Library tutorials & articles

Iteration Methods

By Trevor Misfeldt, published on 18 Apr 2003
Trevor Misfeldt CEO of CenterSpace Software. We make numerical analysis class libraries for the .NET platform. Author of Elements of Java Style and Elements of C++ Style.
Page 3 of 3
  1. Introduction
  2. More Methods
  3. Conclusions

Conclusions

To test the different methods, I allocated 1,000,000 doubles into an array and indexed over all of them. I repeated this 1,000 times to minimize randomness. Here are the results...

Results

Enumeration is always slow. That’s not surprising as I’m using a general data structure to hold the doubles. Each access performs a cast. The three operator/property methods differed very slightly. These are probably all optimized similarly. Using pointer math to traverse over the raw data was significantly faster. This is probably due to the fact that there’s no bounds checking. In summary, if you have large amounts of data and performance is critical, consider using managed C++.

Acknowledgements

Thanks to Mark Vulfson of ProWorks for tips on using Flipper Graph Control. Also, to my colleagues Ken Baldwin and Steve Sneller at CenterSpace Software.
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Comments

  1. Trevor Misfeldt
    06 Aug 2003 at 14:17


    Thanks for the feedback!  I tried putting in the extra step.  The results are virtually unchanged from previous changes.  Please try it out yourself.


    Cheers,
    Trevor



    Trevor Misfeldt
    CEO, CenterSpace Software

  2. aarora@onyxfund.com
    13 May 2003 at 15:47

    You are merely accessing the reference to where the data is kept for the array, but are never actually accessing the data, which you do elsewhere (for example Method #2). If you were to actually access the data, then I think your method would perform similar to Method #2. I don't think that the actual data is read until you access the variable. So perhaps to complete the test, I would perform a d += 1 in each loop to make sure that the data is accessed by each method your base class in which the object exists.

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