C# 用于准确地测量运行时间的Stopwatch中.Start 方法和Stopwatch.Stop 方法

一、Stopwatch 类

        提供一组方法和属性,可用于准确地测量运行时间。

public class Stopwatch

        使用 Stopwatch 类来确定应用程序的执行时间。

// 使用 Stopwatch 类来确定应用程序的执行时间
using System.Diagnostics;
class Program
{
    static void Main(string[] args)
    {
        ArgumentNullException.ThrowIfNull(args);

        Stopwatch stopWatch = new();
        stopWatch.Start();
        Thread.Sleep(10000);
        stopWatch.Stop();
        // Get the elapsed time as a TimeSpan value.
        TimeSpan ts = stopWatch.Elapsed;

        // Format and display the TimeSpan value.
        string elapsedTime = String.Format("{0:00}:{1:00}:{2:00}.{3:00}",
            ts.Hours, ts.Minutes, ts.Seconds,
            ts.Milliseconds / 10);
        Console.WriteLine("RunTime " + elapsedTime);
    }
}
//运行结果:
/*
RunTime 00:00:10.01

 */
// 使用 Stopwatch 类来计算性能数据。
using System.Diagnostics;

namespace StopWatchSample
{
    class OperationsTimer
    {
        public static void Main(string[] args)
        {
            ArgumentNullException.ThrowIfNull(args);

            DisplayTimerProperties();

            Console.WriteLine();
            Console.WriteLine("Press the Enter key to begin:");
            Console.ReadLine();
            Console.WriteLine();

            TimeOperations();
        }

        public static void DisplayTimerProperties()
        {
            // Display the timer frequency and resolution.
            if (Stopwatch.IsHighResolution)
            {
                Console.WriteLine("Operations timed using the system's high-resolution performance counter.");
            }
            else
            {
                Console.WriteLine("Operations timed using the DateTime class.");
            }

            long frequency = Stopwatch.Frequency;
            Console.WriteLine("  Timer frequency in ticks per second = {0}",frequency);
            long nanosecPerTick = (1000L * 1000L * 1000L) / frequency;
            Console.WriteLine("  Timer is accurate within {0} nanoseconds",nanosecPerTick);
        }

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

            // Define the operation title names.
            string[] operationNames = {"Operation: Int32.Parse("0")",
                                           "Operation: Int32.TryParse("0")",
                                           "Operation: Int32.Parse("a")",
                                           "Operation: Int32.TryParse("a")"};

            // Time four different implementations for parsing
            // an integer from a string.

            for (int operation = 0; operation <= 3; operation++)
            {
                // Define variables for operation statistics.
                long numTicks = 0;
                long numRollovers = 0;
                long maxTicks = 0;
                long minTicks = long.MaxValue;
                int indexFastest = -1;
                int indexSlowest = -1;
                Stopwatch time10kOperations = Stopwatch.StartNew();

                // Run the current operation 10001 times.
                // The first execution time will be tossed
                // out, since it can skew the average time.

                for (int i = 0; i <= numIterations; i++)
                {
                    long ticksThisTime = 0;
                    int inputNum;
                    Stopwatch timePerParse;

                    switch (operation)
                    {
                        case 0:
                            // Parse a valid integer using
                            // a try-catch statement.
                            // Start a new stopwatch timer.
                            timePerParse = Stopwatch.StartNew();

                            try
                            {
                                inputNum = int.Parse("0");
                            }
                            catch (FormatException)
                            {
                                inputNum = 0;
                            }

                            // Stop the timer, and save the
                            // elapsed ticks for the operation.

                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        case 1:
                            // Parse a valid integer using
                            // the TryParse statement.

                            // Start a new stopwatch timer.
                            timePerParse = Stopwatch.StartNew();

                            if (!int.TryParse("0", out inputNum))
                            {
                                inputNum = 0;
                            }

                            // Stop the timer, and save the
                            // elapsed ticks for the operation.
                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        case 2:
                            // Parse an invalid value using
                            // a try-catch statement.

                            // Start a new stopwatch timer.
                            timePerParse = Stopwatch.StartNew();

                            try
                            {
                                inputNum = int.Parse("a");
                            }
                            catch (FormatException)
                            {
                                inputNum = 0;
                            }

                            // Stop the timer, and save the
                            // elapsed ticks for the operation.
                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;
                        case 3:
                            // Parse an invalid value using
                            // the TryParse statement.

                            // Start a new stopwatch timer.
                            timePerParse = Stopwatch.StartNew();

                            if (!int.TryParse("a", out inputNum))
                            {
                                inputNum = 0;
                            }

                            // Stop the timer, and save the
                            // elapsed ticks for the operation.
                            timePerParse.Stop();
                            ticksThisTime = timePerParse.ElapsedTicks;
                            break;

                        default:
                            break;
                    }

                    // Skip over the time for the first operation,
                    // just in case it caused a one-time
                    // performance hit.
                    if (i == 0)
                    {
                        time10kOperations.Reset();
                        time10kOperations.Start();
                    }
                    else
                    {

                        // Update operation statistics
                        // for iterations 1-10000.
                        if (maxTicks < ticksThisTime)
                        {
                            indexSlowest = i;
                            maxTicks = ticksThisTime;
                        }
                        if (minTicks > ticksThisTime)
                        {
                            indexFastest = i;
                            minTicks = ticksThisTime;
                        }
                        numTicks += ticksThisTime;
                        if (numTicks < ticksThisTime)
                        {
                            // Keep track of rollovers.
                            numRollovers++;
                        }
                    }
                }

                // Display the statistics for 10000 iterations.

                time10kOperations.Stop();
                long milliSec = time10kOperations.ElapsedMilliseconds;
                Console.WriteLine();
                Console.WriteLine("{0} Summary:", operationNames[operation]);
                Console.WriteLine("  Slowest time:  #{0}/{1} = {2} ticks",
                    indexSlowest, numIterations, maxTicks);
                Console.WriteLine("  Fastest time:  #{0}/{1} = {2} ticks",
                    indexFastest, numIterations, minTicks);
                Console.WriteLine("  Average time:  {0} ticks = {1} nanoseconds",
                    numTicks / numIterations,
                    (numTicks * nanosecPerTick) / numIterations);
                Console.WriteLine("  Total time looping through {0} operations: {1} milliseconds",
                    numIterations, milliSec);
            }
        }
    }
}
//运行结果:
/*
Operations timed using the system's high-resolution performance counter.
  Timer frequency in ticks per second = 10000000
  Timer is accurate within 100 nanoseconds

 */

1.Stopwatch.Start 方法

        开始或继续测量某个时间间隔的运行时间。

        前例中有示例。 

public void Start ();

2.Stopwatch.Stop 方法

        停止测量某个时间间隔的运行时间。

public void Stop ();

        前例中有示例。