12 |
|
import java.util.Collection; |
13 |
|
import java.util.Collections; |
14 |
|
import java.util.List; |
15 |
+ |
import java.util.RandomAccess; |
16 |
|
import java.util.Map; |
17 |
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import java.util.WeakHashMap; |
18 |
|
|
55 |
|
* restriction is in part enforced by not permitting checked |
56 |
|
* exceptions such as {@code IOExceptions} to be thrown. However, |
57 |
|
* computations may still encounter unchecked exceptions, that are |
58 |
< |
* rethrown to callers attempting 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 |
|
* 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 |
100 |
|
* established in a constructor, and then defines a {@code compute} |
101 |
|
* method that somehow uses the control methods supplied by this base |
102 |
|
* class. While these methods have {@code public} access (to allow |
103 |
< |
* instances of different task subclasses to call each others |
103 |
> |
* instances of different task subclasses to call each other's |
104 |
|
* methods), some of them may only be called from within other |
105 |
|
* ForkJoinTasks (as may be determined using method {@link |
106 |
|
* #inForkJoinPool}). Attempts to invoke them in other contexts |
107 |
|
* result in exceptions or errors, possibly including |
108 |
|
* ClassCastException. |
109 |
|
* |
110 |
< |
* <p>Most base support methods are {@code final} because their |
111 |
< |
* implementations are intrinsically tied to the underlying |
112 |
< |
* lightweight task scheduling framework, and so cannot be overridden. |
113 |
< |
* Developers creating new basic styles of fork/join processing should |
114 |
< |
* minimally implement {@code protected} methods |
115 |
< |
* {@link #exec}, {@link #setRawResult}, and |
116 |
< |
* {@link #getRawResult}, while also introducing an abstract |
117 |
< |
* computational method that can be implemented in its subclasses, |
118 |
< |
* possibly relying on other {@code protected} methods provided |
104 |
< |
* by this class. |
110 |
> |
* <p>Most base support methods are {@code final}, to prevent |
111 |
> |
* overriding of implementations that are intrinsically tied to the |
112 |
> |
* underlying lightweight task scheduling framework. Developers |
113 |
> |
* creating new basic styles of fork/join processing should minimally |
114 |
> |
* implement {@code protected} methods {@link #exec}, {@link |
115 |
> |
* #setRawResult}, and {@link #getRawResult}, while also introducing |
116 |
> |
* an abstract computational method that can be implemented in its |
117 |
> |
* subclasses, possibly relying on other {@code protected} methods |
118 |
> |
* provided by this class. |
119 |
|
* |
120 |
|
* <p>ForkJoinTasks should perform relatively small amounts of |
121 |
< |
* computations, otherwise splitting into smaller tasks. As a very |
122 |
< |
* rough rule of thumb, a task should perform more than 100 and less |
123 |
< |
* than 10000 basic computational steps. If tasks are too big, then |
124 |
< |
* parallelism cannot improve throughput. If too small, then memory |
125 |
< |
* and internal task maintenance overhead may overwhelm processing. |
121 |
> |
* computation. Large tasks should be split into smaller subtasks, |
122 |
> |
* usually via recursive decomposition. As a very rough rule of thumb, |
123 |
> |
* a task should perform more than 100 and less than 10000 basic |
124 |
> |
* computational steps. If tasks are too big, then parallelism cannot |
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 |
135 |
< |
* to be used in extensions such as remote execution frameworks. It is |
136 |
< |
* in general sensible to serialize tasks only before or after, but |
137 |
< |
* not during execution. Serialization is not relied on during |
123 |
< |
* execution itself. |
134 |
> |
* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
135 |
> |
* used in extensions such as remote execution frameworks. It is |
136 |
> |
* sensible to serialize tasks only before or after, but not during, |
137 |
> |
* execution. Serialization is not relied on during execution itself. |
138 |
|
* |
139 |
|
* @since 1.7 |
140 |
|
* @author Doug Lea |
392 |
|
|
393 |
|
/** |
394 |
|
* Returns result or throws exception using j.u.c.Future conventions. |
395 |
< |
* Only call when {@code isDone} known to be true. |
395 |
> |
* Only call when {@code isDone} known to be true or thread known |
396 |
> |
* to be interrupted. |
397 |
|
*/ |
398 |
|
private V reportFutureResult() |
399 |
< |
throws ExecutionException, InterruptedException { |
399 |
> |
throws InterruptedException, ExecutionException { |
400 |
> |
if (Thread.interrupted()) |
401 |
> |
throw new InterruptedException(); |
402 |
|
int s = status & COMPLETION_MASK; |
403 |
|
if (s < NORMAL) { |
404 |
|
Throwable ex; |
406 |
|
throw new CancellationException(); |
407 |
|
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
408 |
|
throw new ExecutionException(ex); |
392 |
– |
if (Thread.interrupted()) |
393 |
– |
throw new InterruptedException(); |
409 |
|
} |
410 |
|
return getRawResult(); |
411 |
|
} |
416 |
|
*/ |
417 |
|
private V reportTimedFutureResult() |
418 |
|
throws InterruptedException, ExecutionException, TimeoutException { |
419 |
+ |
if (Thread.interrupted()) |
420 |
+ |
throw new InterruptedException(); |
421 |
|
Throwable ex; |
422 |
|
int s = status & COMPLETION_MASK; |
423 |
|
if (s == NORMAL) |
424 |
|
return getRawResult(); |
425 |
< |
if (s == CANCELLED) |
425 |
> |
else if (s == CANCELLED) |
426 |
|
throw new CancellationException(); |
427 |
< |
if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
427 |
> |
else if (s == EXCEPTIONAL && (ex = exceptionMap.get(this)) != null) |
428 |
|
throw new ExecutionException(ex); |
429 |
< |
if (Thread.interrupted()) |
430 |
< |
throw new InterruptedException(); |
414 |
< |
throw new TimeoutException(); |
429 |
> |
else |
430 |
> |
throw new TimeoutException(); |
431 |
|
} |
432 |
|
|
433 |
|
// internal execution methods |
512 |
|
/** |
513 |
|
* Arranges to asynchronously execute this task. While it is not |
514 |
|
* necessarily enforced, it is a usage error to fork a task more |
515 |
< |
* than once unless it has completed and been reinitialized. This |
516 |
< |
* method may be invoked only from within ForkJoinTask |
517 |
< |
* computations (as may be determined using method {@link |
518 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
519 |
< |
* in exceptions or errors, possibly including ClassCastException. |
515 |
> |
* than once unless it has completed and been reinitialized. |
516 |
> |
* |
517 |
> |
* <p>This method may be invoked only from within {@code |
518 |
> |
* ForkJoinTask} computations (as may be determined using method |
519 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
520 |
> |
* result in exceptions or errors, possibly including {@code |
521 |
> |
* ClassCastException}. |
522 |
|
* |
523 |
< |
* @return {@code this}, to simplify usage. |
523 |
> |
* @return {@code this}, to simplify usage |
524 |
|
*/ |
525 |
|
public final ForkJoinTask<V> fork() { |
526 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
530 |
|
|
531 |
|
/** |
532 |
|
* Returns the result of the computation when it is ready. |
533 |
< |
* This method differs from {@code get} in that abnormal |
534 |
< |
* completion results in RuntimeExceptions or Errors, not |
535 |
< |
* ExecutionExceptions. |
533 |
> |
* This method differs from {@link #get()} in that |
534 |
> |
* abnormal completion results in {@code RuntimeException} or |
535 |
> |
* {@code Error}, not {@code ExecutionException}. |
536 |
|
* |
537 |
|
* @return the computed result |
538 |
|
*/ |
545 |
|
|
546 |
|
/** |
547 |
|
* Commences performing this task, awaits its completion if |
548 |
< |
* necessary, and return its result. |
548 |
> |
* necessary, and return its result, or throws an (unchecked) |
549 |
> |
* exception if the underlying computation did so. |
550 |
|
* |
532 |
– |
* @throws Throwable (a RuntimeException, Error, or unchecked |
533 |
– |
* exception) if the underlying computation did so |
551 |
|
* @return the computed result |
552 |
|
*/ |
553 |
|
public final V invoke() { |
559 |
|
|
560 |
|
/** |
561 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
562 |
< |
* each task or an exception is encountered. This method may be |
563 |
< |
* invoked only from within ForkJoinTask computations (as may be |
564 |
< |
* determined using method {@link #inForkJoinPool}). Attempts to |
565 |
< |
* invoke in other contexts result in exceptions or errors, |
566 |
< |
* possibly including ClassCastException. |
562 |
> |
* each task or an (unchecked) exception is encountered, in which |
563 |
> |
* case the exception is rethrown. If either task encounters an |
564 |
> |
* exception, the other one may be, but is not guaranteed to be, |
565 |
> |
* cancelled. If both tasks throw an exception, then this method |
566 |
> |
* throws one of them. The individual status of each task may be |
567 |
> |
* checked using {@link #getException()} and related methods. |
568 |
> |
* |
569 |
> |
* <p>This method may be invoked only from within {@code |
570 |
> |
* ForkJoinTask} computations (as may be determined using method |
571 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
572 |
> |
* result in exceptions or errors, possibly including {@code |
573 |
> |
* ClassCastException}. |
574 |
|
* |
575 |
|
* @param t1 the first task |
576 |
|
* @param t2 the second task |
577 |
|
* @throws NullPointerException if any task is null |
554 |
– |
* @throws RuntimeException or Error if a task did so |
578 |
|
*/ |
579 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
579 |
> |
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
580 |
|
t2.fork(); |
581 |
|
t1.invoke(); |
582 |
|
t2.join(); |
584 |
|
|
585 |
|
/** |
586 |
|
* Forks the given tasks, returning when {@code isDone} holds for |
587 |
< |
* each task or an exception is encountered. If any task |
588 |
< |
* encounters an exception, others may be, but are not guaranteed |
589 |
< |
* to be, cancelled. This method may be invoked only from within |
590 |
< |
* ForkJoinTask computations (as may be determined using method |
591 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
592 |
< |
* result in exceptions or errors, possibly including |
593 |
< |
* ClassCastException. |
594 |
< |
* |
595 |
< |
* Overloadings of this method exist for the special cases |
596 |
< |
* of one to four arguments. |
587 |
> |
* each task or an (unchecked) exception is encountered, in which |
588 |
> |
* case the exception is rethrown. If any task encounters an |
589 |
> |
* exception, others may be, but are not guaranteed to be, |
590 |
> |
* cancelled. If more than one task encounters an exception, then |
591 |
> |
* this method throws any one of these exceptions. The individual |
592 |
> |
* status of each task may be checked using {@link #getException()} |
593 |
> |
* and related methods. |
594 |
> |
* |
595 |
> |
* <p>This method may be invoked only from within {@code |
596 |
> |
* ForkJoinTask} computations (as may be determined using method |
597 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
598 |
> |
* result in exceptions or errors, possibly including {@code |
599 |
> |
* ClassCastException}. |
600 |
|
* |
601 |
|
* @param tasks the tasks |
602 |
< |
* @throws NullPointerException if tasks or any element are null |
577 |
< |
* @throws RuntimeException or Error if any task did so |
602 |
> |
* @throws NullPointerException if any task is null |
603 |
|
*/ |
604 |
|
public static void invokeAll(ForkJoinTask<?>... tasks) { |
605 |
|
Throwable ex = null; |
635 |
|
} |
636 |
|
|
637 |
|
/** |
638 |
< |
* Forks all tasks in the collection, returning when {@code |
639 |
< |
* isDone} holds for each task or an exception is encountered. If |
640 |
< |
* any task encounters an exception, others may be, but are not |
641 |
< |
* guaranteed to be, cancelled. This method may be invoked only |
642 |
< |
* from within ForkJoinTask computations (as may be determined |
643 |
< |
* using method {@link #inForkJoinPool}). Attempts to invoke in |
644 |
< |
* other contexts result in exceptions or errors, possibly |
645 |
< |
* including ClassCastException. |
638 |
> |
* Forks all tasks in the specified collection, returning when |
639 |
> |
* {@code isDone} holds for each task or an (unchecked) exception |
640 |
> |
* is encountered. If any task encounters an exception, others |
641 |
> |
* may be, but are not guaranteed to be, cancelled. If more than |
642 |
> |
* one task encounters an exception, then this method throws any |
643 |
> |
* one of these exceptions. The individual status of each task |
644 |
> |
* may be checked using {@link #getException()} and related |
645 |
> |
* methods. The behavior of this operation is undefined if the |
646 |
> |
* specified collection is modified while the operation is in |
647 |
> |
* progress. |
648 |
> |
* |
649 |
> |
* <p>This method may be invoked only from within {@code |
650 |
> |
* ForkJoinTask} computations (as may be determined using method |
651 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
652 |
> |
* result in exceptions or errors, possibly including {@code |
653 |
> |
* ClassCastException}. |
654 |
|
* |
655 |
|
* @param tasks the collection of tasks |
656 |
|
* @return the tasks argument, to simplify usage |
657 |
|
* @throws NullPointerException if tasks or any element are null |
625 |
– |
* @throws RuntimeException or Error if any task did so |
658 |
|
*/ |
659 |
|
public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
660 |
< |
if (!(tasks instanceof List<?>)) { |
660 |
> |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
661 |
|
invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
662 |
|
return tasks; |
663 |
|
} |
698 |
|
} |
699 |
|
|
700 |
|
/** |
701 |
< |
* Returns {@code true} if the computation performed by this task |
702 |
< |
* has completed (or has been cancelled). |
703 |
< |
* |
704 |
< |
* @return {@code true} if this computation has completed |
705 |
< |
*/ |
706 |
< |
public final boolean isDone() { |
707 |
< |
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. |
701 |
> |
* Attempts to cancel execution of this task. This attempt will |
702 |
> |
* fail if the task has already completed, has already been |
703 |
> |
* cancelled, or could not be cancelled for some other reason. If |
704 |
> |
* successful, and this task has not started when cancel is |
705 |
> |
* called, execution of this task is suppressed, {@link |
706 |
> |
* #isCancelled} will report true, and {@link #join} will result |
707 |
> |
* in a {@code CancellationException} being thrown. |
708 |
|
* |
709 |
|
* <p>This method may be overridden in subclasses, but if so, must |
710 |
|
* still ensure that these minimal properties hold. In particular, |
716 |
|
* invoke {@link #completeExceptionally}. |
717 |
|
* |
718 |
|
* @param mayInterruptIfRunning this value is ignored in the |
719 |
< |
* default implementation because tasks are not in general |
719 |
> |
* default implementation because tasks are not |
720 |
|
* cancelled via interruption |
721 |
|
* |
722 |
|
* @return {@code true} if this task is now cancelled |
726 |
|
return (status & COMPLETION_MASK) == CANCELLED; |
727 |
|
} |
728 |
|
|
729 |
+ |
public final boolean isDone() { |
730 |
+ |
return status < 0; |
731 |
+ |
} |
732 |
+ |
|
733 |
+ |
public final boolean isCancelled() { |
734 |
+ |
return (status & COMPLETION_MASK) == CANCELLED; |
735 |
+ |
} |
736 |
+ |
|
737 |
|
/** |
738 |
|
* Returns {@code true} if this task threw an exception or was cancelled. |
739 |
|
* |
744 |
|
} |
745 |
|
|
746 |
|
/** |
747 |
+ |
* Returns {@code true} if this task completed without throwing an |
748 |
+ |
* exception and was not cancelled. |
749 |
+ |
* |
750 |
+ |
* @return {@code true} if this task completed without throwing an |
751 |
+ |
* exception and was not cancelled |
752 |
+ |
*/ |
753 |
+ |
public final boolean isCompletedNormally() { |
754 |
+ |
return (status & COMPLETION_MASK) == NORMAL; |
755 |
+ |
} |
756 |
+ |
|
757 |
+ |
/** |
758 |
+ |
* Returns {@code true} if this task threw an exception. |
759 |
+ |
* |
760 |
+ |
* @return {@code true} if this task threw an exception |
761 |
+ |
*/ |
762 |
+ |
public final boolean isCompletedExceptionally() { |
763 |
+ |
return (status & COMPLETION_MASK) == EXCEPTIONAL; |
764 |
+ |
} |
765 |
+ |
|
766 |
+ |
/** |
767 |
|
* Returns the exception thrown by the base computation, or a |
768 |
|
* {@code CancellationException} if cancelled, or {@code null} if |
769 |
|
* none or if the method has not yet completed. |
772 |
|
*/ |
773 |
|
public final Throwable getException() { |
774 |
|
int s = status & COMPLETION_MASK; |
775 |
< |
if (s >= NORMAL) |
776 |
< |
return null; |
777 |
< |
if (s == CANCELLED) |
740 |
< |
return new CancellationException(); |
741 |
< |
return exceptionMap.get(this); |
775 |
> |
return ((s >= NORMAL) ? null : |
776 |
> |
(s == CANCELLED) ? new CancellationException() : |
777 |
> |
exceptionMap.get(this)); |
778 |
|
} |
779 |
|
|
780 |
|
/** |
842 |
|
* there are no potential dependencies between continuation of the |
843 |
|
* current task and that of any other task that might be executed |
844 |
|
* while helping. (This usually holds for pure divide-and-conquer |
845 |
< |
* tasks). This method may be invoked only from within |
846 |
< |
* ForkJoinTask computations (as may be determined using method |
847 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
848 |
< |
* result in exceptions or errors, possibly including |
849 |
< |
* ClassCastException. |
845 |
> |
* tasks). |
846 |
> |
* |
847 |
> |
* <p>This method may be invoked only from within {@code |
848 |
> |
* ForkJoinTask} computations (as may be determined using method |
849 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
850 |
> |
* result in exceptions or errors, possibly including {@code |
851 |
> |
* ClassCastException}. |
852 |
|
* |
853 |
|
* @return the computed result |
854 |
|
*/ |
861 |
|
|
862 |
|
/** |
863 |
|
* Possibly executes other tasks until this task is ready. This |
864 |
< |
* method may be invoked only from within ForkJoinTask |
865 |
< |
* computations (as may be determined using method {@link |
866 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
867 |
< |
* in exceptions or errors, possibly including ClassCastException. |
864 |
> |
* method may be useful when processing collections of tasks when |
865 |
> |
* some have been cancelled or otherwise known to have aborted. |
866 |
> |
* |
867 |
> |
* <p>This method may be invoked only from within {@code |
868 |
> |
* ForkJoinTask} computations (as may be determined using method |
869 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
870 |
> |
* result in exceptions or errors, possibly including {@code |
871 |
> |
* ClassCastException}. |
872 |
|
*/ |
873 |
|
public final void quietlyHelpJoin() { |
874 |
|
if (status >= 0) { |
907 |
|
|
908 |
|
/** |
909 |
|
* Possibly executes tasks until the pool hosting the current task |
910 |
< |
* {@link ForkJoinPool#isQuiescent}. This method may be of use in |
911 |
< |
* designs in which many tasks are forked, but none are explicitly |
912 |
< |
* joined, instead executing them until all are processed. This |
913 |
< |
* method may be invoked only from within ForkJoinTask |
914 |
< |
* computations (as may be determined using method {@link |
915 |
< |
* #inForkJoinPool}). Attempts to invoke in other contexts result |
916 |
< |
* in exceptions or errors, possibly including ClassCastException. |
910 |
> |
* {@link ForkJoinPool#isQuiescent is quiescent}. This method may |
911 |
> |
* be of use in designs in which many tasks are forked, but none |
912 |
> |
* are explicitly joined, instead executing them until all are |
913 |
> |
* processed. |
914 |
> |
* |
915 |
> |
* <p>This method may be invoked only from within {@code |
916 |
> |
* ForkJoinTask} computations (as may be determined using method |
917 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
918 |
> |
* result in exceptions or errors, possibly including {@code |
919 |
> |
* ClassCastException}. |
920 |
|
*/ |
921 |
|
public static void helpQuiesce() { |
922 |
|
((ForkJoinWorkerThread) Thread.currentThread()) |
929 |
|
* this task, but only if reuse occurs when this task has either |
930 |
|
* never been forked, or has been forked, then completed and all |
931 |
|
* outstanding joins of this task have also completed. Effects |
932 |
< |
* under any other usage conditions are not guaranteed, and are |
933 |
< |
* discouraged. This method may be useful when executing |
932 |
> |
* under any other usage conditions are not guaranteed. |
933 |
> |
* This method may be useful when executing |
934 |
|
* pre-constructed trees of subtasks in loops. |
935 |
|
*/ |
936 |
|
public void reinitialize() { |
969 |
|
* by the current thread, and has not commenced executing in |
970 |
|
* another thread. This method may be useful when arranging |
971 |
|
* alternative local processing of tasks that could have been, but |
972 |
< |
* were not, stolen. This method may be invoked only from within |
973 |
< |
* ForkJoinTask computations (as may be determined using method |
974 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
975 |
< |
* result in exceptions or errors, possibly including |
976 |
< |
* ClassCastException. |
972 |
> |
* were not, stolen. |
973 |
> |
* |
974 |
> |
* <p>This method may be invoked only from within {@code |
975 |
> |
* ForkJoinTask} computations (as may be determined using method |
976 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
977 |
> |
* result in exceptions or errors, possibly including {@code |
978 |
> |
* ClassCastException}. |
979 |
|
* |
980 |
|
* @return {@code true} if unforked |
981 |
|
*/ |
988 |
|
* Returns an estimate of the number of tasks that have been |
989 |
|
* forked by the current worker thread but not yet executed. This |
990 |
|
* value may be useful for heuristic decisions about whether to |
991 |
< |
* fork other tasks. This method may be invoked only from within |
992 |
< |
* ForkJoinTask computations (as may be determined using method |
993 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
994 |
< |
* result in exceptions or errors, possibly including |
995 |
< |
* ClassCastException. |
991 |
> |
* fork other tasks. |
992 |
> |
* |
993 |
> |
* <p>This method may be invoked only from within {@code |
994 |
> |
* ForkJoinTask} computations (as may be determined using method |
995 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
996 |
> |
* result in exceptions or errors, possibly including {@code |
997 |
> |
* ClassCastException}. |
998 |
> |
* |
999 |
|
* @return the number of tasks |
1000 |
|
*/ |
1001 |
|
public static int getQueuedTaskCount() { |
1011 |
|
* usages of ForkJoinTasks, at steady state, each worker should |
1012 |
|
* aim to maintain a small constant surplus (for example, 3) of |
1013 |
|
* tasks, and to process computations locally if this threshold is |
1014 |
< |
* exceeded. This method may be invoked only from within |
1015 |
< |
* ForkJoinTask computations (as may be determined using method |
1016 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1017 |
< |
* result in exceptions or errors, possibly including |
1018 |
< |
* ClassCastException. * |
1014 |
> |
* exceeded. |
1015 |
> |
* |
1016 |
> |
* <p>This method may be invoked only from within {@code |
1017 |
> |
* ForkJoinTask} computations (as may be determined using method |
1018 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1019 |
> |
* result in exceptions or errors, possibly including {@code |
1020 |
> |
* ClassCastException}. |
1021 |
> |
* |
1022 |
|
* @return the surplus number of tasks, which may be negative |
1023 |
|
*/ |
1024 |
|
public static int getSurplusQueuedTaskCount() { |
1054 |
|
* called otherwise. The return value controls whether this task |
1055 |
|
* is considered to be done normally. It may return false in |
1056 |
|
* asynchronous actions that require explicit invocations of |
1057 |
< |
* {@link #complete} to become joinable. It may throw exceptions |
1058 |
< |
* to indicate abnormal exit. |
1057 |
> |
* {@link #complete} to become joinable. It may also throw an |
1058 |
> |
* (unchecked) exception to indicate abnormal exit. |
1059 |
|
* |
1060 |
|
* @return {@code true} if completed normally |
1008 |
– |
* @throws Error or RuntimeException if encountered during computation |
1061 |
|
*/ |
1062 |
|
protected abstract boolean exec(); |
1063 |
|
|
1069 |
|
* null even if a task exists but cannot be accessed without |
1070 |
|
* contention with other threads. This method is designed |
1071 |
|
* primarily to support extensions, and is unlikely to be useful |
1072 |
< |
* otherwise. This method may be invoked only from within |
1073 |
< |
* ForkJoinTask computations (as may be determined using method |
1074 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1075 |
< |
* result in exceptions or errors, possibly including |
1076 |
< |
* ClassCastException. |
1072 |
> |
* otherwise. |
1073 |
> |
* |
1074 |
> |
* <p>This method may be invoked only from within {@code |
1075 |
> |
* ForkJoinTask} computations (as may be determined using method |
1076 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1077 |
> |
* result in exceptions or errors, possibly including {@code |
1078 |
> |
* ClassCastException}. |
1079 |
|
* |
1080 |
|
* @return the next task, or {@code null} if none are available |
1081 |
|
*/ |
1088 |
|
* Unschedules and returns, without executing, the next task |
1089 |
|
* queued by the current thread but not yet executed. This method |
1090 |
|
* is designed primarily to support extensions, and is unlikely to |
1091 |
< |
* be useful otherwise. This method may be invoked only from |
1092 |
< |
* within ForkJoinTask computations (as may be determined using |
1093 |
< |
* method {@link #inForkJoinPool}). Attempts to invoke in other |
1094 |
< |
* contexts result in exceptions or errors, possibly including |
1095 |
< |
* ClassCastException. |
1091 |
> |
* be useful otherwise. |
1092 |
> |
* |
1093 |
> |
* <p>This method may be invoked only from within {@code |
1094 |
> |
* ForkJoinTask} computations (as may be determined using method |
1095 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1096 |
> |
* result in exceptions or errors, possibly including {@code |
1097 |
> |
* ClassCastException}. |
1098 |
|
* |
1099 |
|
* @return the next task, or {@code null} if none are available |
1100 |
|
*/ |
1111 |
|
* {@code null} result does not necessarily imply quiescence |
1112 |
|
* of the pool this task is operating in. This method is designed |
1113 |
|
* primarily to support extensions, and is unlikely to be useful |
1114 |
< |
* otherwise. This method may be invoked only from within |
1115 |
< |
* ForkJoinTask computations (as may be determined using method |
1116 |
< |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1117 |
< |
* result in exceptions or errors, possibly including |
1118 |
< |
* ClassCastException. |
1114 |
> |
* otherwise. |
1115 |
> |
* |
1116 |
> |
* <p>This method may be invoked only from within {@code |
1117 |
> |
* ForkJoinTask} computations (as may be determined using method |
1118 |
> |
* {@link #inForkJoinPool}). Attempts to invoke in other contexts |
1119 |
> |
* result in exceptions or errors, possibly including {@code |
1120 |
> |
* ClassCastException}. |
1121 |
|
* |
1122 |
|
* @return a task, or {@code null} if none are available |
1123 |
|
*/ |
1182 |
|
} |
1183 |
|
|
1184 |
|
/** |
1185 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1186 |
< |
* method of the given Runnable as its action, and returns a null |
1187 |
< |
* result upon {@code join}. |
1185 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1186 |
> |
* method of the given {@code Runnable} as its action, and returns |
1187 |
> |
* a null result upon {@link #join}. |
1188 |
|
* |
1189 |
|
* @param runnable the runnable action |
1190 |
|
* @return the task |
1194 |
|
} |
1195 |
|
|
1196 |
|
/** |
1197 |
< |
* Returns a new ForkJoinTask that performs the {@code run} |
1198 |
< |
* method of the given Runnable as its action, and returns the |
1199 |
< |
* given result upon {@code join}. |
1197 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code run} |
1198 |
> |
* method of the given {@code Runnable} as its action, and returns |
1199 |
> |
* the given result upon {@link #join}. |
1200 |
|
* |
1201 |
|
* @param runnable the runnable action |
1202 |
|
* @param result the result upon completion |
1207 |
|
} |
1208 |
|
|
1209 |
|
/** |
1210 |
< |
* Returns a new ForkJoinTask that performs the {@code call} |
1211 |
< |
* method of the given Callable as its action, and returns its |
1212 |
< |
* result upon {@code join}, translating any checked |
1213 |
< |
* exceptions encountered into {@code RuntimeException}. |
1210 |
> |
* Returns a new {@code ForkJoinTask} that performs the {@code call} |
1211 |
> |
* method of the given {@code Callable} as its action, and returns |
1212 |
> |
* its result upon {@link #join}, translating any checked exceptions |
1213 |
> |
* encountered into {@code RuntimeException}. |
1214 |
|
* |
1215 |
|
* @param callable the callable action |
1216 |
|
* @return the task |