Some tests on Opteron cluster (strange???)

[ilya]

Thanks Axel. That what I wanted to know.

PS Interconnect is indeed very poor - 100 Mbps. Now I see the reason
of such performance.

Thanks again.



On Apr 18, 5:44 am, Axel <akoh... at gmail.com> wrote:
> On Apr 17, 7:55 am, ilya <ily... at gmail.com> wrote:
>
> > Hi, All  !!!
> > First of all setting OMP_NUM_THREADS=2 and running 1 MPI process per
> > node makes performance worse (lines 2, 5 and 6) compared to 2 MPI
>
> a proper hybrid OpenMP/MPI compile is tricky. you have
> to compile all of cp2k with OpenMP support _and_ have a
> multi-threaded FFT and BLAS/LAPACK. even then the gain
> is probably most, when you have scaled out the MPI parallelism.
>
> > processes per node (we have 1 dual core CPU per node).
> > Is it normal? CPU time still doubles.
>
> yep. OpenMP comes with a lot of overhead and i have the
> feeling the with intel binaries the threads keep spinning
> instead of sleeping until they are used.
>
> > And is it a normal scaling behavior? ( 4.89 on 8 procs is not very
> > good. I know the system is small but anyway).
>
> please see previous discussions on scaling and dual-core performance.
>
> what kind of interconnect do you have on your cluster?
> cp2k is _very_ demanding is terms of both memory bandwidth
> and communication bandwidth/latency.
>
> cheers,
>    axel.
>
>
>
> > Thanks.