关于Parallel.ForEach的不解，请高人指点-白红宇

关于Parallel.ForEach的不解，请高人指点

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发布时间：2019-06-14

本文共 3435 字，大约阅读时间需要 11 分钟。

刚看CLR VIA C# 关于 Parallel.ForEach讲解，依葫芦画瓢自己写了一个实例，功能实现了，但是不明白如何实现，看源码看的一头雾水，求高人分析，能帮忙写个简单的内部实现过程

废话不多说直接上代码

//通过for实现运算 private static long GetTotalCount(String[] strs) {     long totalCount = 0;    for (int i = 0; i < strs.Length; i++)     {          //假设操作耗时            Thread.Sleep(50);             totalCount += strs[i].Length;       }            return totalCount; }

1 //通过Parallel.ForEach来实现运算 2  private static long GetParallelTotalCount(String[] strs) 3 { 4       long totalCount = 0; 5       Parallel.ForEach
     
      (strs, () => 0, (str, loopState, index, length) => 6            { 7                  //假设操作耗时 8                   Thread.Sleep(50); 9                    return str.Length + length;10             },11                length => Interlocked.Add(ref totalCount, length));12 13        return totalCount;14 }

调用过程

1 private static void Main(string[] args) 2         { 3             string[] strs = new[] {
   "3243","544","5445","dfg","dfgd","hghhhg"}; 4  5             List
     
       list = new List
      
       (); 6             list.AddRange(strs); 7             list.AddRange(strs); 8             list.AddRange(strs); 9             list.AddRange(strs);10             list.AddRange(strs);11             list.AddRange(strs);12             list.AddRange(strs);13             list.AddRange(strs);14             list.AddRange(strs);15             list.AddRange(strs);16             list.AddRange(strs);17             list.AddRange(strs);18             list.AddRange(strs);19             list.AddRange(strs);20             list.AddRange(strs);21             list.AddRange(strs);22             list.AddRange(strs);23             list.AddRange(strs);24             list.AddRange(strs);25             list.AddRange(strs);26 27             string[] strTemp = list.ToArray();28 29             Console.WriteLine("Parallel Start");30             Stopwatch watch = new Stopwatch();31             watch.Start();32             long totalLength =GetParallelTotalCount(strTemp);33             watch.Stop();34             Console.WriteLine("TotalCount:{0},Time:{1}", totalLength, watch.ElapsedMilliseconds);35             Console.WriteLine("Parallel End");36             Console.WriteLine("For Start");37             watch.Restart();38             totalLength = GetTotalCount(strTemp);39             watch.Stop();40             Console.WriteLine("TotalCount:{0},Time:{1}", totalLength, watch.ElapsedMilliseconds);41             Console.WriteLine("For End");42             Console.Read();43         }

得到效果：

求不吝赐教Parallel.ForEach怎么实现的，代码中通过Parallel.ForEach来实现运算中，在ForEach终结委托里他是对长度进行了相加，为什么在主体委托中是 return str.Length + length;而不是return length;对立面如何实现不了解

在提示下，对代码进行了点修改

1 //通过Parallel.ForEach来实现运算 2  private static long GetParallelTotalCount(String[] strs) 3 { 4      long totalCount = 0; 5       Parallel.ForEach
     
      (strs, () => 0, (str, loopState, index, length) => 6       { 7             //假设操作耗时 8                                                           Console.WriteLine("ThreadId:{0},CurrentLength;{1},LastLength:{2}", Thread.CurrentThread.ManagedThreadId, str.Length, length); 9             Thread.Sleep(50);10             return str.Length + length;},11             length => Interlocked.Add(ref totalCount, length));12       return totalCount;13 }

得到效果：

得出的结论也正如我图片上提到的，一些线程得到的数据看上去是数值的累加，其他一些线程驳斥了这一点。还是不太明白，最主要技术不到家，看源码看不懂

转载于:https://www.cnblogs.com/sjr10/p/Parallel_ForEach.html

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