<br><br><div class="gmail_quote">On Thu, Oct 21, 2010 at 5:53 PM, Renato Freitas <span dir="ltr"><<a href="mailto:renatoffs@gmail.com">renatoffs@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
Thanks Roland. I will do a newer test using the fourier spacing equal<br>
to 0.11. </blockquote><div>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.</div>
<div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">However, about the performance of GPU versus CPU (mpi) let me<br>
try to explain it better:<br></blockquote><div> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
GPU<br>
<div class="im"><br>
NODE (s) Real (s) (%)<br>
Time: 6381.840 19210.349 33.2<br>
1h46:21<br>
(Mnbf/s) (MFlops) (ns/day) (hour/ns)<br>
Performance: 0.000 0.001 27.077 0.886<br>
<br>
</div>MPI<br>
<div class="im"><br>
NODE (s) Real (s) (%)<br>
Time: 12621.257 12621.257 100.0<br>
3h30:21<br>
(Mnbf/s) (GFlops) (ns/day) (hour/ns)<br>
Performance: 388.633 28.773 13.691 1.753<br></div></blockquote><div><br></div><div>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.</div>
<div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Looking abobe we can see that the gromacs prints in the output that<br>
the simulation is faster when the GPU is used. But this is not the<br>
reality. The truth is that simulation time with MPI was 106 min faster<br>
thatn that with GPU. It seems correct to you? As I said before, I was<br>
expecting that GPU should take a lower time than the 6 core MPI.<br></blockquote><div> 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.</div>
<div><br></div><div>Roland</div></div>