这似乎并没有做下蹲以下测试程序。难道是因为我测试用小单子?
It doesn't seem to do squat for the following test program. Is this because I'm testing with a small list?
static void Main(string[] args)
{
List<int> list = 0.UpTo(4);
Test(list.AsParallel());
Test(list);
}
private static void Test(IEnumerable<int> input)
{
var timer = new Stopwatch();
timer.Start();
var size = input.Count();
if (input.Where(IsOdd).Count() != size / 2)
throw new Exception("Failed to count the odds");
timer.Stop();
Console.WriteLine("Tested " + size + " numbers in " + timer.Elapsed.TotalSeconds + " seconds");
}
private static bool IsOdd(int n)
{
Thread.Sleep(1000);
return n%2 == 1;
}
两个版本都需要4秒运行。
Both versions take 4 seconds to run.
任务并行库关心的的静态类型的序列。它应该是 IParallelEnumerable&LT; T&GT;
的操作由TPL处理。您是铸造收集回的IEnumerable&LT; T&GT;
当你调用测试
。因此,编译器将解决在序列。凡
呼叫 System.Linq.Enumerable.Where
扩展方法,而不是由TPL提供的并行版本。
Task Parallel Library cares about the static type of the sequence. It should be IParallelEnumerable<T>
for the operations to be handled by the TPL. You are casting the collection back to IEnumerable<T>
when you call Test
. Therefore, the compiler will resolve .Where
call on the sequence to System.Linq.Enumerable.Where
extension method instead of the parallel version provided by the TPL.