On Thu, Oct 21, 2010 at 5:53 PM, Renato Freitas <renato...@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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