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Subject: [OMPI devel] BML problem?
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2008-12-11 21:35:45


I'm not exactly sure where the fix to this should be, but I think I've
found a problem.

Consider, for illustration, launching a multi-process job on a single
node. The function

    mca_bml_r2_add_procs()

calls

    mca_btl_sm_add_procs()

Each process could conceivably return a different value -- OMPI_SUCCESS
or otherwise. E.g., if there isn't enough room for all to allocate all
the shared memory they need, early processes might succeed in their
allocations while laggards won't.

The fact that some processes fail doesn't bother the BML. It just loops
over other BTLs and, quite possibly, finds another BTL to make needed
connections.

Is this a problem? It seems to me to be, but I haven't yet figured out
what the BML does next. I'm guessing it ends up with a hodgepodge of
BTLs. E.g., A talks to B via sm, but B talks to A via tcp. And, I'm
still guessing, this produces badness (like hangs).

Comments?