Question

我有一个大小为n的数组，其中填充了数字1..n。

每次使用两个元素时，我需要使用m个线程对此数组求和，将它们相加并将总和插回到数组中。

这是我试图做的事情。

首先是同步部分

public class MultiThreadedSum {

private ArrayBuffer ArrayBufferInst;
private int Sum;
private boolean Flag;

public MultiThreadedSum(ArrayBuffer ArrayBufferInst)
{
    this.ArrayBufferInst = ArrayBufferInst;
    Sum = 0;
    Flag = false;
}

public synchronized void Sum2Elements()
{

    while(Flag)
    {
        try {wait();}
        catch (InterruptedException e){}
    }

    Flag = true;

    if (ArrayBufferInst.RetunrSize() < 2)
    {
        return;
    }

    System.out.println("Removing 2 elements.");

    Sum = ArrayBufferInst.Sum2Elements();

    notifyAll();
}

public synchronized void InsertElement()
{

    while(!Flag)
    {
        try {wait();}
        catch (InterruptedException e){}
    }

    Flag = false;

    System.out.println("Inserting the sum.");

    ArrayBufferInst.InsertElement(Sum);

    notifyAll();
}

public int RetunrSize()
{
    return ArrayBufferInst.RetunrSize();
}

}

我已经将m个线程拆分为2个组，其中一半将进行汇总，一半将使用wait和notify进行添加。

public class Sum2ElementsThread implements Runnable{

    private MultiThreadedSum MultiThreadedSumInst;    

    public Sum2ElementsThread( MultiThreadedSum MultiThreadedSumInst)
    {
        this.MultiThreadedSumInst = MultiThreadedSumInst;
    }

    @Override
    public void run() {

        while(MultiThreadedSumInst.RetunrSize() > 1)
        {
            MultiThreadedSumInst.Sum2Elements();
        }

    }

}

public class InsertThread implements Runnable{

    private MultiThreadedSum MultiThreadedSumInst;    

    public InsertThread( MultiThreadedSum MultiThreadedSumInst)
    {
        this.MultiThreadedSumInst = MultiThreadedSumInst;
    }

    @Override
    public void run() {

        while(MultiThreadedSumInst.RetunrSize() > 1)
        {
            MultiThreadedSumInst.InsertElement();
        }

    }

}

以下是主要内容的一部分：

ArrayBufferInst = new ArrayBuffer(n);

MultiThreadedSumInst = new MultiThreadedSum(ArrayBufferInst);

ExecutorService Threads = Executors.newCachedThreadPool();

for (i = 0; i < m/2; i++)
{
    Threads.execute( new Sum2ElementsThread(MultiThreadedSumInst) );
}

for (; i < m; i++)
{
    Threads.execute( new InsertThread(MultiThreadedSumInst) );
}

while (MultiThreadedSumInst.RetunrSize() > 1){}

Threads.shutdown();

缓冲区

public class ArrayBuffer {

    private ArrayList<Integer> ArrayBufferInst;

    public ArrayBuffer(int SizeOfBuffer)
    {
        int i;

        ArrayBufferInst = new ArrayList<>(SizeOfBuffer);

        for (i = 0; i < SizeOfBuffer; i++)
        {
            ArrayBufferInst.add(i, i+1);
        }
    }

    public int Sum2Elements()
    {
        if (ArrayBufferInst.size() < 2)
        {
            return -1;
        }

        return ArrayBufferInst.remove(0) + ArrayBufferInst.remove(1);
    }

    public void InsertElement(int Elem)
    {
        ArrayBufferInst.add(Elem);
    }

    public int RetunrSize()
    {
        return ArrayBufferInst.size();
    }
}

我收到了很多java.lang.IndexOutOfBoundsException和RangeCheck错误，这可能与我实现Sum2Elements的方式有关，但我不确定。

任何帮助人员？

感谢。

Answer 1

在ArrayList {a, b, c}

上调用它时

    if (ArrayBufferInst.size() < 2)
    {
        return -1;
    }

    return ArrayBufferInst.remove(0) + ArrayBufferInst.remove(1);

然后ArrayBufferInst.remove(0)将删除并返回a，将ArrayBufferInst更改为{b, c}。然后拨打ArrayBufferInst.remove(1)将移除 c ，这不是您想要的。所以只需将1更改为0。

使用多线程对数组求和

1 个答案: