多线程测试

总结：

thread能启动非常多的线程同时工作，但threadpool和Task同时并行的线程数有限，约20个左右，但Threadpool设置最大并行数后则不会超过此数。

另：thread和threadpool的子线程中如果有未处理的异常，则主程序则会出现“*** 已停止工作”这样的错误（程序自动退出），而Task的子线程中出现未处理的异常时不影响主程序，即主程序不会退出。

 public partial class Form1 : Form
    {
        int count = 0;
        int 总次数 = 0;
        Random r = new Random();
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            //有300多个线程并行
            this.count = 0;
            this.总次数 = 0;
            for (int m = 0; m < 400; m++)
            {
                System.Threading.Thread t = new System.Threading.Thread(new System.Threading.ThreadStart(this.run));
                t.Start();
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //有10到40个线程并行
            this.count = 0;
            this.总次数 = 0;
            int a,b; //得到32767和1000
             System.Threading.ThreadPool.GetMaxThreads(out a,out b);
            for (int m = 0; m < 400; m++)
            {
                System.Threading.ThreadPool.QueueUserWorkItem(new WaitCallback( this.run),0);
            }
        }

        private void button5_Click(object sender, EventArgs e)
        {
            //有10到40个线程并行
            this.count = 0;
            this.总次数 = 0;
            int a, b; //得到32767和1000
            System.Threading.ThreadPool.GetMaxThreads(out a, out b);
            //设置为最大10后，并行数稳定在10个，设置最大100后，最多并行还是10到40个，这应该和机器有关
            System.Threading.ThreadPool.SetMaxThreads(10, 100);  
            for (int m = 0; m < 400; m++)
            {
                System.Threading.ThreadPool.QueueUserWorkItem(new WaitCallback(this.run), 0);
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
            //有10到40多个线程并行，运行效率基本同于QueueUserWorkItem
            this.count = 0;
            this.总次数 = 0;
           
            for (int m = 0; m < 400; m++)
            {
                System.Threading.Tasks.Task.Factory.StartNew(this.run);
            }
        }

        private void run()
        {
            Interlocked.Increment(ref this.总次数);
            Interlocked.Increment(ref this.count);
            System.Threading.Thread.Sleep(r.Next(10) * 1000);

            System.Threading.Interlocked.Decrement(ref this.count);

            this.异常();
        }

        private void run(object ob)
        {
            Interlocked.Increment(ref this.总次数);
            Interlocked.Increment(ref this.count);
         
            System.Threading.Thread.Sleep(r.Next(10) * 1000);

            System.Threading.Interlocked.Decrement(ref this.count);

            this.异常();
        }

        private void 异常()
        {
            throw new Exception("ddd");

            //try
            //{
            //    throw new Exception("ddd");
            //}
            //catch (Exception ex)
            //{

            //}
        }

        private void button4_Click(object sender, EventArgs e)
        {
            this.textBox1.Text = this.count.ToString() + " / " + this.总次数;
        }

      
    }

另外，多线程方式使用  System.Threading.Thread 创建线程时非常慢，创建超过200个创建就会非常明显的阻塞，如：

  private void button4_Click(object sender, EventArgs e)
        {
            for (int m = 0; m < 400; m++)
            {
                System.Threading.Thread t = new System.Threading.Thread(new System.Threading.ThreadStart(this.run));
                t.Start();
            }
        }  //这个是在主线程中创建多个子线程，但界面会明显失去响应。

解决方法：使用async函数，在主界面中创建10000路异步子线程也不会卡顿

 private void button1_Click(object sender, EventArgs e)
        {
            for (int m = 0; m < 1000; m++)
            {
                this.Ping("3");
            }
        }

        async private void Ping(string host)
        {
         
            System.Threading.Interlocked.Increment(ref this.count);
            Random r = new Random();
            await Task.Delay(r.Next( 5000));
            System.Threading.Interlocked.Increment(ref this.count2);
        }