[gmx-users] GPU slower than I7
Roland Schulz
roland at utk.edu
Fri Oct 22 00:35:48 CEST 2010
On Thu, Oct 21, 2010 at 5:53 PM, Renato Freitas <renatoffs at gmail.com> wrote:
> Thanks Roland. I will do a newer test using the fourier spacing equal
> to 0.11.
I'd also suggest to look at g_tune_pme and run with different rcoulomb,
fourier_spacing. As long as the ratio is the same you get the same accuracy.
And you should get better performance (especially on the GPU) for longer
cut-off and larger grid-spacing.
> However, about the performance of GPU versus CPU (mpi) let me
> try to explain it better:
>
> GPU
>
> NODE (s) Real (s) (%)
> Time: 6381.840 19210.349 33.2
> 1h46:21
> (Mnbf/s) (MFlops) (ns/day) (hour/ns)
> Performance: 0.000 0.001 27.077 0.886
>
> MPI
>
> NODE (s) Real (s) (%)
> Time: 12621.257 12621.257 100.0
> 3h30:21
> (Mnbf/s) (GFlops) (ns/day) (hour/ns)
> Performance: 388.633 28.773 13.691 1.753
>
Yes. Sorry I didn't realize that NODE time and Real time is different. Did
you run the GPU calculation on a desktop machine which was also doing other
things at the time. This might explain it. As far as I know for a dedicated
machine not running any other programs NODE and Real time should be the
same.
Looking abobe we can see that the gromacs prints in the output that
> the simulation is faster when the GPU is used. But this is not the
> reality. The truth is that simulation time with MPI was 106 min faster
> thatn that with GPU. It seems correct to you? As I said before, I was
> expecting that GPU should take a lower time than the 6 core MPI.
>
Well the exact time depends on a lot of factors. And you probably can speed
up both. But I would expect them to be both about similar fast.
Roland
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