使用线程池将双数组（矩阵）相加

Question

我想使用线程池将两个矩阵相互相加，这样可以加快进程完成速度。当我不使用执行器框架进行添加时，该程序运行良好，但当我实现线程池时崩溃。问题必须出在加法方法中，任何帮助将其变为运行的方法都会有所帮助！谢谢 :).

这是来自矩阵 class 的代码。我没有包含主要的 class，因为它所做的只是获取创建矩阵的维度。如果你也想要主要的 class 让我知道，我会把它包括在内。

package matrixproject;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class Matrix {
    int row;
    int column;

    int [][] matrixArray;

    public Matrix(){    
    }
    public Matrix (int numberofRows,int numberofColumns,int maxNumber,int minNumber){

        this.row = numberofRows;
        this.column = numberofColumns;

        matrixArray = new int [row][column];

        populateMatrix(minNumber,maxNumber);

    }
    public Matrix(int [][] matrixArrayCopy)
   {
       this.row = matrixArrayCopy.length;
       this.column = (matrixArrayCopy[0]).length;

       matrixArray = new int[row][column];

       for(int i=0; i<row; i++)
       {
           System.arraycopy(matrixArrayCopy[i], 0, matrixArray[i], 0, column);
       }
   }
     private void populateMatrix(int min, int max)
   {
       Random rand = new Random();

       for (int i=0; i<row; i++)
       {
           for (int j=0; j<column; j++)
           {
               matrixArray[i][j] = rand.nextInt((max - min) + 1) + min;
           }
       }
   }
    public Matrix addition (Matrix additionMatrix){
        int threadnum = Runtime.getRuntime().availableProcessors();
        ExecutorService executor = Executors.newFixedThreadPool(threadnum);
        int [][] matrixAddResult = new int [this.row][this.column]; 
        for (int i = 0; i <row; i+=1){
            for (int j =0; j <column; j+=1){
                //made new variables equal to i and j to get around needing a final variable for the lambda function 
                int index = i;
                int jndex = j;

                executor.submit(() -> {
                matrixAddResult[index][jndex] += this.matrixArray[index][jndex] + additionMatrix.matrixArray[index][jndex];

          });
            executor.shutdown();
            }
        }
        return new Matrix(matrixAddResult);
    }

以下是我到达加法时得到的错误：

Exception in thread "main" java.util.concurrent.RejectedExecutionException: Task java.util.concurrent.FutureTask@452b3a41 rejected from java.util.concurrent.ThreadPoolExecutor@4a574795[Shutting down, pool size = 1, active threads = 1, queued tasks = 0, completed tasks = 0]
    at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:2047)
    at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:823)
    at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1369)
    at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:112)
    at matrixproject.Matrix.addition(Matrix.java:65)
    at matrixproject.MatrixProject.main(MatrixProject.java:73)
Java Result: 1

Answer 1

它的字面意思是："Shutting down" 在异常中。 :)

您正在内部循环中调用 shutdown() 方法，这意味着您正在尝试在池已经收到关闭命令后的下一次迭代之后提交新任务，这就是您的原因收到拒绝异常。

将你的 executor.shutdown(); 移到顶层 for 循环之外

Answer 2

与其重复创建和关闭线程池，不如通过并行 Stream 使用内置的 CommonForkJoinPool

public Matrix addition (Matrix additionMatrix){
    int[][] matrixAddResult = new int[this.row][this.column];
    IntStream.range(0, row).parallel()
             .forEach(i -> {
                 for (int j = 0; j < column; j++)
                     matrixAddResult[i][j] = this.matrixArray[i][j] 
                                           + additionMatrix.matrixArray[i][j];
              });
    return new Matrix(matrixAddResult);
}

使用线程池将双数组（矩阵）相加

Adding double arrays(Matrix) together using Thread Pool

java

multithreading

matrix

executorservice

threadpoolexecutor