[Beowulf] New HPCC results, and an MX question

Greg Lindahl lindahl at pathscale.com
Wed Jul 20 17:28:41 EDT 2005


> Unless you want a very selected group to use your software, you'll have
> to take care that multithreaded software also works fast for clusters.

Vincent,

Funny, in all my years of activity in the high performance computing
niche, it's fairly rare that people run multi-threaded programs
accessing MPI. Pure MPI is the most widely used programming model,
followed as a distant second by OpenMP programs where only the main
thread does MPI (so a thread-safe MPI is not required), followed by a
few, rare very codes which are multi-threaded with either OpenMP or
Posix threads, and all the threads call MPI. Admittedly, this last
choice is can be a good one if you have a multi-threaded program and
want to add MPI. But there is a speed hit with low latency networks
due to the extra locking needed. And that was the small point I was
attemping to make.

Perhaps you can point me at some huge existing market of threaded MPI
programs? I'm sure you can speak with authority about your chess
program, but I didn't realize you were an expert on the general MPI
marketplace. With the advent of dual-core cpus, I figured the most
likely future was that most people were going to continue to run their
pure MPI programs as pure MPI programs.

-- greg

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