如何在.net 3.5中实现.net 4中Barrier类的功能

class Program
{
    const int numOfThreads = 3;
    static AutoResetEvent[] barrier = new AutoResetEvent[numOfThreads];
    static Random random = new Random(System.DateTime.Now.Millisecond);
    static void barriers2(object barrierObj)
    {
        AutoResetEvent[] barrierLocal = (AutoResetEvent[])barrierObj;
        string name = Thread.CurrentThread.Name;
        for (int i = 0; i < 10; i++)
        {
            int sleepTime = random.Next(2000, 10000);
            System.Console.Out.WriteLine("Thread {0} at the 'barrier' will sleep for {1}.", name, sleepTime);
            Thread.Sleep(sleepTime);
            System.Console.Out.WriteLine("Thread {0} at the 'barrier' with time {1}.", name, sleepTime);
            int currentId = Convert.ToInt32(name);
            //for(int z = 0; z < numOfThreads; z++)
                barrierLocal[currentId].Set();
            WaitHandle.WaitAll(barrier);
            /*
            for (int k = 0; k < numOfThreads; k++)
            {
                if (k == currentId)
                {
                    continue;
                }
                System.Console.Out.WriteLine("Thread {0} is about to wait for the singla from thread: {1}", name, k);
                barrierLocal[k].WaitOne();
                System.Console.Out.WriteLine("Thread {0} is about to wait for the singla from thread: {1}. done", name, k);
            }
            */
        }
    }
    static void Main(string[] args)
    {
        for (int i = 0; i < numOfThreads; i++)
        {
            barrier[i] = new AutoResetEvent(false);
        }
        for (int i = 0; i < numOfThreads; i++)
        {
            Thread t = new Thread(Program.barriers2);
            t.Name = Convert.ToString(i);
            t.Start(barrier);
        }
    }
}

这是因为你使用了AutoResetEvent。线程的一个WaitAll()调用将首先完成。这会自动在所有AREs上触发Reset()。这会阻止其他线程完成它们的WaitAll()调用。

下载。net 3.5的响应式扩展后端口。您将发现Barrier类以及。net 4.0中发布的其他有用的并发数据结构和同步机制。

这是我在XNA游戏中使用的实现。当我写这篇文章时，Barrier还没有可用，我仍然坚持使用。net 3.5。它需要三组manualreseteevents和一个计数器数组来保持相位。

using System;
using System.Threading;
namespace Colin.Threading
{
    /// <summary>
    /// Threading primitive for "barrier" sync, where N threads must stop at certain points 
    /// and wait for all their bretheren before continuing.
    /// </summary>
    public sealed class NThreadGate
    {
        public int mNumThreads;
        private ManualResetEvent[] mEventsA;
        private ManualResetEvent[] mEventsB;
        private ManualResetEvent[] mEventsC;
        private ManualResetEvent[] mEventsBootStrap;
        private Object mLockObject;
        private int[] mCounter;
        private int mCurrentThreadIndex = 0;
        public NThreadGate(int numThreads)
        {
            this.mNumThreads = numThreads;
            this.mEventsA = new ManualResetEvent[this.mNumThreads];
            this.mEventsB = new ManualResetEvent[this.mNumThreads];
            this.mEventsC = new ManualResetEvent[this.mNumThreads];
            this.mEventsBootStrap = new ManualResetEvent[this.mNumThreads];
            this.mCounter = new int[this.mNumThreads];
            this.mLockObject = new Object();
            for (int i = 0; i < this.mNumThreads; i++)
            {
                this.mEventsA[i] = new ManualResetEvent(false);
                this.mEventsB[i] = new ManualResetEvent(false);
                this.mEventsC[i] = new ManualResetEvent(false);
                this.mEventsBootStrap[i] = new ManualResetEvent(false);
                this.mCounter[i] = 0;
            }
        }
        /// <summary>
        /// Adds a new thread to the gate system.
        /// </summary>
        /// <returns>Returns a thread ID for this thread, to be used later when waiting.</returns>
        public int AddThread()
        {
            lock (this.mLockObject)
            {
                this.mEventsBootStrap[this.mCurrentThreadIndex].Set();
                this.mCurrentThreadIndex++;
                return this.mCurrentThreadIndex - 1;
            }
        }
        /// <summary>
        /// Stop here and wait for all the other threads in the NThreadGate. When all the threads have arrived at this call, they
        /// will unblock and continue.
        /// </summary>
        /// <param name="myThreadID">The thread ID of the caller</param>
        public void WaitForOtherThreads(int myThreadID)
        {
            // Make sure all the threads are ready.
            WaitHandle.WaitAll(this.mEventsBootStrap);
            // Rotate between three phases.
            int phase = this.mCounter[myThreadID];
            if (phase == 0)        // Flip
            {
                this.mEventsA[myThreadID].Set();
                WaitHandle.WaitAll(this.mEventsA);
                this.mEventsC[myThreadID].Reset();
            }
            else if (phase == 1)    // Flop
            {
                this.mEventsB[myThreadID].Set();
                WaitHandle.WaitAll(this.mEventsB);
                this.mEventsA[myThreadID].Reset();
            }
            else    // Floop
            {
                this.mEventsC[myThreadID].Set();
                WaitHandle.WaitAll(this.mEventsC);
                this.mEventsB[myThreadID].Reset();
                this.mCounter[myThreadID] = 0;
                return;
            }
            this.mCounter[myThreadID]++;
        }
    }
}

设置线程门:

private void SetupThreads()
{
    // Make an NThreadGate for N threads.
    this.mMyThreadGate = new NThreadGate(Environment.ProcessorCount);
    // Make some threads...
    // e.g. new Thread(new ThreadStart(this.DoWork);
}

线程工作者方法:

private void DoWork()
{
    int localThreadID = this.mMyThreadGate.AddThread();
    while (this.WeAreStillRunning)
    {
        // Signal this thread as waiting at the barrier
        this.mMyThreadGate.WaitForOtherThreads(localThreadID);
        // Synchronized work here...
        // Signal this thread as waiting at the barrier
        this.mMyThreadGate.WaitForOtherThreads(localThreadID);
        // Synchronized work here...
        // Signal this thread as waiting at the barrier
        this.mMyThreadGate.WaitForOtherThreads(localThreadID);
    }
}