On Thu, Jul 15, 2010 at 10:56 PM, Robert Myers <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.
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