[gmx-users] Testing gromacs on IBM POWER8

Fabricio Cannini fcannini at gmail.com
Wed Sep 2 21:33:50 CEST 2015

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 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.


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