[mpi3-coll] Non-blocking Collectives Proposal Draft

Supalov, Alexander alexander.supalov at intel.com
Fri Oct 17 08:14:18 CDT 2008

Dear Christian,

Thanks for the idea. I play with Ssends a little in the other reply.

Best regards.


-----Original Message-----
From: mpi3-coll-bounces at lists.mpi-forum.org
[mailto:mpi3-coll-bounces at lists.mpi-forum.org] On Behalf Of Christian
Sent: Friday, October 17, 2008 2:42 PM
To: MPI-3 Collective Subgroup Discussions
Subject: Re: [mpi3-coll] Non-blocking Collectives Proposal Draft

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.
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