使用RecursiveTask进行forkJoin求和 (1)_recursivetask 位运算-优快云博客

本文链接：https://blog.youkuaiyun.com/abckingaa/article/details/126692080

该博客介绍了如何利用Java的ForkJoinPool和RecursiveTask进行并行计算，以提高CPU多核环境下数组求和的效率。通过递归地拆分任务，将大任务分解为小任务并行处理，最后合并子任务结果来实现快速求和。示例代码展示了具体实现过程，并在main方法中进行了性能测试。

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使用RecursiveTask进行forkJoin求和 (1)

使用RecursiveTask进行递归拆分任务求和. 可以充分发挥CPU多核的优势!

/*
 * Copyright 2016-2022 the original author.All rights reserved.
 * Kingstar(honeysoft@126.com)
 * The license,see the LICENSE file.
 */


import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.RecursiveTask;

/**
 * @author Kingstar
 * @since  2.0
 */
public class ForkJoinTest3 extends RecursiveTask<Integer> {

	private static final long serialVersionUID = 1L;
	private final static int THRESHOLD = 10;

	private int[] numbers;
	private int start;
	private int end;

	public ForkJoinTest3(int[] numbers, int start, int end) {
		this.numbers = numbers;
		this.start = start;
		this.end = end;
	}

	@Override
	protected Integer compute() {
		if (end - start < THRESHOLD) {
			System.out.println(" from index = " + start + " , toIndex=" + end);
			int result = 0;
			for (int i = start; i <= end; i++) {
				result += numbers[i];
			}
			return result;
		} else {
			int mid = (end + start) / 2;
//		    System.out.println("拆分任务, mid:"+mid);
			ForkJoinTest3 task1 = new ForkJoinTest3(numbers, start, mid);
			ForkJoinTest3 task2 = new ForkJoinTest3(numbers, mid + 1, end);
			task1.fork();
			task2.fork();

			Integer a2 = task2.join();
			Integer a1 = task1.join();
			return a1 + a2;
		}
	}

	public static void main(String[] args) {
		int numbers[] = new int[100];
		for (int i = 0; i < numbers.length; i++) {
			numbers[i] = i + 1;
		}

//		ForkJoinTest3 forkJoinTest=new ForkJoinTest3(numbers, 0, numbers.length-1);
//		int a=ForkJoinPool.commonPool().invoke(forkJoinTest);
//		System.out.println(a);

		ForkJoinPool pool = new ForkJoinPool();
		ForkJoinTest3 forkJoinTest3 = new ForkJoinTest3(numbers, 0, numbers.length - 1);
		long t1 = System.currentTimeMillis();
		pool.invoke(forkJoinTest3);
		int sum=forkJoinTest3.join();
		System.out.println("结果: "+sum);
		long t2 = System.currentTimeMillis();
		System.out.println("求和花费的时间: " + (t2 - t1) + " ms");
	}

}