Hi,
Please be aware that any compilation for Pentium will work
on Opteron; Opteron is backwards-compatible with "normal"
x86 builds. Our normal Absoft x86 builds, done on Athlon
or PIII, run just fine, and benchmark very well, on Opteron.
There may be some special Opteron flags you can specify,
but I doubt they'll do much. For instance, the special
Athlon flags make not a whit of difference when we benchmark
our codes on Athlon.
I suspect the only thing a 64-bit compilation will buy
you on Opteron is extra address space, which is good if
you need it. But we have found on other platforms, such
as IRIX64, that 32-bit executables actually run faster
than 64-bit executables on the 64-bit OS, because of
better cache warmth. On AIX and IRIX, AFAIK, you get
"64-bit numerical performance" even with a nominally
32-bit executable. I suspect that this is true on
Opteron, too, because even 32-bit executables should
be taking care of normal x86 80-bit floating-point
registers.
But I'd welcome being corrected if someone out there
knows better -- which is likely, since I have no
direct experience with Opteron-specific compilation,
and our benchmarks were performed by third parties.
-P.
On Mon, 15 Dec 2003, 2:07pm -0600, [log in to unmask] wrote:
> Portland Group (PGI; www.pgroup.com) offers Fortran and C/C++ compilers
> for Opteron. They also have a cluster package that includes MPI and
> some other features. See their web page for details and pricing.
>
> I've only tried a couple of programs with the PGI Opteron Fortran
> compiler. It seemed to work OK. The compilation was fast. I didn't
> have any comparison base for the speed of the a.out. Others have
> observed that for C programs, the gcc compiler did produce faster code.
> I believe PGI expects better performance in future releases. My only
> complaint is the large number of compiler switches, and the fact that
> you need to hit on some combination of them for good performance. I
> prefer environments where a high optimization level is the default.
>
> If you can wait, g95 might also be a good option for the Opteron, based
> on experience with gcc.
>
> Cheers,
> Bill
>
>
> Aleksandar Donev wrote:
>
> >Hello,
> >
> >I forgot to also ask about Opteron chips.
> >
> >Thanks,
> >Aleksandar
> >
> >
> >
> >>My department is getting a new cluster and they are thinking about what
> >>kinds of processors to use. Among the options is G5.
> >>
> >>I would appreciate any info about Fortran 95 on G5 platforms. As far as I
> >>know, Absoft, NAG and now IBM (still beta) support this chip on OS X.
> >>Experiences as well as any information on web-pages to look at for info
> >>(pricing, requirements, etc.) would be helpful.
> >>
> >>
>
> --
> Bill Long [log in to unmask]
> Fortran Technical Support & voice: 651-605-9024
> Bioinformatics Software Development fax: 651-605-9142
> Cray Inc., 1340 Mendota Heights Rd., Mendota Heights, MN, 55120
>
--
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