[gmx-users] GPU efficiency question

[Mark Abraham]

Probably the part of the calculation done on the GPU is not rate limiting.
There's no point having four chefs to make one dish...

Look at the beginning and end of your .log files for diagnostic
information. If this is a single node, you should be using threadMPI, not
real MPI. Generally four CPU cores vs four GPU cores will require an
extremely large PP load for the GPUs to all be effective.

Mark


On Fri, Apr 26, 2013 at 8:35 PM, Albert <mailmd2011 at gmail.com> wrote:

> Dear:
>
>  I've got two GTX690 in a a workstation and I found that when I run the md
> production with following two command:
>
> mpirun -np 4 md_run_mpi
>
> or
>
> mpirun -np 2 md_run_mpi
>
> the efficiency are the same..... I notice that gromacs can detect 4 GPU
> (probably because GTX690 have two core..):
>
> 4 GPUs detected on host node4:
>   #0: NVIDIA GeForce GTX 690, compute cap.: 3.0, ECC:  no, stat: compatible
>   #1: NVIDIA GeForce GTX 690, compute cap.: 3.0, ECC:  no, stat: compatible
>   #2: NVIDIA GeForce GTX 690, compute cap.: 3.0, ECC:  no, stat: compatible
>   #3: NVIDIA GeForce GTX 690, compute cap.: 3.0, ECC:  no, stat: compatible
>
>
> why the "-np 2" and "-np 4" are the same efficiency? shouldn't it be
> faster for "-np 4" ?
>
> thank you very much
>
> Albert
>
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