[gmx-users] Using Gpus on multiple nodes. (Feature #1591)

[Mark Abraham]

On Tue, Oct 14, 2014 at 10:51 PM, Siva Dasetty <sdasett at g.clemson.edu>
wrote:

> Dear All,
>
> I am currently able to run simulation on a single node containing 2 gpus,
> but I get the following fatal error when I try to run the simulation using
> multiple gpus (2 on each node) on multiple nodes (2 for example) using OPEN
> MPI.
>

Here you say you want 2 ranks on each of two nodes...


> Fatal error:
>
> Incorrect launch configuration: mismatching number of PP MPI processes and
> GPUs
>
> per node.
>
> mdrun was started with 4 PP MPI processes per node,


... but here mdrun means what it says...


> but you provided only 2
> GPUs.
>
> The command I used to run the simulation is
>
> mpirun -np 4 mdrun  -s <tpr file>  -deffnm <...>  -gpu_id 01
>

... which means your MPI environment (hostfile, job script settings,
whatever) doesn't have the settings you think it does, since it's putting
all 4 ranks on one node.

Mark


>
>
> However It at least runs if I use the following command,
>
>
> mpirun -np 4 mdrun  -s <tpr file>  -deffnm <...>  -gpu_id 0011
>
>
> But after referring to the following thread, I highly doubt if I am using
> all the 4 gpus available in the 2 nodes combined.
>
>
>
> https://mailman-1.sys.kth.se/pipermail/gromacs.org_gmx-developers/2014-May/007682.html
>
>
>
> Thank you for your help in advance,
>
> --
> Siva
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