c# - 屏障类C#

我确实了解C#中使用的Barrier类。但是，在下面的代码中，我不明白为什么SignalAndWait()被调用了两次？任务中的电话还不够吗？该代码基本上对以下情况进行了建模:三个 friend (或任务)从A到B，从B到C，有的从B到A，而没有去C。
请帮帮我。顺便说一句，这段代码来自本书:MCSD Certification Exam Toolkit(70-483)。非常感谢你!

static void Main(string[] args)
{
    var participants = 5;
    Barrier barrier = new Barrier(participants + 1,
        b => { // This method is only called when all the paricipants arrived.
            Console.WriteLine("{0} paricipants are at rendez-vous point {1}.",
                b.ParticipantCount -1, // We substract the main thread.
                b.CurrentPhaseNumber);
        });
    for (int i = 0; i < participants; i++)
    {
        var localCopy = i;
        Task.Run(() => {
            Console.WriteLine("Task {0} left point A!", localCopy);
            Thread.Sleep(1000 * localCopy + 1); // Do some "work"
            if (localCopy % 2 == 0) {
                Console.WriteLine("Task {0} arrived at point B!", localCopy);
                barrier.SignalAndWait();
            }
            else
            {
                Console.WriteLine("Task {0} changed its mind and went back!", localCopy);
                barrier.RemoveParticipant();
                return;
            }
            Thread.Sleep(1000 * (participants - localCopy)); // Do some "morework"
            Console.WriteLine("Task {0} arrived at point C!", localCopy);
            barrier.SignalAndWait();
        });
    }

    Console.WriteLine("Main thread is waiting for {0} tasks!",
    barrier.ParticipantCount - 1);
    barrier.SignalAndWait(); // Waiting at the first phase
    barrier.SignalAndWait(); // Waiting at the second phase
    Console.WriteLine("Main thread is done!");
}

最佳答案

您还将看到Console.WriteLine("{0} paricipants are at rendez-vous point {1}.",...)行执行两次。

单个Barrier实例用于在B和C处集合。(剩余的)taks调用SignalAndWait()标记它们到达B和C的位置，因此标记了两个调用。

修改后的代码:

   if (localCopy % 2 == 0)
   {
        ...
        barrier.SignalAndWait();       // arrival at B
    }
    else
    {
        ...
        barrier.RemoveParticipant();   // return to A
        return;
    }
    ...
    barrier.SignalAndWait();           // arrival at C

关于c# - 屏障类C#，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/24975239/