fork-join分支合并完成加法

最新推荐文章于 2025-06-27 16:02:15 发布

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本文介绍了一个使用Java的ForkJoinPool实现的大规模数值求和任务案例。通过将任务分解成更小的子任务并行处理，该案例展示了如何有效利用多核处理器的能力来加速计算密集型任务。

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package ForkJoinPooltest;

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

/**
 * @author 
 * @version 1.0.0
 * @ProjectName: testend
 * @Package: ForkJoinPooltest
 * Created on 2018/7/8 19:45
 * @Description: CountTask
 */

class CountTask extends RecursiveTask<Long>{
    private  static  final int THRESHOLD= 10000;
    private long start ;
    private long end;

    public CountTask(long start,long end){
        this.start = start;
        this.end = end;
    }

    @Override
    protected Long compute() {
        long sum = 0;
        boolean canCompute = ( end- start ) < THRESHOLD;
        if(canCompute){
            for (long i = start; i <=end ; i++) {
                sum += i;
            }
        }else {
            long step = (end - start+1)/100;//分解为100份，每份step个
            System.out.println(step);
            ArrayList<CountTask> subTasks = new ArrayList<CountTask>();
            long pos = start;
            for (long i = 0; i <100 ; i++) {
                long lastOne = pos + step;
                if(lastOne>end){
                    lastOne = end;
                }
                CountTask countTask =new CountTask(pos,lastOne);
                pos=lastOne+1;
                subTasks.add(countTask);
                countTask.fork();
            }
            for (CountTask i: subTasks) {
                sum+=i.join();

            }
        }
        return sum;
    }

    public static void main(String[] args) {
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        CountTask task = new CountTask(0,200000L);
        ForkJoinTask<Long> result = forkJoinPool.submit(task);

        try{
            long res = result.get();
            System.out.println(res);
        }catch(Exception e){
            e.printStackTrace();
        }
    }



}