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Stopwatch - a High-Resolution code timer class

, 27 Nov 2002
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A high-resolution code timer for VB.NET using Kernel32 functions

Introduction

Creating an application requires precisely measuring how long specific operations take to complete. You may be searching for performance bottlenecks prior to shipping, measuring to ensure that changes do not unexpectedly degrade performance, or (in my case), testing alternative architectural approaches. You can use a real stopwatch and measure your application's response time, but fumbling and other miscues will render about a 1/4 second (0.25) resolution, at best. The Tick count available in VB is more accurate and fumble-proof, and it has a resolution of about 10ms (0.01).

The Windows Kernel includes a much finer-grained tick counter, which it exposes in an API call named QueryPerformanceCounter. This timer boasts near microsecond (0.000001) resolution and is easily callable from VB. The Stopwatch class wraps this call, masking all the sordid details.

Background

Stopwatch merely implements the code described in Microsoft Knowledge Base article 306978 (10/02) in a easily used class. I can't claim any originality - the technical details are by Microsoft, and the "stopwatch" class idea is from an old C++ article I read in 1993 or so (and implemented back then using mmsystem.dll in Windows 3.1; yikes!).

Using the code

There are two ways to use Stopwatch: create a Stopwatch instance and tell it to ReportToConsole when the code being measured is done; or reuse a single Stopwatch instance again and again, saving off elapsed time values each time.

Here's a very simple way to display how long a process takes on the console:

Dim swatch as New Stopwatch("My process")
'Perform my process (presumably a loop or one or more method calls)
swatch.ReportToConsole()

'Output: "My process (0.332131039000767 seconds)"

You can use the same Stopwatch instance repeatedly:

Dim firstResult, secondResult as Double
Dim swatch as New Stopwatch()
'...perform process...
firstResult = swatch.ElapsedTime() ' Note: ElapsedTime does 
                                   ' not stop the clock
'...more process work...
swatch.Done()
secondResult = swatch.ElapsedTime()
Console.WriteLine(
    "First took {0} seconds; First and Second took {1} seconds.", _
    firstResult, secondResult)
swatch.Start()
'...a third bunch of work...
swatch.Done()
MsgBox("The third thing took " & CStr(swatch.ElapsedTime()) & " seconds.")

'Output: "First took 0.0131530683368976 seconds; 
'First and Second took 8.8372527793337 seconds."

Points of Interest

This code also manages to demonstrate how to call the Windows API and how to define a custom exception class. Microsoft Knowledge Base article 172338 describes how to use QueryPerformanceCounter in VB 6 and other environments, and it contributed the idea of calculating the API call overhead so that it could be subtracted from the result.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Alastair Dallas
Web Developer
United States United States
Alastair Dallas is a programmer, systems architect, and information designer with over 20 years experience at companies including Ashton-Tate, Lotus, Netscape, Documentum, and a wide variety of startups. Languages include C#, C, C++, Java, JavaScript, Perl, Python, and VB (in alphabetical order) as well as DHTML, XML, and related technologies. He has written 3 books, 2 on computer topics, and is President of Infospect Press.

Comments and Discussions

 
QuestionIs there a way to get the stopwatch instant to callback events? Pinmemberseanclancy15-Oct-08 9:01 
QuestionAccurate???? For real?? Pinmemberbecker66620-May-07 14:50 
GeneralSystem.Diagnostics.Stopwatch() PinmemberJinx10125-Mar-07 6:31 
GeneralRe: System.Diagnostics.Stopwatch() PinmemberAndy Missico20-May-10 10:16 
GeneralGreat post PinmemberJinx10123-Mar-07 16:21 
GeneralAccurate RT timing of User Response needed Pinmemberian_s66628-Jan-07 8:17 
GeneralScreen Resolution PinmemberWahaj Khan7-Jan-05 19:11 
GeneralExtra Code PinmemberVectorX3-Jul-04 15:50 

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