[Beowulf] automount on high ports

Greg Lindahl lindahl at pbm.com
Thu Jul 3 16:50:09 EDT 2008


On Thu, Jul 03, 2008 at 01:45:44PM -0400, Robert G. Brown wrote:

> This is one reason that people use PVM and MPI and so on.  It can be
> argued (and has been argued on this list IIRC) that raw networking code
> will always result in a faster parallel program, all things being equal,
> because encapsulating it in higher level abstractions always comes at a
> cost

Yes, but there is plenty of proof that MPI can be extremely low
overhead -- see InfiniPath MPI. Now if you insist on using TCP for
your MPI and your "bare metal" code, you may beat your MPI because
it's not so good at TCP. But it's probably cheaper to fix the MPI
than re-invent the wheel many times.

There's plenty of good code you can study for writing good network
servers -- the original irc server is a pretty good event-driven
non-blocking program. strace is your friend, too, that's the way you
can see that MPICH-1's TCP driver isn't so hot.

-- greg


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