私は完全に非同期のAPIクライアントを使用しています。つまり、各操作はTask
またはTask<T>
を返します。
static async Task DoSomething(int siteId, int postId, IBlogClient client)
{
await client.DeletePost(siteId, postId); // call API client
Console.WriteLine("Deleted post {0}.", siteId);
}
C#5のasync/await演算子を使用して、複数のタスクを開始し、それらがすべて完了するのを待つ正しい/最も効率的な方法は次のとおりです。
int[] ids = new[] { 1, 2, 3, 4, 5 };
Parallel.ForEach(ids, i => DoSomething(1, i, blogClient).Wait());
または
int[] ids = new[] { 1, 2, 3, 4, 5 };
Task.WaitAll(ids.Select(i => DoSomething(1, i, blogClient)).ToArray());
APIクライアントは内部的にHttpClientを使用しているので、これはすぐに5つのHTTPリクエストを発行し、それぞれが完了したときにコンソールに書き込みます。
int[] ids = new[] { 1, 2, 3, 4, 5 };
Parallel.ForEach(ids, i => DoSomething(1, i, blogClient).Wait());
上記のコードと並行して操作を実行しますが、このコードは各操作が実行される各スレッドをブロックします。たとえば、ネットワークコールに2秒かかると、各スレッドは2秒間ハングしますが、待機する以外は何もしません。
int[] ids = new[] { 1, 2, 3, 4, 5 };
Task.WaitAll(ids.Select(i => DoSomething(1, i, blogClient)).ToArray());
一方、WaitAll
を含む上記のコードもスレッドをブロックしますので、操作が終了するまでスレッドは他の作業を自由に処理できません。
私はWhenAll
をお勧めします。これはあなたの操作をパラレルに非同期的に実行します。
public async Task DoWork() {
int[] ids = new[] { 1, 2, 3, 4, 5 };
await Task.WhenAll(ids.Select(i => DoSomething(1, i, blogClient)));
}
実際には、上記の場合、あなたは
await
さえする必要さえありません、あなたはいかなる継続もないのであなたはただ直接メソッドから戻ることができます:public Task DoWork() { int[] ids = new[] { 1, 2, 3, 4, 5 }; return Task.WhenAll(ids.Select(i => DoSomething(1, i, blogClient))); }
これをバックアップするために、ここにすべての選択肢とそれらの長所/短所を通した詳細なブログ記事があります: ASP.NET Web APIを使った同時非同期I/Oの方法と場所
私は質問で受け入れられた答えと同様に提供された方法の結果を見たかったので、私はそれをテストにかけました。
これがコードです:
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 async Task 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"));
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).Wait());
}
static void PerformTest_TaskWaitAll(List<Worker> workers, DateTime testStart)
{
Task.WaitAll(workers.Select(worker => worker.DoWork(testStart)).ToArray());
}
static Task PerformTest_TaskWhenAll(List<Worker> workers, DateTime testStart)
{
return Task.WhenAll(workers.Select(worker => worker.DoWork(testStart)));
}
}
}
そして結果の出力:
Starting test: Parallel.ForEach...
Worker 1 started on thread 1, beginning 0.21 seconds after test start.
Worker 4 started on thread 5, beginning 0.21 seconds after test start.
Worker 2 started on thread 3, beginning 0.21 seconds after test start.
Worker 5 started on thread 6, beginning 0.21 seconds after test start.
Worker 3 started on thread 4, beginning 0.21 seconds after test start.
Worker 1 stopped; the worker took 1.90 seconds, and it finished 2.11 seconds after the test start.
Worker 2 stopped; the worker took 3.89 seconds, and it finished 4.10 seconds after the test start.
Worker 3 stopped; the worker took 5.89 seconds, and it finished 6.10 seconds after the test start.
Worker 4 stopped; the worker took 5.90 seconds, and it finished 6.11 seconds after the test start.
Worker 5 stopped; the worker took 8.89 seconds, and it finished 9.10 seconds after the test start.
Test finished after 9.10 seconds.
Starting test: Task.WaitAll...
Worker 1 started on thread 1, beginning 0.01 seconds after test start.
Worker 2 started on thread 1, beginning 0.01 seconds after test start.
Worker 3 started on thread 1, beginning 0.01 seconds after test start.
Worker 4 started on thread 1, beginning 0.01 seconds after test start.
Worker 5 started on thread 1, 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 1, beginning 0.00 seconds after test start.
Worker 2 started on thread 1, beginning 0.00 seconds after test start.
Worker 3 started on thread 1, beginning 0.00 seconds after test start.
Worker 4 started on thread 1, beginning 0.00 seconds after test start.
Worker 5 started on thread 1, 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 5.00 seconds after the test start.
Test finished after 5.00 seconds.
呼び出しているAPIは非同期なので、Parallel.ForEach
バージョンはあまり意味がありません。 WaitAll
バージョンでは.Wait
を使用しないでください。並列性が失われる可能性があります。呼び出し側が非同期の場合は、Select
とToArray
を実行した後でTask.WhenAll
を使用してタスクの配列を生成します。第二の選択肢はRx 2.0を使うことです
Parallel.ForEach
は各ワーカーで実行するにはユーザー定義ワーカーのリストと non-async Action
が必要です。
Task.WaitAll
とTask.WhenAll
にはList<Task>
が必要です。これは定義上非同期です。
RiaanDP の response は違いを理解するのに非常に便利ですが、Parallel.ForEach
の修正が必要です。彼のコメントに答えるには十分な評判ではないので、私自身の反応です。
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)));
}
}
}
結果の出力は以下の通りです。実行時間は同程度です。私のコンピューターが毎週アンチウイルススキャンをしている間にこのテストを実行しました。テストの順序を変更すると、テストの実行時間が変わりました。
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.
n tasksを渡すことができるTask.WhenAll
関数を使用できます。 Task.WhenAll
は、Task.WhenAll
に渡したすべてのタスクが完了すると、完了するまで実行するタスクを返します。 UIスレッドをブロックしないように、Task.WhenAll
を非同期に待機する必要があります。
public async Task DoSomeThing() {
var Task[] tasks = new Task[numTasks];
for(int i = 0; i < numTask; i++)
{
tasks[i] = CallSomeAsync();
}
await Task.WhenAll(tasks);
// code that'll execute on UI thread
}