[gmx-developers] Assembler loops on Itanium2 Montecito (again)

[Erik Lindahl]

Hi,

On Feb 26, 2008, at 6:26 PM, Rafael R. Pappalardo wrote:
>
> I was assuming that the assembly code is faster on non Montecito  
> cpus. I read
> somewhere that it achieve something like 80% of peak performance.


It should be; provided the instruction latency timings haven't changed  
we keep the pipeline full.
On the other hand, we first wrote the loops for McKinley, so there  
might have been some instruction timing differences, and ia64 is  
incredibly sensitive to those.

Considering everybody seems to be going x86 nowadays I'm not sure if  
it's worth looking into re-scheduling the ia64 assembly, in particular  
if you're reasonably happy with the fortran performance :-)

Cheers,

Erik

------------
Erik Lindahl   <lindahl at cbr.su.se>  Backup: <erik.lindahl at gmail.com>
Assistant Professor, Computational Structural Biology
Center for Biomembrane Research, Dept. Biochemistry & Biophysics
Stockholm University, SE-106 91 Stockholm, Sweden
Tel: +46(0)8164675  Mobile: +46(0)704218767  Fax: mail a PDF instead