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JPL Clusters XServes
burgburgburg writes "MacSlash has a brief note how NASA's JPL has put together a cluster of 33 XServes that was able to achieve 1/5 teraflop. The original article notes that the Applied Cluster Computing Group, using Pooch (Parallel OperatiOn and Control Heuristic Application) ran the AltiVec Fractal Carbon demo and achieved over 217 billion floating-point operations per second on this XServe cluster. More importantly, their research indicates that no evidence of an intrinsic limit to the size of a Macintosh-based cluster could be found."
Imagine a Beowulf cluster getting beat up by a Xserve cluster on the playground and stealing its lunch cycles!
Vos teneo officium eram periculosus ut vos recipero is.
Maybe the computations were not communications bound... Fractal calculations can be done with a Monte Carlo method, which is highly parallelizable, and requires very little inter-node communication.
Don't believe the Gigaflop myth! Oh wait, that's "MHz Myth"... sorry, as a Mac owner, I have to whip out that response in every thread. Carry on.
Hansel USA - Chut up and read!
The theoretical peak performance for 33 XServes in the test done here was actually 495 GFLOPS, BTW. I don't know what the theoretical performance of double precision on Altivec is, though. LINPACK is all linear algebra (IIRC), so it would see some benefit.
I will admit that there are plenty of applications where the G4 is not the best processor available. I for one will certainly be happy to see the IBM PPC 970, but you shouldn't discount the XServe until the test is actually run.
--
The internet is the greatest source of biased information in the history of mankind.
2004, Jobs WWDC Keynote...
...Apple has long prided itself on the easy of use of our products... [blah, blah] (the tv screen behind jobs shows a room with twenty people wearing apple t-shirts and a stack of X-Serve boxes) ...my friends here have several of our next-generation power-4 based X-Serves running OS 10.3... during this keynote they are going to unpack all of the servers and set up a cluster... ...by the end of the keynote we'll give the cluster a spin and see if we can make it into one of the top 50 supercomputers in the world"
"Today, I'm going to talking about Mac OS 10.3 and a big part of OS 10.3 is our clustering software.... [blah, blah]
There are 10 types of people in this world, those who can count in binary and those who can't.
The latency question is a good one. I'd say the answer to this lies in the driver for the NIC. I've written an IOKit ethernet driver and experienced pretty decent performance at 100 Mb. The system is processing packets as incoming data causes interrupts in the system.
However, I think the interrupt overhead for a 1000Mb link would be so high as to bring the machine to a screeching halt (okay, slow it down perceptibly). What a lot of driver writers do for gigabit links is to move their driver into polling mode. They essentially set a timer to go off every X milliseconds and process all the packets that have been copied into memory during that timeframe.
This gives a lower bound on the latency. A packet will always take X milliseconds to be noticed and processed by the system. Interrupt overhead stays low, but packet latency goes up a smidge.
It's a good trade off. I would bet that on a saturated link, packet latency at gigabit speeds is equivalent or WORSE than 100Mb. I might have to test that out...
cr
I thought a lot of gig-e cards implemented a good deal of packet processing in hardware to deal with this very problem. Am I mistaken? I remember that the first PCI gig-e card I ever saw was installed in an SGI Origin, and when running full-out it pegged an entire CPU with interrupt handlers. Later versions of the card-- or perhaps an entirely different card, but sold by SGI and used with the same Origin servers-- had hardly any interrupt activity at all, even when moving data at rates exceeding 50 MB/s.
I write in my journal
This would put it at #343 on the Top 500 Supercomputers* - right below the University of Edinburgh's Cray and just ahead of the IBM cluster at Williams-Sonoma. Yes, Williams-Sonoma.
Of course I fully expect the employees of the West Hartford Apple store to ceremoniously run three doors down and moon the folks at Williams-Sonoma. Ah, Mall Life.
(*the whole lot of which just got its lunch eaten, dope slapped and girlfriend stolen by the new NEC cluster in Japan - 35,860 GFlops, Los Alamos is 2nd & 3rd at 7,727 with two of their HP server clusters.. sheesh.).
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."