C# 异步等待和并行

我对async/await如何并行工作有点困惑，所以我在这里编写了一个测试代码： 我尝试发送6个我用列表模拟的任务。 每个任务将执行另外3个子任务

您可以复制/粘贴以进行测试

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Threading;

namespace ConsoleApplication1
{
    class Program
    {
         static void Main(string[] args)
        {
            //job simulation 
            Func<int, string, Tuple<int, string>> tc = Tuple.Create;
            var input = new List<Tuple<int, string>>{
                  tc( 6000, "task 1" ),
                  tc( 5000, "task 2" ),
                  tc( 1000, "task 3" ),
                  tc( 1000, "task 4" ),
                  tc( 1000, "task 5" ),
                  tc( 1000, "task 6" )
            };

            List<Tuple<int, string>> JobsList = new List<Tuple<int, string>>(input);

            //paralelism atempt
            List<Task> TaskLauncher = new List<Task>();

            Parallel.ForEach<Tuple<int, string>>(JobsList, item =>  JobDispatcher(item.Item1, item.Item2));

            Console.ReadLine();
        }
        public static async Task JobDispatcher(int time , string query)
        {
          List<Task> TList = new List<Task>();
          Task<string> T1 = SubTask1(time, query);
          Task<string> T2 = SubTask2(time, query);
          Task<string> T3 = SubTask3(time, query);
          TList.Add(T1);
          TList.Add(T2);
          TList.Add(T3);
          Console.WriteLine("{0} Launched ", query);

          await Task.WhenAll(TList.ToArray());


          Console.WriteLine(T1.Result);
          Console.WriteLine(T2.Result);
          Console.WriteLine(T3.Result);

        }


        public static async Task<string> SubTask1(int time, string query)
        {
            //somework
            Thread.Sleep(time);
            return query + "Finshed SubTask1";
        }
        public static async Task<string> SubTask2(int time, string query)
        {
            //somework
            Thread.Sleep(time);
            return query + "Finshed SubTask2";
        }
        public static async Task<string> SubTask3(int time, string query)
         {
             //somework
             Thread.Sleep(time);
             return query + "Finshed SubTask3";
         }


    }
}

然后在这一点上，让所有运行6*3=18线程的任务同时运行 但这里发生的事情似乎并不是同步的

结果如下：

---

使用async/await编写可以作为18个并行线程启动任务和子任务的正确方法是什么？

试试下面的示例代码。请注意，它大约在6秒钟内完成，这表明所有任务都是异步运行的：

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

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            // ThreadPool throttling may cause the speed with which
            // the threads are launched to be throttled.
            // You can avoid that by uncommenting the following line,
            // but that is considered bad form:

            // ThreadPool.SetMinThreads(20, 20);

            var sw = Stopwatch.StartNew();
            Console.WriteLine("Waiting for all tasks to complete");

            RunWorkers().Wait();

            Console.WriteLine("All tasks completed in " + sw.Elapsed);
        }

        public static async Task RunWorkers()
        {
            await Task.WhenAll(
                JobDispatcher(6000, "task 1"),
                JobDispatcher(5000, "task 2"),
                JobDispatcher(4000, "task 3"),
                JobDispatcher(3000, "task 4"),
                JobDispatcher(2000, "task 5"),
                JobDispatcher(1000, "task 6")
            );
        }

        public static async Task JobDispatcher(int time, string query)
        {
            var results = await Task.WhenAll(
                worker(time, query + ": Subtask 1"),
                worker(time, query + ": Subtask 2"),
                worker(time, query + ": Subtask 3")
            );

            Console.WriteLine(string.Join("\n", results));
        }

        static async Task<string> worker(int time, string query)
        {
            return await Task.Run(() =>
            {
                Console.WriteLine("Starting worker " + query);
                Thread.Sleep(time);
                Console.WriteLine("Completed worker " + query);
                return query + ": " + time + ", thread id: " + Thread.CurrentThread.ManagedThreadId;
            });
        }
    }
}

---

它不是同步运行的，任务4在任务3之前启动，但在任务3之后完成。首先，它应该先在控制台中编写，因为我稍后在函数中等待子任务。请看一下。@Zwan:

async

/

await

是关于异步的（没有线程的并发）<代码>并行是关于并行性（通过使用更多线程实现并发）。这些是完全不同的并发方法，您很少同时需要这两种方法。也许，如果你描述一下你实际上想做什么，我们可以建议一个更合理的解决方案？构建线程的有趣方法我可以在静态异步任务工作者（int-time，string-query）方法中添加3个子任务吗？它的反应与我对Parallel的期望完全一样。我还不知道我的代码的某些部分看起来“阻塞”的确切原因当你的代码运行顺利时。稍后将进行调查。无论如何，感谢将在生产代码中尝试此方法。感谢使用第一篇文章中的值时间。你的代码是6秒，当我的12秒证明开始时，有些东西运行不平行…每一个

任务。运行
调用此答案不属于这里。底层操作本质上是异步的。通过在线程池线程中启动异步操作，您将一事无成。@Servy我删除了具有
Task.Run（）
的版本，但我相信它仍然需要
worker（）
中的
Task.Run（）
。（它以前有
wait Task.Delay（）
，但为了使它更像OP的代码，我将其替换为
Thread.Sleep（）
，这意味着现在它需要在任务中运行。）
using System;
using System.Diagnostics;
using System.Threading;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main()
        {
            // ThreadPool throttling may cause the speed with which
            // the threads are launched to be throttled.
            // You can avoid that by uncommenting the following line,
            // but that is considered bad form:

            // ThreadPool.SetMinThreads(20, 20);

            var sw = Stopwatch.StartNew();
            Console.WriteLine("Waiting for all tasks to complete");

            RunWorkers().Wait();

            Console.WriteLine("All tasks completed in " + sw.Elapsed);
        }

        public static async Task RunWorkers()
        {
            await Task.WhenAll(
                JobDispatcher(6000, "task 1"),
                JobDispatcher(5000, "task 2"),
                JobDispatcher(4000, "task 3"),
                JobDispatcher(3000, "task 4"),
                JobDispatcher(2000, "task 5"),
                JobDispatcher(1000, "task 6")
            );
        }

        public static async Task JobDispatcher(int time, string query)
        {
            var results = await Task.WhenAll(
                worker(time, query + ": Subtask 1"),
                worker(time, query + ": Subtask 2"),
                worker(time, query + ": Subtask 3")
            );

            Console.WriteLine(string.Join("\n", results));
        }

        static async Task<string> worker(int time, string query)
        {
            return await Task.Run(() =>
            {
                Console.WriteLine("Starting worker " + query);
                Thread.Sleep(time);
                Console.WriteLine("Completed worker " + query);
                return query + ": " + time + ", thread id: " + Thread.CurrentThread.ManagedThreadId;
            });
        }
    }
}

public static async Task RunWorkers()
{
    Task[] tasks = new Task[6];

    for (int i = 0; i < 6; ++i)
        tasks[i] = JobDispatcher(1000 + i*1000, "task " + i);

    await Task.WhenAll(tasks);
}