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List:       kde-kimageshop
Subject:    Re: A small analysis of vector composition results on different architectures
From:       Boudewijn Rempt <boud () valdyas ! org>
Date:       2012-11-04 12:12:54
Message-ID: alpine.LNX.2.00.1211041312420.3089 () calcifer ! valdyas ! org
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On Sun, 4 Nov 2012, Dmitry Kazakov wrote:

> Hi!
> 
> First, thanks everyone who helped me with running the composition benchmark on \
> their machines! Now I have some important information about what we should do next \
> with these optimizations! 
> In the first attached document you can find a table, comparing the results on \
> various architectures. 
> Here are conclusions I came to:
> 
> 1) On some architectures, e.g. non-Intel, the usage of Vc may degrade the \
> performance, so Krita should have some automatic benchmarking capabilities (in \
> settings dialog, for example), which would select the best available implementation \
> of the composite op. Such benchmark might be executed on the first run of Krita and \
> its result might be written to a Krita config file.
> 
> 2) Some old processors (Nehalem, Merom) have some problems when one of the pixels \
> (src or dst) have alpha channel set to 255. I can't explain right now why this \
> happens. Probably, there is some branch misprediction... The rest of the cases on \
> these CPUs are handled properly. 
> So in general, I   think these two problems should be solved and after that the \
> branch can be merged into master. 

Very cool work!

Boudewijn



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