C#中的Stopwatch如何使用

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C# Stopwatch的使用

什么是Stopwatch

Stopwatch：提供一組方法和屬性，可以準(zhǔn)確的測量運(yùn)行時間。

使用的時候需要引用命名空間：System.Diagnostics。

Stopwatch的簡單使用

//創(chuàng)建Stopwatch實(shí)例
Stopwatch sw = new Stopwatch();
//開始計(jì)時
sw.Start();
for (int i = 0; i < 100; i++)
{
  Console.WriteLine(i);
}
//停止計(jì)時
sw.Stop();
Console.WriteLine("用時：" + sw.ElapsedMilliseconds + "");
//重置 停止時間間隔測量，并將運(yùn)行時間重置為0
sw.Reset();
Console.WriteLine("用時：" + sw.ElapsedMilliseconds + "");
//重啟 停止時間間隔測量，并將運(yùn)行時間重置為0，然后重新開始測量運(yùn)行時間
sw.Restart();
for (int i = 0; i < 100; i++)
{
  Console.WriteLine(i);
}
sw.Stop();
//獲取當(dāng)前實(shí)例測量得出的總運(yùn)行時間（以毫秒為單位）
Console.WriteLine("用時：" + sw.ElapsedMilliseconds + "");
//獲取當(dāng)前實(shí)例測量得出的總運(yùn)行時間
Console.WriteLine("用時："+sw.Elapsed); 
//獲取當(dāng)前實(shí)例測量得出的總運(yùn)行時間（用計(jì)時器刻度表示）。
Console.WriteLine(sw.ElapsedTicks);
Console.Read();

//使用StartNew，相當(dāng)于已經(jīng)實(shí)例化并且啟動計(jì)時
Stopwatch sw=Stopwatch.StartNew();
for (int i = 0; i < 100; i++)
{
  Console.WriteLine(i);
}
sw.Stop();
//獲取當(dāng)前實(shí)例測量得出的總運(yùn)行時間（以毫秒為單位）
Console.WriteLine("用時：" + sw.ElapsedMilliseconds + "");
//獲取當(dāng)前實(shí)例測量得出的總運(yùn)行時間
Console.WriteLine("用時："+sw.Elapsed); 
Console.Read();

C#使用Stopwatch精確測量運(yùn)行時間

一般測量時間間隔使用的是DateTime.Now實(shí)例的DateTime.Ticks當(dāng)前屬性，想要精確測量一個操作的運(yùn)行時間就只能使用Stopwatch類計(jì)時了。

Stopwatch計(jì)時精度取決于硬件，如果安裝的硬件和操作系統(tǒng)支持高分辨率性能計(jì)數(shù)器, 則Stopwatch類將使用該計(jì)數(shù)器來測量運(yùn)行時間。否則，Stopwatch類將使用系統(tǒng)計(jì)時器來測量運(yùn)行時間。

測量耗時操作的運(yùn)行時間

            Stopwatch stopWatch = new Stopwatch();
            stopWatch.Start();
            Thread.Sleep(5000); // 耗時操作
            stopWatch.Stop();
            

            // 將經(jīng)過的時間作為TimeSpan值
            TimeSpan ts = stopWatch.Elapsed;
            // 格式和顯示時間值
            string elapsedTime = String.Format("{0:00}:{1:00}:{2:00}.{3:000}-{4:000}", ts.Hours, ts.Minutes, ts.Seconds, ts.Milliseconds, (ts.Ticks * 100 / 1000)%1000);
            Console.WriteLine("RunTime " + elapsedTime);

            // 將經(jīng)過的時間作為毫秒數(shù)
            long mSeconds = stopWatch.ElapsedMilliseconds;
            Console.WriteLine("RunTime(ms) " + mSeconds);

            // 獲取經(jīng)過時間的計(jì)時器刻度
            // 也可在耗時操作前后使用Stopwatch.GetTimestamp()各獲取1個Ticks值，然后相減得到耗時操作花費(fèi)的計(jì)時器刻度
            // 計(jì)時器采用的計(jì)時方式不同，tick的時間單位不同
            long tick = stopWatch.ElapsedTicks;
            Console.WriteLine("RunTime(tick) " + tick);

            if (Stopwatch.IsHighResolution)
            {
                // 計(jì)時器刻度是高性能計(jì)時器滴答數(shù)
                Console.WriteLine("使用系統(tǒng)高分辨率性能計(jì)數(shù)器計(jì)時：");
                Console.WriteLine("  RunTime(ns) " +tick* ((1000L * 1000L * 1000L)/ Stopwatch.Frequency));
            }
            else
            {
                // 計(jì)時器刻度是DateTime.Now實(shí)例的DateTime.Ticks當(dāng)前屬性
                Console.WriteLine("使用DateTime類計(jì)時：");
                Console.WriteLine("  RunTime(ns) " + tick * 100);
            }

查看Stopwatch計(jì)時器的計(jì)時方式

        /// <summary>
        /// 顯示計(jì)時器屬性
        /// </summary>
        public static void DisplayTimerProperties()
        {
            // 顯示定時器頻率和分辨率
            if (Stopwatch.IsHighResolution)
            {
                Console.WriteLine("操作使用系統(tǒng)高分辨率性能計(jì)數(shù)器計(jì)時");
            }
            else
            {
                Console.WriteLine("操作使用DateTime類計(jì)時");
            }

            long frequency = Stopwatch.Frequency;
            Console.WriteLine("  計(jì)時器頻率，單位為每秒滴答數(shù) = {0}",
                frequency);
            long nanosecPerTick = (1000L * 1000L * 1000L) / frequency;
            Console.WriteLine("  計(jì)時器分辨率為 {0} 納秒/滴答",
                nanosecPerTick);
        }

附上官網(wǎng)上的一個測試實(shí)例

        private static void TimeOperations()
        {
            long nanosecPerTick = (1000L * 1000L * 1000L) / Stopwatch.Frequency;
            const long numIterations = 10000;

            // 定義操作標(biāo)題名稱
            String[] operationNames = {"操作: Int32.Parse(\"0\")",
                                           "操作: Int32.TryParse(\"0\")",
                                           "操作: Int32.Parse(\"a\")",
                                           "操作: Int32.TryParse(\"a\")"};
            Console.WriteLine();
            Console.WriteLine("注：1ticks=100ns，1s=1000ms，1ms=1000us，1us=1000ns");

            // 從字符串解析整數(shù)的四種不同實(shí)現(xiàn)
            for (int operation = 0; operation <= 3; operation++)
            {
                // 定義操作統(tǒng)計(jì)的變量
                long numTicks = 0;
                long numRollovers = 0;
                long maxTicks = 0;
                long minTicks = Int64.MaxValue;
                int indexFastest = -1;
                int indexSlowest = -1;
                long milliSec = 0;

                Stopwatch time10kOperations = Stopwatch.StartNew();

                // 運(yùn)行當(dāng)前操作10001次。
                // 第一次執(zhí)行時間將被丟棄，因?yàn)樗赡軙で骄鶗r間。
                for (int i = 0; i <= numIterations; i++)
                {
                    long ticksThisTime = 0;
                    int inputNum;
                    Stopwatch timePerParse;

                    switch (operation)
                    {
                        case 0:
                            // 使用try-catch語句分析有效整數(shù)
                            // 啟動新的秒表計(jì)時器
                            timePerParse = Stopwatch.StartNew();
                            try
                            {
                                inputNum = Int32.Parse("0");
                            }
                            catch (FormatException)
                            {
                                inputNum = 0;
                            }

                            // 停止計(jì)時器，并保存操作所用的計(jì)時ticks

                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        case 1:                           
                            timePerParse = Stopwatch.StartNew();
                            if (!Int32.TryParse("0", out inputNum))
                            {
                                inputNum = 0;
                            }
                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        case 2:                            
                            timePerParse = Stopwatch.StartNew();
                            try
                            {
                                inputNum = Int32.Parse("a");
                            }
                            catch (FormatException)
                            {
                                inputNum = 0;
                            }
                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        case 3:                           
                            timePerParse = Stopwatch.StartNew();
                            if (!Int32.TryParse("a", out inputNum))
                            {
                                inputNum = 0;
                            }                            
                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        default:
                            break;
                    }
                    // 跳過第一個操作的時間，以防它導(dǎo)致一次性性能下降。
                    if (i == 0)
                    {
                        time10kOperations.Reset();
                        time10kOperations.Start();
                    }
                    else
                    {
                        // 更新迭代1-10001的操作統(tǒng)計(jì)信息。
                        if (maxTicks < ticksThisTime)
                        {
                            indexSlowest = i;
                            maxTicks = ticksThisTime;
                        }
                        if (minTicks > ticksThisTime)
                        {
                            indexFastest = i;
                            minTicks = ticksThisTime;
                        }
                        numTicks += ticksThisTime;
                        if (numTicks < ticksThisTime)
                        {
                            // Keep track of rollovers.
                            numRollovers++;
                        }
                    }
                }

                // 顯示10000次迭代的統(tǒng)計(jì)信息
                time10kOperations.Stop();
                milliSec = time10kOperations.ElapsedMilliseconds;

                Console.WriteLine();
                Console.WriteLine("{0} 統(tǒng)計(jì):", operationNames[operation]);
                Console.WriteLine("  最慢時間:  第{0}/{1}次操作，時間為{2} ticks",
                    indexSlowest, numIterations, maxTicks);
                Console.WriteLine("  最快時間:  第{0}/{1}次操作，時間為{2} ticks",
                    indexFastest, numIterations, minTicks);
                Console.WriteLine("  平均時間:  {0} ticks = {1} ns",
                    numTicks / numIterations,
                    (numTicks * nanosecPerTick) / numIterations);
                Console.WriteLine("  {0} 次操作的總時間: {1} ms",
                    numIterations, milliSec);
            }
        }

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