hello java fork/join for java

追寻北极

于 2014-12-02 14:01:41 发布

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本文介绍了一个使用Java并发包中的RecursiveTask实现的并行计算示例。该示例通过递归分解大任务为小任务，并利用ForkJoinPool进行并行计算。当子任务足够小时，采用直接求和的方式；否则继续分解并行处理。

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1，示例



import java.util.concurrent.RecursiveTask;

public class Calculator extends RecursiveTask<Integer> {  
	  
    private static final int THRESHOLD = 4;  
    private int start;  
    private int end;  
  
    public Calculator(int start, int end) {  
        this.start = start;  
        this.end = end;  
    }  
  
    @Override  
    protected Integer compute() {  
        int sum = 0;  
        if((end-start) < THRESHOLD){  
            for(int i = start; i<= end;i++){  
                sum += i;  
            }
            System.err.println(">>>>>>>>");
        }else{  
            int middle = (start + end) /2;  
            Calculator left = new Calculator(start, middle);  
            Calculator right = new Calculator(middle + 1, end);  
            left.fork();  
            right.fork();  
  
            sum = left.join() + right.join();  
        }  
        return sum;  
    }  
  
}

2 运行


import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;

public class Test {

	/**
	 * @param args
	 * @throws Exception 
	 * @throws InterruptedException 
	 */
	public static void main(String[] args) throws InterruptedException, Exception {
		// TODO Auto-generated method stub
		ForkJoinPool forkJoinPool = new ForkJoinPool();
		Future<Integer> result = forkJoinPool.submit(new Calculator(0, 9));

		//new Integer(49995000)
		System.err.println(result.get());