On Tue, Nov 8, 2011 at 3:03 PM, Darius Buntinas <[email protected]> wrote:

I saw this sentence in the proposal: � �\MPI/ guarantees that eventually all processes in the \MPI/ � �universe will become aware of all process failures.

I think we only want to say all processes will become aware of all failures of _connected_ processes. �Two MPI jobs can technically belong to the same universe, but they don't need to be aware of each other's failures unless they're connected. �Besides, unless they were connected, there would be no way to identify the failed processes of one job to the processes of the other job.

I agree that adding _connected_ here helps clarify this statement.

As an aside, I did some grepping for "universe" in the standard, and found that universe is actually not well defined. �It can refer to communication within a communicator (p29), an implementation defined scope of a port name (p320) and an implementation defined set of processes that can communicate with each other. �Then there's MPI_UNIVERSE_SIZE which is the number of total processes that "can usefully be started," (p308) which implies the definition of universe that I think most people use, namely, the set of all potential processes that some process can be made aware of / be connected to.

Humm... This is an interesting point. I think we are ok using universe in the context of all processes that a single process may be connected to. In terms of the failure detector statement, that would mean that MPI provides a process notification of process failure: - in it's own MPI_COMM_WORLD - in a remote group when the process joins with it (via connect/accept) But not provide the process notification of process failure if it is not connected to it (2 disjoint spawned groups). So at the point where an inter-communicator is created between two disjoint MPI_COMM_WORLDs then they must share failure information with one another regarding the local/remote groups. But if the two disjoin MPI_COMM_WORLDs never collide then they need not know about one another. What do you think? -- Josh

-d

_______________________________________________ mpi3-ft mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi3-ft

-- Joshua Hursey Postdoctoral Research Associate Oak Ridge National Laboratory http://users.nccs.gov/~jjhursey