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Unsung heros: MPI run time environments

September 7, 2014 at 4:39 am PST

Most people immediately think of short message latency, or perhaps large message bandwidth when thinking about MPI.

But have you ever thought about what your MPI implementation has to do before your application even calls MPI_INIT?

Hint: it’s pretty crazy complex, from an engineering perspective.

Think of it this way: operating systems natively provide a runtime system for individual processes.  You can launch, monitor, and terminate a process with that OS’s native tools.  But now think about extending all of those operating system services to gang-support N processes exactly the same way one process is managed.  And don’t forget that those N processes will be spread across M servers / operating system instances.

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Traffic in parallel

August 8, 2014 at 5:00 am PST

In my last entry, I gave a vehicles-driving-in-a-city analogy for network traffic.

Let’s tie that analogy back to HPC and MPI.

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Still more traffic

August 2, 2014 at 5:00 am PST

I periodically write about network traffic, and how general / datacenter network traffic analysis is related to MPI / HPC.

In my last entry, I mentioned how network traffic has many characteristics in common with distributed computing. Routing decisions, for example, are made independently at each network switch.

Consider if you were looking down at a city from above. Look at all the cars driving around the city streets. It’s chaos: each car/truck/bus/etc. makes its own routing decisions. Each one is a different size. Each one potentially goes in a different direction. Each one continually merges and splits from other traffic.

Yet somehow it all works.

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Traffic (redux)

July 28, 2014 at 10:44 am PST

I’ve written about network traffic before (see this post and this post). It’s the subject of endless blog posts, help forums, and instructional guides across the internet.

In a High Performance Computing (HPC) context, there are some fascinating aspects about network traffic that are fairly different than other types of network traffic.
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Networks for MPI

May 24, 2014 at 7:14 am PST

It seems like we’ve gotten a rash of “how do I setup my new cluster for MPI?” questions on the Open MPI mailing list recently.

I take this as a Very Good Thing, actually — it means more and more people are tinkering with and discovering the power of parallel computing, HPC, and MPI.

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