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import java.lang.reflect.*; |
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/** |
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* Abstract base class for tasks that run within a ForkJoinPool. A |
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* ForkJoinTask is a thread-like entity that is much lighter weight |
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* than a normal thread. Huge numbers of tasks and subtasks may be |
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* hosted by a small number of actual threads in a ForkJoinPool, |
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* at the price of some usage limitations. |
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* Abstract base class for tasks that run within a {@link |
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* ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much |
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* lighter weight than a normal thread. Huge numbers of tasks and |
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* subtasks may be hosted by a small number of actual threads in a |
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* ForkJoinPool, at the price of some usage limitations. |
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* |
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* <p> ForkJoinTasks are forms of <tt>Futures</tt> supporting a |
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* limited range of use. The "lightness" of ForkJoinTasks is due to a |
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* set of restrictions (that are only partially statically |
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* enforceable) reflecting their intended use as computational tasks |
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* calculating pure functions or operating on purely isolated objects. |
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* The primary coordination mechanisms supported for ForkJoinTasks are |
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* <tt>fork</tt>, that arranges asynchronous execution, and |
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* <tt>join</tt>, that doesn't proceed until the task's result has |
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* been computed. (Cancellation is also supported). The computation |
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* defined in the <tt>compute</tt> method should avoid |
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* <tt>synchronized</tt> methods or blocks, and should minimize |
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* blocking synchronization apart from joining other tasks or using |
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* <p> A "main" ForkJoinTask begins execution when submitted to a |
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* {@link ForkJoinPool}. Once started, it will usually in turn start |
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* other subtasks. As indicated by the name of this class, many |
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* programs using ForkJoinTasks employ only methods <code>fork</code> |
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* and <code>join</code>, or derivatives such as |
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* <code>invokeAll</code>. However, this class also provides a number |
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* of other methods that can come into play in advanced usages, as |
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* well as extension mechanics that allow support of new forms of |
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* fork/join processing. |
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* |
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* <p>A ForkJoinTask is a lightweight form of {@link Future}. The |
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* efficiency of ForkJoinTasks stems from a set of restrictions (that |
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* are only partially statically enforceable) reflecting their |
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* intended use as computational tasks calculating pure functions or |
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* operating on purely isolated objects. The primary coordination |
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* mechanisms are {@link #fork}, that arranges asynchronous execution, |
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* and {@link #join}, that doesn't proceed until the task's result has |
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* been computed. Computations should avoid <code>synchronized</code> |
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* methods or blocks, and should minimize other blocking |
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* synchronization apart from joining other tasks or using |
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* synchronizers such as Phasers that are advertised to cooperate with |
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* fork/join scheduling. Tasks should also not perform blocking IO, |
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* and should ideally access variables that are completely independent |
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* restrictions, for example using shared output streams, may be |
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* tolerable in practice, but frequent use may result in poor |
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* performance, and the potential to indefinitely stall if the number |
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* of threads not waiting for external synchronization becomes |
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* exhausted. This usage restriction is in part enforced by not |
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* permitting checked exceptions such as IOExceptions to be |
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* thrown. However, computations may still encounter unchecked |
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* of threads not waiting for IO or other external synchronization |
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* becomes exhausted. This usage restriction is in part enforced by |
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* not permitting checked exceptions such as <code>IOExceptions</code> |
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* to be thrown. However, computations may still encounter unchecked |
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* exceptions, that are rethrown to callers attempting join |
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* them. These exceptions may additionally include |
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* RejectedExecutionExceptions stemming from internal resource |
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* exhaustion such as failure to allocate internal task queues. |
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* |
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* <p> The <tt>ForkJoinTask</tt> class is not usually directly |
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* subclassed. Instead, you subclass one of the abstract classes that |
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* support different styles of fork/join processing. Normally, a |
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* concrete ForkJoinTask subclass declares fields comprising its |
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* parameters, established in a constructor, and then defines a |
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* <tt>compute</tt> method that somehow uses the control methods |
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* supplied by this base class. While these methods have |
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* <tt>public</tt> access, some of them may only be called from within |
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* other ForkJoinTasks. Attempts to invoke them in other contexts |
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* result in exceptions or errors including ClassCastException. The |
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* only way to invoke a "main" driver task is to submit it to a |
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* ForkJoinPool. Once started, this will usually in turn start other |
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* subtasks. |
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* <p>The primary method for awaiting completion and extracting |
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* results of a task is {@link #join}, but there are several variants: |
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* The {@link Future#get} methods support interruptible and/or timed |
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* waits for completion and report results using <code>Future</code> |
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* conventions. Method {@link #helpJoin} enables callers to actively |
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* execute other tasks while awaiting joins, which is sometimes more |
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* efficient but only applies when all subtasks are known to be |
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* strictly tree-structured. Method {@link #invoke} is semantically |
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* equivalent to <code>fork(); join()</code> but always attempts to |
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* begin execution in the current thread. The "<em>quiet</em>" forms |
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* of these methods do not extract results or report exceptions. These |
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* may be useful when a set of tasks are being executed, and you need |
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* to delay processing of results or exceptions until all complete. |
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* Method <code>invokeAll</code> (available in multiple versions) |
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* performs the most common form of parallel invocation: forking a set |
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* of tasks and joining them all. |
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* |
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* <p> The ForkJoinTask class is not usually directly subclassed. |
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* Instead, you subclass one of the abstract classes that support a |
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* particular style of fork/join processing. Normally, a concrete |
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* ForkJoinTask subclass declares fields comprising its parameters, |
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* established in a constructor, and then defines a <code>compute</code> |
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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</code> access (to allow |
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* instances of different task subclasses to call each others |
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* methods), some of them may only be called from within other |
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* ForkJoinTasks. Attempts to invoke them in other contexts result in |
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* exceptions or errors possibly including ClassCastException. |
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* |
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* <p>Most base support methods are <tt>final</tt> because their |
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* <p>Most base support methods are <code>final</code> 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 protected methods <tt>exec</tt>, |
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* <tt>setRawResult</tt>, and <tt>getRawResult</tt>, while also |
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* introducing an abstract computational method that can be |
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* implemented in its subclasses. To support such extensions, |
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* instances of ForkJoinTasks maintain an atomically updated |
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* <tt>short</tt> representing user-defined control state. Control |
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* state is guaranteed initially to be zero, and to be negative upon |
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* completion, but may otherwise be used for any other control |
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* purposes, such as maintaining join counts. The {@link |
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* ForkJoinWorkerThread} class supports additional inspection and |
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* tuning methods that can be useful when developing extensions. |
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* minimally implement <code>protected</code> methods |
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* <code>exec</code>, <code>setRawResult</code>, and |
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* <code>getRawResult</code>, 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</code> methods provided |
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* by this class. |
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* |
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* <p>ForkJoinTasks should perform relatively small amounts of |
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* computations, othewise splitting into smaller tasks. As a very |
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* parellelism cannot improve throughput. If too small, then memory |
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* and internal task maintenance overhead may overwhelm processing. |
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* |
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* <p>ForkJoinTasks are <tt>Serializable</tt>, which enables them to |
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* be used in extensions such as remote execution frameworks. However, |
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* it is in general safe to serialize tasks only before or after, but |
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* <p>ForkJoinTasks are <code>Serializable</code>, 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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*/ |
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public abstract class ForkJoinTask<V> implements Future<V>, Serializable { |
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/** |
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* Status field holding all run status. We pack this into a single |
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* int both to minimize footprint overhead and to ensure atomicity |
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* (updates are via CAS). |
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* |
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* Status is initially zero, and takes on nonnegative values until |
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* Run control status bits packed into a single int to minimize |
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* footprint and to ensure atomicity (via CAS). Status is |
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* initially zero, and takes on nonnegative values until |
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* completed, upon which status holds COMPLETED. CANCELLED, or |
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* EXCEPTIONAL, which use the top 3 bits. Tasks undergoing |
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* blocking waits by other threads have SIGNAL_MASK bits set -- |
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(ForkJoinWorkerThread)t : null); |
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} |
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|
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– |
/** |
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* Get pool of current worker thread, or null if not a worker thread |
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*/ |
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static ForkJoinPool getWorkerPool() { |
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Thread t = Thread.currentThread(); |
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return ((t instanceof ForkJoinWorkerThread)? |
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((ForkJoinWorkerThread)t).pool : null); |
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} |
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|
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final boolean casStatus(int cmp, int val) { |
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return _unsafe.compareAndSwapInt(this, statusOffset, cmp, val); |
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} |
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* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL |
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*/ |
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final void setCompletion(int completion) { |
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ForkJoinPool pool = getWorkerPool(); |
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ForkJoinPool pool = getPool(); |
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if (pool != null) { |
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int s; // Clear signal bits while setting completion status |
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do;while ((s = status) >= 0 && !casStatus(s, completion)); |
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* surrounded with pool notifications. |
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* @return status upon exit |
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*/ |
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final int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
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private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) { |
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ForkJoinPool pool = w == null? null : w.pool; |
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int s; |
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while ((s = status) >= 0) { |
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* Timed version of awaitDone |
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* @return status upon exit |
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*/ |
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final int awaitDone(ForkJoinWorkerThread w, long nanos) { |
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private int awaitDone(ForkJoinWorkerThread w, long nanos) { |
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ForkJoinPool pool = w == null? null : w.pool; |
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int s; |
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while ((s = status) >= 0) { |
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} |
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} |
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|
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/** |
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* Handle interruptions during waits. |
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*/ |
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private void onInterruptedWait() { |
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< |
Thread t = Thread.currentThread(); |
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< |
if (t instanceof ForkJoinWorkerThread) { |
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< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread)t; |
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if (w.isTerminating()) |
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cancelIgnoreExceptions(); |
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} |
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else { // re-interrupt |
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try { |
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t.interrupt(); |
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} catch (SecurityException ignore) { |
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} |
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} |
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> |
ForkJoinWorkerThread w = getWorker(); |
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if (w == null) |
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Thread.currentThread().interrupt(); // re-interrupt |
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else if (w.isTerminating()) |
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cancelIgnoringExceptions(); |
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// else if FJworker, ignore interrupt |
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} |
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|
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// Recording and reporting exceptions |
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/** |
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* Cancel, ignoring any exceptions it throws |
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*/ |
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< |
final void cancelIgnoreExceptions() { |
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> |
final void cancelIgnoringExceptions() { |
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try { |
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cancel(false); |
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} catch(Throwable ignore) { |
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} |
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} |
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|
459 |
+ |
/** |
460 |
+ |
* Main implementation of helpJoin |
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*/ |
462 |
+ |
private int busyJoin(ForkJoinWorkerThread w) { |
463 |
+ |
int s; |
464 |
+ |
ForkJoinTask<?> t; |
465 |
+ |
while ((s = status) >= 0 && (t = w.scanWhileJoining(this)) != null) |
466 |
+ |
t.quietlyExec(); |
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return (s >= 0)? awaitDone(w, false) : s; // block if no work |
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} |
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|
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// public methods |
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|
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/** |
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* Arranges to asynchronously execute this task. While it is not |
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* necessarily enforced, it is a usage error to fork a task more |
475 |
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* than once unless it has completed and been reinitialized. This |
476 |
< |
* method may be invoked only from within other ForkJoinTask |
476 |
> |
* method may be invoked only from within ForkJoinTask |
477 |
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* computations. Attempts to invoke in other contexts result in |
478 |
< |
* exceptions or errors including ClassCastException. |
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> |
* exceptions or errors possibly including ClassCastException. |
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*/ |
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public final void fork() { |
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((ForkJoinWorkerThread)(Thread.currentThread())).pushTask(this); |
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|
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/** |
485 |
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* Returns the result of the computation when it is ready. |
486 |
< |
* This method differs from <tt>get</tt> in that abnormal |
486 |
> |
* This method differs from <code>get</code> in that abnormal |
487 |
|
* completion results in RuntimeExceptions or Errors, not |
488 |
|
* ExecutionExceptions. |
489 |
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* |
496 |
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return getRawResult(); |
497 |
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} |
498 |
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|
483 |
– |
public final V get() throws InterruptedException, ExecutionException { |
484 |
– |
ForkJoinWorkerThread w = getWorker(); |
485 |
– |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
486 |
– |
awaitDone(w, true); |
487 |
– |
return reportFutureResult(); |
488 |
– |
} |
489 |
– |
|
490 |
– |
public final V get(long timeout, TimeUnit unit) |
491 |
– |
throws InterruptedException, ExecutionException, TimeoutException { |
492 |
– |
ForkJoinWorkerThread w = getWorker(); |
493 |
– |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
494 |
– |
awaitDone(w, unit.toNanos(timeout)); |
495 |
– |
return reportTimedFutureResult(); |
496 |
– |
} |
497 |
– |
|
499 |
|
/** |
500 |
< |
* Possibly executes other tasks until this task is ready, then |
501 |
< |
* returns the result of the computation. This method may be more |
501 |
< |
* efficient than <tt>join</tt>, but is only applicable when there |
502 |
< |
* are no potemtial dependencies between continuation of the |
503 |
< |
* current task and that of any other task that might be executed |
504 |
< |
* while helping. (This usually holds for pure divide-and-conquer |
505 |
< |
* tasks). |
506 |
< |
* @return the computed result |
507 |
< |
*/ |
508 |
< |
public final V helpJoin() { |
509 |
< |
ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread()); |
510 |
< |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
511 |
< |
reportException(w.helpJoinTask(this)); |
512 |
< |
return getRawResult(); |
513 |
< |
} |
514 |
< |
|
515 |
< |
/** |
516 |
< |
* Performs this task, awaits its completion if necessary, and |
517 |
< |
* return its result. |
500 |
> |
* Commences performing this task, awaits its completion if |
501 |
> |
* necessary, and return its result. |
502 |
|
* @throws Throwable (a RuntimeException, Error, or unchecked |
503 |
|
* exception) if the underlying computation did so. |
504 |
|
* @return the computed result |
511 |
|
} |
512 |
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|
513 |
|
/** |
514 |
< |
* Joins this task, without returning its result or throwing an |
515 |
< |
* exception. This method may be useful when processing |
516 |
< |
* collections of tasks when some have been cancelled or otherwise |
517 |
< |
* known to have aborted. |
514 |
> |
* Forks both tasks, returning when <code>isDone</code> holds for |
515 |
> |
* both of them or an exception is encountered. This method may be |
516 |
> |
* invoked only from within ForkJoinTask computations. Attempts to |
517 |
> |
* invoke in other contexts result in exceptions or errors |
518 |
> |
* possibly including ClassCastException. |
519 |
> |
* @param t1 one task |
520 |
> |
* @param t2 the other task |
521 |
> |
* @throws NullPointerException if t1 or t2 are null |
522 |
> |
* @throws RuntimeException or Error if either task did so. |
523 |
|
*/ |
524 |
< |
public final void quietlyJoin() { |
525 |
< |
if (status >= 0) { |
526 |
< |
ForkJoinWorkerThread w = getWorker(); |
527 |
< |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
539 |
< |
awaitDone(w, true); |
540 |
< |
} |
524 |
> |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
525 |
> |
t2.fork(); |
526 |
> |
t1.invoke(); |
527 |
> |
t2.join(); |
528 |
|
} |
529 |
|
|
530 |
|
/** |
531 |
< |
* Possibly executes other tasks until this task is ready. |
531 |
> |
* Forks the given tasks, returning when <code>isDone</code> holds |
532 |
> |
* for all of them. If any task encounters an exception, others |
533 |
> |
* may be cancelled. This method may be invoked only from within |
534 |
> |
* ForkJoinTask computations. Attempts to invoke in other contexts |
535 |
> |
* result in exceptions or errors possibly including ClassCastException. |
536 |
> |
* @param tasks the array of tasks |
537 |
> |
* @throws NullPointerException if tasks or any element are null. |
538 |
> |
* @throws RuntimeException or Error if any task did so. |
539 |
|
*/ |
540 |
< |
public final void quietlyHelpJoin() { |
541 |
< |
if (status >= 0) { |
542 |
< |
ForkJoinWorkerThread w = |
543 |
< |
(ForkJoinWorkerThread)(Thread.currentThread()); |
544 |
< |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
545 |
< |
w.helpJoinTask(this); |
540 |
> |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
541 |
> |
Throwable ex = null; |
542 |
> |
int last = tasks.length - 1; |
543 |
> |
for (int i = last; i >= 0; --i) { |
544 |
> |
ForkJoinTask<?> t = tasks[i]; |
545 |
> |
if (t == null) { |
546 |
> |
if (ex == null) |
547 |
> |
ex = new NullPointerException(); |
548 |
> |
} |
549 |
> |
else if (i != 0) |
550 |
> |
t.fork(); |
551 |
> |
else { |
552 |
> |
t.quietlyInvoke(); |
553 |
> |
if (ex == null) |
554 |
> |
ex = t.getException(); |
555 |
> |
} |
556 |
> |
} |
557 |
> |
for (int i = 1; i <= last; ++i) { |
558 |
> |
ForkJoinTask<?> t = tasks[i]; |
559 |
> |
if (t != null) { |
560 |
> |
if (ex != null) |
561 |
> |
t.cancel(false); |
562 |
> |
else { |
563 |
> |
t.quietlyJoin(); |
564 |
> |
if (ex == null) |
565 |
> |
ex = t.getException(); |
566 |
> |
} |
567 |
> |
} |
568 |
|
} |
569 |
+ |
if (ex != null) |
570 |
+ |
rethrowException(ex); |
571 |
|
} |
572 |
|
|
573 |
|
/** |
574 |
< |
* Performs this task and awaits its completion if necessary, |
575 |
< |
* without returning its result or throwing an exception. This |
576 |
< |
* method may be useful when processing collections of tasks when |
577 |
< |
* some have been cancelled or otherwise known to have aborted. |
574 |
> |
* Forks all tasks in the collection, returning when |
575 |
> |
* <code>isDone</code> holds for all of them. If any task |
576 |
> |
* encounters an exception, others may be cancelled. This method |
577 |
> |
* may be invoked only from within ForkJoinTask |
578 |
> |
* computations. Attempts to invoke in other contexts resul!t in |
579 |
> |
* exceptions or errors possibly including ClassCastException. |
580 |
> |
* @param tasks the collection of tasks |
581 |
> |
* @throws NullPointerException if tasks or any element are null. |
582 |
> |
* @throws RuntimeException or Error if any task did so. |
583 |
|
*/ |
584 |
< |
public final void quietlyInvoke() { |
585 |
< |
if (status >= 0 && !tryQuietlyInvoke()) |
586 |
< |
quietlyJoin(); |
584 |
> |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
585 |
> |
if (!(tasks instanceof List)) { |
586 |
> |
invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()])); |
587 |
> |
return; |
588 |
> |
} |
589 |
> |
List<? extends ForkJoinTask<?>> ts = |
590 |
> |
(List<? extends ForkJoinTask<?>>)tasks; |
591 |
> |
Throwable ex = null; |
592 |
> |
int last = ts.size() - 1; |
593 |
> |
for (int i = last; i >= 0; --i) { |
594 |
> |
ForkJoinTask<?> t = ts.get(i); |
595 |
> |
if (t == null) { |
596 |
> |
if (ex == null) |
597 |
> |
ex = new NullPointerException(); |
598 |
> |
} |
599 |
> |
else if (i != 0) |
600 |
> |
t.fork(); |
601 |
> |
else { |
602 |
> |
t.quietlyInvoke(); |
603 |
> |
if (ex == null) |
604 |
> |
ex = t.getException(); |
605 |
> |
} |
606 |
> |
} |
607 |
> |
for (int i = 1; i <= last; ++i) { |
608 |
> |
ForkJoinTask<?> t = ts.get(i); |
609 |
> |
if (t != null) { |
610 |
> |
if (ex != null) |
611 |
> |
t.cancel(false); |
612 |
> |
else { |
613 |
> |
t.quietlyJoin(); |
614 |
> |
if (ex == null) |
615 |
> |
ex = t.getException(); |
616 |
> |
} |
617 |
> |
} |
618 |
> |
} |
619 |
> |
if (ex != null) |
620 |
> |
rethrowException(ex); |
621 |
|
} |
622 |
|
|
623 |
|
/** |
638 |
|
} |
639 |
|
|
640 |
|
/** |
584 |
– |
* Returns true if this task threw an exception or was cancelled |
585 |
– |
* @return true if this task threw an exception or was cancelled |
586 |
– |
*/ |
587 |
– |
public final boolean completedAbnormally() { |
588 |
– |
return (status & COMPLETION_MASK) < NORMAL; |
589 |
– |
} |
590 |
– |
|
591 |
– |
/** |
592 |
– |
* Returns the exception thrown by the base computation, or a |
593 |
– |
* CancellationException if cancelled, or null if none or if the |
594 |
– |
* method has not yet completed. |
595 |
– |
* @return the exception, or null if none |
596 |
– |
*/ |
597 |
– |
public final Throwable getException() { |
598 |
– |
int s = status & COMPLETION_MASK; |
599 |
– |
if (s >= NORMAL) |
600 |
– |
return null; |
601 |
– |
if (s == CANCELLED) |
602 |
– |
return new CancellationException(); |
603 |
– |
return exceptionMap.get(this); |
604 |
– |
} |
605 |
– |
|
606 |
– |
/** |
641 |
|
* Asserts that the results of this task's computation will not be |
642 |
< |
* used. If a cancellation occurs before this task is processed, |
643 |
< |
* then its <tt>compute</tt> method will not be executed, |
644 |
< |
* <tt>isCancelled</tt> will report true, and <tt>join</tt> will |
645 |
< |
* result in a CancellationException being thrown. Otherwise, when |
642 |
> |
* used. If a cancellation occurs before atempting to execute this |
643 |
> |
* task, then execution will be suppressed, <code>isCancelled</code> |
644 |
> |
* will report true, and <code>join</code> will result in a |
645 |
> |
* <code>CancellationException</code> being thrown. Otherwise, when |
646 |
|
* cancellation races with completion, there are no guarantees |
647 |
< |
* about whether <tt>isCancelled</tt> will report true, whether |
648 |
< |
* <tt>join</tt> will return normally or via an exception, or |
647 |
> |
* about whether <code>isCancelled</code> will report true, whether |
648 |
> |
* <code>join</code> will return normally or via an exception, or |
649 |
|
* whether these behaviors will remain consistent upon repeated |
650 |
|
* invocation. |
651 |
|
* |
656 |
|
* <p> This method is designed to be invoked by <em>other</em> |
657 |
|
* tasks. To terminate the current task, you can just return or |
658 |
|
* throw an unchecked exception from its computation method, or |
659 |
< |
* invoke <tt>completeExceptionally(someException)</tt>. |
659 |
> |
* invoke <code>completeExceptionally</code>. |
660 |
|
* |
661 |
|
* @param mayInterruptIfRunning this value is ignored in the |
662 |
|
* default implementation because tasks are not in general |
670 |
|
} |
671 |
|
|
672 |
|
/** |
673 |
+ |
* Returns true if this task threw an exception or was cancelled |
674 |
+ |
* @return true if this task threw an exception or was cancelled |
675 |
+ |
*/ |
676 |
+ |
public final boolean isCompletedAbnormally() { |
677 |
+ |
return (status & COMPLETION_MASK) < NORMAL; |
678 |
+ |
} |
679 |
+ |
|
680 |
+ |
/** |
681 |
+ |
* Returns the exception thrown by the base computation, or a |
682 |
+ |
* CancellationException if cancelled, or null if none or if the |
683 |
+ |
* method has not yet completed. |
684 |
+ |
* @return the exception, or null if none |
685 |
+ |
*/ |
686 |
+ |
public final Throwable getException() { |
687 |
+ |
int s = status & COMPLETION_MASK; |
688 |
+ |
if (s >= NORMAL) |
689 |
+ |
return null; |
690 |
+ |
if (s == CANCELLED) |
691 |
+ |
return new CancellationException(); |
692 |
+ |
return exceptionMap.get(this); |
693 |
+ |
} |
694 |
+ |
|
695 |
+ |
/** |
696 |
|
* Completes this task abnormally, and if not already aborted or |
697 |
|
* cancelled, causes it to throw the given exception upon |
698 |
< |
* <tt>join</tt> and related operations. This method may be used |
698 |
> |
* <code>join</code> and related operations. This method may be used |
699 |
|
* to induce exceptions in asynchronous tasks, or to force |
700 |
< |
* completion of tasks that would not otherwise complete. This |
701 |
< |
* method is overridable, but overridden versions must invoke |
702 |
< |
* <tt>super</tt> implementation to maintain guarantees. |
700 |
> |
* completion of tasks that would not otherwise complete. Its use |
701 |
> |
* in other situations is likely to be wrong. This method is |
702 |
> |
* overridable, but overridden versions must invoke <code>super</code> |
703 |
> |
* implementation to maintain guarantees. |
704 |
> |
* |
705 |
|
* @param ex the exception to throw. If this exception is |
706 |
|
* not a RuntimeException or Error, the actual exception thrown |
707 |
|
* will be a RuntimeException with cause ex. |
714 |
|
|
715 |
|
/** |
716 |
|
* Completes this task, and if not already aborted or cancelled, |
717 |
< |
* returning a <tt>null</tt> result upon <tt>join</tt> and related |
717 |
> |
* returning a <code>null</code> result upon <code>join</code> and related |
718 |
|
* operations. This method may be used to provide results for |
719 |
|
* asynchronous tasks, or to provide alternative handling for |
720 |
< |
* tasks that would not otherwise complete normally. |
720 |
> |
* tasks that would not otherwise complete normally. Its use in |
721 |
> |
* other situations is likely to be wrong. This method is |
722 |
> |
* overridable, but overridden versions must invoke <code>super</code> |
723 |
> |
* implementation to maintain guarantees. |
724 |
|
* |
725 |
|
* @param value the result value for this task. |
726 |
|
*/ |
734 |
|
setNormalCompletion(); |
735 |
|
} |
736 |
|
|
737 |
< |
/** |
738 |
< |
* Resets the internal bookkeeping state of this task, allowing a |
739 |
< |
* subsequent <tt>fork</tt>. This method allows repeated reuse of |
740 |
< |
* this task, but only if reuse occurs when this task has either |
741 |
< |
* never been forked, or has been forked, then completed and all |
742 |
< |
* outstanding joins of this task have also completed. Effects |
743 |
< |
* under any other usage conditions are not guaranteed, and are |
744 |
< |
* almost surely wrong. This method may be useful when executing |
745 |
< |
* pre-constructed trees of subtasks in loops. |
746 |
< |
*/ |
747 |
< |
public void reinitialize() { |
748 |
< |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
749 |
< |
exceptionMap.remove(this); |
688 |
< |
status = 0; |
737 |
> |
public final V get() throws InterruptedException, ExecutionException { |
738 |
> |
ForkJoinWorkerThread w = getWorker(); |
739 |
> |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
740 |
> |
awaitDone(w, true); |
741 |
> |
return reportFutureResult(); |
742 |
> |
} |
743 |
> |
|
744 |
> |
public final V get(long timeout, TimeUnit unit) |
745 |
> |
throws InterruptedException, ExecutionException, TimeoutException { |
746 |
> |
ForkJoinWorkerThread w = getWorker(); |
747 |
> |
if (w == null || status < 0 || !w.unpushTask(this) || !tryQuietlyInvoke()) |
748 |
> |
awaitDone(w, unit.toNanos(timeout)); |
749 |
> |
return reportTimedFutureResult(); |
750 |
|
} |
751 |
|
|
752 |
|
/** |
753 |
< |
* Tries to unschedule this task for execution. This method will |
754 |
< |
* typically succeed if this task is the next task that would be |
755 |
< |
* executed by the current thread, and will typically fail (return |
756 |
< |
* false) otherwise. This method may be useful when arranging |
757 |
< |
* faster local processing of tasks that could have been, but were |
758 |
< |
* not, stolen. |
759 |
< |
* @return true if unforked |
753 |
> |
* Possibly executes other tasks until this task is ready, then |
754 |
> |
* returns the result of the computation. This method may be more |
755 |
> |
* efficient than <code>join</code>, but is only applicable when |
756 |
> |
* there are no potemtial dependencies between continuation of the |
757 |
> |
* current task and that of any other task that might be executed |
758 |
> |
* while helping. (This usually holds for pure divide-and-conquer |
759 |
> |
* tasks). This method may be invoked only from within |
760 |
> |
* ForkJoinTask computations. Attempts to invoke in other contexts |
761 |
> |
* resul!t in exceptions or errors possibly including ClassCastException. |
762 |
> |
* @return the computed result |
763 |
|
*/ |
764 |
< |
public boolean tryUnfork() { |
765 |
< |
return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this); |
764 |
> |
public final V helpJoin() { |
765 |
> |
ForkJoinWorkerThread w = (ForkJoinWorkerThread)(Thread.currentThread()); |
766 |
> |
if (status < 0 || !w.unpushTask(this) || !tryExec()) |
767 |
> |
reportException(busyJoin(w)); |
768 |
> |
return getRawResult(); |
769 |
|
} |
770 |
|
|
771 |
|
/** |
772 |
< |
* Forks both tasks, returning when <tt>isDone</tt> holds for both |
773 |
< |
* of them or an exception is encountered. This method may be |
774 |
< |
* invoked only from within other ForkJoinTask |
775 |
< |
* computations. Attempts to invoke in other contexts result in |
709 |
< |
* exceptions or errors including ClassCastException. |
710 |
< |
* @param t1 one task |
711 |
< |
* @param t2 the other task |
712 |
< |
* @throws NullPointerException if t1 or t2 are null |
713 |
< |
* @throws RuntimeException or Error if either task did so. |
772 |
> |
* Possibly executes other tasks until this task is ready. This |
773 |
> |
* method may be invoked only from within ForkJoinTask |
774 |
> |
* computations. Attempts to invoke in other contexts resul!t in |
775 |
> |
* exceptions or errors possibly including ClassCastException. |
776 |
|
*/ |
777 |
< |
public static void invokeAll(ForkJoinTask<?>t1, ForkJoinTask<?> t2) { |
778 |
< |
t2.fork(); |
779 |
< |
t1.invoke(); |
780 |
< |
t2.join(); |
777 |
> |
public final void quietlyHelpJoin() { |
778 |
> |
if (status >= 0) { |
779 |
> |
ForkJoinWorkerThread w = |
780 |
> |
(ForkJoinWorkerThread)(Thread.currentThread()); |
781 |
> |
if (!w.unpushTask(this) || !tryQuietlyInvoke()) |
782 |
> |
busyJoin(w); |
783 |
> |
} |
784 |
|
} |
785 |
|
|
786 |
|
/** |
787 |
< |
* Forks the given tasks, returning when <tt>isDone</tt> holds for |
788 |
< |
* all of them. If any task encounters an exception, others may be |
789 |
< |
* cancelled. This method may be invoked only from within other |
790 |
< |
* ForkJoinTask computations. Attempts to invoke in other contexts |
726 |
< |
* result in exceptions or errors including ClassCastException. |
727 |
< |
* @param tasks the array of tasks |
728 |
< |
* @throws NullPointerException if tasks or any element are null. |
729 |
< |
* @throws RuntimeException or Error if any task did so. |
787 |
> |
* Joins this task, without returning its result or throwing an |
788 |
> |
* exception. This method may be useful when processing |
789 |
> |
* collections of tasks when some have been cancelled or otherwise |
790 |
> |
* known to have aborted. |
791 |
|
*/ |
792 |
< |
public static void invokeAll(ForkJoinTask<?>... tasks) { |
793 |
< |
Throwable ex = null; |
794 |
< |
int last = tasks.length - 1; |
795 |
< |
for (int i = last; i >= 0; --i) { |
796 |
< |
ForkJoinTask<?> t = tasks[i]; |
736 |
< |
if (t == null) { |
737 |
< |
if (ex == null) |
738 |
< |
ex = new NullPointerException(); |
739 |
< |
} |
740 |
< |
else if (i != 0) |
741 |
< |
t.fork(); |
742 |
< |
else { |
743 |
< |
t.quietlyInvoke(); |
744 |
< |
if (ex == null) |
745 |
< |
ex = t.getException(); |
746 |
< |
} |
747 |
< |
} |
748 |
< |
for (int i = 1; i <= last; ++i) { |
749 |
< |
ForkJoinTask<?> t = tasks[i]; |
750 |
< |
if (t != null) { |
751 |
< |
if (ex != null) |
752 |
< |
t.cancel(false); |
753 |
< |
else { |
754 |
< |
t.quietlyJoin(); |
755 |
< |
if (ex == null) |
756 |
< |
ex = t.getException(); |
757 |
< |
} |
758 |
< |
} |
792 |
> |
public final void quietlyJoin() { |
793 |
> |
if (status >= 0) { |
794 |
> |
ForkJoinWorkerThread w = getWorker(); |
795 |
> |
if (w == null || !w.unpushTask(this) || !tryQuietlyInvoke()) |
796 |
> |
awaitDone(w, true); |
797 |
|
} |
760 |
– |
if (ex != null) |
761 |
– |
rethrowException(ex); |
798 |
|
} |
799 |
|
|
800 |
|
/** |
801 |
< |
* Forks all tasks in the collection, returning when |
802 |
< |
* <tt>isDone</tt> holds for all of them. If any task encounters |
803 |
< |
* an exception, others may be cancelled. This method may be |
804 |
< |
* invoked only from within other ForkJoinTask |
805 |
< |
* computations. Attempts to invoke in other contexts result in |
770 |
< |
* exceptions or errors including ClassCastException. |
771 |
< |
* @param tasks the collection of tasks |
772 |
< |
* @throws NullPointerException if tasks or any element are null. |
773 |
< |
* @throws RuntimeException or Error if any task did so. |
801 |
> |
* Commences performing this task and awaits its completion if |
802 |
> |
* necessary, without returning its result or throwing an |
803 |
> |
* exception. This method may be useful when processing |
804 |
> |
* collections of tasks when some have been cancelled or otherwise |
805 |
> |
* known to have aborted. |
806 |
|
*/ |
807 |
< |
public static void invokeAll(Collection<? extends ForkJoinTask<?>> tasks) { |
808 |
< |
if (!(tasks instanceof List)) { |
809 |
< |
invokeAll(tasks.toArray(new ForkJoinTask[tasks.size()])); |
778 |
< |
return; |
779 |
< |
} |
780 |
< |
List<? extends ForkJoinTask<?>> ts = |
781 |
< |
(List<? extends ForkJoinTask<?>>)tasks; |
782 |
< |
Throwable ex = null; |
783 |
< |
int last = ts.size() - 1; |
784 |
< |
for (int i = last; i >= 0; --i) { |
785 |
< |
ForkJoinTask<?> t = ts.get(i); |
786 |
< |
if (t == null) { |
787 |
< |
if (ex == null) |
788 |
< |
ex = new NullPointerException(); |
789 |
< |
} |
790 |
< |
else if (i != 0) |
791 |
< |
t.fork(); |
792 |
< |
else { |
793 |
< |
t.quietlyInvoke(); |
794 |
< |
if (ex == null) |
795 |
< |
ex = t.getException(); |
796 |
< |
} |
797 |
< |
} |
798 |
< |
for (int i = 1; i <= last; ++i) { |
799 |
< |
ForkJoinTask<?> t = ts.get(i); |
800 |
< |
if (t != null) { |
801 |
< |
if (ex != null) |
802 |
< |
t.cancel(false); |
803 |
< |
else { |
804 |
< |
t.quietlyJoin(); |
805 |
< |
if (ex == null) |
806 |
< |
ex = t.getException(); |
807 |
< |
} |
808 |
< |
} |
809 |
< |
} |
810 |
< |
if (ex != null) |
811 |
< |
rethrowException(ex); |
807 |
> |
public final void quietlyInvoke() { |
808 |
> |
if (status >= 0 && !tryQuietlyInvoke()) |
809 |
> |
quietlyJoin(); |
810 |
|
} |
811 |
|
|
812 |
|
/** |
821 |
|
} |
822 |
|
|
823 |
|
/** |
824 |
+ |
* Resets the internal bookkeeping state of this task, allowing a |
825 |
+ |
* subsequent <code>fork</code>. This method allows repeated reuse of |
826 |
+ |
* this task, but only if reuse occurs when this task has either |
827 |
+ |
* never been forked, or has been forked, then completed and all |
828 |
+ |
* outstanding joins of this task have also completed. Effects |
829 |
+ |
* under any other usage conditions are not guaranteed, and are |
830 |
+ |
* almost surely wrong. This method may be useful when executing |
831 |
+ |
* pre-constructed trees of subtasks in loops. |
832 |
+ |
*/ |
833 |
+ |
public void reinitialize() { |
834 |
+ |
if ((status & COMPLETION_MASK) == EXCEPTIONAL) |
835 |
+ |
exceptionMap.remove(this); |
836 |
+ |
status = 0; |
837 |
+ |
} |
838 |
+ |
|
839 |
+ |
/** |
840 |
+ |
* Returns the pool hosting the current task execution, or null |
841 |
+ |
* if this task is executing outside of any pool. |
842 |
+ |
* @return the pool, or null if none. |
843 |
+ |
*/ |
844 |
+ |
public static ForkJoinPool getPool() { |
845 |
+ |
Thread t = Thread.currentThread(); |
846 |
+ |
return ((t instanceof ForkJoinWorkerThread)? |
847 |
+ |
((ForkJoinWorkerThread)t).pool : null); |
848 |
+ |
} |
849 |
+ |
|
850 |
+ |
/** |
851 |
+ |
* Tries to unschedule this task for execution. This method will |
852 |
+ |
* typically succeed if this task is the most recently forked task |
853 |
+ |
* by the current thread, and has not commenced executing in |
854 |
+ |
* another thread. This method may be useful when arranging |
855 |
+ |
* alternative local processing of tasks that could have been, but |
856 |
+ |
* were not, stolen. This method may be invoked only from within |
857 |
+ |
* ForkJoinTask computations. Attempts to invoke in other contexts |
858 |
+ |
* result in exceptions or errors possibly including ClassCastException. |
859 |
+ |
* @return true if unforked |
860 |
+ |
*/ |
861 |
+ |
public boolean tryUnfork() { |
862 |
+ |
return ((ForkJoinWorkerThread)(Thread.currentThread())).unpushTask(this); |
863 |
+ |
} |
864 |
+ |
|
865 |
+ |
/** |
866 |
+ |
* Returns an estimate of the number of tasks that have been |
867 |
+ |
* forked by the current worker thread but not yet executed. This |
868 |
+ |
* value may be useful for heuristic decisions about whether to |
869 |
+ |
* fork other tasks. |
870 |
+ |
* @return the number of tasks |
871 |
+ |
*/ |
872 |
+ |
public static int getQueuedTaskCount() { |
873 |
+ |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
874 |
+ |
getQueueSize(); |
875 |
+ |
} |
876 |
+ |
|
877 |
+ |
/** |
878 |
|
* Returns a estimate of how many more locally queued tasks are |
879 |
|
* held by the current worker thread than there are other worker |
880 |
< |
* threads that might want to steal them. This value may be |
881 |
< |
* useful for heuristic decisions about whether to fork other |
882 |
< |
* tasks. In many usages of ForkJoinTasks, at steady state, each |
883 |
< |
* worker should aim to maintain a small constant surplus (for |
884 |
< |
* example, 3) of tasks, and to process computations locally if |
885 |
< |
* this threshold is exceeded. |
880 |
> |
* threads that might steal them. This value may be useful for |
881 |
> |
* heuristic decisions about whether to fork other tasks. In many |
882 |
> |
* usages of ForkJoinTasks, at steady state, each worker should |
883 |
> |
* aim to maintain a small constant surplus (for example, 3) of |
884 |
> |
* tasks, and to process computations locally if this threshold is |
885 |
> |
* exceeded. |
886 |
|
* @return the surplus number of tasks, which may be negative |
887 |
|
*/ |
888 |
< |
public static int surplus() { |
888 |
> |
public static int getSurplusQueuedTaskCount() { |
889 |
|
return ((ForkJoinWorkerThread)(Thread.currentThread())) |
890 |
|
.getEstimatedSurplusTaskCount(); |
891 |
|
} |
892 |
|
|
893 |
< |
// Extension kit |
893 |
> |
// Extension methods |
894 |
|
|
895 |
|
/** |
896 |
< |
* Returns the result that would be returned by <tt>join</tt>, or |
897 |
< |
* null if this task is not known to have been completed. This |
898 |
< |
* method is designed to aid debugging, as well as to support |
899 |
< |
* extensions. Its use in any other context is discouraged. |
896 |
> |
* Returns the result that would be returned by <code>join</code>, |
897 |
> |
* even if this task completed abnormally, or null if this task is |
898 |
> |
* not known to have been completed. This method is designed to |
899 |
> |
* aid debugging, as well as to support extensions. Its use in any |
900 |
> |
* other context is discouraged. |
901 |
|
* |
902 |
|
* @return the result, or null if not completed. |
903 |
|
*/ |
918 |
|
* called otherwise. The return value controls whether this task |
919 |
|
* is considered to be done normally. It may return false in |
920 |
|
* asynchronous actions that require explicit invocations of |
921 |
< |
* <tt>complete</tt> to become joinable. It may throw exceptions |
921 |
> |
* <code>complete</code> to become joinable. It may throw exceptions |
922 |
|
* to indicate abnormal exit. |
923 |
|
* @return true if completed normally |
924 |
|
* @throws Error or RuntimeException if encountered during computation |
925 |
|
*/ |
926 |
|
protected abstract boolean exec(); |
927 |
|
|
928 |
+ |
/** |
929 |
+ |
* Returns, but does not unschedule or execute, the task most |
930 |
+ |
* recently forked by the current thread but not yet executed, if |
931 |
+ |
* one is available. There is no guarantee that this task will |
932 |
+ |
* actually be polled or executed next. |
933 |
+ |
* This method is designed primarily to support extensions, |
934 |
+ |
* and is unlikely to be useful otherwise. |
935 |
+ |
* This method may be invoked only from within |
936 |
+ |
* ForkJoinTask computations. Attempts to invoke in other contexts |
937 |
+ |
* result in exceptions or errors possibly including ClassCastException. |
938 |
+ |
* |
939 |
+ |
* @return the next task, or null if none are available |
940 |
+ |
*/ |
941 |
+ |
protected static ForkJoinTask<?> peekNextLocalTask() { |
942 |
+ |
return ((ForkJoinWorkerThread)(Thread.currentThread())).peekTask(); |
943 |
+ |
} |
944 |
+ |
|
945 |
+ |
/** |
946 |
+ |
* Unschedules and returns, without executing, the task most |
947 |
+ |
* recently forked by the current thread but not yet executed. |
948 |
+ |
* This method is designed primarily to support extensions, |
949 |
+ |
* and is unlikely to be useful otherwise. |
950 |
+ |
* This method may be invoked only from within |
951 |
+ |
* ForkJoinTask computations. Attempts to invoke in other contexts |
952 |
+ |
* result in exceptions or errors possibly including ClassCastException. |
953 |
+ |
* |
954 |
+ |
* @return the next task, or null if none are available |
955 |
+ |
*/ |
956 |
+ |
protected static ForkJoinTask<?> pollNextLocalTask() { |
957 |
+ |
return ((ForkJoinWorkerThread)(Thread.currentThread())).popTask(); |
958 |
+ |
} |
959 |
+ |
|
960 |
+ |
/** |
961 |
+ |
* Unschedules and returns, without executing, the task most |
962 |
+ |
* recently forked by the current thread but not yet executed, if |
963 |
+ |
* one is available, or if not available, a task that was forked |
964 |
+ |
* by some other thread, if available. Availability may be |
965 |
+ |
* transient, so a <code>null</code> result does not necessarily |
966 |
+ |
* imply quiecence of the pool this task is operating in. |
967 |
+ |
* This method is designed primarily to support extensions, |
968 |
+ |
* and is unlikely to be useful otherwise. |
969 |
+ |
* This method may be invoked only from within |
970 |
+ |
* ForkJoinTask computations. Attempts to invoke in other contexts |
971 |
+ |
* result in exceptions or errors possibly including ClassCastException. |
972 |
+ |
* |
973 |
+ |
* @return a task, or null if none are available |
974 |
+ |
*/ |
975 |
+ |
protected static ForkJoinTask<?> pollTask() { |
976 |
+ |
return ((ForkJoinWorkerThread)(Thread.currentThread())). |
977 |
+ |
pollTask(); |
978 |
+ |
} |
979 |
+ |
|
980 |
|
// Serialization support |
981 |
|
|
982 |
|
private static final long serialVersionUID = -7721805057305804111L; |
1001 |
|
private void readObject(java.io.ObjectInputStream s) |
1002 |
|
throws java.io.IOException, ClassNotFoundException { |
1003 |
|
s.defaultReadObject(); |
1004 |
< |
// status &= ~INTERNAL_SIGNAL_MASK; // todo: define policy |
1004 |
> |
status &= ~INTERNAL_SIGNAL_MASK; // clear internal signal counts |
1005 |
> |
status |= EXTERNAL_SIGNAL; // conservatively set external signal |
1006 |
|
Object ex = s.readObject(); |
1007 |
|
if (ex != null) |
1008 |
|
setDoneExceptionally((Throwable)ex); |