Dave, yes, this is for two MPI tasks only.
the MPI subroutine could/should return with an error if the communicator is made of more than 3 tasks. an other option would be to abort at initialization time if no collective modules provide a barrier implementation. or maybe the tuned module should have not used the two_procs algorithm, but what should it do instead ? use a default one ? do not implement barrier ? warn/error the end user ? note the error message might be a bit obscure. I write "could" because you explicitly forced something that cannot work, and I am not convinced OpenMPI should protect end users from themselves, even when they make an honest mistake. George, any thoughts ? Cheers, Gilles On Wednesday, May 4, 2016, Dave Love <d.l...@liverpool.ac.uk> wrote: > With OMPI 1.10.2 and earlier on Infiniband, IMB generally spins with no > output for the barrier benchmark if you run it with algorithm 5, i.e. > > mpirun --mca coll_tuned_use_dynamic_rules 1 --mca > coll_tuned_barrier_algorithm 5 IMB-MPI1 barrier > > This is "two proc only". Does that mean it will only work for two > processes (which seems true experimentally)? If so, should it report an > error if used with more? > _______________________________________________ > users mailing list > us...@open-mpi.org <javascript:;> > Subscription: https://www.open-mpi.org/mailman/listinfo.cgi/users > Link to this post: > http://www.open-mpi.org/community/lists/users/2016/05/29081.php >
