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import java.util.concurrent.atomic.AtomicLong; |
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/** |
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* An {@link ExecutorService} for running {@link ForkJoinTask}s. A |
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* ForkJoinPool provides the entry point for submissions from |
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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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* (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 |
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* {@code setAsyncMode}, a ForkJoinPools may also be appropriate for |
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* use with fine-grained tasks that are never joined. Otherwise, other |
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* ExecutorService implementations are typically more appropriate |
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* choices. |
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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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* 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 {@code ManagedBlocker} interface enables extension of |
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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 ({@code setParallelism}) |
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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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* {@code setMaximumPoolSize} and/or |
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* {@code setMaintainsParallelism}. |
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* {@link #setMaximumPoolSize} and/or |
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* {@link #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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* {@code getStealCount}) that are intended to aid in developing, |
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* {@link #getStealCount}) that are intended to aid in developing, |
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* tuning, and monitoring fork/join applications. Also, method |
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* {@code toString} returns indications of pool state in a |
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* {@link #toString} returns indications of pool state in a |
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* convenient form for informal monitoring. |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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/** |
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* Returns the number of worker threads that have started but not |
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* yet terminated. This result returned by this method may differ |
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* from {@code getParallelism} when threads are created to |
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* from {@link #getParallelism} when threads are created to |
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* maintain parallelism when others are cooperatively blocked. |
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* |
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* @return the number of worker threads |
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* tasks that are never joined. This mode may be more appropriate |
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* than default locally stack-based mode in applications in which |
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* worker threads only process asynchronous tasks. This method is |
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* designed to be invoked only when pool is quiescent, and |
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* designed to be invoked only when the pool is quiescent, and |
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* typically only before any tasks are submitted. The effects of |
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* invocations at other times may be unpredictable. |
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* |
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* @param async if true, use locally FIFO scheduling |
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* @param async if {@code true}, use locally FIFO scheduling |
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* @return the previous mode |
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* @see #getAsyncMode |
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*/ |
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public boolean setAsyncMode(boolean async) { |
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boolean oldMode = locallyFifo; |
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* scheduling mode for forked tasks that are never joined. |
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* |
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* @return {@code true} if this pool uses async mode |
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* @see #setAsyncMode |
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*/ |
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public boolean getAsyncMode() { |
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return locallyFifo; |
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* method may or may not be rejected. Unlike some other executors, |
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* this method cancels rather than collects non-executed tasks |
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* upon termination, so always returns an empty list. However, you |
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* can use method {@code drainTasksTo} before invoking this |
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* can use method {@link #drainTasksTo} before invoking this |
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* method to transfer unexecuted tasks to another collection. |
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* |
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* @return an empty list |
