通过

Barrier 类

  • 参考

定义

命名空间:
System.Threading
程序集:
System.Threading.dll
程序集:
System.dll
程序集:
netstandard.dll

使多个任务能够采用并行方式依据某种算法在多个阶段中协同工作。

public ref class Barrier : IDisposable
public class Barrier : IDisposable
[System.Runtime.InteropServices.ComVisible(false)]
public class Barrier : IDisposable
type Barrier = class
    interface IDisposable
[<System.Runtime.InteropServices.ComVisible(false)>]
type Barrier = class
    interface IDisposable
Public Class Barrier
Implements IDisposable
继承
Object
Barrier
属性
ComVisibleAttribute
实现
IDisposable

示例

以下示例演示如何使用屏障：

using System;
using System.Threading;
using System.Threading.Tasks;

class BarrierDemo
{
    // Demonstrates:
    //      Barrier constructor with post-phase action
    //      Barrier.AddParticipants()
    //      Barrier.RemoveParticipant()
    //      Barrier.SignalAndWait(), incl. a BarrierPostPhaseException being thrown
    static void BarrierSample()
    {
        int count = 0;

        // Create a barrier with three participants
        // Provide a post-phase action that will print out certain information
        // And the third time through, it will throw an exception
        Barrier barrier = new Barrier(3, (b) =>
        {
            Console.WriteLine("Post-Phase action: count={0}, phase={1}", count, b.CurrentPhaseNumber);
            if (b.CurrentPhaseNumber == 2) throw new Exception("D'oh!");
        });

        // Nope -- changed my mind.  Let's make it five participants.
        barrier.AddParticipants(2);

        // Nope -- let's settle on four participants.
        barrier.RemoveParticipant();

        // This is the logic run by all participants
        Action action = () =>
        {
            Interlocked.Increment(ref count);
            barrier.SignalAndWait(); // during the post-phase action, count should be 4 and phase should be 0
            Interlocked.Increment(ref count);
            barrier.SignalAndWait(); // during the post-phase action, count should be 8 and phase should be 1

            // The third time, SignalAndWait() will throw an exception and all participants will see it
            Interlocked.Increment(ref count);
            try
            {
                barrier.SignalAndWait();
            }
            catch (BarrierPostPhaseException bppe)
            {
                Console.WriteLine("Caught BarrierPostPhaseException: {0}", bppe.Message);
            }

            // The fourth time should be hunky-dory
            Interlocked.Increment(ref count);
            barrier.SignalAndWait(); // during the post-phase action, count should be 16 and phase should be 3
        };

        // Now launch 4 parallel actions to serve as 4 participants
        Parallel.Invoke(action, action, action, action);

        // This (5 participants) would cause an exception:
        // Parallel.Invoke(action, action, action, action, action);
        //      "System.InvalidOperationException: The number of threads using the barrier
        //      exceeded the total number of registered participants."

        // It's good form to Dispose() a barrier when you're done with it.
        barrier.Dispose();
    }
}

Imports System.Threading
Imports System.Threading.Tasks

Module BarrierSample

    ' Demonstrates:
    ' Barrier constructor with post-phase action
    ' Barrier.AddParticipants()
    ' Barrier.RemoveParticipant()
    ' Barrier.SignalAndWait(), incl. a BarrierPostPhaseException being thrown
    Sub Main()
        Dim count As Integer = 0

        ' Create a barrier with three participants
        ' Provide a post-phase action that will print out certain information
        ' And the third time through, it will throw an exception
        Dim barrier As New Barrier(3,
                                   Sub(b)
                                       Console.WriteLine("Post-Phase action: count={0}, phase={1}", count, b.CurrentPhaseNumber)
                                       If b.CurrentPhaseNumber = 2 Then
                                           Throw New Exception("D'oh!")
                                       End If
                                   End Sub)

        ' Nope -- changed my mind. Let's make it five participants.
        barrier.AddParticipants(2)

        ' Nope -- let's settle on four participants.
        barrier.RemoveParticipant()


        ' This is the logic run by all participants
        Dim action As Action =
            Sub()
                Interlocked.Increment(count)
                barrier.SignalAndWait()
                ' during the post-phase action, count should be 4 and phase should be 0

                Interlocked.Increment(count)
                barrier.SignalAndWait()
                ' during the post-phase action, count should be 8 and phase should be 1

                ' The third time, SignalAndWait() will throw an exception and all participants will see it
                Interlocked.Increment(count)
                Try
                    barrier.SignalAndWait()
                Catch bppe As BarrierPostPhaseException
                    Console.WriteLine("Caught BarrierPostPhaseException: {0}", bppe.Message)
                End Try

                ' The fourth time should be hunky-dory
                Interlocked.Increment(count)
                ' during the post-phase action, count should be 16 and phase should be 3
                barrier.SignalAndWait()

            End Sub

        ' Now launch 4 parallel actions to serve as 4 participants
        Parallel.Invoke(action, action, action, action)

        ' This (5 participants) would cause an exception:
        '   Parallel.Invoke(action, action, action, action, action)
        ' "System.InvalidOperationException: The number of threads using the barrier
        ' exceeded the total number of registered participants."

        ' It's good form to Dispose() a barrier when you're done with it.
        barrier.Dispose()
    End Sub
End Module

注解

一组任务通过一系列阶段进行协作，其中组中的每个任务都表示已到达 Barrier 给定阶段，并隐式等待其他人到达。 同一 Barrier 个阶段可用于多个阶段。

构造函数

Barrier(Int32)

初始化 Barrier 类的新实例。
Barrier(Int32, Action<Barrier>)

初始化 Barrier 类的新实例。

属性

CurrentPhaseNumber

获取屏障的当前阶段的编号。
ParticipantCount

获取屏障中参与者的总数。
ParticipantsRemaining

获取屏障中尚未在当前阶段发出信号的参与者的数量。

方法

AddParticipant()

通知 Barrier，告知其将会有另一个参与者。
AddParticipants(Int32)

通知 Barrier，告知其将会有多个其他参与者。
Dispose()

释放 Barrier 类的当前实例所使用的所有资源。
Dispose(Boolean)

释放由 Barrier 占用的非托管资源，还可以另外再释放托管资源。
Equals(Object)

确定指定对象是否等于当前对象。

(继承自 Object)
GetHashCode()

作为默认哈希函数。

(继承自 Object)
GetType()

获取当前实例的 Type。

(继承自 Object)
MemberwiseClone()

创建当前 Object 的浅表副本。

(继承自 Object)
RemoveParticipant()

通知 Barrier，告知其将会减少一个参与者。
RemoveParticipants(Int32)

通知 Barrier，告知其将会减少一些参与者。
SignalAndWait()

发出参与者已达到屏障并等待所有其他参与者也达到屏障。
SignalAndWait(CancellationToken)

发出参与者已达到屏障的信号，并等待所有其他参与者达到屏障，同时观察取消标记。
SignalAndWait(Int32)

发出参与者已达到屏障的信号，并等待所有其他参与者也达到屏障，同时使用 32 位带符号整数测量超时。
SignalAndWait(Int32, CancellationToken)

发出参与者已达到屏障的信号，并等待所有其他参与者也达到屏障，使用 32 位带符号整数测量超时，同时观察取消标记。
SignalAndWait(TimeSpan)

发出参与者已达到屏障的信号，并等待所有其他参与者也达到屏障，同时使用 TimeSpan 对象测量时间间隔。
SignalAndWait(TimeSpan, CancellationToken)

发出参与者已达到屏障的信号，并等待所有其他参与者也达到屏障，使用 TimeSpan 对象测量时间间隔，同时观察取消标记。
ToString()

返回表示当前对象的字符串。

(继承自 Object)

适用于

线程安全性

所有公共成员和受保护的成员 Barrier 都是线程安全的，并且可能同时从多个线程使用，但 Dispose 除外，只有在完成所有其他操作 Barrier 时才使用。

另请参阅