Core: use Java's built-in ConcurrentHashMap
It's risky to have our own snapshot of Java 8's ConcurrentHashMap: unless we keep the sources in sync over time (and OpenJDK's version had already diverged), then we won't get bug/performance fixes. Users can choose to upgrade to Java 8 to see the improvements of CHM. Closes #7392 Closes #7296
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// Rev 1.31 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/CountedCompleter.java?view=log
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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 actions.
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* CountedCompleters are in general more robust in the
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* presence of subtask stalls and blockage than are other forms of
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* ForkJoinTasks, but are less intuitive to program. Uses of
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* 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 completion action {@link #onCompletion(CountedCompleter)},
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* not just one.
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* Unless initialized otherwise, the {@linkplain #getPendingCount pending
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* count} starts at zero, but may be (atomically) changed using
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* methods {@link #setPendingCount}, {@link #addToPendingCount}, and
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* {@link #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. As illustrated below, utility methods
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* supporting customization of completion traversals are also
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* provided. However, 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, fields, and additional
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* support 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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* #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(CountedCompleter)}
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* to perform an action upon normal completion, and method
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* {@link #onExceptionalCompletion(Throwable, CountedCompleter)} to
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* 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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* rarely applicable, to override this method to maintain other
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* objects or fields holding result data.
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*
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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},
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* {@link ForkJoinTask#completeExceptionally(Throwable)} or upon
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* exceptional completion of method {@code compute}. Upon any
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* exceptional completion, the exception may be relayed to a task's
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* completer (and its completer, and so on), if one exists and it has
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* not otherwise already completed. Similarly, cancelling an internal
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* CountedCompleter has only a local effect on that completer, so is
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* 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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* 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 I/O) 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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* <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).
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* A 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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* 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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* {@code 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 exist.
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* Instead of creating a new one, we can iterate using the original task,
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* and add a pending count for each fork. Additionally, because no task
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* in this tree implements an {@link #onCompletion(CountedCompleter)} method,
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* {@code tryComplete()} can be replaced with {@link #propagateCompletion}.
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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 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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* propagateCompletion();
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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>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
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* java.util.concurrent.atomic.AtomicReference AtomicReference} as
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* soon as one is found. The others can poll the result to avoid
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* unnecessary work. (You could additionally {@linkplain #cancel
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* cancel} other tasks, but it is usually simpler and more efficient
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* to just let them notice that the result is set and if so skip
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* further 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 (result.get() == null && h >= l) {
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* if (h - l >= 2) {
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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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* else {
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* E x = array[l];
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* if (matches(x) && result.compareAndSet(null, x))
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* quietlyCompleteRoot(); // root task is now joinable
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* break;
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* }
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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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* <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(CountedCompleter)}. 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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* 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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*
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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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* class MapReducer<E> extends CountedCompleter<E> {
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* final E[] array; final MyMapper<E> mapper;
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* final MyReducer<E> reducer; final int lo, hi;
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* MapReducer<E> sibling;
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* 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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* public E getRawResult() { return result; }
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*
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* 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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* }
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* }}</pre>
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*
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* 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. Assuming 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>Completion Traversals</b>. If using {@code onCompletion} to
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* process completions is inapplicable or inconvenient, you can use
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* methods {@link #firstComplete} and {@link #nextComplete} to create
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* custom traversals. For example, to define a MapReducer that only
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* splits out right-hand tasks in the form of the third ForEach
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* example, the completions must cooperatively reduce along
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* unexhausted subtask links, which can be done as follows:
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*
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* <pre> {@code
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* class MapReducer<E> extends CountedCompleter<E> { // version 2
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* final E[] array; final MyMapper<E> mapper;
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* final MyReducer<E> reducer; final int lo, hi;
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* MapReducer<E> forks, next; // record subtask forks in list
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* 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, MapReducer<E> next) {
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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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* this.next = next;
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* }
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* public void compute() {
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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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* (forks = new MapReducer(this, array, mapper, reducer, mid, h, forks)).fork();
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* h = mid;
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||||
* }
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* if (h > l)
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* result = mapper.apply(array[l]);
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* // process completions by reducing along and advancing subtask links
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* for (CountedCompleter<?> c = firstComplete(); c != null; c = c.nextComplete()) {
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* for (MapReducer t = (MapReducer)c, s = t.forks; s != null; s = t.forks = s.next)
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* t.result = reducer.apply(t.result, s.result);
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* }
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* }
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* public E getRawResult() { return result; }
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*
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* 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, null).invoke();
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* }
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||||
* }}</pre>
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*
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||||
* <p><b>Triggers.</b> Some CountedCompleters are themselves never
|
||||
* forked, but instead serve as bits of plumbing in other designs;
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||||
* including those in which the completion of one or more async tasks
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||||
* triggers another async task. For example:
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||||
*
|
||||
* <pre> {@code
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||||
* class HeaderBuilder extends CountedCompleter<...> { ... }
|
||||
* class BodyBuilder extends CountedCompleter<...> { ... }
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||||
* class PacketSender extends CountedCompleter<...> {
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||||
* PacketSender(...) { super(null, 1); ... } // trigger on second completion
|
||||
* public void compute() { } // never called
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||||
* public void onCompletion(CountedCompleter<?> caller) { sendPacket(); }
|
||||
* }
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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();
|
||||
* }</pre>
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||||
*
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||||
* @since 1.8
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* @author Doug Lea
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||||
*/
|
||||
public abstract class CountedCompleter<T> extends ForkJoinTask<T> {
|
||||
private static final long serialVersionUID = 5232453752276485070L;
|
||||
|
||||
/** This task's completer, or null if none */
|
||||
final CountedCompleter<?> completer;
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||||
/** The number of pending tasks until completion */
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||||
volatile int pending;
|
||||
|
||||
/**
|
||||
* Creates a new CountedCompleter with the given completer
|
||||
* and initial pending count.
|
||||
*
|
||||
* @param completer this task's completer, or {@code null} if none
|
||||
* @param initialPendingCount the initial pending count
|
||||
*/
|
||||
protected CountedCompleter(CountedCompleter<?> completer,
|
||||
int initialPendingCount) {
|
||||
this.completer = completer;
|
||||
this.pending = initialPendingCount;
|
||||
}
|
||||
|
||||
/**
|
||||
* Creates a new CountedCompleter with the given completer
|
||||
* and an initial pending count of zero.
|
||||
*
|
||||
* @param completer this task's completer, or {@code null} if none
|
||||
*/
|
||||
protected CountedCompleter(CountedCompleter<?> completer) {
|
||||
this.completer = completer;
|
||||
}
|
||||
|
||||
/**
|
||||
* Creates a new CountedCompleter with no completer
|
||||
* and an initial pending count of zero.
|
||||
*/
|
||||
protected CountedCompleter() {
|
||||
this.completer = null;
|
||||
}
|
||||
|
||||
/**
|
||||
* The main computation performed by this task.
|
||||
*/
|
||||
public abstract void compute();
|
||||
|
||||
/**
|
||||
* Performs an action when method {@link #tryComplete} is invoked
|
||||
* and the pending count is zero, or when the unconditional
|
||||
* method {@link #complete} is invoked. By default, this method
|
||||
* does nothing. You can distinguish cases by checking the
|
||||
* identity of the given caller argument. If not equal to {@code
|
||||
* this}, then it is typically a subtask that may contain results
|
||||
* (and/or links to other results) to combine.
|
||||
*
|
||||
* @param caller the task invoking this method (which may
|
||||
* be this task itself)
|
||||
*/
|
||||
public void onCompletion(CountedCompleter<?> caller) {
|
||||
}
|
||||
|
||||
/**
|
||||
* Performs an action when method {@link
|
||||
* #completeExceptionally(Throwable)} is invoked or method {@link
|
||||
* #compute} throws an exception, and this task has not already
|
||||
* otherwise completed normally. On entry to this method, this task
|
||||
* {@link ForkJoinTask#isCompletedAbnormally}. The return value
|
||||
* of this method controls further propagation: If {@code true}
|
||||
* and this task has a completer that has not completed, then that
|
||||
* completer is also completed exceptionally, with the same
|
||||
* exception as this completer. The default implementation of
|
||||
* this method does nothing except return {@code true}.
|
||||
*
|
||||
* @param ex the exception
|
||||
* @param caller the task invoking this method (which may
|
||||
* be this task itself)
|
||||
* @return {@code true} if this exception should be propagated to this
|
||||
* task's completer, if one exists
|
||||
*/
|
||||
public boolean onExceptionalCompletion(Throwable ex, CountedCompleter<?> caller) {
|
||||
return true;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the completer established in this task's constructor,
|
||||
* or {@code null} if none.
|
||||
*
|
||||
* @return the completer
|
||||
*/
|
||||
public final CountedCompleter<?> getCompleter() {
|
||||
return completer;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the current pending count.
|
||||
*
|
||||
* @return the current pending count
|
||||
*/
|
||||
public final int getPendingCount() {
|
||||
return pending;
|
||||
}
|
||||
|
||||
/**
|
||||
* Sets the pending count to the given value.
|
||||
*
|
||||
* @param count the count
|
||||
*/
|
||||
public final void setPendingCount(int count) {
|
||||
pending = count;
|
||||
}
|
||||
|
||||
/**
|
||||
* Adds (atomically) the given value to the pending count.
|
||||
*
|
||||
* @param delta the value to add
|
||||
*/
|
||||
public final void addToPendingCount(int delta) {
|
||||
int c;
|
||||
do {} while (!U.compareAndSwapInt(this, PENDING, c = pending, c+delta));
|
||||
}
|
||||
|
||||
/**
|
||||
* Sets (atomically) the pending count to the given count only if
|
||||
* it currently holds the given expected value.
|
||||
*
|
||||
* @param expected the expected value
|
||||
* @param count the new value
|
||||
* @return {@code true} if successful
|
||||
*/
|
||||
public final boolean compareAndSetPendingCount(int expected, int count) {
|
||||
return U.compareAndSwapInt(this, PENDING, expected, count);
|
||||
}
|
||||
|
||||
/**
|
||||
* If the pending count is nonzero, (atomically) decrements it.
|
||||
*
|
||||
* @return the initial (undecremented) pending count holding on entry
|
||||
* to this method
|
||||
*/
|
||||
public final int decrementPendingCountUnlessZero() {
|
||||
int c;
|
||||
do {} while ((c = pending) != 0 &&
|
||||
!U.compareAndSwapInt(this, PENDING, c, c - 1));
|
||||
return c;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the root of the current computation; i.e., this
|
||||
* task if it has no completer, else its completer's root.
|
||||
*
|
||||
* @return the root of the current computation
|
||||
*/
|
||||
public final CountedCompleter<?> getRoot() {
|
||||
CountedCompleter<?> a = this, p;
|
||||
while ((p = a.completer) != null)
|
||||
a = p;
|
||||
return a;
|
||||
}
|
||||
|
||||
/**
|
||||
* If the pending count is nonzero, decrements the count;
|
||||
* otherwise invokes {@link #onCompletion(CountedCompleter)}
|
||||
* and then similarly tries to complete this task's completer,
|
||||
* if one exists, else marks this task as complete.
|
||||
*/
|
||||
public final void tryComplete() {
|
||||
CountedCompleter<?> a = this, s = a;
|
||||
for (int c;;) {
|
||||
if ((c = a.pending) == 0) {
|
||||
a.onCompletion(s);
|
||||
if ((a = (s = a).completer) == null) {
|
||||
s.quietlyComplete();
|
||||
return;
|
||||
}
|
||||
}
|
||||
else if (U.compareAndSwapInt(a, PENDING, c, c - 1))
|
||||
return;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Equivalent to {@link #tryComplete} but does not invoke {@link
|
||||
* #onCompletion(CountedCompleter)} along the completion path:
|
||||
* If the pending count is nonzero, decrements the count;
|
||||
* otherwise, similarly tries to complete this task's completer, if
|
||||
* one exists, else marks this task as complete. This method may be
|
||||
* useful in cases where {@code onCompletion} should not, or need
|
||||
* not, be invoked for each completer in a computation.
|
||||
*/
|
||||
public final void propagateCompletion() {
|
||||
CountedCompleter<?> a = this, s = a;
|
||||
for (int c;;) {
|
||||
if ((c = a.pending) == 0) {
|
||||
if ((a = (s = a).completer) == null) {
|
||||
s.quietlyComplete();
|
||||
return;
|
||||
}
|
||||
}
|
||||
else if (U.compareAndSwapInt(a, PENDING, c, c - 1))
|
||||
return;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Regardless of pending count, invokes
|
||||
* {@link #onCompletion(CountedCompleter)}, marks this task as
|
||||
* complete and further triggers {@link #tryComplete} on this
|
||||
* task's completer, if one exists. The given rawResult is
|
||||
* used as an argument to {@link #setRawResult} before invoking
|
||||
* {@link #onCompletion(CountedCompleter)} or marking this task
|
||||
* as complete; its value is meaningful only for classes
|
||||
* overriding {@code setRawResult}. This method does not modify
|
||||
* the pending count.
|
||||
*
|
||||
* <p>This method may be useful when forcing completion as soon as
|
||||
* any one (versus all) of several subtask results are obtained.
|
||||
* However, in the common (and recommended) case in which {@code
|
||||
* setRawResult} is not overridden, this effect can be obtained
|
||||
* more simply using {@code quietlyCompleteRoot();}.
|
||||
*
|
||||
* @param rawResult the raw result
|
||||
*/
|
||||
public void complete(T rawResult) {
|
||||
CountedCompleter<?> p;
|
||||
setRawResult(rawResult);
|
||||
onCompletion(this);
|
||||
quietlyComplete();
|
||||
if ((p = completer) != null)
|
||||
p.tryComplete();
|
||||
}
|
||||
|
||||
|
||||
/**
|
||||
* If this task's pending count is zero, returns this task;
|
||||
* otherwise decrements its pending count and returns {@code
|
||||
* null}. This method is designed to be used with {@link
|
||||
* #nextComplete} in completion traversal loops.
|
||||
*
|
||||
* @return this task, if pending count was zero, else {@code null}
|
||||
*/
|
||||
public final CountedCompleter<?> firstComplete() {
|
||||
for (int c;;) {
|
||||
if ((c = pending) == 0)
|
||||
return this;
|
||||
else if (U.compareAndSwapInt(this, PENDING, c, c - 1))
|
||||
return null;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* If this task does not have a completer, invokes {@link
|
||||
* ForkJoinTask#quietlyComplete} and returns {@code null}. Or, if
|
||||
* the completer's pending count is non-zero, decrements that
|
||||
* pending count and returns {@code null}. Otherwise, returns the
|
||||
* completer. This method can be used as part of a completion
|
||||
* traversal loop for homogeneous task hierarchies:
|
||||
*
|
||||
* <pre> {@code
|
||||
* for (CountedCompleter<?> c = firstComplete();
|
||||
* c != null;
|
||||
* c = c.nextComplete()) {
|
||||
* // ... process c ...
|
||||
* }}</pre>
|
||||
*
|
||||
* @return the completer, or {@code null} if none
|
||||
*/
|
||||
public final CountedCompleter<?> nextComplete() {
|
||||
CountedCompleter<?> p;
|
||||
if ((p = completer) != null)
|
||||
return p.firstComplete();
|
||||
else {
|
||||
quietlyComplete();
|
||||
return null;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Equivalent to {@code getRoot().quietlyComplete()}.
|
||||
*/
|
||||
public final void quietlyCompleteRoot() {
|
||||
for (CountedCompleter<?> a = this, p;;) {
|
||||
if ((p = a.completer) == null) {
|
||||
a.quietlyComplete();
|
||||
return;
|
||||
}
|
||||
a = p;
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Supports ForkJoinTask exception propagation.
|
||||
*/
|
||||
void internalPropagateException(Throwable ex) {
|
||||
CountedCompleter<?> a = this, s = a;
|
||||
while (a.onExceptionalCompletion(ex, s) &&
|
||||
(a = (s = a).completer) != null && a.status >= 0 &&
|
||||
a.recordExceptionalCompletion(ex) == EXCEPTIONAL)
|
||||
;
|
||||
}
|
||||
|
||||
/**
|
||||
* Implements execution conventions for CountedCompleters.
|
||||
*/
|
||||
protected final boolean exec() {
|
||||
compute();
|
||||
return false;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the result of the computation. By default,
|
||||
* returns {@code null}, which is appropriate for {@code Void}
|
||||
* actions, but in other cases should be overridden, almost
|
||||
* always to return a field or function of a field that
|
||||
* holds the result upon completion.
|
||||
*
|
||||
* @return the result of the computation
|
||||
*/
|
||||
public T getRawResult() { return null; }
|
||||
|
||||
/**
|
||||
* A method that result-bearing CountedCompleters may optionally
|
||||
* use to help maintain result data. By default, does nothing.
|
||||
* Overrides are not recommended. However, if this method is
|
||||
* overridden to update existing objects or fields, then it must
|
||||
* in general be defined to be thread-safe.
|
||||
*/
|
||||
protected void setRawResult(T t) { }
|
||||
|
||||
// Unsafe mechanics
|
||||
private static final sun.misc.Unsafe U;
|
||||
private static final long PENDING;
|
||||
static {
|
||||
try {
|
||||
U = getUnsafe();
|
||||
PENDING = U.objectFieldOffset
|
||||
(CountedCompleter.class.getDeclaredField("pending"));
|
||||
} catch (Exception e) {
|
||||
throw new Error(e);
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package.
|
||||
* Replace with a simple call to Unsafe.getUnsafe when integrating
|
||||
* into a jdk.
|
||||
*
|
||||
* @return a sun.misc.Unsafe
|
||||
*/
|
||||
private static sun.misc.Unsafe getUnsafe() {
|
||||
try {
|
||||
return sun.misc.Unsafe.getUnsafe();
|
||||
} catch (SecurityException tryReflectionInstead) {}
|
||||
try {
|
||||
return java.security.AccessController.doPrivileged
|
||||
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
|
||||
public sun.misc.Unsafe run() throws Exception {
|
||||
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
|
||||
for (java.lang.reflect.Field f : k.getDeclaredFields()) {
|
||||
f.setAccessible(true);
|
||||
Object x = f.get(null);
|
||||
if (k.isInstance(x))
|
||||
return k.cast(x);
|
||||
}
|
||||
throw new NoSuchFieldError("the Unsafe");
|
||||
}});
|
||||
} catch (java.security.PrivilegedActionException e) {
|
||||
throw new RuntimeException("Could not initialize intrinsics",
|
||||
e.getCause());
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
File diff suppressed because it is too large
Load Diff
File diff suppressed because it is too large
Load Diff
|
|
@ -1,125 +0,0 @@
|
|||
// Rev 1.5 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ForkJoinWorkerThread.java?view=co
|
||||
|
||||
/*
|
||||
* Written by Doug Lea with assistance from members of JCP JSR-166
|
||||
* Expert Group and released to the public domain, as explained at
|
||||
* http://creativecommons.org/publicdomain/zero/1.0/
|
||||
*/
|
||||
|
||||
package jsr166e;
|
||||
|
||||
|
||||
/**
|
||||
* A thread managed by a {@link ForkJoinPool}, which executes
|
||||
* {@link ForkJoinTask}s.
|
||||
* This class is subclassable solely for the sake of adding
|
||||
* functionality -- there are no overridable methods dealing with
|
||||
* scheduling or execution. However, you can override initialization
|
||||
* and termination methods surrounding the main task processing loop.
|
||||
* If you do create such a subclass, you will also need to supply a
|
||||
* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to
|
||||
* {@linkplain ForkJoinPool#ForkJoinPool use it} in a {@code ForkJoinPool}.
|
||||
*
|
||||
* @since 1.7
|
||||
* @author Doug Lea
|
||||
*/
|
||||
public class ForkJoinWorkerThread extends Thread {
|
||||
/*
|
||||
* ForkJoinWorkerThreads are managed by ForkJoinPools and perform
|
||||
* ForkJoinTasks. For explanation, see the internal documentation
|
||||
* of class ForkJoinPool.
|
||||
*
|
||||
* This class just maintains links to its pool and WorkQueue. The
|
||||
* pool field is set immediately upon construction, but the
|
||||
* workQueue field is not set until a call to registerWorker
|
||||
* completes. This leads to a visibility race, that is tolerated
|
||||
* by requiring that the workQueue field is only accessed by the
|
||||
* owning thread.
|
||||
*/
|
||||
|
||||
final ForkJoinPool pool; // the pool this thread works in
|
||||
final ForkJoinPool.WorkQueue workQueue; // work-stealing mechanics
|
||||
|
||||
/**
|
||||
* Creates a ForkJoinWorkerThread operating in the given pool.
|
||||
*
|
||||
* @param pool the pool this thread works in
|
||||
* @throws NullPointerException if pool is null
|
||||
*/
|
||||
protected ForkJoinWorkerThread(ForkJoinPool pool) {
|
||||
// Use a placeholder until a useful name can be set in registerWorker
|
||||
super("aForkJoinWorkerThread");
|
||||
this.pool = pool;
|
||||
this.workQueue = pool.registerWorker(this);
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the pool hosting this thread.
|
||||
*
|
||||
* @return the pool
|
||||
*/
|
||||
public ForkJoinPool getPool() {
|
||||
return pool;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the unique index number of this thread in its pool.
|
||||
* The returned value ranges from zero to the maximum number of
|
||||
* threads (minus one) that may exist in the pool, and does not
|
||||
* change during the lifetime of the thread. This method may be
|
||||
* useful for applications that track status or collect results
|
||||
* per-worker-thread rather than per-task.
|
||||
*
|
||||
* @return the index number
|
||||
*/
|
||||
public int getPoolIndex() {
|
||||
return workQueue.poolIndex >>> 1; // ignore odd/even tag bit
|
||||
}
|
||||
|
||||
/**
|
||||
* Initializes internal state after construction but before
|
||||
* processing any tasks. If you override this method, you must
|
||||
* invoke {@code super.onStart()} at the beginning of the method.
|
||||
* Initialization requires care: Most fields must have legal
|
||||
* default values, to ensure that attempted accesses from other
|
||||
* threads work correctly even before this thread starts
|
||||
* processing tasks.
|
||||
*/
|
||||
protected void onStart() {
|
||||
}
|
||||
|
||||
/**
|
||||
* Performs cleanup associated with termination of this worker
|
||||
* thread. If you override this method, you must invoke
|
||||
* {@code super.onTermination} at the end of the overridden method.
|
||||
*
|
||||
* @param exception the exception causing this thread to abort due
|
||||
* to an unrecoverable error, or {@code null} if completed normally
|
||||
*/
|
||||
protected void onTermination(Throwable exception) {
|
||||
}
|
||||
|
||||
/**
|
||||
* This method is required to be public, but should never be
|
||||
* called explicitly. It performs the main run loop to execute
|
||||
* {@link ForkJoinTask}s.
|
||||
*/
|
||||
public void run() {
|
||||
Throwable exception = null;
|
||||
try {
|
||||
onStart();
|
||||
pool.runWorker(workQueue);
|
||||
} catch (Throwable ex) {
|
||||
exception = ex;
|
||||
} finally {
|
||||
try {
|
||||
onTermination(exception);
|
||||
} catch (Throwable ex) {
|
||||
if (exception == null)
|
||||
exception = ex;
|
||||
} finally {
|
||||
pool.deregisterWorker(this, exception);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
|
|
@ -1,199 +0,0 @@
|
|||
// Rev 1.2 from http://gee.cs.oswego.edu/cgi-bin/viewcvs.cgi/jsr166/src/jsr166e/ThreadLocalRandom.java?revision=1.2
|
||||
|
||||
/*
|
||||
* Written by Doug Lea with assistance from members of JCP JSR-166
|
||||
* Expert Group and released to the public domain, as explained at
|
||||
* http://creativecommons.org/publicdomain/zero/1.0/
|
||||
*/
|
||||
|
||||
package jsr166e;
|
||||
|
||||
import java.util.Random;
|
||||
|
||||
/**
|
||||
* A random number generator isolated to the current thread. Like the
|
||||
* global {@link java.util.Random} generator used by the {@link
|
||||
* java.lang.Math} class, a {@code ThreadLocalRandom} is initialized
|
||||
* with an internally generated seed that may not otherwise be
|
||||
* modified. When applicable, use of {@code ThreadLocalRandom} rather
|
||||
* than shared {@code Random} objects in concurrent programs will
|
||||
* typically encounter much less overhead and contention. Use of
|
||||
* {@code ThreadLocalRandom} is particularly appropriate when multiple
|
||||
* tasks (for example, each a {@link ForkJoinTask}) use random numbers
|
||||
* in parallel in thread pools.
|
||||
*
|
||||
* <p>Usages of this class should typically be of the form:
|
||||
* {@code ThreadLocalRandom.current().nextX(...)} (where
|
||||
* {@code X} is {@code Int}, {@code Long}, etc).
|
||||
* When all usages are of this form, it is never possible to
|
||||
* accidently share a {@code ThreadLocalRandom} across multiple threads.
|
||||
*
|
||||
* <p>This class also provides additional commonly used bounded random
|
||||
* generation methods.
|
||||
*
|
||||
* @since 1.7
|
||||
* @author Doug Lea
|
||||
*/
|
||||
public class ThreadLocalRandom extends Random {
|
||||
// same constants as Random, but must be redeclared because private
|
||||
private static final long multiplier = 0x5DEECE66DL;
|
||||
private static final long addend = 0xBL;
|
||||
private static final long mask = (1L << 48) - 1;
|
||||
|
||||
/**
|
||||
* The random seed. We can't use super.seed.
|
||||
*/
|
||||
private long rnd;
|
||||
|
||||
/**
|
||||
* Initialization flag to permit calls to setSeed to succeed only
|
||||
* while executing the Random constructor. We can't allow others
|
||||
* since it would cause setting seed in one part of a program to
|
||||
* unintentionally impact other usages by the thread.
|
||||
*/
|
||||
boolean initialized;
|
||||
|
||||
// Padding to help avoid memory contention among seed updates in
|
||||
// different TLRs in the common case that they are located near
|
||||
// each other.
|
||||
private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
|
||||
|
||||
/**
|
||||
* The actual ThreadLocal
|
||||
*/
|
||||
private static final ThreadLocal<ThreadLocalRandom> localRandom =
|
||||
new ThreadLocal<ThreadLocalRandom>() {
|
||||
protected ThreadLocalRandom initialValue() {
|
||||
return new ThreadLocalRandom();
|
||||
}
|
||||
};
|
||||
|
||||
|
||||
/**
|
||||
* Constructor called only by localRandom.initialValue.
|
||||
*/
|
||||
ThreadLocalRandom() {
|
||||
super();
|
||||
initialized = true;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the current thread's {@code ThreadLocalRandom}.
|
||||
*
|
||||
* @return the current thread's {@code ThreadLocalRandom}
|
||||
*/
|
||||
public static ThreadLocalRandom current() {
|
||||
return localRandom.get();
|
||||
}
|
||||
|
||||
/**
|
||||
* Throws {@code UnsupportedOperationException}. Setting seeds in
|
||||
* this generator is not supported.
|
||||
*
|
||||
* @throws UnsupportedOperationException always
|
||||
*/
|
||||
public void setSeed(long seed) {
|
||||
if (initialized)
|
||||
throw new UnsupportedOperationException();
|
||||
rnd = (seed ^ multiplier) & mask;
|
||||
}
|
||||
|
||||
protected int next(int bits) {
|
||||
rnd = (rnd * multiplier + addend) & mask;
|
||||
return (int) (rnd >>> (48-bits));
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a pseudorandom, uniformly distributed value between the
|
||||
* given least value (inclusive) and bound (exclusive).
|
||||
*
|
||||
* @param least the least value returned
|
||||
* @param bound the upper bound (exclusive)
|
||||
* @return the next value
|
||||
* @throws IllegalArgumentException if least greater than or equal
|
||||
* to bound
|
||||
*/
|
||||
public int nextInt(int least, int bound) {
|
||||
if (least >= bound)
|
||||
throw new IllegalArgumentException();
|
||||
return nextInt(bound - least) + least;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a pseudorandom, uniformly distributed value
|
||||
* between 0 (inclusive) and the specified value (exclusive).
|
||||
*
|
||||
* @param n the bound on the random number to be returned. Must be
|
||||
* positive.
|
||||
* @return the next value
|
||||
* @throws IllegalArgumentException if n is not positive
|
||||
*/
|
||||
public long nextLong(long n) {
|
||||
if (n <= 0)
|
||||
throw new IllegalArgumentException("n must be positive");
|
||||
// Divide n by two until small enough for nextInt. On each
|
||||
// iteration (at most 31 of them but usually much less),
|
||||
// randomly choose both whether to include high bit in result
|
||||
// (offset) and whether to continue with the lower vs upper
|
||||
// half (which makes a difference only if odd).
|
||||
long offset = 0;
|
||||
while (n >= Integer.MAX_VALUE) {
|
||||
int bits = next(2);
|
||||
long half = n >>> 1;
|
||||
long nextn = ((bits & 2) == 0) ? half : n - half;
|
||||
if ((bits & 1) == 0)
|
||||
offset += n - nextn;
|
||||
n = nextn;
|
||||
}
|
||||
return offset + nextInt((int) n);
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a pseudorandom, uniformly distributed value between the
|
||||
* given least value (inclusive) and bound (exclusive).
|
||||
*
|
||||
* @param least the least value returned
|
||||
* @param bound the upper bound (exclusive)
|
||||
* @return the next value
|
||||
* @throws IllegalArgumentException if least greater than or equal
|
||||
* to bound
|
||||
*/
|
||||
public long nextLong(long least, long bound) {
|
||||
if (least >= bound)
|
||||
throw new IllegalArgumentException();
|
||||
return nextLong(bound - least) + least;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a pseudorandom, uniformly distributed {@code double} value
|
||||
* between 0 (inclusive) and the specified value (exclusive).
|
||||
*
|
||||
* @param n the bound on the random number to be returned. Must be
|
||||
* positive.
|
||||
* @return the next value
|
||||
* @throws IllegalArgumentException if n is not positive
|
||||
*/
|
||||
public double nextDouble(double n) {
|
||||
if (n <= 0)
|
||||
throw new IllegalArgumentException("n must be positive");
|
||||
return nextDouble() * n;
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns a pseudorandom, uniformly distributed value between the
|
||||
* given least value (inclusive) and bound (exclusive).
|
||||
*
|
||||
* @param least the least value returned
|
||||
* @param bound the upper bound (exclusive)
|
||||
* @return the next value
|
||||
* @throws IllegalArgumentException if least greater than or equal
|
||||
* to bound
|
||||
*/
|
||||
public double nextDouble(double least, double bound) {
|
||||
if (least >= bound)
|
||||
throw new IllegalArgumentException();
|
||||
return nextDouble() * (bound - least) + least;
|
||||
}
|
||||
|
||||
private static final long serialVersionUID = -5851777807851030925L;
|
||||
}
|
||||
|
|
@ -19,16 +19,17 @@
|
|||
|
||||
package org.elasticsearch.common.util.concurrent;
|
||||
|
||||
import com.google.common.collect.Sets;
|
||||
|
||||
import org.apache.lucene.util.Constants;
|
||||
|
||||
import java.util.Deque;
|
||||
import java.util.Queue;
|
||||
import java.util.Set;
|
||||
import java.util.concurrent.*;
|
||||
import java.util.concurrent.BlockingQueue;
|
||||
import java.util.concurrent.ConcurrentHashMap;
|
||||
import java.util.concurrent.ConcurrentLinkedDeque;
|
||||
import java.util.concurrent.ConcurrentLinkedQueue;
|
||||
import java.util.concurrent.ConcurrentMap;
|
||||
import java.util.concurrent.LinkedTransferQueue;
|
||||
|
||||
import jsr166e.ConcurrentHashMapV8;
|
||||
import com.google.common.collect.Sets;
|
||||
|
||||
/**
|
||||
*
|
||||
|
|
@ -47,21 +48,11 @@ public abstract class ConcurrentCollections {
|
|||
* Creates a new CHM with an aggressive concurrency level, aimed at high concurrent update rate long living maps.
|
||||
*/
|
||||
public static <K, V> ConcurrentMap<K, V> newConcurrentMapWithAggressiveConcurrency() {
|
||||
if (Constants.JRE_IS_MINIMUM_JAVA8) {
|
||||
// Just use JDK's impl when we are on Java8:
|
||||
return new ConcurrentHashMap<>(16, 0.75f, aggressiveConcurrencyLevel);
|
||||
} else {
|
||||
return new ConcurrentHashMapV8<>(16, 0.75f, aggressiveConcurrencyLevel);
|
||||
}
|
||||
}
|
||||
|
||||
public static <K, V> ConcurrentMap<K, V> newConcurrentMap() {
|
||||
if (Constants.JRE_IS_MINIMUM_JAVA8) {
|
||||
// Just use JDK's impl when we are on Java8:
|
||||
return new ConcurrentHashMap<>();
|
||||
} else {
|
||||
return new ConcurrentHashMapV8<>();
|
||||
}
|
||||
}
|
||||
|
||||
/**
|
||||
|
|
|
|||
Loading…
Reference in New Issue