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From Gilles Sadowski <gil...@harfang.homelinux.org>
Subject Re: [Math] linearCombination
Date Sat, 06 Aug 2011 11:15:39 GMT
Hi.
 
> > [...]
> 
> I've allowed myself to adapt your code to an array version of the
> accurate "linearCombination" (committed in revision 1154416).
> 
> Here is a micro-benchmark (for an array of length 3):
> -----
> linearCombination (runs per timed block: 10000, timed blocks: 1000)
>   direct inline: 1.789185e-05 (1.580520e-05) ms
>    direct array: 2.009243e-05 (1.257636e-05) ms
> accurate inline: 4.244761e-05 (5.882379e-05) ms
>  accurate array: 9.365895e-05 (6.902221e-05) ms
> -----

Mre efficient implementation in revision 1154485:
-----
linearCombination (runs per timed block: 10000, timed blocks: 1000)
  direct inline: 1.899314e-05 (5.587518e-05) ms
   direct array: 1.918198e-05 (1.133822e-05) ms
accurate inline: 4.178593e-05 (5.697845e-05) ms
 accurate array: 7.144897e-05 (3.897243e-05) ms
-----

However, I'm concerned that the "stress" test ("testLinearCombination1")
taken from your test case for Vector3D might not be stringent enough. [I
think that while changing my implemementation, the test was still passing
just before I dicovered that I was using an unitialized (set to 0 by
default) variable.]
Could you devise one sure to detect bugs like this (i.e. where all the
various variables in "linearCombination" would be significant)?


Best,
Gilles

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