Re: confused about performance
On Thu, 14 Jun 2007, Leopold Palomo-Avellaneda wrote:
The last test I ran on my Athlon64 X2 4200+ (2.2 GHz) got me about 10
gigaflops in 32-bit arithmetic and about half of that in 64-bit
arithmetic.
I don't understand that. Are you saying that the 64-bits was really
worst tha 32?
He is saying that the version distributed by default in debian of the
ATLAS linear algebra libraries is much better optimised for performance in
the 32 bit version than in the 64 bit version. However, if you are in for
speed, you are way better off using a better optimised linear algebra
library, such as the GOTO library (hand-optimised assembler written by
masatoshi goto), or the acml libraries provided by AMD for AMD processors
or the MKML libraries provided by Intel for Intel processors. All of these
provide vastly better performance than the current incarnations of ATLAS
in 64bit. ATLAS can be expected to improve a lot quickly, but currently is
far behind in the 64 bit version. Also, if you are after performance, you
should consider using some commercial compiler (if you can afford it)
instead of the GCC suite, until GNU compilers become as good at optimising
for x86_64 processors as they are for x86. Again, this will happen in the
near future, but it's not there yet.
bye
Giacomo
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Giacomo Mulas <gmulas@ca.astro.it>
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