[mpi3-coll] Non-blocking Collectives Proposal Draft

[Christian Siebert]

Dear Alexander,

as Rich pointed out, your example will not deadlock (try to understand 
his good explanation). I think that your progression question is not 
really related to nonblocking collectives. The same question could be 
asked with an example using MPI-1:

process 0              process 1
---------              ---------
                        MPI_Irecv(.., req)
MPI_Barrier(comm)      MPI_Barrier(comm)
MPI_Ssend(..)
MPI_Bcast(..)          MPI_Bcast(..)
                        MPI_Wait(req, ..)

The barrier only ensures that the send gets started after the 
incompleted Irecv returned to the user (to simulate the outstanding 
Ibarrier). Although the broadcast has nothing to do with the Irecv(), it 
will still ensure the required progress.

Best regards,
    Christian

-- 
Christian Siebert, Dipl.-Inf.               Research Associate

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