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Re: [lammps-users] How to accelerate the calculation speed by using existing hardware ?
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Re: [lammps-users] How to accelerate the calculation speed by using existing hardware ?


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 10 Jul 2017 07:04:56 -0400

On Sun, Jul 9, 2017 at 10:40 PM, 王淑婷 <wangshuting@...36.....6572...> wrote:
> Dear lammps-users,
>
> Now I have several intel xeon processors e5 v4 with 280 cores. I find that
> the calculation speed is the fastest by using 54 cores when I use hybrid
> force field.
>
> I still have a NVIDIA Tesla P100 GPU. When the force field is tersoff, the
> calculation speed tested by one GPU core and one CPU core is four times
> higher than the 28 CPU cores. But when the force field is hybrid, the
> calculation speed tested by one GPU and one CPU core is two times lower than
> the 28 CPU cores.

that is because with a hybrid pair potential, you must compute the
neighbor lists on the CPU and then transfer it to the GPU, even if all
individual pair styles are GPU accelerated.
that will cause a significant slowdown, in your case, since you are
using only one CPU. you can try to minimize this by using multiple
CPUs with the same GPU, but the additional overhead of computing
neighbor lists on the CPU and transferring significant additional data
to the GPU cannot be completely avoided.

> I don't know how to use existing hardware to accelerate the calculation
> speed when my force field is hybrid. It's OK if I should buy some more
> hardware. Could you please give me some suggestions? Thank you for your help
> in advance.

the best way to get the most performance with the GPU package, is to
avoid a hybrid pair style.
there are also many other, simulation specific factors, that can
affect performance, where it is not possible to give general advice.

axel.

>
> Yours sincerely
> Shuting Wang
>
>
>
>
>
>
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-- 
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.