93 lines
3.1 KiB
Java
93 lines
3.1 KiB
Java
/*
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* The MIT License (MIT)
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*
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* Copyright © 2020 xrv <xrg@live.com>
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package io.github.ehlxr.forkjoin;
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import java.util.concurrent.ForkJoinPool;
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import java.util.concurrent.RecursiveAction;
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/**
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* @author ehlxr
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* @since 2020-12-30 17:59.
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*/
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public class Main {
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public static void main(String[] args) {
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System.out.println(sumOfSquares(ForkJoinPool.commonPool(), new double[]{1.2, 2.4, 3.5, 4.2, 5.0, 6, 7.6}));
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}
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static double sumOfSquares(ForkJoinPool pool, double[] array) {
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int n = array.length;
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Applyer a = new Applyer(array, 0, n, null);
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pool.invoke(a);
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return a.result;
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}
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static class Applyer extends RecursiveAction {
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final double[] array;
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final int lo, hi;
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double result;
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Applyer next; // keeps track of right-hand-side tasks
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Applyer(double[] array, int lo, int hi, Applyer next) {
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this.array = array;
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this.lo = lo;
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this.hi = hi;
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this.next = next;
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}
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double atLeaf(int l, int h) {
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double sum = 0;
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for (int i = l; i < h; ++i) {// perform leftmost base step}
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sum += array[i] * array[i];
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}
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return sum;
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}
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@Override
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protected void compute() {
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int l = lo;
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int h = hi;
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Applyer right = null;
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while (h - l > 1 && getSurplusQueuedTaskCount() <= 3) {
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int mid = (l + h) >>> 1;
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right = new Applyer(array, mid, h, right);
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right.fork();
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h = mid;
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}
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double sum = atLeaf(l, h);
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while (right != null) {
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if (right.tryUnfork()) {// directly calculate if not stolen}
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sum += right.atLeaf(right.lo, right.hi);
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} else {
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right.join();
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sum += right.result;
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}
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right = right.next;
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}
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result = sum;
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}
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}
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}
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