Exact time measurement for performance testing

Question

What is the most exact way of seeing how long something  for example a method call  took in code   The easiest and quickest I would guess is this   DateTime start   DateTime Now           Do some work   TimeSpan timeItTook   DateTime Now - start    But how exact is this  Are there better ways

User · Answer

System Diagnostics Stopwatch is designed for this task

User · Answer

As others have said  Stopwatch is a good class to use here  You can wrap it in a helpful method   public static TimeSpan Time Action action        Stopwatch stopwatch   Stopwatch StartNew        action        stopwatch Stop        return stopwatch Elapsed       Note the use of Stopwatch StartNew    I prefer this to creating a Stopwatch and then calling Start   in terms of simplicity   Obviously this incurs the hit of invoking a delegate  but in the vast majority of cases that won t be relevant  You d then write   TimeSpan time   StopwatchUtil Time      gt           Do some work       You could even make an ITimer interface for this  with implementations of StopwatchTimer  CpuTimer etc where available

User · Answer

I m using this    HttpWebRequest request    HttpWebRequest WebRequest Create myUrl   System Diagnostics Stopwatch timer   new Stopwatch     timer Start     HttpWebResponse response    HttpWebResponse request GetResponse     statusCode   response StatusCode ToString     response Close     timer Stop

User · Answer

A better way is to use the Stopwatch class   using System Diagnostics          Stopwatch sw   new Stopwatch     sw Start             sw Stop     Console WriteLine  Elapsed  0   sw Elapsed

User · Answer

Use the Stopwatch class

User · Answer

As others said  Stopwatch should be the right tool for this  There can be few improvements made to it though  see this thread specifically  Benchmarking small code samples in C   can this implementation be improved    I have seen some useful tips by Thomas Maierhofer here  Basically his code looks like      prevent the JIT Compiler from optimizing Fkt calls away long seed   Environment TickCount     use the second Core Processor for the test Process GetCurrentProcess   ProcessorAffinity   new IntPtr 2      prevent  Normal  Processes from interrupting Threads Process GetCurrentProcess   PriorityClass   ProcessPriorityClass High     prevent  Normal  Threads from interrupting this thread Thread CurrentThread Priority   ThreadPriority Highest     warm up method     var stopwatch   new Stopwatch   for  int i   0  i  lt  repetitions  i          stopwatch Reset        stopwatch Start        for  int j   0  j  lt  iterations  j            method        stopwatch Stop        print stopwatch Elapsed TotalMilliseconds      Another approach is to rely on Process TotalProcessTime to measure how long the CPU has been kept busy running the very code process  as shown here This can reflect more real scenario since no other process affects the measurement  It does something like    var start   Process GetCurrentProcess   TotalProcessorTime   method     var stop   Process GetCurrentProcess   TotalProcessorTime   print  end - begin  TotalMilliseconds    A naked  detailed implementation of the samething can be found here    I wrote a helper class to perform both in an easy to use manner   public class Clock       interface IStopwatch               bool IsRunning   get            TimeSpan Elapsed   get             void Start            void Stop            void Reset                 class TimeWatch   IStopwatch               Stopwatch stopwatch   new Stopwatch             public TimeSpan Elapsed                       get   return stopwatch Elapsed                       public bool IsRunning                       get   return stopwatch IsRunning                         public TimeWatch                         if   Stopwatch IsHighResolution                  throw new NotSupportedException  Your hardware doesn t support high resolution counter                   prevent the JIT Compiler from optimizing Fkt calls away             long seed   Environment TickCount                 use the second Core Processor for the test             Process GetCurrentProcess   ProcessorAffinity   new IntPtr 2                  prevent  Normal  Processes from interrupting Threads             Process GetCurrentProcess   PriorityClass   ProcessPriorityClass High                 prevent  Normal  Threads from interrupting this thread             Thread CurrentThread Priority   ThreadPriority Highest                       public void Start                         stopwatch Start                       public void Stop                         stopwatch Stop                       public void Reset                         stopwatch Reset                           class CpuWatch   IStopwatch               TimeSpan startTime          TimeSpan endTime          bool isRunning             public TimeSpan Elapsed                       get                               if  IsRunning                      throw new NotImplementedException  Getting elapsed span while watch is running is not implemented                     return endTime - startTime                                   public bool IsRunning                       get   return isRunning                         public void Start                         startTime   Process GetCurrentProcess   TotalProcessorTime              isRunning   true                     public void Stop                         endTime   Process GetCurrentProcess   TotalProcessorTime              isRunning   false                     public void Reset                         startTime   TimeSpan Zero              endTime   TimeSpan Zero                         public static void BenchmarkTime Action action  int iterations   10000                Benchmark lt TimeWatch gt  action  iterations              static void Benchmark lt T gt  Action action  int iterations  where T   IStopwatch  new                   clean Garbage         GC Collect               wait for the finalizer queue to empty         GC WaitForPendingFinalizers               clean Garbage         GC Collect               warm up         action             var stopwatch   new T            var timings   new double 5           for  int i   0  i  lt  timings Length  i                          stopwatch Reset                stopwatch Start                for  int j   0  j  lt  iterations  j                    action                stopwatch Stop                timings i    stopwatch Elapsed TotalMilliseconds              print timings i                     print  normalized mean      timings NormalizedMean   ToString               public static void BenchmarkCpu Action action  int iterations   10000                Benchmark lt CpuWatch gt  action  iterations             Just call   Clock BenchmarkTime      gt          code     10000000     or  Clock BenchmarkCpu      gt          code     10000000     The last part of the Clock is the tricky part  If you want to display the final timing  its up to you to choose what sort of timing you want  I wrote an extension method NormalizedMean which gives you the mean of the read timings discarding the noise  I mean I calculate the the deviation of each timing from the actual mean  and then I discard the values which was farer  only the slower ones  from the mean of deviation  called absolute deviation  note that its not the often heard standard deviation   and finally return the mean of remaining values  This means  for instance  if timed values are   1  2  3  2  100    in ms or whatever   it discards 100  and returns the mean of   1  2  3  2   which is 2  Or if timings are   240  220  200  220  220  270    it discards 270  and returns the mean of   240  220  200  220  220   which is 220   public static double NormalizedMean this ICollection lt double gt  values        if  values Count    0          return double NaN       var deviations   values Deviations   ToArray        var meanDeviation   deviations Sum t   gt  Math Abs t Item2     values Count      return deviations Where t   gt  t Item2  gt  0    Math Abs t Item2   lt   meanDeviation  Average t   gt  t Item1      public static IEnumerable lt Tuple lt double  double gt  gt  Deviations this ICollection lt double gt  values        if  values Count    0          yield break       var avg   values Average        foreach  var d in values          yield return Tuple Create d  avg - d

User · Answer

Stopwatch is fine  but loop the work 10 6 times  then divide by 10 6  You ll get a lot more precision

[c#] Exact time measurement for performance testing

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