Thanks Jeff, and.. what about RDMA? It works only with point-to-point or also with collectives?
2010/9/22 Jeff Squyres <jsquy...@cisco.com> > On Sep 22, 2010, at 3:46 AM, Gabriele Fatigati wrote: > > > i'm tuning collectives of OpenMPI 1.4.2 with OTPO. I have a little > question about BTL. This layer is involves just in point-to-point > communication or also in collectives routines? > > > > Because i've noted that changing some blt parameters like > btl_sm_eager_limit and doing one collective routine, performances can have > very different behaviour. > > The BTLs are dumb byte transport layers -- they have no idea of any MPI > semantics. > > But that being said, they act as the lowest layers for the MPI > point-to-point functions (MPI_SEND and the like). They may *also* act as > the lowest layers for all of the collective functions. Some collective > algorithms call MPI_SEND to do their individual sends, for example. Others > may invoke BTL send/receive functions directly. Others don't use the BTLs > at all. > > -- > Jeff Squyres > jsquy...@cisco.com > For corporate legal information go to: > http://www.cisco.com/web/about/doing_business/legal/cri/ > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > > -- Ing. Gabriele Fatigati Parallel programmer CINECA Systems & Tecnologies Department Supercomputing Group Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy www.cineca.it Tel: +39 051 6171722 g.fatigati [AT] cineca.it
