[Beowulf] Re: Beowulf Digest, Vol 45, Issue 28

[Håkon Bugge]

At 21:00 17.11.2007, Chris Samuel <csamuel at vpac.org> wrote:
>I should also point out that we're using the PGI 7.x series of
>compilers and tell our users to build with:
>
>-tp k8-64,barcelona-64
>
>so that they get the optimisations for both dual and quad core chips
>(with the appropriate path selected at run time).

While I did the SPEC MPI 2007 for the Barcelona, I got the following 
projections (8 nodes, 8 cores per node) for SPECmpiM_base2007:
    * PathScale 3.0, -march=core: 5.53
    * PathScale 3.0, -march=opteron -msse3: 5.32
    * PGI 7.0-7, -tp barcelona-64 + lots of fancy switches: 4.71
    * PGI 7.0-7, -tp barcelona-64 -nomovnt -fast: 4.75
I didn't have much time to play with compiler options. It was 
interesting to see that the "wrong" architecture was better using the 
PathScale compiler. Further, PathScale was significant better than 
PGI 7.0-7, even though PGI had support for the "right" architecture.

The switches used for the PathScale compiler can be found at the SPEC 
web, http://www.spec.org/mpi2007/results/res2007q4/

The final rate (5.61) was better, due improved memory bandwidth (due 
to a better BIOS).



Hakon