MPICH vs LAM
josip at lanl.gov
Tue Sep 23 12:49:56 EDT 2003
Mathias Brito wrote:
> What implmentation of MPI should i use? There's the
> mpich and the lam implamentations, what's the best
> choice, and have more improviments of resources and
Why not install both and give yourself a choice?
MPICH is very popular and works fine, but LAM is a bit cleaner
implementation which delivers a bit lower latency. Other than that, the
main difference is process startup. With MPICH, "mpirun" does the job
directly and accepts the usual rsh or ssh authorization overhead. With
LAM, you "lamboot" LAM daemons on your nodes (w/usual overhead) but then
those daemons can start your MPI processes quicker. After your MPI jobs
(possibly many in sequence) are done, you use "wipe" to clean up LAM
On the Coral cluster at ICASE (now absorbed by NIA), LAM was the default
due to slightly lower latency. LAM is very nicely done, but having only
one flavor of MPI can be limiting, so people could use MPICH, MPI/Pro
(in VIA/TCP/interrupt/polling modes), or MVICH as they saw fit. For
example, some codes assume MPICH-specific implementation details, which
is non-standard but easy to accomodate.
My suggestion is to install both LAM and MPICH, then benchmark your
applications with both and use the better choice as the default.
P.S. There are other MPIs out there: various vendor MPIs, enhanced
flavors of MPICH, etc. Some of these cost $/CPU/year; others are free.
A commercial MPI (e.g. MPI/Pro) buys you enhanced robustness and some
interesting features, e.g. interrupt-driven receive which can improve
performance of certain applications.
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