[Pw_forum] Strange benchmark results

[Fabricio Cannini]

Hi there


I'm running some tests on the following machine :
- 2x AMD Opteron 6380 ( 32 cores )
- 64GB RAM
- Ubuntu 12.04 ( gfortran 4.6, fftw 3.3.1, openblas 0.2.8, openmpi 1.4.3 )


Using these benchmarks :
- Medium size DEISA benchmark :
http://qe-forge.org/gf/project/q-e/frs/?action=FrsReleaseView&release_id=45

- Medium-size :
http://qe-forge.org/gf/project/q-e/frs/?action=FrsReleaseView&release_id=44


And the machines behavior was exactly the same. An example:

DEISA Benchmark:

-8 cores : 46m57.62s
16 cores : 38m26.81s
24 cores : 39m48.91s
32 cores : 46m2.46s




After more research on it, i've found the following graphic from other, 
older tests of quantum espresso, which shows the same behavior ( Page 8 ) :

http://hpcadvisorycouncil.com/pdf/ESPRESSO_Analysis_Intel_x5670.pdf


Is this the expected behavior of QE for these benchmarks ? If yes, why ?