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Subject: Re: [OMPI users] Redefine proc in cartesian topologies
From: Jingcha Joba (pukkimonkey_at_[hidden])
Date: 2012-03-01 14:28:51


mpirun -np 4 --host node1,node2,node1,node2 ./app

Is this what you want?

On Thu, Mar 1, 2012 at 10:57 AM, Claudio Pastorino <
claudio.pastorino_at_[hidden]> wrote:

> Dear all,
> I apologize in advance if this is not the right list to post this. I
> am a newcomer and please let me know if I should be sending this to
> another list.
>
> I program MPI trying to do HPC parallel programs. In particular I
> wrote a parallel code
> for molecular dynamics simulations. The program splits the work in a
> matrix of procs and
> I send messages along rows and columns in an equal basis. I learnt
> that the typical
> arrangement of cartesian topology is not usually the best option,
> because in a matrix, let's say of 4x4 procs with quad procs, the
> procs are arranged so that
> through columns one stays inside the same quad proc and through rows
> you are always going out to the network. This means procs are
> arranged as one quad per row.
>
> I try to explain this for a 2x2 case. The cartesian topology does this
> assignment, typically:
> cartesian mpi_comm_world
> 0,0 --> 0
> 0,1 --> 1
> 1,0 --> 2
> 1,1 --> 3
> The question is, how do I get a "user defined" assignment such as:
> 0,0 --> 0
> 0,1 --> 2
> 1,0 --> 1
> 1,1 --> 3
>
> ?
>
> Thanks in advance and I hope to have made this more or less
> understandable.
> Claudio
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