如何将此代码转换为任务并行库

时间:2014-05-21 00:21:32

标签: c# multithreading parallel-processing task-parallel-library

我是c#.net中多线程编程的新手,我需要帮助将此代码显示转换为C#中的任务并行。

    private void thisIsMethodA()
    {
        //Vertical database
        Dictionary<int, Bitmap> verticalDB = new Dictionary<int, Bitmap>();
        // for each item
        foreach (KeyValuePair<int, Bitmap> entry in verticalDB)
        {
            // We call the depth first search method 
            dfsPruning(prefix, entry.Value, frequentItems, frequentItems, entry.Key, 2);
        }
    }
    private void dfsPruning(Prefix prefix, Bitmap prefixBitmap, List<int> sn, List<int> inl, int hasToBeGreaterThanForIStep, int m)
    {
        int maximumPatternLength = 100;

        for (int k = 0; k < sn.Count; k++)
        {

            if (maximumPatternLength > m)
            {
                dfsPruning(prefixSStep, newBitmap, sTemp, sTemp, item, m + 1);
            }
        }
        for (int k = 0; k < inl.Count; k++)
        {
            if (maximumPatternLength > m)
            {
                dfsPruning(prefixIStep, newBitmap, sTemp, iTemp, item, m + 1);
            }
        }

    }

我应该使用下面的代码吗?

使用Task实现是对的吗?你能告诉我我还能做些什么以及如何提高效率?

private void thisIsMethodA()
{
    //Vertical database
    Dictionary<int, Bitmap> verticalDB = new Dictionary<int, Bitmap>();
    // for each item
    Parallel.ForEach(verticalDB, (entry) =>
        {

            // We call the depth first search method 
            dfsPruning(prefix, entry.Value, frequentItems, frequentItems, entry.Key, 2);
        });
}
private void dfsPruning(Prefix prefix, Bitmap prefixBitmap, List<int> sn, List<int> inl, int hasToBeGreaterThanForIStep, int m)
{
    int maximumPatternLength = 100;
    var tasks = new List<Task>();
    for (int k = 0; k < sn.Count; k++)
    {

        if (maximumPatternLength > m)
        {
            tasks.Add(Task.Factory.StartNew(() => dfsPruning(prefixSStep, newBitmap, sTemp, sTemp, item, m + 1)));
        }
    }
    for (int k = 0; k < inl.Count; k++)
    {
        if (maximumPatternLength > m)
        {
            tasks.Add(Task.Factory.StartNew(() => dfsPruning(prefixSStep, newBitmap, sTemp, sTemp, item, m + 1)));
        }
    }
    Task.WaitAll(tasks.ToArray());

}

所以我的问题是,如何将此代码转换为任务并行库。所以.net只关注并行运行这个任务。 dfsPruning()方法是递归的,我需要帮助将此方法转换为任务并行。

非常感谢您抽出时间阅读我的信,我期待着我收到的任何信息。

2 个答案:

答案 0 :(得分:0)

您可以做的一件简单事情是使用Parallel.ForEach来并行thisIsMethodA而不是dfsPruning。这将根据您的执行环境处理不同线程上的每个条目,但您需要小心从不同线程修改的数据

private void thisIsMethodA()
{
    //Vertical database
    Dictionary<int, Bitmap> verticalDB = new Dictionary<int, Bitmap>();
    // for each item
    Parallel.ForEach (vertocalDB, (entry) => 
    {
        // We call the depth first search method 
        dfsPruning(prefix, entry.Value, frequentItems, frequentItems, entry.Key, 2);
    });
}

答案 1 :(得分:0)

这可以是Parallel.For

的候选者

由于循环可能非常递归,我建议根据您的服务器配置设置MaxDegreeOfParallelism,这样就不会创建任务并继续等待线程或处理器释放。

private void thisIsMethodA()
{
    //Vertical database
    Dictionary<int, Bitmap> verticalDB = new Dictionary<int, Bitmap>();
    // for each item
    Parallel.ForEach (vertocalDB, (entry) => 
    {
        // We call the depth first search method 
        dfsPruning(prefix, entry.Value, frequentItems, frequentItems, entry.Key, 2);
    }
}

private void dfsPruning(Prefix prefix, Bitmap prefixBitmap, List<int> sn, List<int> inl, int hasToBeGreaterThanForIStep, int m)
{
    int maximumPatternLength = 100;

    Parallel.For(0,sn.Count,  new ParallelOptions { MaxDegreeOfParallelism = 10 }, (k) =>
    {
        if (maximumPatternLength > m)
        {
            dfsPruning(prefixSStep, newBitmap, sTemp, sTemp, item, m + 1);
        }
    });

    Parallel.For(0,inl.Count, new ParallelOptions { MaxDegreeOfParallelism = 10 }, (k) => 
    {
        if (maximumPatternLength > m)
        {
            dfsPruning(prefixIStep, newBitmap, sTemp, iTemp, item, m + 1);
        }
    });
}