Re: confused about performance
On Fri, 15 Jun 2007, M. Edward (Ed) Borasky wrote:
had very deep pipelines. If NWChem is anything like that, I'm not
surprised the Intel compilers do a better job than GCC -- I don't think
GCC knows much about all the specifics of tweaking such things as
keeping data in caches, re-use, chip-level parallelism, etc. If NWChem
is open source, I'm sure someone will come along and profile/tweak it.
Actually, gcc does not do a bad job at all for the x86, it's the performance
of x86_64 code that sucks (so far). NWChem is not properly open source: the
developers, at the NorthWest university, make it available (for free) on
request, including sources, after filling in a form in which you agree not
to redistribute it. Essentially they are glad if people use it, but want to
retain control due to US export regulations (for some reasons some people
think it is sort of strategic weapon? I don't know). It's good stuff anyway.
I wouldn't throw away that Intel compiler just yet. For that matter, I'd
give serious consideration to switching to a Core 2 Duo and a copy of
Intel's tuning tools ... they are quite good. Life's too short to wait
for calculations. :)
Yes, sure. But also compiling, testing etc. kills heaps of time which I have
better ways of using, e.g. publishing some good results of my calculations...
:)
bye
Giacomo
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Giacomo Mulas <gmulas@ca.astro.it>
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