On 07/16/2010 04:49 PM, Robert Myers wrote: > On Fri, Jul 16, 2010 at 6:36 PM, Christofer C. Bell > <christofer.c.bell@xxxxxxxxx <mailto:christofer.c.bell@xxxxxxxxx>> wrote: > > On Thu, Jul 15, 2010 at 10:56 PM, Robert Myers > <rbmyersusa@xxxxxxxxx <mailto:rbmyersusa@xxxxxxxxx>> wrote: > > > This is a technical forum, not a debating society. Science is > awash already in useless flops. > > > You're showing your ignorance, Robert. FLOPS is a very useful > measure and more is always good, but I don't think you know what > it means. It means FLoating Point Operations Per Second. It's > nothing more than a measure of computational speed and says > nothing about the accuracy of the models being computed. > > In one of these long-running public debates, I pointed out to > a national decision-maker how relatively meaningless and > frequently wrong NOAA's hurricane season predictions have > been. Guess what? The most recent forecast was wrapped in > all kinds of weasel words. That won't stop them from drawing > their paychecks and burning megawatts producing useless pictures. > > > If the forecast is wrong, the either the model was inaccurate or > the input data was wrong. It says absolutely nothing about the > value of computing the answer fast (what FLOPS provides). While I > totally get you're going to somehow try to refute the idea that > "having a fast computer is good" and thus, I can only imagine, > make the case that "a slow computer is even better," you're not > going to convince anyone. > > > Whether you like it or not, and whether, even more important, you > understand it or not, the architecture of a computer has a big impact > on the kinds of models you can implement with any degree of efficiency > on the computer. Hanging lots of flops on inadequate bandwidth is > popular because you can get a high ranking on the Top 500 list with a > minimal expenditure, but it also means that you can't do an important > calculation like a global FFT at anything like reasonable efficiency. > Flops are almost free. Bandwidth is expensive. Unfortunately, what > is almost free (flops) can be nearly useless for, say, an FFT unless > you have the bandwidth to move data around globally fast enough. > > Skimping on global bandwidth so that you can't do global operations > effectively forces you to approximations that require only local > computation, that's the kind of modeling we get, and the fact that > there is an inherent disconnect between the way the equations behave > and the way the discretized model behaves gets swept under the rug. > Nonlinear systems interact globally at all scales at every time step. > If your discretization scheme forces an inaccurate representation of > that global interaction, then you shouldn't ever trust what's coming > out of your simulation of nonlinear systems. > > Attempting to simulate hurricanes is about as nonlinear as it gets. > When your weatherman on TV knowingly talks about tropical waves as a > cause of concern, he's talking about a large scale flow pattern that > might or might not go through some tortuous nonlinear processes that > will turn it into a hurricane. Modelling the interaction of hugely > different physical scales accurately is essential to accurate > prediction, and modern "supercomputers" are notably and chronically > short of the bandwidth required to do so. > > > Anyway, technical forum or not, it's a forum made up of people and > that makes it a community. To get along in a community, it helps > to not be an asshole. While you may not care about being an > asshole, do note that "getting along in a community" does > influence if anyone takes you seriously. And you seem very much > to want to be taken seriously. > > > Calling other people names helps to build a community? From your > pompous and condescending tone unbacked by actual knowledge, I'd be > inclined to label you in the same way you have chosen to label me, > with the addition of the word "ignorant" in front of it, but I don't > think name-calling and labeling ever helps. > > Robert. > > So, what would you say is/are the class/classes of problems that would benefit greatly from a high flops gpu, but without the sort of bus bandwidth you would like to see? -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
