So, you mean that it guarantees the value received after the bcast call is consistent with value sent from root, but it doesn't have to wait till all the ranks have received it?
Still, in this benchmark shouldn't the max time for bcast be equal to that of barrier? On Mon, May 30, 2016 at 9:33 AM, Gilles Gouaillardet < gilles.gouaillar...@gmail.com> wrote: > These are very different algorithms, so performance might differ (greatly) > > for example, MPI_Bcast on root rank can MPI_Send() and return, if the > message is short, this is likely an eager send which is very fast. > that means MPI_Bcast() returns before all ranks received the data, or even > entered MPI_Bcast. > > On the other hand, MPI_Barrier() cannot return before all ranks entered > the barrier. > > also, you might find https://github.com/open-mpi/ompi/issues/1713 useful. > > Cheers, > > Gilles > > > On Monday, May 30, 2016, Saliya Ekanayake <esal...@gmail.com> wrote: > >> Hi, >> >> I ran Ohio micro benchmarks for openmpi and noticed broadcast with >> smaller number of bytes is faster than a barrier - 2us vs 120us. >> >> I'm trying to understand how this could happen? >> >> Thank you >> Saliya >> > > _______________________________________________ > users mailing list > us...@open-mpi.org > Subscription: https://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/05/29326.php > -- Saliya Ekanayake Ph.D. Candidate | Research Assistant School of Informatics and Computing | Digital Science Center Indiana University, Bloomington
