[英]Join threads from thread pool
我有30多个可以并行执行的任务。
我为每个任务使用ThreadPool。
但是,在所有任务完成之前,父功能不应返回。
我需要一个线程同步句柄,当其计数达到0时将释放WaitOne。
foo.StartWith(myTasks.Count);
foreach (var task in myTasks) {
ThreadPool.QueueUserWorkItem(state => { task(state); foo.Release(); });
}
foo.WaitOne();
Semaphore
感觉不错,只是无法弄清楚如何在此处应用它。
int running = myTasks.Count;
AutoResetEvent done = new AutoResetEvent(false);
foreach (var task in myTasks) {
ThreadPool.QueueUserWorkItem(state => {
task(state);
if (0 == Interlocked.Decrement(ref running))
done.Set ();
});
}
done.WaitOne();
在C#4.0中,您可以使用新的CountdownEvent原语。
根据本文的介绍: 同步基元概述
C#在此情况下具有内置类型CountDownEvent: CountdownEvent类
或类似的一种: 屏障(.NET Framework)
对于较新的版本,请使用TPL(任务并行库),对于此场景,此代码是相关的:
// Create an ActionBlock<int> object that prints its input
// and throws ArgumentOutOfRangeException if the input
// is less than zero.
var throwIfNegative = new ActionBlock<int>(n =>
{
Console.WriteLine("n = {0}", n);
if (n < 0)
{
throw new ArgumentOutOfRangeException();
}
});
// Post values to the block.
throwIfNegative.Post(0);
throwIfNegative.Post(-1);
throwIfNegative.Post(1);
throwIfNegative.Post(-2);
throwIfNegative.Complete();
// Wait for completion in a try/catch block.
try
{
throwIfNegative.Completion.Wait();
}
catch (AggregateException ae)
{
// If an unhandled exception occurs during dataflow processing, all
// exceptions are propagated through an AggregateException object.
ae.Handle(e =>
{
Console.WriteLine("Encountered {0}: {1}",
e.GetType().Name, e.Message);
return true;
});
}
/* Output:
n = 0
n = -1
Encountered ArgumentOutOfRangeException: Specified argument was out of the range
of valid values.
*/
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