C# .Net Core6 多執行緒處理ThreadPool PartII

從上一篇可知ThreadPool的基本設定了，不過接下來又遇上新的問題。

1.  如何確認所有執行緒完成？
2.  將主控台專案改為WinForm專案使用ThreadPool...

首先，先說明如何確認所有執行緒完成工作？
在此我使用者WaitHandle.WaitAll()來確認。
依照官網的說明，必須將doneEvent = new ManualResetEvent(false)帶入ThreadPool，最終使用doneEvent陣列帶入WaitHandle.WaitAll()即可。
二話不說，先上程式碼。

internal class Program
{
    static void Main(string[] args)
    {
        const int FibonacciCalculations = 10;
        firtstTest(FibonacciCalculations);
    }
    
    private static void ThreadPoolCallbackV1(object obj)
    {
        if(obj == null) return;
        ManualResetEvent doneEvent = (ManualResetEvent)obj;
        Console.WriteLine(nameof(ThreadPoolCallbackV1));
        doneEvent.Set();
    }
    
    private static void firtstTest(int theadCount)
    {
        ThreadPool.SetMinThreads(2, 2);
        ThreadPool.SetMaxThreads(3, 3);
        ManualResetEvent[] doneEvents = new ManualResetEvent[theadCount];
        for(var i = 0; i < theadCount; i++)
        {
            doneEvents[i] = new ManualResetEvent(false);
            Console.WriteLine($"{nameof(firtstTest)} 第 {i} 次執行...");
            ThreadPool.QueueUserWorkItem(ThreadPoolCallbackV1, doneEvents[i]);
        }
        
        WaitHandle.WaitAll(doneEvents);
        Console.WriteLine("All calculations are complete.");
    }
}

是的，這個是主控台的程式碼，當所有執行緒完成後，才會印出最後一個句子。

接下來的問題，就是要把這段程式碼改道WomForm的專案了...
最剛開始，我想...在主控台都測通過了，沒有問題。於是，隨便開了個空的Form表單，就把程式碼貼過去了。
結果？ 當然是失敗了...

我花了至少三天才搞定它，雖然解法非常簡單...
二話不說，先上程式碼。

Program.cs

internal static class Program
{
    /// 

    ///  The main entry point for the application.
    /// 
    //[STAThread] 將STAThread改為MTAThread，WaitHandle.WaitAll不支援STAThread，改為MTAThread就能夠執行...
    [MTAThread]
    static void Main()
    {
        // To customize application configuration such as set high DPI settings or default font,
        // see https://aka.ms/applicationconfiguration.
        ApplicationConfiguration.Initialize();
        Application.Run(new Form1());
    }
}

Form1.cs

private string _content = string.Empth;
public partial class Form1 : Form
{
    public TpcGrpcStressTest()
    {
        InitializeComponent();
    }
    
    private static void ThreadPoolCallbackV1(object obj)
    {
    	if(obj == null) return;
    	ManualResetEvent doneEvent = (ManualResetEvent)obj;
    	_content += nameof(ThreadPoolCallbackV1) + Environment.NewLine;
    	doneEvent.Set();
    }

    private static void firtstTest(int theadCount)
    {
    	ThreadPool.SetMinThreads(2, 2);
    	ThreadPool.SetMaxThreads(3, 3);
    	ManualResetEvent[] doneEvents = new ManualResetEvent[theadCount];
    	for(var i = 0; i < theadCount; i++)
    	{
    		doneEvents[i] = new ManualResetEvent(false);
    		_content += $"{nameof(firtstTest)} 第 {i} 次執行..." + Environment.NewLine;
    		ThreadPool.QueueUserWorkItem(ThreadPoolCallbackV1, doneEvents[i]);
    	}
        
        WaitHandle.WaitAll(doneEvents);
    }

    private void SubmitBtn_Click(object sender, EventArgs e)
    {
        firtstTest(10);
        TextBox1.Text = _content + "All calculations are complete.";
    }
}

答案超簡單，但困擾我許久，特別記錄下來，免得下次又發生。

參考網址： AutoResetEvent.WaitAll 等到人生三大事，然后大笑开心。

---

本以為到此為止，但是當我測試超過100筆執行緒時，又一個問題出現了...
System.NotSupportedException: 'The number of WaitHandles must be less than or equal to 64.'

再去查了資訊，才發現原來超過64個執行緒使用WaitHandle.WaitAll會錯誤...
實際找到解法後，說明不需要使用WaitHandle.WaitAll來檢查程序是否執行完成，那麼二話不說，修改程式碼...

Program.cs

internal static class Program
{
    /// 

    ///  The main entry point for the application.
    /// 
    [STAThread]
    static void Main()
    {
        // To customize application configuration such as set high DPI settings or default font,
        // see https://aka.ms/applicationconfiguration.
        ApplicationConfiguration.Initialize();
        Application.Run(new Form1());
    }
}

Form1.cs

public partial class Form1 : Form
{
    private string _content = string.Empth;
    private static int _numerOfThreadsNotYetCompleted = 0;
    private static ManualResetEvent _doneEvent = new ManualResetEvent(false);
    
    public TpcGrpcStressTest()
    {
        InitializeComponent();
    }
    
    private static void ThreadPoolCallbackV1(object obj)
    {
    	if(obj == null) return;
        try
        {
            ManualResetEvent doneEvent = (ManualResetEvent)obj;
            _content += $"{nameof(ThreadPoolCallbackV1)} 第 {(int)i} 次執行...") + Environment.NewLine;
            doneEvent.Set();
        }
        finally
        {
            if (Interlocked.Decrement(ref _numerOfThreadsNotYetCompleted) == 0)
                _doneEvent.Set();
        }
    }

    private static void firtstTest(int theadCount)
    {
    	ThreadPool.SetMinThreads(2, 2);
    	ThreadPool.SetMaxThreads(3, 3);
    	for(var i = 0; i < theadCount; i++)
    	{
    		_content += nameof(firtstTest) + Environment.NewLine;
    		ThreadPool.QueueUserWorkItem(ThreadPoolCallbackV1, (object)i);
    	}
        _doneEvent.WaitOne();
    }

    private void SubmitBtn_Click(object sender, EventArgs e)
    {
        _numerOfThreadsNotYetCompleted = 100;
        firtstTest(100);
        TextBox1.Text = _content + "All calculations are complete.";
    }
}

參考網址： Solved: “The number of WaitHandles must be less than or equal to 64″