Hello, Are you making these rules manually or in some automated way?
Regards, Pavel Mezentsev. 2012/9/21 Iliev, Hristo <il...@rz.rwth-aachen.de> > Hi, > > Open MPI uses several different algorithms depending on which module from > the "coll" framework is selected to perform the logic of the broadcast > operation. The "tuned" module which usually gets selected on cluster > installations uses a heuristic rule, based on the message size and the size > of the communicator, to choose between building a pipeline, binomial tree > or > split binary tree. There are also other algorithms that go unused by the > default rule logic, but you can force them with MCA parameters if you'd > like. > > The default rules might not be optimal for your hardware. You can > reevaluate > each algorithm and create a rule file that you can then give to Open MPI. > That's what I'm doing now on our cluster. > > Kind regards, > Hristo > -- > Hristo Iliev, Ph.D. -- High Performance Computing > RWTH Aachen University, Center for Computing and Communication > Rechen- und Kommunikationszentrum der RWTH Aachen > Seffenter Weg 23, D 52074 Aachen (Germany) > Tel: +49 241 80 24367 -- Fax/UMS: +49 241 80 624367 > > > > -----Original Message----- > > From: users-boun...@open-mpi.org [mailto:users-boun...@open-mpi.org] > > On Behalf Of Mohammed El Mehdi DIOURI > > Sent: Friday, September 21, 2012 2:13 AM > > To: us...@open-mpi.org > > Cc: Mohammed El Mehdi DIOURI > > Subject: [OMPI users] Algorithms used in MPI_BCast > > > > Hi, > > > > I would like to know what are the algorithms used in MPI_BCast() in the > > OpenMPI implementation. > > > > For example, in MPICH2, depending on the number of processes and the size > > of data to broadcast, the broadcasting algorithm used can be different : > a > > binomial tree if the message is short or MPI_Scatter followed by > > MPI_AllGather if the message to broadcast is long. > > > > Is it the same for OpenMPI ? > > It doesn't seem to be the case since the broadcasting time is different > when I > > use OpenMPI or MPICH2. > > > > Thanks for your help, > > > > Mehdi. > > _______________________________________________ > > users mailing list > > us...@open-mpi.org > > http://www.open-mpi.org/mailman/listinfo.cgi/users > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users >
