[gmx-users] Testing gromacs on IBM POWER8

[Mark Abraham]

Hi,

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.

Mark

> - 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.
>
> 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.
>
>
>
> TIA,
> Fabricio
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