Regarding "...There are probably simple algorithms which are efficient in a single processor environment, but become egregiously inefficient when distributed..." What about the old random number generator: take a 16 bit seed, square it, take the middle 16 bits, and repeat. They'd want a large number in order (so you can repeat an experiment, or a run of a model, with the same "random" numbers), and it's easy to computer sequentially; but if you want a million of them it would be nice to distribute the job, but I don't think you can. But maybe "can't parallelize" isn't the same as "badly inefficient to parallelize". But I'd use something like that (besides the famous example that 9 women can't make a baby in one month) as an algrorithm that has to be done sequentially. Peter
On Wed, Aug 21, 2013 at 10:10 AM, Lux, Jim (337C) <[email protected]>wrote: > Sorts in general.. Good idea. > > Yes, we'll do a distributed computing bubble sort. > > Interesting, though.. There are probably simple algorithms which are > efficient in a single processor environment, but become egregiously > inefficient when distributed. > > Jim > > > > On 8/20/13 12:11 PM, "Max R. Dechantsreiter" <[email protected]> > wrote: > > >Hi Jim, > > > >How about bucket sort? > > > >Make N as small as need be for cluster capability. > > > >Regards, > > > >Max > >--- > > > > > > > >On Tue, 20 Aug 2013 [email protected] wrote: > > > >> Date: Tue, 20 Aug 2013 00:23:53 +0000 > >> From: "Lux, Jim (337C)" <[email protected]> > >> Subject: [Beowulf] Good demo applications for small, slow cluster > >> To: "[email protected]" <[email protected]> > >> Message-ID: > >> <[email protected]> > >> Content-Type: text/plain; charset="us-ascii" > >> > >> I'm looking for some simple demo applications for a small, very slow > >>cluster that would provide a good introduction to using message passing > >>to implement parallelism. > >> > >> The processors are quite limited in performance (maybe a few MFLOP), > >>and they can be arranged in a variety of topologies (shared bus, rings, > >>hypercube) with 3 network interfaces on each node. The processor to > >>processor link probably runs at about 1 Mbit/second, so sending 1 kByte > >>takes 8 milliseconds > >> > >> > >> So I'd like some computational problems that can be given as > >>assignments on this toy cluster, and someone can thrash through getting > >>it to work, and in the course of things, understand about things like > >>bus contention, multihop vs single hop paths, distributing data and > >>collecting results, etc. > >> > >> There's things like N-body gravity simulations, parallelized FFTs, and > >>so forth. All of these would run faster in parallel than serially on > >>one node, and the performance should be strongly affected by the > >>interconnect topology. They also have real-world uses (so, while toys, > >>they are representative of what people really do with clusters) > >> > >> Since sending data takes milliseconds, it seems that computational > >>chunks which also take milliseconds is of the right scale. And, of > >>course, we could always slow down the communication, to look at the > >>effect. > >> > >> There's no I/O on the nodes other than some LEDs, which could blink in > >>different colors to indicate what's going on in that node (e.g. > >>communicating, computing, waiting) > >> > >> Yes, this could all be done in simulation with virtual machines (and > >>probably cheaper), but it's more visceral and tactile if you're > >>physically connecting and disconnecting cables between nodes, and it's > >>learning about error behaviors and such that's what I'm getting at. > >> > >> Kind of like doing biology dissection, physics lab or chem lab for > >>real, as opposed to simulation. You want the experience of "oops, I > >>connected the cables in the wrong order" > >> > >> Jim Lux > >> > >_______________________________________________ > >Beowulf mailing list, [email protected] sponsored by Penguin Computing > >To change your subscription (digest mode or unsubscribe) visit > >http://www.beowulf.org/mailman/listinfo/beowulf > > _______________________________________________ > Beowulf mailing list, [email protected] sponsored by Penguin Computing > To change your subscription (digest mode or unsubscribe) visit > http://www.beowulf.org/mailman/listinfo/beowulf >
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