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import java.util.Collection; |
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import java.util.Collections; |
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import java.util.List; |
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import java.util.RandomAccess; |
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import java.util.Map; |
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import java.util.WeakHashMap; |
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|
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* restriction is in part enforced by not permitting checked |
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* exceptions such as {@code IOExceptions} to be thrown. However, |
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* computations may still encounter unchecked exceptions, that are |
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* rethrown to callers attempting join them. These exceptions may |
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* rethrown to callers attempting to join them. These exceptions may |
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* additionally include RejectedExecutionExceptions stemming from |
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* internal resource exhaustion such as failure to allocate internal |
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* task queues. |
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* established in a constructor, and then defines a {@code compute} |
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* method that somehow uses the control methods supplied by this base |
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* class. While these methods have {@code public} access (to allow |
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* instances of different task subclasses to call each others |
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* instances of different task subclasses to call each other's |
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* methods), some of them may only be called from within other |
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* ForkJoinTasks (as may be determined using method {@link |
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* #inForkJoinPool}). Attempts to invoke them in other contexts |
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* result in exceptions or errors, possibly including |
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* ClassCastException. |
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* |
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* <p>Most base support methods are {@code final} because their |
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* implementations are intrinsically tied to the underlying |
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* lightweight task scheduling framework, and so cannot be overridden. |
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* Developers creating new basic styles of fork/join processing should |
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* minimally implement {@code protected} methods |
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* {@link #exec}, {@link #setRawResult}, and |
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* {@link #getRawResult}, while also introducing an abstract |
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* computational method that can be implemented in its subclasses, |
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* possibly relying on other {@code protected} methods provided |
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* by this class. |
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* <p>Most base support methods are {@code final}, to prevent |
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> |
* overriding of implementations that are intrinsically tied to the |
| 98 |
> |
* underlying lightweight task scheduling framework. Developers |
| 99 |
> |
* creating new basic styles of fork/join processing should minimally |
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> |
* implement {@code protected} methods {@link #exec}, {@link |
| 101 |
> |
* #setRawResult}, and {@link #getRawResult}, while also introducing |
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* an abstract computational method that can be implemented in its |
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* subclasses, possibly relying on other {@code protected} methods |
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* provided by this class. |
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* |
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* <p>ForkJoinTasks should perform relatively small amounts of |
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* computations, otherwise splitting into smaller tasks. As a very |
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* rough rule of thumb, a task should perform more than 100 and less |
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* than 10000 basic computational steps. If tasks are too big, then |
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* parallelism cannot improve throughput. If too small, then memory |
| 111 |
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* and internal task maintenance overhead may overwhelm processing. |
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* computation. Large tasks should be split into smaller subtasks, |
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* usually via recursive decomposition. As a very rough rule of thumb, |
| 109 |
> |
* a task should perform more than 100 and less than 10000 basic |
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* computational steps. If tasks are too big, then parallelism cannot |
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* improve throughput. If too small, then memory and internal task |
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* maintenance overhead may overwhelm processing. |
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* |
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* <p>This class provides {@code adapt} methods for {@link |
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* java.lang.Runnable} and {@link java.util.concurrent.Callable}, that |
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* kinds of tasks. When all tasks are of this form, consider using a |
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* pool in {@link ForkJoinPool#setAsyncMode}. |
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* |
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* <p>ForkJoinTasks are {@code Serializable}, which enables them |
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* to be used in extensions such as remote execution frameworks. It is |
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* in general sensible to serialize tasks only before or after, but |
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* not during execution. Serialization is not relied on during |
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* execution itself. |
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* <p>ForkJoinTasks are {@code Serializable}, which enables them to be |
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* used in extensions such as remote execution frameworks. It is |
| 122 |
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* sensible to serialize tasks only before or after, but not during, |
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* execution. Serialization is not relied on during execution itself. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
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* result in exceptions or errors, possibly including {@code |
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* ClassCastException}. |
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* |
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– |
* <p>Overloadings of this method exist for the special cases |
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– |
* of one to four arguments. |
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– |
* |
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* @param tasks the tasks |
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* @throws NullPointerException if tasks or any element are null |
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* @throws RuntimeException or Error if any task did so |
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} |
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|
| 615 |
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/** |
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* Forks all tasks in the collection, returning when {@code |
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* isDone} holds for each task or an exception is encountered. |
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* If any task encounters an exception, others may be, but are |
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* not guaranteed to be, cancelled. |
| 616 |
> |
* Forks all tasks in the specified collection, returning when |
| 617 |
> |
* {@code isDone} holds for each task or an exception is |
| 618 |
> |
* encountered. If any task encounters an exception, others may |
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> |
* be, but are not guaranteed to be, cancelled. The behavior of |
| 620 |
> |
* this operation is undefined if the specified collection is |
| 621 |
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* modified while the operation is in progress. |
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* |
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* <p>This method may be invoked only from within {@code |
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* ForkJoinTask} computations (as may be determined using method |
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* @throws RuntimeException or Error if any task did so |
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*/ |
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public static <T extends ForkJoinTask<?>> Collection<T> invokeAll(Collection<T> tasks) { |
| 635 |
< |
if (!(tasks instanceof List<?>)) { |
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> |
if (!(tasks instanceof RandomAccess) || !(tasks instanceof List<?>)) { |
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invokeAll(tasks.toArray(new ForkJoinTask<?>[tasks.size()])); |
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return tasks; |
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} |
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} |
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|
| 833 |
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/** |
| 834 |
< |
* Possibly executes other tasks until this task is ready. |
| 834 |
> |
* Possibly executes other tasks until this task is ready. This |
| 835 |
> |
* method may be useful when processing collections of tasks when |
| 836 |
> |
* some have been cancelled or otherwise known to have aborted. |
| 837 |
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* |
| 838 |
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* <p>This method may be invoked only from within {@code |
| 839 |
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* ForkJoinTask} computations (as may be determined using method |
