The btl interface is used. The nodes in both subclusters have the same architecture so no need for two binaries. The MPI libraries for the interconnect can be selected at runtime, for example through the value of the OMPI_MCA_btl environment variable. However that variable should then somehow be set once SGE has decided on which subcluster to run the job, thus avoiding it to be set in advance when submitting. I tried a couple of things like different PEs but there does not seem to be an elegant solution; I mean something completely transparent to the user like
mpirun -np $NSLOTS executable
as I have seen in some of the OpenMPI FAQs.

From: on behalf of Reuti
Sent: Fri 6/6/2008 6:47 PM
To: Open MPI Users
Subject: Re: [OMPI users] using OpenMPI + SGE in a heterogeneous network

Am 06.06.2008 um 19:31 schrieb Patrick Geoffray:

> SLIM H.A. wrote:
>> I would be grateful for any advice
> Just to check, you are not using the MTL for MX, right ? Only the BTL
> interface allow to choose between several devices at run time.

At least there would be the option to built two binaries and decide 
at runtime which to use in your jobscript - depending on the machine 
you landed on.

-- Reuti
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