[gmx-users] Testing gromacs on IBM POWER8
mark.j.abraham at gmail.com
Mon Sep 7 10:54:56 CEST 2015
On Wed, Sep 2, 2015 at 9:34 PM Fabricio Cannini <fcannini at gmail.com> wrote:
> On 27-08-2015 10:03, Szilárd Páll wrote:
> > 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;
> That was our hypothesis after seeing the results.
> One of our goals was to assess the readiness of some softwares that are
> popular among our clients; See if is it too early for them to consider
> purchasing POWER8 hardware.
As Szilard notes, we have not yet optimized POWER8 for CPU-only runs. It
will likely be optimized by the 2016 version of GROMACS. POWER8+CUDA is OK
now, and will improve further.
> - 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
> > 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.
> Are any of the inputs in the 'water' benchmark useful for this purpose?
> > What motivates your choice of compiler flags?
> We had reports of good performance using these flags in a POWER7 machine.
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