Cluster Challenge 2008 – an adviser’s perspective

I did the Cluster Challenge again this year. Last year was fun, but this year was better – we won! Here’s the story:

We started Saturday morning in Bloomington. The travel went pretty
smooth and Guido picked us up at the airport in Austin. We went directly
to the Conference location. The time before that was very stressful
because the machine wasn’t working quite as nice as we would like to.
The biggest problem was that the we could not change the CPU frequency
of the new iDataplex system. However, we were able to change it on the
older version and saw significant gains. We benchmarked that we could
run 16 nodes during the challenge and use 12 of them for HPCC (while 4
were idle) with our power constraints (2×13 A). So we convinced IBM to
give us a pre-release BIOS update which was supposed to enable CPU
frequency scaling. And it looked good! We were able to reduce the CPU
clock to 2.0 GHz (as on the older systems). However, it was 4am and we
had to ship at 6, so we didn’t have the time to test more. But back to
Austin …

The guys from Dresden were already waiting for us because the organizers
did not allow them to unpack the cluster alone (it was supposed to be a
team effort). We unpacked our huge box and rolled our 900 pound cluster into
our booth.

Our Cluster

We spent the remaining day with installing the system and pimping (;-))
our booth. It went pretty well. Then we began to deploy our hardware and
boot it from USB to do some performance benchmarks.

Installing the fragile Fiber Myrinet equipment (we didn’t break anything!)

We started with HPCC and were shocked twice. Number one was that the CPU
scaling that costed us so many sleepless night did not seem to help. All
tools and /proc/cpuinfo showed 2.0 GHz – but the power consumption was
still as high as with 2.5 GHz. So we wrote a small RDTSC benchmark to
check the CPU frequency – it still ran at 2.5 GHz. The BIOS was lying to
us :-(.  The second shock was that HPL was twice as slow as it should
be. So much to the sleep …
Quite some time after midnight … still hacking on stuff. I’m trying to motivate (I am a good slave driver) our guys to go on.

The students tried to fix it … all night long. The conclusion was that
we had to drop our cool booting from USB idea due to the performance
loss. Later, it turned out that shared memory communication uses /tmp
(which was mounted via NFS) and was thus really slow (WTF!). Anyway, we
decided about one hour before the challenge started to fall back to
disks. This worked.

How high can one stack harddrives? Not too high actually ;). Man, this was hard to plug them back into the system.

The second problem was a tough one. The BIOS … lying to us. We were
finally able to get hold of an engineer from IBM. He tried hard but
couldn’t help us either. So the students had to make the hard decision
to run with two nodes less :-(.

In the meantime, me and Bob had fun while biking in order to power
laptops ;).

Bob Beck (UA) generating power on our fancy machine ;).

I was driving my laptop with the sandwiches I ate before :).

The Challenge finally starts

The challenge was about to start, the advisors couldn’t do anything
anymore, so we decided to get some fuel from the opening banquet for our
students in the nightshift ;).
Guido and me thinking about getting some good stuff for the students!

We finally found some good stuff on the showfloor *yay*.Advisor’s success!

Some of us were not totally up to speed all the time 😉 – It looks like somebody missed the start:

So the Challenge ran, and we had nothing to do (especially the advisers
who were just hanging around to feed and motivate the students). So we
did all kinds of weird things over night – and we had a bike ;).

I also started some coding during the challenge because I didn’t really
do anything but it was way to noisy to work on papers. I had to pose
inside the microsoft booth, while my laptop finished up some cool
things! Thanks to Erez for taking the picture at exactly the right time.

Some Linux-based “research” performed/finished inside the Microsoft booth.
Guido explains Vampir to the other teams on one of our three ultra-cool
41” displays (again, around midinght ;)). We had really nice speakers
at the challenge. Especially on Sunday, when all the others left, we
cranked them up and listened to the soundtrack of Black Hawk down. The
security guys seemed kind of confused to hear really loud base at 4am in
the morning ;).

Guido! Don’t help the “enemies” ;).

Youtube made it also on our display :). And nearly costed us a point by
disturbing the sound output of our power warning system. But Jens
realized it fortunately.

Watch yourself:  Achmed the Dead Terrorist

Oh, and there was this Novell penguin that spontaneously caught fire. I
guess this happens when experienced computer scientists spend two days
to install a completely retarded operating system (with InfiniBand – ask
me about details if you’re interested). I love Linux, but it’s a shame
that the abbreviation SLES has the word “Linux” in it. Debian or Ubuntu
is so much better! But apparently, SLES is better prepared for the
applications (clearly not for administration or software maintenance

Each booth was “armed” with at least one student during all the time.
Here are some images from after midnight.

The MIT booth – doesn’t it look more like Stonybrook?

The folks from Arizona State – they had a neat Cray – with Windows though. But it seems that it worked for them.

The guys from Colorado with Aspen systems (don’t ask them about their vendor partner).

The National Tsing Hua University – excellent people but their system was more of a jet engine than a cluster.

Our booth … note the image on the big screen ;).

The Alberta folks – last year’s champions. Darn good hackers!

Purdue with their SciCortex – they seemed rather annoyed all the time.

Our social corner: At 2am, most students didn’t have to do a lot (just
watching jobs). So they all gathered in front of our booth and played
cards :).

Two fluffy spectators were watching our oscilloscope animation during
the show-off on Thursday.

The team of judges, led by Jack Dongarra, talked to our students to
assess their abilities

After that, we won! We don’t have a picture of our fabulous win yet, but I’ll post it with some more links after I got it.