[Insight-developers] Empty FixedArray destructor: Performancehit using gcc : [ Mac Guru needed ! ]

[Bradley Lowekamp]

As this just showed up on just the apple "Release" build I think that  
it's just due to different standard "-03" optimizations options on the  
apple versions of gcc (I am not sure if it's changed with gcc 4):

http://developer.apple.com/documentation/DeveloperTools/gcc-3.3/gcc/Optimize-Options.html

I also tried a third timed loop on the test, and the performance of  
the later two passes were the same, so I think there is also cacheing  
involved in the perforce difference. But this does not explain it all  
since increasing the number of passes per timed loop produces linear  
increase in the time of the passes.


>
> still have a 50% change in performance when moving the base
> pointer of an array of FixedArrays, despite the fact that
> the empty destructor of the FixedArray has been removed.

It does not look like the pointer moves between the two passes since  
it's 8 byte aligned to begin with.


I also noticed that a lot of test passed with 0ms for both of the times.



On Jun 10, 2008, at 9:21 AM, Luis Ibanez wrote:

>
> Mac Guru Needed !
>
>
> We need help from a Mac Guru to understand why the following
> Mac builds:
>
> http://www.cdash.org/CDash/testSummary.php?project=2&name=itkFixedArrayTest2&date=20080610
>
> still have a 50% change in performance when moving the base
> pointer of an array of FixedArrays, despite the fact that
> the empty destructor of the FixedArray has been removed.
>
>
> Thanks for any help, advice or hint,
>
>
>   Luis
>
> _______________________________________________
> Insight-developers mailing list
> Insight-developers at itk.org
> http://www.itk.org/mailman/listinfo/insight-developers

========================================================
Bradley Lowekamp
Lockheed Martin Contractor for
Office of High Performance Computing and Communications
National Library of Medicine
blowekamp at mail.nih.gov


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