[Beowulf] MPICH vs. OpenMPI

Philippe Blaise philippe.blaise at cea.fr
Thu Apr 24 15:39:33 PDT 2008

Prentice Bisbal a écrit :
> Can anyone give me a quick comparison of OpenMPI vs. MPICH? I've always
> used MPICH (I never liked lam), and just recently heard about OpenMPI.
> Anyone here using it?
I use OpenMPI since a few months and run programs like Abinit, Siesta 
with success every days (on a small
IB cluster - 100 opteron cores under linux).
I have done some comparisons using M(VA)PICH(2) on IB instead of OpenMPI 
and haven't seen any great differences ;
the performances are comparable, for example on a Alltoall, depending on 
the message size, sometimes MVAPICH
is better, sometimes OpenMPI is better.

Also, I have to said that OpenMPI is quite appealing because of its ease 
of use, a very good web site (FAQs, mailing list),
and has several advantages : it is well integrated with a PBS-like batch 
system, a same binary can run on different networks (IB, ethernet)
without recompiling or reliking your application, and there are some 
possibilities to exploit numa placement of the tasks, on these
last two points I'm not sure that MPICH can do the same.

But, as the other guys have said before, it is very useful to have the 
two implementations on the same cluster.
Another thing : my own experience shows that ISVs usually send you a 
binary which is compatible with mpich or mpich2,
but not with OpenMPI.



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