[Beowulf] Alternative to MPI ABI
patrick at myri.com
Fri Mar 25 11:47:44 PST 2005
It looks a lot more like a runtime environement (care about resources,
scheduling, failover) than a programming model to me. MPI is much more a
programming model than a runtime environement, so I don't think they are
Donald Becker wrote:
> MPI has a model of initialize-compute-terminate.
> There is no explicit support for checkpointing, executing as a
> service, or running "forever".
There is no explicit support but people have been checkpointing parallel
jobs for a while. You just need to be flush all pending communications:
pass a token a couple of times and you will have a clean cut.
> MPI's strength is collective mathematically-oriented operations, not
> communication. I understand that even the name "Message Passing.."
> indicates that stream communication isn't the focus, but many
> applications expect and work well with a sockets-based model.
Aaargh. Sockets are definitively not a programming model suited for
parallel codes. Client/server, maybe, not tighlty coupled applications.
Look at the bodies left from trying to do zero-copy and OS-bypass
sockets: when you apply all of the constraints, you basically gut out
the stream paradigm.
> Communicators besides MPI_COMM_WORLD are rarely used. The capability
> adds complexity with little benefit.
Most libraries use communicators for isolation. Look at the BLACS
contexts for example.
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