JAVA-forkJoin框架-计算矩阵加法

主程序

package text.ght03;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;

public class forkJoinText {

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        //创建执行线程池
        ForkJoinPool pool = new ForkJoinPool();
        //ForkJoinPool pool = new ForkJoinPool(4);

        //开始时间
        long startTime = System.currentTimeMillis();

        //创建任务
        SumTask task = new SumTask(1, 2000);

        //提交任务
        ForkJoinTask result = pool.submit(task);

        //等待结果
        do {
            System.out.printf("Main: Thread Count: %dn",pool.getActiveThreadCount());
            System.out.printf("Main: Paralelism: %dn",pool.getParallelism());
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        } while (!task.isDone());

        //结束时间
        long endTime = System.currentTimeMillis();
        //输出结果
        System.out.println("程序串行运行时间为 "+(endTime - startTime));
    }
}

 任务

package text.ght03;

import java.util.concurrent.RecursiveTask;

public class SumTask extends RecursiveTask {
    private int start;
    private int end;

    public volatile double[][] d1 = new double[2000][2000];
    public volatile double[][] d2 = new double[2000][2000];

    public volatile double[][] result = new double[2000][2000];//结果矩阵

    public void init() {
        System.out.println("调用init函数-------");
        for (int i = 0; i < 200; i++) {
            for (int j = 0; j < 200; j++) {
                d1[i][j] = Math.random();
                d2[i][j] = Math.random();
            }
        }
    }

    public SumTask(int start, int end) {
        this.start = start;
        this.end = end;
    }

    public static final int threadhold = 500;

    @Override
    protected Long compute() {
        Long sum = 1L;


        // 如果任务足够小, 就直接执行
        boolean canCompute = (end - start) <= threadhold;
        if (canCompute) {
            for (int i = 0; i < 2000; i++) {
                //实现业务代码
                //执行矩阵的加法
                for (int j = start - 1; j < end; j++) {
                    //d1[i][j] = Math.random();
                    //d2[i][j] = Math.random();
                    d1[i][j] = 1;
                    d2[i][j] = 1;
                    result[i][j] = d1[i][j] + d2[i][j];
                }
            }
//            for(int i = start -1;i < end ;i++){
//                //实现业务代码
//                //矩阵的乘法
//                for(int j = start -1;j < end;j++){
//                    for(int k = start -1;k < end;k++){
//
//                    }
//                }
//            }
            System.out.println("线程 "+Thread.currentThread().getName()+" 当前任务的结果：");
            for (int i = 0; i < 2000; i++) {
                for (int j = start - 1; j < end; j++) {
                    //System.out.print(result[i][j] + " ");
                }
                //System.out.println("");
            }
            //System.out.println("end"+end);
        } else {
            // 任务大于阈值, 分裂为2个任务
            int middle = (start + end) / 2;
            SumTask subTask1 = new SumTask(start, middle);
            SumTask subTask2 = new SumTask(middle + 1, end);

            //执行任务
            subTask1.fork();
            subTask2.fork();

            //invokeAll(subTask1, subTask2);//提交两个子任务

            //When the subtask 1 thread ends, sum is assigned
            Long sum1 = subTask1.join();
            Long sum2 = subTask2.join();

             //结果合并
            //sum = sum1 + sum2;
        }
        //return sum;

        return sum;
    }
}