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Subject: Re: [OMPI users] Accessing OpenMPI processes over Internet using ssh
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2011-11-30 15:36:18

On Nov 30, 2011, at 3:02 PM, Jaison Paul wrote:

> We are not setting up --mca btl_tcp_if_include / --mca oob_tcp_if_include at all
> at the moment. What will be the best setup to access EC2 hosts over internet for
> --mca btl_tcp_if_include / --mca oob_tcp_if_include? I dont understand --mca
> very well.

I don't know; I've never run on EC2 before. My meeting with the EC2 folks is next week, so that's the earliest possibility of me gaining a little knowledge into what the Right way is to run with OMPI on EC2 (where "Right" = "run without horrid latency"). It may take a bit longer than that, though, depending on my time availability.

The two parameters I'm referring to simply limit the Ethernet interfaces that are used for Open MPI's MPI messaging and out-of-band messaging. For example, on a commodity linux system, you could run with:

mpirun --mca oob_tcp_if_include eth0 \
    --mca btl_tcp_if_include eth1 ...

Where eth0 will be used for OMPI's control traffic (e.g., perhaps it's a commodity 1GB network) and eth1 will be used for OMPI's MPI traffic (e.g., perhaps it's a 10GB network).

Jeff Squyres
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