105 lines
3.3 KiB
Java
105 lines
3.3 KiB
Java
/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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/*
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* This file is available under and governed by the GNU General Public
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* License version 2 only, as published by the Free Software Foundation.
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* However, the following notice accompanied the original version of this
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* file:
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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 java.util.concurrent;
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/**
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* A recursive result-bearing {@link ForkJoinTask}.
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*
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* <p>For a classic example, here is a task computing Fibonacci numbers:
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*
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* <pre> {@code
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* class Fibonacci extends RecursiveTask<Integer> {
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* final int n;
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* Fibonacci(int n) { this.n = n; }
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* protected Integer compute() {
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* if (n <= 1)
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* return n;
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* Fibonacci f1 = new Fibonacci(n - 1);
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* f1.fork();
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* Fibonacci f2 = new Fibonacci(n - 2);
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* return f2.compute() + f1.join();
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* }
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* }}</pre>
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*
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* However, besides being a dumb way to compute Fibonacci functions
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* (there is a simple fast linear algorithm that you'd use in
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* practice), this is likely to perform poorly because the smallest
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* subtasks are too small to be worthwhile splitting up. Instead, as
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* is the case for nearly all fork/join applications, you'd pick some
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* minimum granularity size (for example 10 here) for which you always
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* sequentially solve rather than subdividing.
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*
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* @since 1.7
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* @author Doug Lea
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*/
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public abstract class RecursiveTask<V> extends ForkJoinTask<V> {
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private static final long serialVersionUID = 5232453952276485270L;
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/**
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* Constructor for subclasses to call.
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*/
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public RecursiveTask() {}
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/**
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* The result of the computation.
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*/
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@SuppressWarnings("serial") // Conditionally serializable
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V result;
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/**
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* The main computation performed by this task.
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* @return the result of the computation
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*/
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protected abstract V compute();
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public final V getRawResult() {
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return result;
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}
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protected final void setRawResult(V value) {
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result = value;
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}
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/**
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* Implements execution conventions for RecursiveTask.
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*/
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protected final boolean exec() {
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result = compute();
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return true;
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}
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}
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