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C# 事件 : How to process event in a parallel manner

转载 作者:太空狗 更新时间:2023-10-30 00:17:30 25 4
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我想以并行方式处理一个事件。我的想法是将每个回调添加到 ThreadPool,有效地让每个方法注册由 ThreadPool 处理的事件。

我的试用代码如下所示:

Delegate[] delegates = myEvent.GetInvocationList();
IAsyncResult[] results = new IAsyncResult[ delegates.Count<Delegate>() ];

for ( int i = 0; i < delegates.Count<Delegate>(); i++ )
{
IAsyncResult result = ( ( TestDelegate )delegates[ i ] ).BeginInvoke( "BeginInvoke/EndInvoke", null, null );
results[ i ] = result;
}

for ( int i = 0; i < delegates.Length; i++ )
{
( ( TestDelegate )delegates[ i ] ).EndInvoke( results[ i ] );
}

这只是为了玩玩,因为我很好奇如何去做。我相信有更好的方法来做到这一点。 我不喜欢 Func 创建一个包含 lambda 的 WaitCallback。此外,与直接调用委托(delegate)相比,DynamicInvoke 非常慢。我怀疑这种处理事件的方式是否比按顺序处理更快。

我的问题是:如何以并行方式处理事件,最好是使用 ThreadPool?

因为我通常使用 Mono,所以 .NET 4.0 或任务并行库都不是一个选项。

谢谢!

编辑:- 由于 Earwickers 的回答更正了示例。- 更新试用代码

最佳答案

我会选择一种使用 DynamicMethod (LCG) 和状态对象的方法,该对象携带参数并跟踪调用(以便您可以等待它们完成)。

代码:应该做这样的事情(虽然还没有经过全面测试,因此在某些情况下可能会抛出一些讨厌的异常):

/// <summary>
/// Class for dynamic parallel invoking of a MulticastDelegate.
/// (C) 2009 Arsène von Wyss, avw@gmx.ch
/// No warranties of any kind, use at your own risk. Copyright notice must be kept in the source when re-used.
/// </summary>
public static class ParallelInvoke {
private class ParallelInvokeContext<TDelegate> where TDelegate: class {
private static readonly DynamicMethod invoker;
private static readonly Type[] parameterTypes;

static ParallelInvokeContext() {
if (!typeof(Delegate).IsAssignableFrom(typeof(TDelegate))) {
throw new InvalidOperationException("The TDelegate type must be a delegate");
}
Debug.Assert(monitor_enter != null, "Could not find the method Monitor.Enter()");
Debug.Assert(monitor_pulse != null, "Could not find the method Monitor.Pulse()");
Debug.Assert(monitor_exit != null, "Could not find the method Monitor.Exit()");
FieldInfo parallelInvokeContext_activeCalls = typeof(ParallelInvokeContext<TDelegate>).GetField("activeCalls", BindingFlags.Instance|BindingFlags.NonPublic);
Debug.Assert(parallelInvokeContext_activeCalls != null, "Could not find the private field ParallelInvokeContext.activeCalls");
FieldInfo parallelInvokeContext_arguments = typeof(ParallelInvokeContext<TDelegate>).GetField("arguments", BindingFlags.Instance|BindingFlags.NonPublic);
Debug.Assert(parallelInvokeContext_arguments != null, "Could not find the private field ParallelInvokeContext.arguments");
MethodInfo delegate_invoke = typeof(TDelegate).GetMethod("Invoke", BindingFlags.Instance|BindingFlags.Public);
Debug.Assert(delegate_invoke != null, string.Format("Could not find the method {0}.Invoke()", typeof(TDelegate).FullName));
if (delegate_invoke.ReturnType != typeof(void)) {
throw new InvalidOperationException("The TDelegate delegate must not have a return value");
}
ParameterInfo[] parameters = delegate_invoke.GetParameters();
parameterTypes = new Type[parameters.Length];
invoker = new DynamicMethod(string.Format("Invoker<{0}>", typeof(TDelegate).FullName), typeof(void), new[] {typeof(ParallelInvokeContext<TDelegate>), typeof(object)},
typeof(ParallelInvokeContext<TDelegate>), true);
ILGenerator il = invoker.GetILGenerator();
LocalBuilder args = (parameters.Length > 2) ? il.DeclareLocal(typeof(object[])) : null;
bool skipLoad = false;
il.BeginExceptionBlock();
il.Emit(OpCodes.Ldarg_1); // the delegate we are going to invoke
if (args != null) {
Debug.Assert(args.LocalIndex == 0);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldfld, parallelInvokeContext_arguments);
il.Emit(OpCodes.Dup);
il.Emit(OpCodes.Stloc_0);
skipLoad = true;
}
foreach (ParameterInfo parameter in parameters) {
if (parameter.ParameterType.IsByRef) {
throw new InvalidOperationException("The TDelegate delegate must note have out or ref parameters");
}
parameterTypes[parameter.Position] = parameter.ParameterType;
if (args == null) {
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Ldfld, parallelInvokeContext_arguments);
} else if (skipLoad) {
skipLoad = false;
} else {
il.Emit(OpCodes.Ldloc_0);
}
il.Emit(OpCodes.Ldc_I4, parameter.Position);
il.Emit(OpCodes.Ldelem_Ref);
if (parameter.ParameterType.IsValueType) {
il.Emit(OpCodes.Unbox_Any, parameter.ParameterType);
}
}
il.Emit(OpCodes.Callvirt, delegate_invoke);
il.BeginFinallyBlock();
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Call, monitor_enter);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Dup);
il.Emit(OpCodes.Ldfld, parallelInvokeContext_activeCalls);
il.Emit(OpCodes.Ldc_I4_1);
il.Emit(OpCodes.Sub);
il.Emit(OpCodes.Dup);
Label noPulse = il.DefineLabel();
il.Emit(OpCodes.Brtrue, noPulse);
il.Emit(OpCodes.Stfld, parallelInvokeContext_activeCalls);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Call, monitor_pulse);
Label exit = il.DefineLabel();
il.Emit(OpCodes.Br, exit);
il.MarkLabel(noPulse);
il.Emit(OpCodes.Stfld, parallelInvokeContext_activeCalls);
il.MarkLabel(exit);
il.Emit(OpCodes.Ldarg_0);
il.Emit(OpCodes.Call, monitor_exit);
il.EndExceptionBlock();
il.Emit(OpCodes.Ret);
}

[Conditional("DEBUG")]
private static void VerifyArgumentsDebug(object[] args) {
for (int i = 0; i < parameterTypes.Length; i++) {
if (args[i] == null) {
if (parameterTypes[i].IsValueType) {
throw new ArgumentException(string.Format("The parameter {0} cannot be null, because it is a value type", i));
}
} else if (!parameterTypes[i].IsAssignableFrom(args[i].GetType())) {
throw new ArgumentException(string.Format("The parameter {0} is not compatible", i));
}
}
}

private readonly object[] arguments;
private readonly WaitCallback invokeCallback;
private int activeCalls;

public ParallelInvokeContext(object[] args) {
if (parameterTypes.Length > 0) {
if (args == null) {
throw new ArgumentNullException("args");
}
if (args.Length != parameterTypes.Length) {
throw new ArgumentException("The parameter count does not match");
}
VerifyArgumentsDebug(args);
arguments = args;
} else if ((args != null) && (args.Length > 0)) {
throw new ArgumentException("This delegate does not expect any parameters");
}
invokeCallback = (WaitCallback)invoker.CreateDelegate(typeof(WaitCallback), this);
}

public void QueueInvoke(Delegate @delegate) {
Debug.Assert(@delegate is TDelegate);
activeCalls++;
ThreadPool.QueueUserWorkItem(invokeCallback, @delegate);
}
}

private static readonly MethodInfo monitor_enter;
private static readonly MethodInfo monitor_exit;
private static readonly MethodInfo monitor_pulse;

static ParallelInvoke() {
monitor_enter = typeof(Monitor).GetMethod("Enter", BindingFlags.Static|BindingFlags.Public, null, new[] {typeof(object)}, null);
monitor_pulse = typeof(Monitor).GetMethod("Pulse", BindingFlags.Static|BindingFlags.Public, null, new[] {typeof(object)}, null);
monitor_exit = typeof(Monitor).GetMethod("Exit", BindingFlags.Static|BindingFlags.Public, null, new[] {typeof(object)}, null);
}

public static void Invoke<TDelegate>(TDelegate @delegate) where TDelegate: class {
Invoke(@delegate, null);
}

public static void Invoke<TDelegate>(TDelegate @delegate, params object[] args) where TDelegate: class {
if (@delegate == null) {
throw new ArgumentNullException("delegate");
}
ParallelInvokeContext<TDelegate> context = new ParallelInvokeContext<TDelegate>(args);
lock (context) {
foreach (Delegate invocationDelegate in ((Delegate)(object)@delegate).GetInvocationList()) {
context.QueueInvoke(invocationDelegate);
}
Monitor.Wait(context);
}
}
}

用法:

ParallelInvoke.Invoke(yourDelegate, arguments);

注意事项:

  • 事件处理程序中的异常未得到处理(但 IL 代码有一个 finally 来递减计数器,因此该方法应该正确结束),这可能会导致麻烦。也可以在 IL 代码中捕获和传输异常。

  • 不执行继承以外的隐式转换(例如 int 到 double)并会抛出异常。

  • 所使用的同步技术不分配操作系统等待句柄,这通常有利于提高性能。可以在 Joseph Albahari's page 上找到关于监视器工作原理的描述。 .

  • 经过一些性能测试后,这种方法似乎比任何使用“ native ”BeginInvoke/EndInvoke 调用委托(delegate)的方法(至少在 MS CLR 中)都好得多。

关于C# 事件 : How to process event in a parallel manner,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1516119/

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