Parallel.ForEachyêu cầu một danh sách các công nhân do người dùng định nghĩa và không đồng bộ Action để thực hiện với mỗi công nhân.
Task.WaitAllvà Task.WhenAllyêu cầu một List<Task>, theo định nghĩa không đồng bộ.
Tôi thấy phản hồi của RiaanDP rất hữu ích để hiểu sự khác biệt, nhưng nó cần một sự điều chỉnh cho . Không đủ danh tiếng để trả lời bình luận của anh ấy, do đó phản ứng của riêng tôi.Parallel.ForEach
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading;
using System.Threading.Tasks;
namespace AsyncTest
{
class Program
{
class Worker
{
public int Id;
public int SleepTimeout;
public void DoWork(DateTime testStart)
{
var workerStart = DateTime.Now;
Console.WriteLine("Worker {0} started on thread {1}, beginning {2} seconds after test start.",
Id, Thread.CurrentThread.ManagedThreadId, (workerStart - testStart).TotalSeconds.ToString("F2"));
Thread.Sleep(SleepTimeout);
var workerEnd = DateTime.Now;
Console.WriteLine("Worker {0} stopped; the worker took {1} seconds, and it finished {2} seconds after the test start.",
Id, (workerEnd - workerStart).TotalSeconds.ToString("F2"), (workerEnd - testStart).TotalSeconds.ToString("F2"));
}
public async Task DoWorkAsync(DateTime testStart)
{
var workerStart = DateTime.Now;
Console.WriteLine("Worker {0} started on thread {1}, beginning {2} seconds after test start.",
Id, Thread.CurrentThread.ManagedThreadId, (workerStart - testStart).TotalSeconds.ToString("F2"));
await Task.Run(() => Thread.Sleep(SleepTimeout));
var workerEnd = DateTime.Now;
Console.WriteLine("Worker {0} stopped; the worker took {1} seconds, and it finished {2} seconds after the test start.",
Id, (workerEnd - workerStart).TotalSeconds.ToString("F2"), (workerEnd - testStart).TotalSeconds.ToString("F2"));
}
}
static void Main(string[] args)
{
var workers = new List<Worker>
{
new Worker { Id = 1, SleepTimeout = 1000 },
new Worker { Id = 2, SleepTimeout = 2000 },
new Worker { Id = 3, SleepTimeout = 3000 },
new Worker { Id = 4, SleepTimeout = 4000 },
new Worker { Id = 5, SleepTimeout = 5000 },
};
var startTime = DateTime.Now;
Console.WriteLine("Starting test: Parallel.ForEach...");
PerformTest_ParallelForEach(workers, startTime);
var endTime = DateTime.Now;
Console.WriteLine("Test finished after {0} seconds.\n",
(endTime - startTime).TotalSeconds.ToString("F2"));
startTime = DateTime.Now;
Console.WriteLine("Starting test: Task.WaitAll...");
PerformTest_TaskWaitAll(workers, startTime);
endTime = DateTime.Now;
Console.WriteLine("Test finished after {0} seconds.\n",
(endTime - startTime).TotalSeconds.ToString("F2"));
startTime = DateTime.Now;
Console.WriteLine("Starting test: Task.WhenAll...");
var task = PerformTest_TaskWhenAll(workers, startTime);
task.Wait();
endTime = DateTime.Now;
Console.WriteLine("Test finished after {0} seconds.\n",
(endTime - startTime).TotalSeconds.ToString("F2"));
Console.ReadKey();
}
static void PerformTest_ParallelForEach(List<Worker> workers, DateTime testStart)
{
Parallel.ForEach(workers, worker => worker.DoWork(testStart));
}
static void PerformTest_TaskWaitAll(List<Worker> workers, DateTime testStart)
{
Task.WaitAll(workers.Select(worker => worker.DoWorkAsync(testStart)).ToArray());
}
static Task PerformTest_TaskWhenAll(List<Worker> workers, DateTime testStart)
{
return Task.WhenAll(workers.Select(worker => worker.DoWorkAsync(testStart)));
}
}
}
Đầu ra kết quả là dưới đây. Thời gian thực hiện là tương đương. Tôi đã chạy thử nghiệm này trong khi máy tính của tôi đang thực hiện quét chống vi-rút hàng tuần. Thay đổi thứ tự của các bài kiểm tra đã thay đổi thời gian thực hiện trên chúng.
Starting test: Parallel.ForEach...
Worker 1 started on thread 9, beginning 0.02 seconds after test start.
Worker 2 started on thread 10, beginning 0.02 seconds after test start.
Worker 3 started on thread 11, beginning 0.02 seconds after test start.
Worker 4 started on thread 13, beginning 0.03 seconds after test start.
Worker 5 started on thread 14, beginning 0.03 seconds after test start.
Worker 1 stopped; the worker took 1.00 seconds, and it finished 1.02 seconds after the test start.
Worker 2 stopped; the worker took 2.00 seconds, and it finished 2.02 seconds after the test start.
Worker 3 stopped; the worker took 3.00 seconds, and it finished 3.03 seconds after the test start.
Worker 4 stopped; the worker took 4.00 seconds, and it finished 4.03 seconds after the test start.
Worker 5 stopped; the worker took 5.00 seconds, and it finished 5.03 seconds after the test start.
Test finished after 5.03 seconds.
Starting test: Task.WaitAll...
Worker 1 started on thread 9, beginning 0.00 seconds after test start.
Worker 2 started on thread 9, beginning 0.00 seconds after test start.
Worker 3 started on thread 9, beginning 0.00 seconds after test start.
Worker 4 started on thread 9, beginning 0.00 seconds after test start.
Worker 5 started on thread 9, beginning 0.01 seconds after test start.
Worker 1 stopped; the worker took 1.00 seconds, and it finished 1.01 seconds after the test start.
Worker 2 stopped; the worker took 2.00 seconds, and it finished 2.01 seconds after the test start.
Worker 3 stopped; the worker took 3.00 seconds, and it finished 3.01 seconds after the test start.
Worker 4 stopped; the worker took 4.00 seconds, and it finished 4.01 seconds after the test start.
Worker 5 stopped; the worker took 5.00 seconds, and it finished 5.01 seconds after the test start.
Test finished after 5.01 seconds.
Starting test: Task.WhenAll...
Worker 1 started on thread 9, beginning 0.00 seconds after test start.
Worker 2 started on thread 9, beginning 0.00 seconds after test start.
Worker 3 started on thread 9, beginning 0.00 seconds after test start.
Worker 4 started on thread 9, beginning 0.00 seconds after test start.
Worker 5 started on thread 9, beginning 0.00 seconds after test start.
Worker 1 stopped; the worker took 1.00 seconds, and it finished 1.00 seconds after the test start.
Worker 2 stopped; the worker took 2.00 seconds, and it finished 2.00 seconds after the test start.
Worker 3 stopped; the worker took 3.00 seconds, and it finished 3.00 seconds after the test start.
Worker 4 stopped; the worker took 4.00 seconds, and it finished 4.00 seconds after the test start.
Worker 5 stopped; the worker took 5.00 seconds, and it finished 5.01 seconds after the test start.
Test finished after 5.01 seconds.