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<H1>[Mageia-dev] Packages not rebuilt since Mageia 1</H1>
<B>eatdirt</B>
<A HREF="mailto:mageia-dev%40mageia.org?Subject=Re%3A%20%5BMageia-dev%5D%20Packages%20not%20rebuilt%20since%20Mageia%201&In-Reply-To=%3Ckivscj%244jl%241%40ger.gmane.org%3E"
TITLE="[Mageia-dev] Packages not rebuilt since Mageia 1">dirteat at gmail.com
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<I>Wed Mar 27 23:38:15 CET 2013</I>
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<PRE>On 26/03/13 15:24, Pascal Terjan wrote:
><i> There are 26 packages.
</I>><i>
</I>><i> atlas
</I>
I think, and unless someone complains, this one should be dropped. Atlas
is supposed to provice fast routines already provided by blas and lapack
(that we have), but:
<A HREF="http://math-atlas.sourceforge.net/atlas_install/node27.html">http://math-atlas.sourceforge.net/atlas_install/node27.html</A>
says:
"Many users ask how ATLAS can be used to build libraries that will run
on all x86 platforms. In general, this is a bad idea: ATLAS gets its
speed by specializing for particular platforms, so the more generic a
library is the less performance it will achieve!"
and this is what we are doing. We even compile it with sseX options
which is soon worse than doing nothing:
"
Never use these libraries unless this portability is absolutely
required. They must use portable settings for blocking, for instance,
which will mean that on many platforms they will use only a fraction of
the actual cache, causing large performance drops. Even worse, peak
performance may by reduced by as much as factor of 8, due to not using
the proper ISA extension. The most portable ISA uses only the x87 unit,
which has a much lower peak rate on most modern machines (eg., an Intel
sandy bridge can do 16 flops/cycle using AVX in single precision, but
only 8 flops/cycle if using SSE, and only 2 flops/cycle using the x87 unit).
"
Cheers,
Chris,
</PRE>
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