Question

我正在使用以下.NET代码

 Class MonitorSample
  Shared Sub RunMonitor()
    Dim o As New Object()
    For i As Integer = 0 To 99
    ThreadPool.QueueUserWorkItem(Function()
       Try
       Monitor.Enter(o)
       Console.WriteLine("Thread {0} acquired lock...working", Thread.CurrentThread.ManagedThreadId)
       Console.WriteLine("Thread {0} performing some I/O operation so yielding the lock temporarily...", Thread.CurrentThread.ManagedThreadId)
       Monitor.PulseAll(o)
       Monitor.Wait(o)
       Console.WriteLine("Thread {0} reacquired lock", Thread.CurrentThread.ManagedThreadId)
       Finally
       Console.WriteLine("Thread {0} released lock", Thread.CurrentThread.ManagedThreadId)
       Monitor.PulseAll(o)
       Monitor.Exit(o)
       End Try
     Return Nothing
   End Function
  )
  Next
  Console.ReadLine()
 End Sub
 Shared Sub Main()
 Dim stopwatch As New Stopwatch()
   stopwatch.Start()
   RunMonitor()
   stopwatch.Stop()
   Console.WriteLine("Time elapsed: {0}", stopwatch.Elapsed)
 End Sub
End Class

在主方法中，这是通过线程计算时间的正确方法，或者我们应该在其他方面进行计算。

实际上，打印时间的步骤首先打印，而线程稍后执行。

Answer 1

您的Sub不会按照您的意愿执行 - 这里有2个问题

还有Console.Readline等待用户在StopWatch中的输入
您没有正确地同步线程 - 幸运的是，线程通常在等待用户输入时完成，但这不允许您为线程计时。

以下内容应通过将秒表紧紧围绕线程移动来解决此问题，并提供CountDownEvent以允许每个线程指示它何时完成。

    Shared Sub RunMonitor()
        Dim stopwatch As New Stopwatch()
        stopwatch.Start()
        Dim o As New Object()
        Const numThreads As Integer = 10
        ' Create an Event which signals when we are finished
        Dim allDoneEvent As New CountdownEvent(numThreads)
        For i As Integer = 0 To numThreads - 1
            ThreadPool.QueueUserWorkItem(Function()
                                             Try
                                                 Monitor.Enter(o)
                                                 Console.WriteLine("Thread {0} acquired lock...working", Thread.CurrentThread.ManagedThreadId)
                                                 Console.WriteLine("Thread {0} performing some I/O operation so yielding the lock temporarily...", Thread.CurrentThread.ManagedThreadId)
                                                 Monitor.PulseAll(o)
                                                 Monitor.Wait(o)
                                                 Console.WriteLine("Thread {0} reacquired lock", Thread.CurrentThread.ManagedThreadId)
                                             Finally
                                                 Console.WriteLine("Thread {0} released lock", Thread.CurrentThread.ManagedThreadId)
                                                 Monitor.PulseAll(o)
                                                 Monitor.Exit(o)
                                                 ' This thread indicates that it has finished its work
                                                 allDoneEvent.Signal()
                                             End Try
                                             Return Nothing
                                         End Function
          )
        Next
        ' Wait for all events to finish, or after a timeout
        allDoneEvent.Wait(10000)
        ' Stop the stopwatch before the readline
        stopwatch.Stop()
        Console.WriteLine("Time elapsed: {0}", stopwatch.Elapsed)
        Console.ReadLine()
    End Sub

如何计算所有线程所用的时间

1 个答案: