[gmx-users] 2018-beta1: PME/GPU performance question

[Jochen Hub]

Dear all,

I have a question on the performance of the new PME-on-GPU code 
(2018-beta1) on a Xeon 12-core / GTX 1080 node (Cuda 8, gcc 4.85).

With a 84 kAtoms system, I get that the simulations do not benefit from 
a strong CPU any more. See, using 6 Xeon cores with a GTX 1080 is 
sufficient.

#CPU  ns/day
  2    92.88
  4   113.18
  6   123.36
  8   122.62
10   125.76
12   128.84

(This is nice, as we can buy cheap CPUs).

(with pinning, pinstride 1, one GPU, -ntmpi 1)

On a small system (Charmm36 lipid patch, 30 kAtoms), in contrast, the 
simulations strongly benefit from more CPU cores.

#CPU  ns/day
  4    84.11
  6   119.24
  8   150.84
10   159.63
12   171.30

Is this the expected behaviour? Do you know why?

Thank you for any hints,
Jochen

-- 
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Dr. Jochen Hub
Computational Molecular Biophysics Group
Institute for Microbiology and Genetics
Georg-August-University of Göttingen
Justus-von-Liebig-Weg 11, 37077 Göttingen, Germany.
Phone: +49-551-39-14189
http://cmb.bio.uni-goettingen.de/
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