George, Thank you for your answer. Is [1] the paper mentioned by Jeff in an earlier message (ICS 2004)? Thanks
Matthieu ________________________________ From: users [[email protected]] on behalf of George Bosilca [[email protected]] Sent: Tuesday, April 19, 2016 2:03 PM To: Open MPI Users Subject: Re: [OMPI users] MPI_Bcast implementations in OpenMPI Matthieu, If you are talking about how Open MPI selects between different broadcast algorithms you might want to read [1]. We have implemented a dozen different broadcast algorithms and have run a set of tests to measure their performance. We then used a quad tree clasiffication algorithm to minimize the number of switch points, and then generated the C code to dynamically make the selection based on the message size and the number of participants. Take a look at the function ompi_coll_tuned_bcast_intra_dec_fixed in ompi/mca/coll/tuned/coll_tuned_decision_fixed.c. George. On Tue, Apr 19, 2016 at 4:13 PM, Jeff Squyres (jsquyres) <[email protected]<mailto:[email protected]>> wrote: On Apr 15, 2016, at 9:18 AM, Dorier, Matthieu <[email protected]<mailto:[email protected]>> wrote: > > I'd like to know how OpenMPI implements MPI_Bcast. And if different > implementations are provided, how one is selected. This is a fairly complicated topic. This old paper is the foundation for how Open MPI works (it's a bit different these days, but the basic concepts described in this paper are still mostly relevant): https://www.open-mpi.org/papers/ics-2004/ -- Jeff Squyres [email protected]<mailto:[email protected]> For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/ _______________________________________________ users mailing list [email protected]<mailto:[email protected]> Subscription: http://www.open-mpi.org/mailman/listinfo.cgi/users Link to this post: http://www.open-mpi.org/community/lists/users/2016/04/28967.php
