[Pw_forum] Problem with QE 4.2.1 and AMD Opteron 6200 / 6300

[Fabricio Cannini]

Em 12-12-2013 08:20, Ivan Girotto escreveu:

Hi there

I've finally figured out the problem.

First, i changed the benchmark to DEISA Medium so that i could use a 
wider range of machines, as it ( predictably ) used less than half of 
the memory than the PRACE medium benchmark demanded. Then i started to 
have results.

http://qe-forge.org/gf/project/q-e/frs/?action=FrsReleaseView&release_id=45


Second, i noticed that no matter what, the machines running ubuntu 12.04 
were faster than the machines running debian 6.0 , and that it was 
causing by a series of factors. In order :

- OS runtime :
http://www.eglibc.org/cgi-bin/viewvc.cgi/branches/eglibc-2_15/libc/NEWS?view=markup
( "Lots of generic, 64-bit, and x86-64-specific performance 
optimizations to math functions." )


- Math Library :
Old MKL ( 10.0 ) and ACML ( 5.1.0 ) versions . Openblas gave much better 
results in both debian and ubuntu, even better in ubuntu.


- Compiler :
And this is why openblas ran even better in ubuntu.
http://gcc.gnu.org/gcc-4.6/changes.html
( "Support for AMD Bulldozer (family 15) processors is now available 
through the -march=bdver1 and -mtune=bdver1 options" )

The machines were running old versions of intel ifort ( 11.1 ), which 
could not possibly have good performance in a much newer machine.


Once again, Thanks for your time.
Fabricio