| 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 |
|
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 |
| 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 |
|
* |
| 534 |
– |
* @throws Throwable (a RuntimeException, Error, or unchecked |
| 535 |
– |
* exception) if the underlying computation did so |
| 551 |
|
* @return the computed result |
| 552 |
|
*/ |
| 553 |
|
public final V invoke() { |
| 558 |
|
} |
| 559 |
|
|
| 560 |
|
/** |
| 561 |
< |
* Forks the given tasks, returning when {@code isDone} holds |
| 562 |
< |
* for each task or an exception is encountered. |
| 561 |
> |
* Forks the given tasks, returning when {@code isDone} holds for |
| 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 |
| 575 |
|
* @param t1 the first task |
| 576 |
|
* @param t2 the second task |
| 577 |
|
* @throws NullPointerException if any task is null |
| 558 |
– |
* @throws RuntimeException or Error if a task did so |
| 578 |
|
*/ |
| 579 |
|
public static void invokeAll(ForkJoinTask<?> t1, ForkJoinTask<?> t2) { |
| 580 |
|
t2.fork(); |
| 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. |
| 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 |
| 598 |
|
* result in exceptions or errors, possibly including {@code |
| 599 |
|
* ClassCastException}. |
| 600 |
|
* |
| 578 |
– |
* <p>Overloadings of this method exist for the special cases |
| 579 |
– |
* of one to four arguments. |
| 580 |
– |
* |
| 601 |
|
* @param tasks the tasks |
| 602 |
< |
* @throws NullPointerException if tasks or any element are null |
| 583 |
< |
* @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. |
| 640 |
< |
* If any task encounters an exception, others may be, but are |
| 641 |
< |
* not guaranteed to be, cancelled. |
| 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 |
| 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 |
| 633 |
– |
* @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; |
| 684 |
< |
} |
| 685 |
< |
|
| 686 |
< |
/** |
| 687 |
< |
* Returns {@code true} if this task was cancelled. |
| 688 |
< |
* |
| 689 |
< |
* @return {@code true} if this task was cancelled |
| 690 |
< |
*/ |
| 691 |
< |
public final boolean isCancelled() { |
| 692 |
< |
return (status & COMPLETION_MASK) == CANCELLED; |
| 693 |
< |
} |
| 694 |
< |
|
| 695 |
< |
/** |
| 696 |
< |
* Asserts that the results of this task's computation will not be |
| 697 |
< |
* used. If a cancellation occurs before attempting to execute this |
| 698 |
< |
* task, execution will be suppressed, {@link #isCancelled} |
| 699 |
< |
* will report true, and {@link #join} will result in a |
| 700 |
< |
* {@code CancellationException} being thrown. Otherwise, when |
| 701 |
< |
* cancellation races with completion, there are no guarantees |
| 702 |
< |
* about whether {@code isCancelled} will report {@code true}, |
| 703 |
< |
* whether {@code join} will return normally or via an exception, |
| 704 |
< |
* or whether these behaviors will remain consistent upon repeated |
| 705 |
< |
* 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) |
| 748 |
< |
return new CancellationException(); |
| 749 |
< |
return exceptionMap.get(this); |
| 775 |
> |
return ((s >= NORMAL) ? null : |
| 776 |
> |
(s == CANCELLED) ? new CancellationException() : |
| 777 |
> |
exceptionMap.get(this)); |
| 778 |
|
} |
| 779 |
|
|
| 780 |
|
/** |
| 860 |
|
} |
| 861 |
|
|
| 862 |
|
/** |
| 863 |
< |
* Possibly executes other tasks until this task is ready. |
| 863 |
> |
* Possibly executes other tasks until this task is ready. This |
| 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 |
| 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. |
| 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 |
| 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 |
| 1030 |
– |
* @throws Error or RuntimeException if encountered during computation |
| 1061 |
|
*/ |
| 1062 |
|
protected abstract boolean exec(); |
| 1063 |
|
|
