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To: gentoo-science@g.o
From: Xavier Fernández i Marín <xfim.ll@...>
Subject: Atlas giving wrong results on matrix multiplication
Date: Wed, 14 Sep 2011 10:48:14 +0200
Dear all,

I recently submitted a question to the R-help mailing list, because I
noticed that matrix multiplication was giving me trouble (basically, that
there were some times when a result was NaN):
http://tolstoy.newcastle.edu.au/R/e15/help/11/09/7165.html


As it is mentioned in the end of the thread, the solution was to recompile
R against the reference blas and lapack libraries, and avoid the atlas
that I was using.

So it seems that the problem is not R-related, but atlas-related, and
linked to gentoo, I would like to share the problem with you, just in case
somebody has any clue on what is wrong with atlas.

Although I have firstly used a very aggressive cflags to compile atlas
(-Ofast), I suspected that the problem was that, but I recompiled atlas
using -O2 and the problem still presists with atlas, but is solved with
reference.

I am using atlas-3.9.23-r4, R-2.13.1 and gcc-4.6.1

Thank you,

-- 
-  Xavier  -


Replies:
Re: Atlas giving wrong results on matrix multiplication
-- Andrea Arteaga
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Updated Jul 05, 2012

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