[gmx-users] Gromacs 2019.2 on Power9 + Volta GPUs (building and running)

[Alex]

Hi all,

Our institution decided to be all fancy, so now we have a bunch of Power9
nodes, each with 80 cores + 4 Volta GPUs. Stuff is managed by slurm. Today
I did a simple EM ('gmx mdrun -ntomp 4 -ntmpi 4 -pme cpu -nb cpu') and the
performance is abysmal, I would guess 100 times slower than on anything
I've ever seen before.

Our admin person emailed me the following:
"-- it would not surprise me if the GCC compilers were relatively bad at
taking advantage of POWER9 vectorization, they're likely optimized for
x86_64 vector stuff like SSE and AVX operations.  This was an issue in the
build, I selected "-DGMX_SIMD=IBM_VSX" for the config, but according to my
notes, that was part of an attempt to fix the "unimplemented SIMD" error
that was dogging me at first, and/but which was eventually cleared by
switching to gcc-6."

Does anyone have any comments/suggestions on building and running GMX on
Power9?

Thank you,

Alex