[gmx-users] Cuda CC 2.0 restrictions

Mirco Wahab mirco.wahab at chemie.tu-freiberg.de
Tue Sep 9 22:59:00 CEST 2014

Thank you very much for your answer. After reading
Mark's very detailed posting on the topic, I played
with some parameters but did not manage to get under
64K grid dimension.

On 09.09.2014 21:35, Szilárd Páll wrote:
> Is this rather large box a system that can actually be simulated with
> a useful speed on a single Fermi GPU? Even with 5 fs time-step you
> won't get much more than 1-1.5 ns/day on a fast Fermi GPU like a GTX
> 580.

This is a rather simple toy system used for machine comparison and
as a hardware reliability test. ~36nm^3 SPC water box, ~1.56x10^6
water (GTX-780 on 3770K is 0.45ns/day).

I posted the question because I did not understand why this
happened on the GTX-580. mdrun -nstlist x did not work (4.6.7).

> Given that you are quite a bit above the limit, unless you are using a
> quite large nstlist, you may not be able to decrease it enough to fit
> the system on the GPU. What you can do instead is to use
> domain-decomposition and start multiple ranks per GPU. In your case
> two-way DD should be enough.

This sounds interesting. I'll try to accomplish that (I never thought
this *this* is possible ...). Thank you very much (and Mark)


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