Re: [ESPResSo-devel] processor optimization

[Axel Arnold]

Am Samstag 04 April 2009 13:58 schrieb Ahmad A. J. Agung:
> Dear All,
>
> First, Thanks for all suggestion, where in espresso-request I ask help for
> parallel configuration. Now we are using LAM for ESPResSo. It seems works
> for SMP machine and we plan for HPC.
>
> Attached is a file where I record the performance of our processor. I would
> like to ask, whether ESPResSo apply a certain flag for processor
> optimization?
> specifically for Intel(R) Xeon(R) CPU
> X5272  @ 3.40GHz and Dual-Core Intel(R) Itanium(R) Processor 9130M?

Hi,

this depends on the C-Compiler you are using. From the config.log you send 
previously, it seems to be the Intel-Compiler. For this compiler and a 
EM64T-Xeon or Itanium, our configure does not use processor-specific 
optimization flags, since we didn't have that case so far. You can verify 
this by looking at the output of ./configure: it should say "WARNING: could 
not recognize your cpu type, relying on generic optimization".

If you want to try different compiler flags, simply specify them manually 
using ./configure CFLAGS="-my -super -flags" 
--disable-processor-optimization.

I would suggest to try for the Xeon "-wd 1572,1173 -w1 -unroll -ip -O3 
-mcpu=core2" and for the Itanium "-wd 1572,1173 -w1 -unroll -ip -O3 
-mcpu=itanium2"; the latter only works if you compile on the Itanium system. 
If you find out what parameters are optimally for both CPUs, please mail them 
to the mailing list, then we can built them into our build-system.

Axel

-- 
Dr. Axel Arnold 
Fraunhofer SCAI
Schloss Birlinghoven, 53754 Sankt Augustin, Germany
Tel: +49 2241 14 2575