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Which code runs faster? The answer may surprise you....

, 25 Feb 2013
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This code compares object types instead of the name for the object type.

I saw some code that piqued my interest a few days ago. Basically, this code compared object types instead of the name for the object type.  Being the developer that I am, it set me to thinking about which way is faster.  Here are a couple of routines that do the exact same thing. Which one do you think will run faster? This code is targeted for .NET 4 Client, but should also work in .NET 2 and later.

The StopWatch objects (oStopWatchA and oStopWatchB) are defined as Class level private System.Diagnostics.Stopwatch objects and initialized before the call to the Subs.  The Object object (oObject) is defined as a Class level private System.Object object and initialized before the call to the Subs.  Each routine was run 1,000 times, swapping with each execution to eliminate external factors to the timing.

Private Sub CompareA()
  Dim iLoop As Integer

  oStopWatchA.Start()
  For iLoop = 1 To 1000000
    Select Case oObject.GetType().Name
      Case "Object"
      Case "Exception"
      Case Else
    End Select
  Next
  oStopWatchA.Stop()
End Sub
Private Sub CompareB()
  Dim iLoop As Integer

  oStopWatchB.Start()
  For iLoop = 1 To 1000000
    Select Case oObject.GetType()
      Case GetType(Object)
      Case GetType(Exception)
      Case Else
    End Select
  Next
  oStopWatchB.Stop()
End Sub

The elapsed time for each is listed below (lower numbers are better):

RoutineElapsed Time (seconds)
CompareA32.9136874
CompareB7.7228856

Were you surprised? I was!

Edit: The whole point of this article is to not just do the same thing the same way you always have.  Look at other methods to accomplish your goal.  I was surprised by the speed difference of changing the comparison from a string to a type reference, mainly because I expected the compiler to be able to generate code that pulled the type's name once for the comparison.  I was also expecting the GetType() calls to be executed on every comparison (each Case statement).  

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

Adam Zuckerman
Software Developer (Senior)
United States United States
Long time software engineer who rambles occasionally about coding, best practices, and other random things.
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Comments and Discussions

 
Questionsurprising ^_* PinmemberBesSo W Bas20-Mar-13 2:21 
Questionok PinmemberCIDev14-Mar-13 5:17 
GeneralMy vote of 1 PinmemberWilliam E. Kempf25-Feb-13 11:02 
GeneralRe: My vote of 1 PinmemberAdam Zuckerman25-Feb-13 11:55 
GeneralRe: My vote of 1 PinmemberPIEBALDconsult25-Feb-13 12:55 
QuestionWRONG PinmemberMember 970941720-Feb-13 8:32 
YOU MUST INCLUDE THE ASSEMBLER GENERATE.
AnswerRe: WRONG PinmemberPIEBALDconsult25-Feb-13 12:31 
GeneralMy vote of 3 PinmemberAnDev201320-Feb-13 6:52 
QuestionYou're surprized? PinmemberMatt T Heffron19-Feb-13 7:12 
GeneralMy vote of 4 Pinmembernot_starman19-Feb-13 5:45 
GeneralMy vote of 2 PinmemberCarlos190719-Feb-13 5:40 
GeneralRe: My vote of 2 PinmemberAdam Zuckerman19-Feb-13 15:55 

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