[gmx-users] PME on GPU4.6.2)
mark.j.abraham at gmail.com
Sun Mar 23 23:33:56 CET 2014
On Sun, Mar 23, 2014 at 6:40 PM, Albert Romano <albertmano at aol.com> wrote:
> Dear list,
> I have noticed the following changelog from Gromacs 4.6.2:
> --> Added CUDA PME kernels with analytical Ewald correction
> Does that mean we can now offload PME computation to GPU?
No. That refers to short-ranged kernels used with PME.
More generally, there'd be little/no advantage in CUDA offload, because it
would leave the CPU idle in many cases. In parallel, the CPU-based FFT for
PME is latency-bound already, and adding CUDA offload latency would be
silly, unless/until GPUs come with on-board network connects, and/or are
coupled with really weak CPUs.
> I have not found how... I have noticed two environment variables:
> GMX_CUDA_NB_ANA_EWALD and GMX_CUDA_NB_TAB_EWALD but even if I export them
> it does not seem to activate PME on GPU.
> My technique for verifying is: raise PME accuracy by means of
> fourierspacing, interpolation etc... and see from the force evaluation time
> GPU/CPU that the CPU time has increased.
> Thank you
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