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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166e; |
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/** |
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* A {@link ForkJoinTask} with a completion action performed when |
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* triggered and there are no remaining pending |
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* actions. CountedCompleters are in general more robust in the |
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* presence of subtask stalls and blockage than are other forms for |
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* ForkJoinTasks, but are in general less intuitive to program. Uses |
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* of CountedCompleter are similar to those of other completion based |
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* components (such as {@link java.nio.channels.CompletionHandler}) |
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* except that multiple <em>pending</em> completions may be necessary |
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* to trigger the {@link #onCompletion} action, not just one. Unless |
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* initialized otherwise, the {@link #getPendingCount pending count} |
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* starts at zero, but may be (atomically) changed using methods |
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* {@link #setPendingCount}, {@link #addToPendingCount}, and {@link |
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* #compareAndSetPendingCount}. Upon invocation of {@link |
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* #tryComplete}, if the pending action count is nonzero, it is |
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* decremented; otherwise, the completion action is performed, and if |
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* this completer itself has a completer, the process is continued |
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* with its completer. As is the case with related synchronization |
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* components such as {@link java.util.concurrent.Phaser Phaser} and |
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* {@link java.util.concurrent.Semaphore Semaphore}, these methods |
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* affect only internal counts; they do not establish any further |
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* internal bookkeeping. In particular, the identities of pending |
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* tasks are not maintained. As illustrated below, you can create |
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* subclasses that do record some or all pending tasks or their |
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* results when needed. Because CountedCompleters provide only basic |
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* synchronization mechanisms, it may be useful to create further |
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* abstract subclasses that maintain linkages and fields and support |
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* methods appropriate for a set of related usages. |
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* |
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* <p>A concrete CountedCompleter class must define method {@link |
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1.13 |
* #compute}, that should in most cases (as illustrated below), invoke |
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* {@code tryComplete()} once before returning. The class may also |
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* optionally override method {@link #onCompletion} to perform an |
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* action upon normal completion, and method {@link |
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* #onExceptionalCompletion} to perform an action upon any exception. |
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* |
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* <p>CountedCompleters most often do not bear results, in which case |
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* they are normally declared as {@code CountedCompleter<Void>}, and |
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* will always return {@code null} as a result value. In other cases, |
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* you should override method {@link #getRawResult} to provide a |
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* result from {@code join(), invoke()}, and related methods. In |
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* general, this method should return the value of a field (or a |
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* function of one or more fields) of the CountedCompleter object that |
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* holds the result upon completion. Method {@link #setRawResult} by |
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* default plays no role in CountedCompleters. It is possible, but |
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* not usually applicable, to override this method to maintain other |
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* objects or fields holding result data. |
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1.2 |
* |
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* <p>A CountedCompleter that does not itself have a completer (i.e., |
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* one for which {@link #getCompleter} returns {@code null}) can be |
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* used as a regular ForkJoinTask with this added functionality. |
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* However, any completer that in turn has another completer serves |
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* only as an internal helper for other computations, so its own task |
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* status (as reported in methods such as {@link ForkJoinTask#isDone}) |
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* is arbitrary; this status changes only upon explicit invocations of |
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* {@link #complete}, {@link ForkJoinTask#cancel}, {@link |
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* ForkJoinTask#completeExceptionally} or upon exceptional completion |
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* of method {@code compute}. Upon any exceptional completion, the |
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* exception may be relayed to a task's completer (and its completer, |
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* and so on), if one exists and it has not otherwise already |
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* completed. Similarly, cancelling an internal CountedCompleter has |
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* only a local effect on that completer, so is not often useful. |
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* |
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* <p><b>Sample Usages.</b> |
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* |
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* <p><b>Parallel recursive decomposition.</b> CountedCompleters may |
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* be arranged in trees similar to those often used with {@link |
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* RecursiveAction}s, although the constructions involved in setting |
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* them up typically vary. Here, the completer of each task is its |
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* parent in the computation tree. Even though they entail a bit more |
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1.1 |
* bookkeeping, CountedCompleters may be better choices when applying |
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* a possibly time-consuming operation (that cannot be further |
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* subdivided) to each element of an array or collection; especially |
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* when the operation takes a significantly different amount of time |
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* to complete for some elements than others, either because of |
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* intrinsic variation (for example IO) or auxiliary effects such as |
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* garbage collection. Because CountedCompleters provide their own |
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* continuations, other threads need not block waiting to perform |
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* them. |
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* |
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1.12 |
* <p>For example, here is an initial version of a class that uses |
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* divide-by-two recursive decomposition to divide work into single |
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* pieces (leaf tasks). Even when work is split into individual calls, |
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* tree-based techniques are usually preferable to directly forking |
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* leaf tasks, because they reduce inter-thread communication and |
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* improve load balancing. In the recursive case, the second of each |
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* pair of subtasks to finish triggers completion of its parent |
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* (because no result combination is performed, the default no-op |
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* implementation of method {@code onCompletion} is not overridden). A |
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* static utility method sets up the base task and invokes it |
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* (here, implicitly using the {@link ForkJoinPool#commonPool()}). |
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* |
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* <pre> {@code |
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* class MyOperation<E> { void apply(E e) { ... } } |
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* |
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* class ForEach<E> extends CountedCompleter<Void> { |
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* |
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* public static <E> void forEach(E[] array, MyOperation<E> op) { |
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* new ForEach<E>(null, array, op, 0, array.length).invoke(); |
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* } |
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* |
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* final E[] array; final MyOperation<E> op; final int lo, hi; |
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* ForEach(CountedCompleter<?> p, E[] array, MyOperation<E> op, int lo, int hi) { |
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1.1 |
* super(p); |
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* this.array = array; this.op = op; this.lo = lo; this.hi = hi; |
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* } |
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* |
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* public void compute() { // version 1 |
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* if (hi - lo >= 2) { |
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* int mid = (lo + hi) >>> 1; |
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* setPendingCount(2); // must set pending count before fork |
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* new ForEach(this, array, op, mid, hi).fork(); // right child |
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* new ForEach(this, array, op, lo, mid).fork(); // left child |
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* } |
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* else if (hi > lo) |
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* op.apply(array[lo]); |
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* tryComplete(); |
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* } |
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* } }</pre> |
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* |
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* This design can be improved by noticing that in the recursive case, |
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* the task has nothing to do after forking its right task, so can |
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* directly invoke its left task before returning. (This is an analog |
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* of tail recursion removal.) Also, because the task returns upon |
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* executing its left task (rather than falling through to invoke |
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* tryComplete) the pending count is set to one: |
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* |
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* <pre> {@code |
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* class ForEach<E> ... |
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* public void compute() { // version 2 |
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* if (hi - lo >= 2) { |
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* int mid = (lo + hi) >>> 1; |
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* setPendingCount(1); // only one pending |
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* new ForEach(this, array, op, mid, hi).fork(); // right child |
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* new ForEach(this, array, op, lo, mid).compute(); // direct invoke |
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* } |
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* else { |
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* if (hi > lo) |
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* op.apply(array[lo]); |
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* tryComplete(); |
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* } |
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* } |
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* }</pre> |
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* |
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* As a further improvement, notice that the left task need not even |
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* exist. Instead of creating a new one, we can iterate using the |
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jsr166 |
1.10 |
* original task, and add a pending count for each fork. |
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1.1 |
* |
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* <pre> {@code |
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* class ForEach<E> ... |
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* public void compute() { // version 3 |
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* int l = lo, h = hi; |
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* while (h - l >= 2) { |
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* int mid = (l + h) >>> 1; |
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* addToPendingCount(1); |
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* new ForEach(this, array, op, mid, h).fork(); // right child |
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* h = mid; |
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* } |
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* if (h > l) |
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* op.apply(array[l]); |
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* tryComplete(); |
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* } |
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* }</pre> |
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* |
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* Additional improvements of such classes might entail precomputing |
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* pending counts so that they can be established in constructors, |
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* specializing classes for leaf steps, subdividing by say, four, |
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* instead of two per iteration, and using an adaptive threshold |
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* instead of always subdividing down to single elements. |
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* |
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* <p><b>Recording subtasks.</b> CountedCompleter tasks that combine |
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* results of multiple subtasks usually need to access these results |
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* in method {@link #onCompletion}. As illustrated in the following |
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* class (that performs a simplified form of map-reduce where mappings |
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* and reductions are all of type {@code E}), one way to do this in |
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* divide and conquer designs is to have each subtask record its |
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* sibling, so that it can be accessed in method {@code onCompletion}. |
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1.2 |
* This technique applies to reductions in which the order of |
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* combining left and right results does not matter; ordered |
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* reductions require explicit left/right designations. Variants of |
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* other streamlinings seen in the above examples may also apply. |
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1.1 |
* |
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* <pre> {@code |
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* class MyMapper<E> { E apply(E v) { ... } } |
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* class MyReducer<E> { E apply(E x, E y) { ... } } |
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1.2 |
* class MapReducer<E> extends CountedCompleter<E> { |
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1.1 |
* final E[] array; final MyMapper<E> mapper; |
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* final MyReducer<E> reducer; final int lo, hi; |
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1.2 |
* MapReducer<E> sibling; |
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1.1 |
* E result; |
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* MapReducer(CountedCompleter p, E[] array, MyMapper<E> mapper, |
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* MyReducer<E> reducer, int lo, int hi) { |
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* super(p); |
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* this.array = array; this.mapper = mapper; |
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* this.reducer = reducer; this.lo = lo; this.hi = hi; |
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* } |
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* public void compute() { |
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* if (hi - lo >= 2) { |
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* int mid = (lo + hi) >>> 1; |
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* MapReducer<E> left = new MapReducer(this, array, mapper, reducer, lo, mid); |
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* MapReducer<E> right = new MapReducer(this, array, mapper, reducer, mid, hi); |
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* left.sibling = right; |
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* right.sibling = left; |
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* setPendingCount(1); // only right is pending |
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* right.fork(); |
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* left.compute(); // directly execute left |
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* } |
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* else { |
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* if (hi > lo) |
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* result = mapper.apply(array[lo]); |
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* tryComplete(); |
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* } |
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* } |
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* public void onCompletion(CountedCompleter caller) { |
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* if (caller != this) { |
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* MapReducer<E> child = (MapReducer<E>)caller; |
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* MapReducer<E> sib = child.sibling; |
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* if (sib == null || sib.result == null) |
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* result = child.result; |
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* else |
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* result = reducer.apply(child.result, sib.result); |
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* } |
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* } |
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1.2 |
* public E getRawResult() { return result; } |
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1.1 |
* |
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1.13 |
* public static <E> E mapReduce(E[] array, MyMapper<E> mapper, MyReducer<E> reducer) { |
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* return new MapReducer<E>(null, array, mapper, reducer, |
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* 0, array.length).invoke(); |
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1.1 |
* } |
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* } }</pre> |
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* |
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1.13 |
* Here, method {@code onCompletion} takes a form common to many |
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* completion designs that combine results. This callback-style method |
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* is triggered once per task, in either of the two different contexts |
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* in which the pending count is, or becomes, zero: (1) by a task |
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* itself, if its pending count is zero upon invocation of {@code |
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* tryComplete}, or (2) by any of its subtasks when they complete and |
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* decrement the pending count to zero. The {@code caller} argument |
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* distinguishes cases. Most often, when the caller is {@code this}, |
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* no action is necessary. Otherwise the caller argument can be used |
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* (usually via a cast) to supply a value (and/or links to other |
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* values) to be combined. Asuuming proper use of pending counts, the |
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* actions inside {@code onCompletion} occur (once) upon completion of |
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* a task and its subtasks. No additional synchronization is required |
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* within this method to ensure thread safety of accesses to fields of |
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* this task or other completed tasks. |
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* |
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* <p><b>Searching.</b> A tree of CountedCompleters can search for a |
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* value or property in different parts of a data structure, and |
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* report a result in an {@link java.util.concurrent.AtomicReference} |
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* as soon as one is found. The others can poll the result to avoid |
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* unnecessary work. (You could additionally {@link #cancel} other |
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* tasks, but it is usually simpler and more efficient to just let |
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* them notice that the result is set and if so skip further |
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* processing.) Illustrating again with an array using full |
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* partitioning (again, in practice, leaf tasks will almost always |
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* process more than one element): |
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* |
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* <pre> {@code |
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* class Searcher<E> extends CountedCompleter<E> { |
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* final E[] array; final AtomicReference<E> result; final int lo, hi; |
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* Searcher(CountedCompleter<?> p, E[] array, AtomicReference<E> result, int lo, int hi) { |
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* super(p); |
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* this.array = array; this.result = result; this.lo = lo; this.hi = hi; |
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* } |
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* public E getRawResult() { return result.get(); } |
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* public void compute() { // similar to ForEach version 3 |
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* int l = lo, h = hi; |
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* while (h - l >= 2 && result.get() == null) { |
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* int mid = (l + h) >>> 1; |
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* addToPendingCount(1); |
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* new Searcher(this, array, result, mid, h).fork(); |
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* h = mid; |
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* } |
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* if (h > l && result.get() == null && matches(array[l]) && |
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* result.compareAndSet(null, array[l])) |
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* getRoot().quietlyComplete(); // root task is now joinable |
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* |
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* tryComplete(); // normally complete whether or not found |
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* } |
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* boolean matches(E e) { ... } // return true if found |
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* |
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* public static <E> E search(E[] array) { |
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* return new Searcher<E>(null, array, new AtomicReference<E>(), 0, array.length).invoke(); |
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* } |
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*}}</pre> |
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* |
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* In this example, as well as others in which tasks have no other |
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* effects except to compareAndSet a common result, the trailing |
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* unconditional invocation of {@code tryComplete} could be made |
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* conditional ({@code if (result.get() == null) tryComplete();}) |
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* because no further bookkeeping is required to manage completions |
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* once the root task completes. |
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* |
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1.1 |
* <p><b>Triggers.</b> Some CountedCompleters are themselves never |
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* forked, but instead serve as bits of plumbing in other designs; |
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* including those in which the completion of one of more async tasks |
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* triggers another async task. For example: |
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* |
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* <pre> {@code |
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dl |
1.2 |
* class HeaderBuilder extends CountedCompleter<...> { ... } |
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* class BodyBuilder extends CountedCompleter<...> { ... } |
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* class PacketSender extends CountedCompleter<...> { |
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dl |
1.1 |
* PacketSender(...) { super(null, 1); ... } // trigger on second completion |
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* public void compute() { } // never called |
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1.2 |
* public void onCompletion(CountedCompleter<?> caller) { sendPacket(); } |
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1.1 |
* } |
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* // sample use: |
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* PacketSender p = new PacketSender(); |
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* new HeaderBuilder(p, ...).fork(); |
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* new BodyBuilder(p, ...).fork(); |
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* }</pre> |
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* |
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* @since 1.8 |
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* @author Doug Lea |
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*/ |
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1.2 |
public abstract class CountedCompleter<T> extends ForkJoinTask<T> { |
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dl |
1.1 |
private static final long serialVersionUID = 5232453752276485070L; |
327 |
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|
328 |
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/** This task's completer, or null if none */ |
329 |
dl |
1.2 |
final CountedCompleter<?> completer; |
330 |
dl |
1.1 |
/** The number of pending tasks until completion */ |
331 |
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volatile int pending; |
332 |
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|
333 |
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/** |
334 |
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* Creates a new CountedCompleter with the given completer |
335 |
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* and initial pending count. |
336 |
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* |
337 |
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* @param completer this tasks completer, or {@code null} if none |
338 |
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* @param initialPendingCount the initial pending count |
339 |
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*/ |
340 |
dl |
1.2 |
protected CountedCompleter(CountedCompleter<?> completer, |
341 |
dl |
1.1 |
int initialPendingCount) { |
342 |
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this.completer = completer; |
343 |
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this.pending = initialPendingCount; |
344 |
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} |
345 |
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|
346 |
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/** |
347 |
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* Creates a new CountedCompleter with the given completer |
348 |
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* and an initial pending count of zero. |
349 |
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* |
350 |
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* @param completer this tasks completer, or {@code null} if none |
351 |
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*/ |
352 |
dl |
1.2 |
protected CountedCompleter(CountedCompleter<?> completer) { |
353 |
dl |
1.1 |
this.completer = completer; |
354 |
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} |
355 |
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|
356 |
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/** |
357 |
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* Creates a new CountedCompleter with no completer |
358 |
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* and an initial pending count of zero. |
359 |
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*/ |
360 |
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protected CountedCompleter() { |
361 |
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this.completer = null; |
362 |
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} |
363 |
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|
364 |
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/** |
365 |
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* The main computation performed by this task. |
366 |
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*/ |
367 |
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public abstract void compute(); |
368 |
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|
369 |
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/** |
370 |
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* Performs an action when method {@link #tryComplete} is invoked |
371 |
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* and there are no pending counts, or when the unconditional |
372 |
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* method {@link #complete} is invoked. By default, this method |
373 |
dl |
1.13 |
* does nothing. You can distinguish cases by checking the |
374 |
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* identity of the given caller argument. If not equal to {@code |
375 |
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* this}, then it is typically a subtask that may contain results |
376 |
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* (and/or links to other results) to combine. |
377 |
dl |
1.1 |
* |
378 |
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* @param caller the task invoking this method (which may |
379 |
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* be this task itself). |
380 |
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*/ |
381 |
dl |
1.2 |
public void onCompletion(CountedCompleter<?> caller) { |
382 |
dl |
1.1 |
} |
383 |
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|
384 |
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/** |
385 |
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* Performs an action when method {@link #completeExceptionally} |
386 |
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* is invoked or method {@link #compute} throws an exception, and |
387 |
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* this task has not otherwise already completed normally. On |
388 |
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* entry to this method, this task {@link |
389 |
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* ForkJoinTask#isCompletedAbnormally}. The return value of this |
390 |
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* method controls further propagation: If {@code true} and this |
391 |
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* task has a completer, then this completer is also completed |
392 |
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* exceptionally. The default implementation of this method does |
393 |
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* nothing except return {@code true}. |
394 |
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* |
395 |
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* @param ex the exception |
396 |
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* @param caller the task invoking this method (which may |
397 |
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* be this task itself). |
398 |
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* @return true if this exception should be propagated to this |
399 |
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* tasks completer, if one exists. |
400 |
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*/ |
401 |
dl |
1.2 |
public boolean onExceptionalCompletion(Throwable ex, CountedCompleter<?> caller) { |
402 |
dl |
1.1 |
return true; |
403 |
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} |
404 |
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|
405 |
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/** |
406 |
|
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* Returns the completer established in this task's constructor, |
407 |
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* or {@code null} if none. |
408 |
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* |
409 |
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* @return the completer |
410 |
|
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*/ |
411 |
dl |
1.2 |
public final CountedCompleter<?> getCompleter() { |
412 |
dl |
1.1 |
return completer; |
413 |
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} |
414 |
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|
415 |
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/** |
416 |
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* Returns the current pending count. |
417 |
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* |
418 |
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* @return the current pending count |
419 |
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*/ |
420 |
|
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public final int getPendingCount() { |
421 |
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return pending; |
422 |
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} |
423 |
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|
424 |
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/** |
425 |
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* Sets the pending count to the given value. |
426 |
|
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* |
427 |
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* @param count the count |
428 |
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*/ |
429 |
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public final void setPendingCount(int count) { |
430 |
|
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pending = count; |
431 |
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} |
432 |
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|
433 |
|
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/** |
434 |
|
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* Adds (atomically) the given value to the pending count. |
435 |
|
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* |
436 |
|
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* @param delta the value to add |
437 |
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*/ |
438 |
|
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public final void addToPendingCount(int delta) { |
439 |
|
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int c; // note: can replace with intrinsic in jdk8 |
440 |
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do {} while (!U.compareAndSwapInt(this, PENDING, c = pending, c+delta)); |
441 |
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} |
442 |
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|
443 |
|
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/** |
444 |
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* Sets (atomically) the pending count to the given count only if |
445 |
|
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* it currently holds the given expected value. |
446 |
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* |
447 |
|
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* @param expected the expected value |
448 |
|
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* @param count the new value |
449 |
|
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* @return true is successful |
450 |
|
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*/ |
451 |
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public final boolean compareAndSetPendingCount(int expected, int count) { |
452 |
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return U.compareAndSwapInt(this, PENDING, expected, count); |
453 |
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} |
454 |
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|
455 |
|
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/** |
456 |
dl |
1.5 |
* Returns the root of the current computation; i.e., this |
457 |
|
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* task if it has no completer, else its completer's root. |
458 |
|
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* |
459 |
|
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* @return the root of the current computation |
460 |
|
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*/ |
461 |
|
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public final CountedCompleter<?> getRoot() { |
462 |
|
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CountedCompleter<?> a = this, p; |
463 |
|
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while ((p = a.completer) != null) |
464 |
|
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a = p; |
465 |
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return a; |
466 |
|
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} |
467 |
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|
468 |
|
|
/** |
469 |
dl |
1.1 |
* If the pending count is nonzero, decrements the count; |
470 |
|
|
* otherwise invokes {@link #onCompletion} and then similarly |
471 |
|
|
* tries to complete this task's completer, if one exists, |
472 |
|
|
* else marks this task as complete. |
473 |
|
|
*/ |
474 |
|
|
public final void tryComplete() { |
475 |
dl |
1.2 |
CountedCompleter<?> a = this, s = a; |
476 |
dl |
1.1 |
for (int c;;) { |
477 |
|
|
if ((c = a.pending) == 0) { |
478 |
|
|
a.onCompletion(s); |
479 |
|
|
if ((a = (s = a).completer) == null) { |
480 |
|
|
s.quietlyComplete(); |
481 |
|
|
return; |
482 |
|
|
} |
483 |
|
|
} |
484 |
|
|
else if (U.compareAndSwapInt(a, PENDING, c, c - 1)) |
485 |
|
|
return; |
486 |
|
|
} |
487 |
|
|
} |
488 |
|
|
|
489 |
|
|
/** |
490 |
|
|
* Regardless of pending count, invokes {@link #onCompletion}, |
491 |
dl |
1.2 |
* marks this task as complete and further triggers {@link |
492 |
dl |
1.13 |
* #tryComplete} on this task's completer, if one exists. The |
493 |
dl |
1.2 |
* given rawResult is used as an argument to {@link #setRawResult} |
494 |
dl |
1.13 |
* before invoking {@link #onCompletion} or marking this task as |
495 |
|
|
* complete; its value is meaningful only for classes overriding |
496 |
|
|
* {@code setRawResult}. |
497 |
|
|
* |
498 |
|
|
* <p>This method may be useful when forcing completion as soon as |
499 |
|
|
* any one (versus all) of several subtask results are obtained. |
500 |
|
|
* However, in the common (and recommended) case in which {@code |
501 |
|
|
* setRawResult} is not overridden, this effect can be obtained |
502 |
|
|
* more simply using {@code getRoot().quietlyComplete();}. |
503 |
dl |
1.1 |
* |
504 |
dl |
1.2 |
* @param rawResult the raw result |
505 |
dl |
1.1 |
*/ |
506 |
dl |
1.2 |
public void complete(T rawResult) { |
507 |
|
|
CountedCompleter<?> p; |
508 |
dl |
1.13 |
setRawResult(rawResult); |
509 |
dl |
1.1 |
onCompletion(this); |
510 |
|
|
quietlyComplete(); |
511 |
|
|
if ((p = completer) != null) |
512 |
|
|
p.tryComplete(); |
513 |
|
|
} |
514 |
|
|
|
515 |
|
|
/** |
516 |
|
|
* Support for FJT exception propagation |
517 |
|
|
*/ |
518 |
|
|
void internalPropagateException(Throwable ex) { |
519 |
dl |
1.2 |
CountedCompleter<?> a = this, s = a; |
520 |
dl |
1.1 |
while (a.onExceptionalCompletion(ex, s) && |
521 |
|
|
(a = (s = a).completer) != null && a.status >= 0) |
522 |
|
|
a.recordExceptionalCompletion(ex); |
523 |
|
|
} |
524 |
|
|
|
525 |
|
|
/** |
526 |
|
|
* Implements execution conventions for CountedCompleters |
527 |
|
|
*/ |
528 |
|
|
protected final boolean exec() { |
529 |
|
|
compute(); |
530 |
|
|
return false; |
531 |
|
|
} |
532 |
|
|
|
533 |
|
|
/** |
534 |
dl |
1.2 |
* Returns the result of the computation. By default |
535 |
|
|
* returns {@code null}, which is appropriate for {@code Void} |
536 |
|
|
* actions, but in other cases should be overridden. |
537 |
dl |
1.1 |
* |
538 |
dl |
1.2 |
* @return the result of the computation |
539 |
dl |
1.1 |
*/ |
540 |
dl |
1.2 |
public T getRawResult() { return null; } |
541 |
dl |
1.1 |
|
542 |
|
|
/** |
543 |
dl |
1.2 |
* A method that result-bearing CountedCompleters may optionally |
544 |
|
|
* use to help maintain result data. By default, does nothing. |
545 |
dl |
1.13 |
* If this method is overridden to update existing objects or |
546 |
|
|
* fields, then it must in general be defined to be thread-safe. |
547 |
dl |
1.1 |
*/ |
548 |
dl |
1.2 |
protected void setRawResult(T t) { } |
549 |
dl |
1.1 |
|
550 |
|
|
// Unsafe mechanics |
551 |
|
|
private static final sun.misc.Unsafe U; |
552 |
|
|
private static final long PENDING; |
553 |
|
|
static { |
554 |
|
|
try { |
555 |
dl |
1.13 |
U = sun.misc.Unsafe.getUnsafe(); |
556 |
dl |
1.1 |
PENDING = U.objectFieldOffset |
557 |
|
|
(CountedCompleter.class.getDeclaredField("pending")); |
558 |
|
|
} catch (Exception e) { |
559 |
|
|
throw new Error(e); |
560 |
|
|
} |
561 |
|
|
} |
562 |
jsr166 |
1.11 |
|
563 |
dl |
1.1 |
/** |
564 |
|
|
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package. |
565 |
|
|
* Replace with a simple call to Unsafe.getUnsafe when integrating |
566 |
|
|
* into a jdk. |
567 |
|
|
* |
568 |
|
|
* @return a sun.misc.Unsafe |
569 |
|
|
*/ |
570 |
|
|
private static sun.misc.Unsafe getUnsafe() { |
571 |
|
|
try { |
572 |
|
|
return sun.misc.Unsafe.getUnsafe(); |
573 |
|
|
} catch (SecurityException se) { |
574 |
|
|
try { |
575 |
|
|
return java.security.AccessController.doPrivileged |
576 |
|
|
(new java.security |
577 |
|
|
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
578 |
|
|
public sun.misc.Unsafe run() throws Exception { |
579 |
|
|
java.lang.reflect.Field f = sun.misc |
580 |
|
|
.Unsafe.class.getDeclaredField("theUnsafe"); |
581 |
|
|
f.setAccessible(true); |
582 |
|
|
return (sun.misc.Unsafe) f.get(null); |
583 |
|
|
}}); |
584 |
|
|
} catch (java.security.PrivilegedActionException e) { |
585 |
|
|
throw new RuntimeException("Could not initialize intrinsics", |
586 |
|
|
e.getCause()); |
587 |
|
|
} |
588 |
|
|
} |
589 |
|
|
} |
590 |
|
|
} |