Chris Samuel wrote:
----- "John Hearns" <[email protected]> wrote:
A commercial compiler - Intel / Pathscale /Portland
will always give you better performance from an application.
The feedback from a number of our users on our Barcelona/
Shanghai cluster is that GCC beats the Intel compilers
hands down [1] and that the PGI ones don't tend to hold
a significant margin over GCC either.
Interestingly using the -march=amdfam10 option in GCC 4.3.3
to emit Barcelona specific optimisations produces real
application code that runs slower than the standard
optimisation options (confirmed by a couple of users).
Hi Chris, list
Thanks for the info!
I have been blindly using "-march=amdfam10" (and -O3)
out of the gcc 4.1.2 man page,
simply because it is recommended for Barcelona
(and hopefully also the Shanghais we have).
What would be the right level of optimization then?
I've built GCC 4.4.0, but we've not tested with it
(or announced it to users) yet.
[1] - Not surprising, it's hardly their home turf. ;-)
On Opteron Shanghai the Intel 10.1 compilers seem to reject
any architecture-dependent optimization flag above -xW (SSE and SSE2),
although the processor has SSE3, etc, and would qualify for
higher levels of optimization, or not?
Is this deliberate?
cheers,
Chris
Thank you,
Gus Correa
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Gustavo Correa
Lamont-Doherty Earth Observatory - Columbia University
Palisades, NY, 10964-8000 - USA
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