[gmx-users] Testing gromacs on IBM POWER8
pall.szilard at gmail.com
Thu Aug 27 15:03:32 CEST 2015
A few more things to add:
- we don't have CPU SIMD kernels for Power8, so comparing the plain C
kernels against AVX kernels on AMD is not exactly fair;
- as Mark pointed out, to use resources efficiently, you'll have to manage
thread affinity on Power8 (by default you'll need a stride of 8 to use one
thread per core, a stride of 4 to use two, etc.);
- for a realistic performance measurement use ~100-1000 atoms/core; the
"0000.96" benchmark in a 960 atom input, running that cross 192 threads
makes little sense.
What motivates your choice of compiler flags?
On Thu, Aug 27, 2015 at 9:17 AM, Mark Abraham <mark.j.abraham at gmail.com>
> I have no idea what you're trying to show with these graphs. Your vertical
> axis of time makes it looks like a 2.5 year old AMD chip is walking all
> over POWER8?
> Other points
> 1) GROMACS doesn't use configure or fortran, so don't mention that
> 2) these simulations do not use lapack or blas, so don't mention that
> 3) you need to clarify what a "CPU" is... core, hardware thread?
> 4) when you're using fewer cores than the whole node, then you need to
> report how you are managing thread affinity
> 5) the splines on the graphs are misleading when reporting discrete
> 6) you need to report times that are measured after auto-tuning completes
> 7) you need to report whether you are using MPI, thread-MPI or OpenMP to
> distribute work to threads.
> On Tue, Aug 25, 2015 at 11:54 PM Fabricio Cannini <fcannini at gmail.com>
> > Hello there
> > We've been testing gromacs-5.1-beta1 in an IBM POWER8. The input used is
> > 'pme.mdp' within the "0000.96" directory of the following benchmark:
> > ftp://ftp.gromacs.org/pub/benchmarks/water_GMX50_bare.tar.gz
> > The following link shows our results:
> > http://suporte.versatushpc.com.br/power/gromacs.php
> > These are our first results. We're now running more tests using IBM XL
> > compilers, the just launched 5.1.0 version and OpenBLAS port to POWER8.
> > Please feel free to ask questions, suggests improvements and spot errors.
> > --
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