Good timing... Jeff Squyres just posted yesterday about this topic.
You can find his suggestions here:
On Tue, Jun 14, 2011 at 11:10 AM, Lawrence Stewart
> I apologize for asking elementary questions, I have spent some time looking through the open-mpi.org site and the list archives, without notable success.
> I am contemplating writing a btl component in order to make OpenMPI work on the fos experimental message-based operating system under construction at csail. The network semantics provided are reliable, in-order messages to process mailboxes, which may be shared. This <ought> to be straightforward, but
> * A search around open-mpi.org did not uncover a "how to write a BTL component" document. Is there one?
> * A quick survey through .../ompi/mca/btl did not uncover an obvious "example". Is there one? Or which existing component is the simplest non-rdma one? It might be that elan is the simplest,
> based on source lines, but it is a little tricky to untangle the elan-parts from the open-mpi parts.
> The other thing I'll have to tackle is figuring out whether fos has enough of the os interfaces needed by the rest of open-mpi, and how to get the job launch machinery working.
> devel mailing list
Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/
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