ATHLON vs XEON: number crunching

[Ivan Oleynik]

> As others suggested, you may be seeing memory throughput problems.
> 
> Specify the best optimization options. Experiment a little - perhaps one
> set yields better performance on one CPU than the other. Then use the
> best set of options for each processor type.
> 
> Is there any chance you can re-run the benchmarks with better
> optimization enabled ?   That would be really interesting to a lot of us
> here on the list.
> 

What are optimization options for PGI compiler that you can suggest to
optimize memory throughput problems? I am more than willing to test this.
My original thought was just to avoid any substantial optimization tuning,
and use generic -O1 option for both platforms. By the way, running Xeon
binary (PGI compiled with -tp piv) on Athlon and vise versa does not make
any substantial difference.


> > The code itself contains a lot of FFTs, vector & matrix algebra, it
> > includes BLAS and LAPACK sources and minimal IO. All the systems have 2 GB
> > RAM and the code consumes only 50 Mb.
> 
> Any chance you can try using ATLAS ?
> 
> You would need to compile one ATLAS for the Intel CPUs and one for the
> AMD ones.
> 

For the purpose of comparison, I don't need to use ATLAS, because the same
pieces of BLAS and LAPACK source code is compiled for both plaforms. It
would make sense to use them if I could prove that by playing with
optimization options I can tweak binary to make Athlon to overperform
Xeon.

By the way, I followed up one of the suggestion to load both processors on
each Athlon and Xeon nodes to check memory bandwidth for 2 processors
running simultaneously. My conclusion remains the same: Xeon 2.2 GHz is
50% faster than Athlon XP 2100+.

Ivan

------------------------------------------------------------------------
Ivan I. Oleynik                       E-mail : oleynik at chuma.cas.usf.edu
Department of Physics
University of South Florida
4202 East Fowler Avenue                  Tel : (813) 974-8186
Tampa, Florida 33620-5700                Fax : (813) 974-5813
------------------------------------------------------------------------