |
136 |
|
* |
137 |
|
* @since 1.7 |
138 |
|
* @author Doug Lea |
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; |
401 |
|
if (s < NORMAL) { |
402 |
|
Throwable ex; |
404 |
|
throw new CancellationException(); |
405 |
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
406 |
|
throw new ExecutionException(ex); |
392 |
– |
if (Thread.interrupted()) |
393 |
– |
throw new InterruptedException(); |
407 |
|
} |
408 |
|
return getRawResult(); |
409 |
|
} |
414 |
|
*/ |
415 |
|
private V reportTimedFutureResult() |
416 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
417 |
+ |
if (Thread.interrupted()) |
418 |
+ |
throw new InterruptedException(); |
419 |
|
Throwable ex; |
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 |
< |
if (Thread.interrupted()) |
428 |
< |
throw new InterruptedException(); |
414 |
< |
throw new TimeoutException(); |
427 |
> |
else |
428 |
> |
throw new TimeoutException(); |
429 |
|
} |
430 |
|
|
431 |
|
// internal execution methods |
510 |
|
/** |
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. This |
514 |
< |
* method may be invoked only from within ForkJoinTask |
515 |
< |
* computations (as may be determined using method {@link |
516 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
517 |
< |
* in exceptions or errors, possibly including ClassCastException. |
513 |
> |
* than once unless it has completed and been reinitialized. |
514 |
> |
* |
515 |
> |
* <p>This method may be invoked only from within {@code |
516 |
> |
* ForkJoinTask} computations (as may be determined using method |
517 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
518 |
> |
* result in exceptions or errors, possibly including {@code |
519 |
> |
* ClassCastException}. |
520 |
|
* |
521 |
< |
* @return {@code this}, to simplify usage. |
521 |
> |
* @return {@code this}, to simplify usage |
522 |
|
*/ |
523 |
|
public final ForkJoinTask<V> fork() { |
524 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
527 |
|
} |
528 |
|
|
529 |
|
/** |
530 |
< |
* Returns the result of the computation when it is ready. |
531 |
< |
* This method differs from {@code get} in that abnormal |
532 |
< |
* completion results in RuntimeExceptions or Errors, not |
533 |
< |
* ExecutionExceptions. |
530 |
> |
* Returns the result of the computation when it {@link #isDone is done}. |
531 |
> |
* This method differs from {@link #get()} in that |
532 |
> |
* abnormal completion results in {@code RuntimeException} or |
533 |
> |
* {@code Error}, not {@code ExecutionException}. |
534 |
|
* |
535 |
|
* @return the computed result |
536 |
|
*/ |
543 |
|
|
544 |
|
/** |
545 |
|
* Commences performing this task, awaits its completion if |
546 |
< |
* necessary, and return its result. |
546 |
> |
* necessary, and return its result, or throws an (unchecked) |
547 |
> |
* exception if the underlying computation did so. |
548 |
|
* |
532 |
– |
* @throws Throwable (a RuntimeException, Error, or unchecked |
533 |
– |
* exception) if the underlying computation did so |
549 |
|
* @return the computed result |
550 |
|
*/ |
551 |
|
public final V invoke() { |
557 |
|
|
558 |
|
/** |
559 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
560 |
< |
* each task or an exception is encountered. This method may be |
561 |
< |
* invoked only from within ForkJoinTask computations (as may be |
562 |
< |
* determined using method {@link #inForkJoinPool}). Attempts to |
563 |
< |
* invoke in other contexts result in exceptions or errors, |
564 |
< |
* possibly including ClassCastException. |
560 |
> |
* each task or an (unchecked) exception is encountered, in which |
561 |
> |
* case the exception is rethrown. If either task encounters an |
562 |
> |
* exception, the other one may be, but is not guaranteed to be, |
563 |
> |
* cancelled. If both tasks throw an exception, then this method |
564 |
> |
* throws one of them. 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 |
569 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
570 |
> |
* result in exceptions or errors, possibly including {@code |
571 |
> |
* ClassCastException}. |
572 |
|
* |
573 |
|
* @param t1 the first task |
574 |
|
* @param t2 the second task |
575 |
|
* @throws NullPointerException if any task is null |
554 |
– |
* @throws RuntimeException or Error if a task did so |
576 |
|
*/ |
577 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
577 |
> |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
578 |
|
t2.fork(); |
579 |
|
t1.invoke(); |
580 |
|
t2.join(); |
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. This method may be invoked only from within |
588 |
< |
* ForkJoinTask computations (as may be determined using method |
589 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
590 |
< |
* result in exceptions or errors, possibly including |
591 |
< |
* ClassCastException. |
592 |
< |
* |
593 |
< |
* Overloadings of this method exist for the special cases |
594 |
< |
* of one to four arguments. |
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 |
595 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
596 |
> |
* result in exceptions or errors, possibly including {@code |
597 |
> |
* ClassCastException}. |
598 |
|
* |
599 |
|
* @param tasks the tasks |
600 |
< |
* @throws NullPointerException if tasks or any element are null |
577 |
< |
* @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; |
633 |
|
} |
634 |
|
|
635 |
|
/** |
636 |
< |
* Forks all tasks in the collection, returning when {@code |
637 |
< |
* isDone} holds for each task or an exception is encountered. If |
638 |
< |
* any task encounters an exception, others may be, but are not |
639 |
< |
* guaranteed to be, cancelled. This method may be invoked only |
640 |
< |
* from within ForkJoinTask computations (as may be determined |
641 |
< |
* using method {@link #inForkJoinPool}). Attempts to invoke in |
642 |
< |
* other contexts result in exceptions or errors, possibly |
643 |
< |
* including ClassCastException. |
636 |
> |
* Forks all tasks in the specified collection, returning when |
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 |
649 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
650 |
> |
* result in exceptions or errors, possibly including {@code |
651 |
> |
* ClassCastException}. |
652 |
|
* |
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 |
625 |
– |
* @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 List<?>)) { |
658 |
> |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
659 |
|
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
660 |
|
return tasks; |
661 |
|
} |
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; |
676 |
< |
} |
677 |
< |
|
678 |
< |
/** |
679 |
< |
* Returns {@code true} if this task was cancelled. |
680 |
< |
* |
681 |
< |
* @return {@code true} if this task was cancelled |
682 |
< |
*/ |
683 |
< |
public final boolean isCancelled() { |
684 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
685 |
< |
} |
686 |
< |
|
687 |
< |
/** |
688 |
< |
* Asserts that the results of this task's computation will not be |
689 |
< |
* used. If a cancellation occurs before attempting to execute this |
690 |
< |
* task, execution will be suppressed, {@link #isCancelled} |
691 |
< |
* will report true, and {@link #join} will result in a |
692 |
< |
* {@code CancellationException} being thrown. Otherwise, when |
693 |
< |
* cancellation races with completion, there are no guarantees |
694 |
< |
* about whether {@code isCancelled} will report {@code true}, |
695 |
< |
* whether {@code join} will return normally or via an exception, |
696 |
< |
* or whether these behaviors will remain consistent upon repeated |
697 |
< |
* 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, |
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 |
724 |
|
return (status & COMPLETION_MASK) == CANCELLED; |
725 |
|
} |
726 |
|
|
727 |
+ |
public final boolean isDone() { |
728 |
+ |
return status < 0; |
729 |
+ |
} |
730 |
+ |
|
731 |
+ |
public final boolean isCancelled() { |
732 |
+ |
return (status & COMPLETION_MASK) == CANCELLED; |
733 |
+ |
} |
734 |
+ |
|
735 |
|
/** |
736 |
|
* Returns {@code true} if this task threw an exception or was cancelled. |
737 |
|
* |
742 |
|
} |
743 |
|
|
744 |
|
/** |
745 |
+ |
* Returns {@code true} if this task completed without throwing an |
746 |
+ |
* exception and was not cancelled. |
747 |
+ |
* |
748 |
+ |
* @return {@code true} if this task completed without throwing an |
749 |
+ |
* exception and was not cancelled |
750 |
+ |
*/ |
751 |
+ |
public final boolean isCompletedNormally() { |
752 |
+ |
return (status & COMPLETION_MASK) == NORMAL; |
753 |
+ |
} |
754 |
+ |
|
755 |
+ |
/** |
756 |
|
* Returns the exception thrown by the base computation, or a |
757 |
|
* {@code CancellationException} if cancelled, or {@code null} if |
758 |
|
* none or if the method has not yet completed. |
761 |
|
*/ |
762 |
|
public final Throwable getException() { |
763 |
|
int s = status & COMPLETION_MASK; |
764 |
< |
if (s >= NORMAL) |
765 |
< |
return null; |
766 |
< |
if (s == CANCELLED) |
740 |
< |
return new CancellationException(); |
741 |
< |
return exceptionMap.get(this); |
764 |
> |
return ((s >= NORMAL) ? null : |
765 |
> |
(s == CANCELLED) ? new CancellationException() : |
766 |
> |
exceptionMap.get(this)); |
767 |
|
} |
768 |
|
|
769 |
|
/** |
825 |
|
} |
826 |
|
|
827 |
|
/** |
828 |
< |
* Possibly executes other tasks until this task is ready, then |
829 |
< |
* returns the result of the computation. This method may be more |
830 |
< |
* efficient than {@code join}, but is only applicable when |
831 |
< |
* there are no potential dependencies between continuation of the |
832 |
< |
* current task and that of any other task that might be executed |
833 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
834 |
< |
* tasks). This method may be invoked only from within |
835 |
< |
* ForkJoinTask computations (as may be determined using method |
836 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
837 |
< |
* result in exceptions or errors, possibly including |
838 |
< |
* ClassCastException. |
828 |
> |
* Possibly executes other tasks until this task {@link #isDone is |
829 |
> |
* done}, then returns the result of the computation. This method |
830 |
> |
* may be more efficient than {@code join}, but is only applicable |
831 |
> |
* when there are no potential dependencies between continuation |
832 |
> |
* of the current task and that of any other task that might be |
833 |
> |
* executed while helping. (This usually holds for pure |
834 |
> |
* divide-and-conquer tasks). |
835 |
> |
* |
836 |
> |
* <p>This method may be invoked only from within {@code |
837 |
> |
* ForkJoinTask} computations (as may be determined using method |
838 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
839 |
> |
* result in exceptions or errors, possibly including {@code |
840 |
> |
* ClassCastException}. |
841 |
|
* |
842 |
|
* @return the computed result |
843 |
|
*/ |
849 |
|
} |
850 |
|
|
851 |
|
/** |
852 |
< |
* Possibly executes other tasks until this task is ready. This |
853 |
< |
* method may be invoked only from within ForkJoinTask |
854 |
< |
* computations (as may be determined using method {@link |
855 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
856 |
< |
* in exceptions or errors, possibly including ClassCastException. |
852 |
> |
* Possibly executes other tasks until this task {@link #isDone is |
853 |
> |
* done}. This method may be useful when processing collections |
854 |
> |
* of tasks when some have been cancelled or otherwise known to |
855 |
> |
* have aborted. |
856 |
> |
* |
857 |
> |
* <p>This method may be invoked only from within {@code |
858 |
> |
* ForkJoinTask} computations (as may be determined using method |
859 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
860 |
> |
* result in exceptions or errors, possibly including {@code |
861 |
> |
* ClassCastException}. |
862 |
|
*/ |
863 |
|
public final void quietlyHelpJoin() { |
864 |
|
if (status >= 0) { |
897 |
|
|
898 |
|
/** |
899 |
|
* Possibly executes tasks until the pool hosting the current task |
900 |
< |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
901 |
< |
* designs in which many tasks are forked, but none are explicitly |
902 |
< |
* joined, instead executing them until all are processed. This |
903 |
< |
* method may be invoked only from within ForkJoinTask |
904 |
< |
* computations (as may be determined using method {@link |
905 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
906 |
< |
* in exceptions or errors, possibly including ClassCastException. |
900 |
> |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
901 |
> |
* be of use in designs in which many tasks are forked, but none |
902 |
> |
* are explicitly joined, instead executing them until all are |
903 |
> |
* processed. |
904 |
> |
* |
905 |
> |
* <p>This method may be invoked only from within {@code |
906 |
> |
* ForkJoinTask} computations (as may be determined using method |
907 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
908 |
> |
* result in exceptions or errors, possibly including {@code |
909 |
> |
* ClassCastException}. |
910 |
|
*/ |
911 |
|
public static void helpQuiesce() { |
912 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
919 |
|
* this task, but only if reuse occurs when this task has either |
920 |
|
* never been forked, or has been forked, then completed and all |
921 |
|
* outstanding joins of this task have also completed. Effects |
922 |
< |
* under any other usage conditions are not guaranteed, and are |
923 |
< |
* discouraged. This method may be useful when executing |
922 |
> |
* under any other usage conditions are not guaranteed. |
923 |
> |
* This method may be useful when executing |
924 |
|
* pre-constructed trees of subtasks in loops. |
925 |
|
*/ |
926 |
|
public void reinitialize() { |
959 |
|
* by the current thread, and has not commenced executing in |
960 |
|
* another thread. This method may be useful when arranging |
961 |
|
* alternative local processing of tasks that could have been, but |
962 |
< |
* were not, stolen. This method may be invoked only from within |
963 |
< |
* ForkJoinTask computations (as may be determined using method |
964 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
965 |
< |
* result in exceptions or errors, possibly including |
966 |
< |
* ClassCastException. |
962 |
> |
* were not, stolen. |
963 |
> |
* |
964 |
> |
* <p>This method may be invoked only from within {@code |
965 |
> |
* ForkJoinTask} computations (as may be determined using method |
966 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
967 |
> |
* result in exceptions or errors, possibly including {@code |
968 |
> |
* ClassCastException}. |
969 |
|
* |
970 |
|
* @return {@code true} if unforked |
971 |
|
*/ |
978 |
|
* Returns an estimate of the number of tasks that have been |
979 |
|
* forked by the current worker thread but not yet executed. This |
980 |
|
* value may be useful for heuristic decisions about whether to |
981 |
< |
* fork other tasks. This method may be invoked only from within |
982 |
< |
* ForkJoinTask computations (as may be determined using method |
983 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
984 |
< |
* result in exceptions or errors, possibly including |
985 |
< |
* ClassCastException. |
981 |
> |
* fork other tasks. |
982 |
> |
* |
983 |
> |
* <p>This method may be invoked only from within {@code |
984 |
> |
* ForkJoinTask} computations (as may be determined using method |
985 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
986 |
> |
* result in exceptions or errors, possibly including {@code |
987 |
> |
* ClassCastException}. |
988 |
> |
* |
989 |
|
* @return the number of tasks |
990 |
|
*/ |
991 |
|
public static int getQueuedTaskCount() { |
1001 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
1002 |
|
* aim to maintain a small constant surplus (for example, 3) of |
1003 |
|
* tasks, and to process computations locally if this threshold is |
1004 |
< |
* exceeded. This method may be invoked only from within |
1005 |
< |
* ForkJoinTask computations (as may be determined using method |
1006 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1007 |
< |
* result in exceptions or errors, possibly including |
1008 |
< |
* ClassCastException. * |
1004 |
> |
* exceeded. |
1005 |
> |
* |
1006 |
> |
* <p>This method may be invoked only from within {@code |
1007 |
> |
* ForkJoinTask} computations (as may be determined using method |
1008 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1009 |
> |
* result in exceptions or errors, possibly including {@code |
1010 |
> |
* ClassCastException}. |
1011 |
> |
* |
1012 |
|
* @return the surplus number of tasks, which may be negative |
1013 |
|
*/ |
1014 |
|
public static int getSurplusQueuedTaskCount() { |
1044 |
|
* called otherwise. The return value controls whether this task |
1045 |
|
* is considered to be done normally. It may return false in |
1046 |
|
* asynchronous actions that require explicit invocations of |
1047 |
< |
* {@link #complete} to become joinable. It may throw exceptions |
1048 |
< |
* to indicate abnormal exit. |
1047 |
> |
* {@link #complete} to become joinable. It may also throw an |
1048 |
> |
* (unchecked) exception to indicate abnormal exit. |
1049 |
|
* |
1050 |
|
* @return {@code true} if completed normally |
1008 |
– |
* @throws Error or RuntimeException if encountered during computation |
1051 |
|
*/ |
1052 |
|
protected abstract boolean exec(); |
1053 |
|
|
1059 |
|
* null even if a task exists but cannot be accessed without |
1060 |
|
* contention with other threads. This method is designed |
1061 |
|
* primarily to support extensions, and is unlikely to be useful |
1062 |
< |
* otherwise. This method may be invoked only from within |
1063 |
< |
* ForkJoinTask computations (as may be determined using method |
1064 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1065 |
< |
* result in exceptions or errors, possibly including |
1066 |
< |
* ClassCastException. |
1062 |
> |
* 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 |
|
*/ |
1078 |
|
* Unschedules and returns, without executing, the next task |
1079 |
|
* queued by the current thread but not yet executed. This method |
1080 |
|
* is designed primarily to support extensions, and is unlikely to |
1081 |
< |
* be useful otherwise. This method may be invoked only from |
1082 |
< |
* within ForkJoinTask computations (as may be determined using |
1083 |
< |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
1084 |
< |
* contexts result in exceptions or errors, possibly including |
1085 |
< |
* ClassCastException. |
1081 |
> |
* be useful otherwise. |
1082 |
> |
* |
1083 |
> |
* <p>This method may be invoked only from within {@code |
1084 |
> |
* ForkJoinTask} computations (as may be determined using method |
1085 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1086 |
> |
* result in exceptions or errors, possibly including {@code |
1087 |
> |
* ClassCastException}. |
1088 |
|
* |
1089 |
|
* @return the next task, or {@code null} if none are available |
1090 |
|
*/ |
1101 |
|
* {@code null} result does not necessarily imply quiescence |
1102 |
|
* of the pool this task is operating in. This method is designed |
1103 |
|
* primarily to support extensions, and is unlikely to be useful |
1104 |
< |
* otherwise. This method may be invoked only from within |
1105 |
< |
* ForkJoinTask computations (as may be determined using method |
1106 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1107 |
< |
* result in exceptions or errors, possibly including |
1108 |
< |
* ClassCastException. |
1104 |
> |
* otherwise. |
1105 |
> |
* |
1106 |
> |
* <p>This method may be invoked only from within {@code |
1107 |
> |
* ForkJoinTask} computations (as may be determined using method |
1108 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1109 |
> |
* result in exceptions or errors, possibly including {@code |
1110 |
> |
* ClassCastException}. |
1111 |
|
* |
1112 |
|
* @return a task, or {@code null} if none are available |
1113 |
|
*/ |
1172 |
|
} |
1173 |
|
|
1174 |
|
/** |
1175 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1176 |
< |
* method of the given Runnable as its action, and returns a null |
1177 |
< |
* result upon {@code join}. |
1175 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1176 |
> |
* method of the given {@code Runnable} as its action, and returns |
1177 |
> |
* a null result upon {@link #join}. |
1178 |
|
* |
1179 |
|
* @param runnable the runnable action |
1180 |
|
* @return the task |
1184 |
|
} |
1185 |
|
|
1186 |
|
/** |
1187 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1188 |
< |
* method of the given Runnable as its action, and returns the |
1189 |
< |
* given result upon {@code join}. |
1187 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1188 |
> |
* method of the given {@code Runnable} as its action, and returns |
1189 |
> |
* the given result upon {@link #join}. |
1190 |
|
* |
1191 |
|
* @param runnable the runnable action |
1192 |
|
* @param result the result upon completion |
1197 |
|
} |
1198 |
|
|
1199 |
|
/** |
1200 |
< |
* Returns a new ForkJoinTask that performs the {@code call} |
1201 |
< |
* method of the given Callable as its action, and returns its |
1202 |
< |
* result upon {@code join}, translating any checked |
1203 |
< |
* exceptions encountered into {@code RuntimeException}. |
1200 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1201 |
> |
* method of the given {@code Callable} as its action, and returns |
1202 |
> |
* its result upon {@link #join}, translating any checked exceptions |
1203 |
> |
* encountered into {@code RuntimeException}. |
1204 |
|
* |
1205 |
|
* @param callable the callable action |
1206 |
|
* @return the task |