[mpi3-coll] Non-blocking Collectives Proposal Draft

Christian Siebert siebert at it.neclab.eu
Fri Oct 17 07:42:21 CDT 2008

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_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 Siebert, Dipl.-Inf.               Research Associate

            NEC Laboratories Europe, NEC Europe Ltd.
        Rathausallee 10, D-53757 Sankt Augustin, Germany

Phone: +49 (0) 2241 - 92 52 44    Fax: +49 (0) 2241 - 92 52 99

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