c# - 比较时间 - 单线程与多线程的结果不同

Question

我编写此代码的目的是测试多线程和单线程速度。感谢所有的反馈！我根据收到的好评重写了大部分内容。这现在可以正常运行（可能这里或那里有错误），首先测试多线程，并取平均值以找到更准确的速度：（滚动到底部以继续。）

主要方法类

using System;

namespace SingleAndMultiThreading
{
internal class Threads
{
    private static void Main(string[] args)
    {

        long numOfObjCreated;
        int numberOfTests;

        while (true)
        {
            try
            {
                Console.Write("Number of objects to create: ");
                numOfObjCreated = Convert.ToInt64(Console.ReadLine());
                break;
            }
            catch (Exception)
            {
                Console.WriteLine("Invalid input.");
            }
        }


        while (true)
        {
            try
            {
                Console.Write("Number of tests to run: ");
                numberOfTests = Convert.ToInt32(Console.ReadLine());
                break;
            }
            catch (Exception)
            {
                Console.WriteLine("Invalid input.");
            }
        }


        CalculateResults(numOfObjCreated, numberOfTests);

        Console.ReadKey();

    }


    private static void CalculateResults(long numOfObjCreated, int numberOfTests)
    {
        double totalPercentages = 0;
        for (var i = 0; i < numberOfTests; i++)
        {
            totalPercentages += CompleteTests(numOfObjCreated);
        }

        var accuracy = totalPercentages / numberOfTests;

        if ((int)accuracy == 0)
        {
            Console.WriteLine("\nIn this case, neither single threading or multithreading is faster.\n" +
                              "They both run equally well under these conditions.\n");
            return;
        }

        if (accuracy < 0)
        {
            Console.WriteLine("\nIn this case with {0} objects being created, single threading is faster!\n",
                string.Format("{0:#,###0}", numOfObjCreated));
            return;
        }

        Console.WriteLine("\nFrom {0} test(s), {1}% was the average percentage of increased speed in multithreading.\n",
            string.Format("{0:#,###0}", numberOfTests), string.Format("{0:#,###0}", accuracy));
    }

    private static double CompleteTests(long numOfObjCreated)
    {
        Console.WriteLine("Computing...");

        var numOfCores = Environment.ProcessorCount;

        var timeForMultiThread = MultiThread.Run(numOfObjCreated, numOfCores);
        var timeForSingleThread = SingleThread.Run(numOfObjCreated);

        var percentFaster = ((timeForSingleThread / timeForMultiThread) * 100) - 100;

        //note: .NET does its part in assigning a certian thread to its own core

        Console.WriteLine("Using all {0} cores, creating {1} objects is {2}% faster.",
            numOfCores, string.Format("{0:#,###0}", numOfObjCreated), string.Format("{0:#,###0}", percentFaster));

        return percentFaster;
    }
}
}

单线程类

using System;
using System.Diagnostics;

namespace SingleAndMultiThreading
{
internal class SingleThread
{
    public static double Run(long numOfObjCreated)
    {
        var watch = new Stopwatch();

        watch.Start();

        for (long i = 0; i < numOfObjCreated; i++)
        {
            new object();
        }

        watch.Stop();

        var totalTime = watch.ElapsedTicks;

        Console.WriteLine("The time to create {0} objects with 1 thread is: {1} ticks.",
            string.Format("{0:#,###0}", numOfObjCreated), string.Format("{0:#,###0}", totalTime));

        return totalTime;

    }
}
}

多线程类

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Threading;

namespace SingleAndMultiThreading
{
internal class MultiThread
{
    public static double Run(long numOfObjCreated, int numOfCores)
    {
        var watch = new Stopwatch();

        var workerObject = new Worker(numOfObjCreated / numOfCores);

        var listOfThreads = new List<Thread>();


        for (long k = 0; k < numOfCores; k++)
        {
            var workerThread = new Thread(workerObject.DoWork);
            listOfThreads.Add(workerThread);
        }

        watch.Start();
        foreach (var thread in listOfThreads)
        {
            thread.Start();
        }

        byte countOfCompletedThreads = 0;

        while (true)
        {
            foreach (var thread in listOfThreads)
                if (!thread.IsAlive)
                    countOfCompletedThreads++;

            if (countOfCompletedThreads == numOfCores)
                break;
            countOfCompletedThreads = 0;

        }

        watch.Stop();

        var totalTime = watch.ElapsedTicks;

        Console.WriteLine("The time to create {0} objects utilizing all {1} cores is: {2} ticks.",
            string.Format("{0:#,###0}", numOfObjCreated), numOfCores, string.Format("{0:#,###0}", totalTime));

        return totalTime;

    }
}
}

工人阶级

namespace SingleAndMultiThreading
{
public class Worker
{
    private readonly long _numOfObjToCreate;
    public bool IsDone;

    public Worker(long numOfObjToCreate)
    {
        _numOfObjToCreate = numOfObjToCreate;
    }

    public void DoWork()
    {
        for (long i = 0; i < _numOfObjToCreate; i++)
        {
            new object();
        }

        IsDone = true;
    }
}
}

这段代码的输出有点太长，无法发布（我强烈建议您复制并粘贴到自己的 IDE 中，这真的很吸引人）。我想公认的答案是每次测试都不会给出相同的结果，这是由于 CPU 调度、其他或小问题（如 ASLR 等）造成的。除了运行该程序的 Visual Studio 之外，还发生了不止一件事，并且优先级不同。还要感谢您指出首先运行多线程会有所帮助，因为已经完成了内存分配！

需要指出的另一件事是，我在运行时发现了这一点：

尖峰是多线程过程发生的时候。