將不確定變為確定~老趙寫的CodeTimer是代碼性能測試的利器

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首先，非常感謝趙老大的CodeTimer，它讓我們更好的了解到代碼執行的性能，從而可以讓我們從性能的角度來考慮問題，有些東西可能我們認為是這樣的，但經理測試並非如何，這正應了我之前的那名話：“機器最能證明一切”！

費話就不說了，看代碼吧：

    /// <summary>
    /// 執行代碼規范
    /// </summary>
    public interface IAction
    {
        void Action();
    }

    /// <summary>
    /// 老趙的性能測試工具
    /// </summary>
    public static class CodeTimer
    {
        [DllImport("kernel32.dll", SetLastError = true)]
        static extern bool GetThreadTimes(IntPtr hThread, out long lpCreationTime, out long lpExitTime, out long lpKernelTime, out long lpUserTime);

        [DllImport("kernel32.dll")]
        static extern IntPtr GetCurrentThread();
        public delegate void ActionDelegate();
        private static long GetCurrentThreadTimes()
        {
            long l;
            long kernelTime, userTimer;
            GetThreadTimes(GetCurrentThread(), out l, out l, out kernelTime, out userTimer);
            return kernelTime + userTimer;
        }
        static CodeTimer()
        {
            Process.GetCurrentProcess().PriorityClass = ProcessPriorityClass.High;
            Thread.CurrentThread.Priority = ThreadPriority.Highest;
        }
        public static void Time(string name, int iteration, ActionDelegate action)
        {
            if (String.IsNullOrEmpty(name))
            {
                return;
            }
            if (action == null)
            {
                return;
            }

            //1. Print name
            ConsoleColor currentForeColor = Console.ForegroundColor;
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine(name);

            // 2. Record the latest GC counts
            //GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
            GC.Collect(GC.MaxGeneration);
            int[] gcCounts = new int[GC.MaxGeneration + 1];
            for (int i = 0; i <= GC.MaxGeneration; i++)
            {
                gcCounts[i] = GC.CollectionCount(i);
            }

            // 3. Run action
            Stopwatch watch = new Stopwatch();
            watch.Start();
            long ticksFst = GetCurrentThreadTimes(); //100 nanosecond one tick
            for (int i = 0; i < iteration; i++) action();
            long ticks = GetCurrentThreadTimes() - ticksFst;
            watch.Stop();

            // 4. Print CPU
            Console.ForegroundColor = currentForeColor;
            Console.WriteLine("\tTime Elapsed:\t\t" +
               watch.ElapsedMilliseconds.ToString("N0") + "ms");
            Console.WriteLine("\tTime Elapsed (one time):" +
               (watch.ElapsedMilliseconds / iteration).ToString("N0") + "ms");
            Console.WriteLine("\tCPU time:\t\t" + (ticks * 100).ToString("N0")
               + "ns");
            Console.WriteLine("\tCPU time (one time):\t" + (ticks * 100 /
               iteration).ToString("N0") + "ns");

            // 5. Print GC
            for (int i = 0; i <= GC.MaxGeneration; i++)
            {
                int count = GC.CollectionCount(i) - gcCounts[i];
                Console.WriteLine("\tGen " + i + ": \t\t\t" + count);
            }
            Console.WriteLine();
        }



        public static void Time(string name, int iteration, IAction action)
        {
            if (String.IsNullOrEmpty(name))
            {
                return;
            }

            if (action == null)
            {
                return;
            }

            //1. Print name
            ConsoleColor currentForeColor = Console.ForegroundColor;
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine(name);

            // 2. Record the latest GC counts
            //GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
            GC.Collect(GC.MaxGeneration);
            int[] gcCounts = new int[GC.MaxGeneration + 1];
            for (int i = 0; i <= GC.MaxGeneration; i++)
            {
                gcCounts[i] = GC.CollectionCount(i);
            }

            // 3. Run action
            Stopwatch watch = new Stopwatch();
            watch.Start();
            long ticksFst = GetCurrentThreadTimes(); //100 nanosecond one tick
            for (int i = 0; i < iteration; i++) action.Action();
            long ticks = GetCurrentThreadTimes() - ticksFst;
            watch.Stop();

            // 4. Print CPU
            Console.ForegroundColor = currentForeColor;
            Console.WriteLine("\tTime Elapsed:\t\t" +
               watch.ElapsedMilliseconds.ToString("N0") + "ms");
            Console.WriteLine("\tTime Elapsed (one time):" +
               (watch.ElapsedMilliseconds / iteration).ToString("N0") + "ms");
            Console.WriteLine("\tCPU time:\t\t" + (ticks * 100).ToString("N0")
                + "ns");
            Console.WriteLine("\tCPU time (one time):\t" + (ticks * 100 /
                iteration).ToString("N0") + "ns");

            // 5. Print GC
            for (int i = 0; i <= GC.MaxGeneration; i++)
            {
                int count = GC.CollectionCount(i) - gcCounts[i];
                Console.WriteLine("\tGen " + i + ": \t\t\t" + count);
            }
            Console.WriteLine();
        }
    }

有了上面的codeTimer我們就來測試一個吧，如字條串和並的問題，用+=還是用StringBuilder呢，有點經驗的程序員肯定說是StringBuilder，是的，確實是后者，那我們就來看看這

兩種方法測試的結果吧

     CodeTimer.Time("String  Concat", 100000,
                 () =>
                 {
                     var s = "1";
                     for (int i = 1; i < 10; i++)
                         s = s + "1";
                 });

      CodeTimer.Time("StringBuilder Concat", 100000,
               () =>
               {
                   var s = new StringBuilder();
                   for (int i = 1; i < 10; i++)
                       s.Append("1");
               });

測試的結果如下：

從圖中我們可以看到StringBuilder快的很明顯，無論是執行時間，還是對CPU的消耗及GC回收都遠低於String的拼結，所以，才有以下結論：

在字符串拼結時，請使用StringBuilder吧！

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