[Pw_forum] openmp vs mpich performance with MKL 10.x

[Axel Kohlmeyer]

On Tue, 6 May 2008, Eduardo Ariel Menendez Proupin wrote:

EAMP> Dear Axel,
EAMP> 
EAMP> > you should also compare against the parallel executable
EAMP> > run with -np 1 against the serial executable.
EAMP> 
EAMP> It is a bit slower.

eduardo,

ok. thanks, here are some timing results on my desktop.
the machine was not entirely idle and freshly booted, so 
take the numbers with a bit of caution.

i have a one year old two-socket intel dual core 2.66GHz machine
(i.e. more or less equivalent to a single socket 
intel quad-core, with two dual-core dies in one case).

this is using the latest cvs code:

with serial MKL, serial FFTW-2.1.5 and OpenMPI with 4 mpi tasks. 
i get a wall time of 12m12s and cpu time of 10m40s.
changing MKL to threaded MKL using 4 threads and 1 mpi task 
i get a wall time of 18m8s and cpu time of 28m30s
(which means that roughly 40% of the time the code
was running multi-threaded BLAS/LAPACK).
with serial FFT, threaded MKL using 2 threads and 2 mpi tasks
i get a wall time of 12m45s and cpu time of 14.42s

now when i swap the serial FFTW2 against the 
intel MKL FFTW2 wrapper i get with 2 threads and 2 MPI tasks
a wall time of 15m2s and a cpu time of 24m11s.
and with 4 threads and 1 MPI task i get
a wall time of 0h19m   and a cpu time of 1h 2m
and finally when disabling threading and with 
4 MPI tasks i get 12m38 wall time and 11m14s cpu time.

obviously, switching to the intel fft didn't help.

your system with many states and only gamma point 
is definitely a case that benefits the most from
multi-threaded BLAS/LAPACK. 

i'm curious to learn how these number match up
with your performance measurements. 

cheers,
   axel.


EAMP> 
EAMP> Attached is my input.
EAMP> 
EAMP> 
EAMP> 
EAMP> 

-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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