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/** |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. |
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* A ForkJoinPool provides the entry point for submissions from |
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* non-ForkJoinTasks, as well as management and monitoring operations. |
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* Normally a single ForkJoinPool is used for a large number of |
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* submitted tasks. Otherwise, use would not usually outweigh the |
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* construction and bookkeeping overhead of creating a large set of |
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* threads. |
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* A {@code ForkJoinPool} provides the entry point for submissions |
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* from non-{@code ForkJoinTask}s, as well as management and |
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* monitoring operations. Normally a single {@code ForkJoinPool} is |
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* used for a large number of submitted tasks. Otherwise, use would |
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* not usually outweigh the construction and bookkeeping overhead of |
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* creating a large set of threads. |
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* |
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* <p>ForkJoinPools differ from other kinds of Executors mainly in |
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* that they provide <em>work-stealing</em>: all threads in the pool |
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* attempt to find and execute subtasks created by other active tasks |
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* (eventually blocking if none exist). This makes them efficient when |
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* most tasks spawn other subtasks (as do most ForkJoinTasks), as well |
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* as the mixed execution of some plain Runnable- or Callable- based |
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* activities along with ForkJoinTasks. When setting {@linkplain |
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* #setAsyncMode async mode}, a ForkJoinPool may also be appropriate |
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* for use with fine-grained tasks that are never joined. Otherwise, |
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* other ExecutorService implementations are typically more |
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* <p>{@code ForkJoinPool}s differ from other kinds of {@link |
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* Executor}s mainly in that they provide <em>work-stealing</em>: all |
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* threads in the pool attempt to find and execute subtasks created by |
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* other active tasks (eventually blocking if none exist). This makes |
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* them efficient when most tasks spawn other subtasks (as do most |
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* {@code ForkJoinTask}s), as well as the mixed execution of some |
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* plain {@code Runnable}- or {@code Callable}- based activities along |
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* with {@code ForkJoinTask}s. When setting {@linkplain #setAsyncMode |
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* async mode}, a {@code ForkJoinPool} may also be appropriate for use |
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* with fine-grained tasks that are never joined. Otherwise, other |
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* {@code ExecutorService} implementations are typically more |
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* appropriate choices. |
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* |
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* <p>A ForkJoinPool may be constructed with a given parallelism level |
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* (target pool size), which it attempts to maintain by dynamically |
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* adding, suspending, or resuming threads, even if some tasks are |
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* waiting to join others. However, no such adjustments are performed |
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* in the face of blocked IO or other unmanaged synchronization. The |
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* nested {@link ManagedBlocker} interface enables extension of |
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* the kinds of synchronization accommodated. The target parallelism |
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* level may also be changed dynamically ({@link #setParallelism}) |
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* and thread construction can be limited using methods |
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* {@link #setMaximumPoolSize} and/or |
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* {@link #setMaintainsParallelism}. |
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* <p>A {@code ForkJoinPool} may be constructed with a given |
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* parallelism level (target pool size), which it attempts to maintain |
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* by dynamically adding, suspending, or resuming threads, even if |
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* some tasks are waiting to join others. However, no such adjustments |
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* are performed in the face of blocked IO or other unmanaged |
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* synchronization. The nested {@link ManagedBlocker} interface |
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* enables extension of the kinds of synchronization accommodated. |
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* The target parallelism level may also be changed dynamically |
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* ({@link #setParallelism}) and thread construction can be limited |
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* using methods {@link #setMaximumPoolSize} and/or {@link |
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* #setMaintainsParallelism}. |
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* |
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* <p>In addition to execution and lifecycle control methods, this |
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* class provides status check methods (for example |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of running threads to 32767. Attempts to create |
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* pools with greater than the maximum result in |
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* IllegalArgumentExceptions. |
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* {@code IllegalArgumentException}. |
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* |
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* @since 1.7 |
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* @author Doug Lea |
