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An app for that

Doug Eadline wrote a cluster rant recently entitled “A Cluster in your Pocket“, talking about the possibility of “What if your cell phone could bring you real time results from a supercomputer?”

We’ve actually idly chatted about such things in the Open MPI community for a while.  It would be tremendously fun to write an iPhone/Android app that could talk to an MPI implementation and/or application.  Perhaps a good starting point would be to have the MPI implementation talk to an iPhone/Android phone.


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Hot Interconnects conference roundup

Hot Interconnects sign on a Google bikeAs I mentioned in a few prior posts, I attended the Hot Interconnects conference last week, which happened to be hosted at the Googleplex.

Beautiful weather, interesting talks, and lively discussion are three good phrases to describe the conference. 

It’s always good to run into the same people you tend to see at these conferences and catch up on their latest work.  But it’s equally fun to talk to new people whom you’ve never met before.  Get a new perspective, hear a different way of looking at something, or even just listen to the youthful exuberance of the next generation of network researchers.

It’s all good stuff!

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Sockets vs. MPI

I briefly mentioned in a prior blog entry that I’m on a panel at the Hot Interconnects conference this Wednesday evening entitled, “Stuck with Sockets: Why is the network programming interface still from the 1980s?“.

The topic is an interesting one: sockets are, by far, the dominant user-level networking abstraction.  Countless millions (billions?) of lines of code exist that use various forms and features of the BSD sockets API (there are other sockets APIs, but let’s limit the discussion here to just the BSD API for the sake of brevity).  But networking hardware (and software!) has advanced significantly since the sockets API was introduced.  Several attempts have been made to advance the state of the art of the sockets API — to include replacing it with something else — but none have succeeded.  Why?  Is the inertia of existing sockets code too resistant to any change?

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int MPI_Vacation(short duration);

The little-known “vacation” MPI function allows one to suspend the calling MPI process for brief periods of time.  The return value is an array of events that were missed while the process was inactive.  Note that the “duration” parameter is constrained to be a short value.

Programmers should also note that the returned array size tends to be large (typically regardless of the duration parameter value).  Care should be taken to ensure that enough resources are dedicated to to processing the pending events while also responding to new events in a timely manner.

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Why do different MPI’s perform differently?

Sometimes my wife wonders why I have a job.  She asks me: “Aren’t you just moving bytes from point A to point B?  How hard is that?”

In some ways, she’s right — it’s not hard. Any computer users effects the act of moving bytes from point A to point B oodles of times a day.  Email, for example, is message passing — the heart of email is moving bytes from point A to point B.

But like most real-world engineering issues, it’s not quite that simple.  Indeed, if you talk to most email server administrators, they will readily launch into highly complex discussions of how delivering an email from point A to point B is an incredibly intricate, complicated process.

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