[gmx-users] Performance difference when using Gromacs 5.0 with different vector instructions

[MING HA]

Hi all,


I am running several resources using Gromacs 5.0 to run my simulations.
On some resources, Gromacs is compiled using SSE4.1 SIMD instructions,
while on others AVX_256 or AVX2_256 is used. While I don't find much of a
performance difference between AVX_256 and AVX2_256 instructions, there
is a large performance difference between resources that use SSE4.1 and
AVX instructions. Specifically, resources using SSE4.1 are about 2-3x slower
than those that use AVX.

I'm kind of new to the SIMD instructions used by Gromacs, so I was
wondering
whether the instruction set is causing the large performance difference.


Sincerely,
Ming