Re: confused about performance
On Thu, 14 Jun 2007, M. Edward (Ed) Borasky wrote:
All of these provide vastly better performance than the current
incarnations of ATLAS in 64bit.
How recent is your data? I was under the impression that Atlas had
caught up with GOTO and ACML, and possibly even the Intel libraries on
the Core 2 Duo. I'm on the Atlas mailing list -- I can ask there. In any
event, there is enough assembly code in Atlas that I'd expect it to be
competitive with both GOTO and the vendor libraries on AMD 64-bit and
Intel 64-bit chips. And I think 3.7.32 cleaned out some bottlenecks in
the 64-bit SPARC code as well, so it's undoubtedly worthwhile for Debian
to put it in the repositories for SPARC at 3.7.32 and probably not for
older versions.
Two or three months, when I last compiled the latest version of the big
quantum chemistry code (NWChem) I use (which spends a lot of time doing
floating point linear algebra). The computer on which I tested is a
relatively old Athlon 64 3500+, your mileage may vary on other machines.
Oddly enough, an old version of GOTO was the fastest, followed closely by
the optimised acml, then head to head the internal implementation provided
by the quantum chemistry package and the (then) current GOTO, then atlas.
Differences among all but atlas were measurable (i.e. reproducible) but very
small, within 2%, atlas was ~10% slower. The Intel compilers produced much
faster code than the gcc suite (both 3.4 and 4.1), despite running on AMD
processors. This is a VERY specific test, of course, so I do not claim
my conclusions should apply to anyone but me. On the other hand, they
do apply rather well to my scenario by definition :)
I will obviously evaluate again atlas and new versions of the gcc suite
if/when it's worth the effort. I look forward seeing an up-to-date version
of atlas being included in debian. I would actually be very glad to be able
to switch to a completely clean environment using gcc, since I currently
have to keep around hosts of libraries compiled with different compilers and
it's somewhat messy to maintain.
Bye
Giacomo
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Giacomo Mulas <gmulas@ca.astro.it>
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