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Wielding Supercomputers To Make High-Stakes Predictions

Posted by timothy on from the but-sir-this-research-could-explode dept.

aarondubrow writes "The emergence of the uncertainty quantification field was initially spurred in the mid-1990s by the federal government's desire to use computer models to predict the reliability of nuclear weapons. Since then, the toll of high-stake events that could potentially have been better anticipated if improved predictive computer models had been available — like the Columbia disaster, Hurricane Katrina and the World Trade Center collapse after the 9/11 terrorist attacks — has catapulted research on uncertainty quantification to the scientific and engineering forefronts." (Read this with your Texas propaganda filter turned to High.)

13 of 65 comments (clear)

  1. "Texas propaganda filter"???? by SrJsignal · · Score: 3, Insightful

    ...thanks a lot....Ass

    1. Re:"Texas propaganda filter"???? by Overunderrated · · Score: 2

      Don't read too much into it. It's a utexas.edu news bite about an upcoming large research project at... UTexas. Literally every major university's website has a front page link about a big new research project on campus.

  2. Like Global Climate Change ? by RichMan · · Score: 5, Interesting

    Seems to me all the supercomputer models are predicting the disaster called global climate change is powered by human CO2 emissions. We have predicted it. It has a decided human cause against which we can take direct action. Over the next 50 years billions of people will be displaced. Trillions or more of infrastructure will be lost to rising oceans.

    Are we doing anything? Seems to me the whole prediction thing is useless if we are unwilling to take action on the results.
    Is it because the results are wrong or is it because it involves money in peoples pockets.

    We can make the predictions, we need to remove the barriers to action.

    1. Re:Like Global Climate Change ? by khallow · · Score: 2

      Over the next 50 years billions of people will be displaced.

      By what? Those supercomputer models aren't predicting that global warming will be the cause.

  3. Chaotic Systems by Tokolosh · · Score: 3, Insightful

    Some things can be well-modeled by using good input data and fine-grained analysis, which may require supercomputers.

    A problem arises when inherently chaotic (in the mathematical sense) systems are modeled. No amount of computing power will improve the quality of the results.

    It may be hard to know what type of system you are dealing with.

    And by definition, black swans cannot be modeled at all.

    --
    Prove anything by multiplying Huge Number times Tiny Number
    1. Re:Chaotic Systems by Overunderrated · · Score: 2

      As a researcher in computational sciences (and chaotic systems) similar to the news blurb posted here, no. There are many methods for dealing with chaotic/uncertain inputs. Monte Carlo approaches, for example.

    2. Re:Chaotic Systems by Overunderrated · · Score: 2

      Ok, so I assume you use a Monte Carlo technique to generate probabilities of outcomes. But does having supercomputers improve the accuracy of the results, with any certainty?

      Well yes, of course. That's the entire purpose of uncertainty prediction, and HPC simulations in general. In any kind of complex numerical simulation (say, turbulent aerodynamics), the accuracy with which you can simulate a given physical situation is entirely constrained by your available computational power. You must find a balance between the level of detail you need versus computer power available (i.e., direct numerical simulation of turbulence for a full-sized aircraft is both entirely unfeasible computationally, and provides drastically more information than is necessary for analysis). These are well-studied problems, and not "guesswork" as you seem to imply. Extending that to a situation where the inputs themselves are uncertain clearly is a situation where more computer power leads to more accurate results. Basic statistics tells you the more data points you have (in this case, results from a range of inputs), the more reliable your predictions of uncertainty.

  4. federal government's desire to use computer models by mcgrew · · Score: 5, Interesting

    What was old is new again.

    In a few hours on Nov. 4, 1952, Univac altered politics, changed the world's perception of computers and upended the tech industry's status quo. Along the way, it embarrassed CBS long before Dan Rather could do that all by himself.

    Computers were the stuff of science fiction and wide-eyed articles about "electric brains." Few people had actually seen one. Only a handful had been built, among them the first computer, ENIAC, created by J. Presper Eckert and John Mauchly at the University of Pennsylvania in the 1940s.

    In summer 1952, a Remington Rand executive approached CBS News chief Sig Mickelson and said the Univac might be able to plot early election-night returns against past voting patterns and spit out a predicted winner. Mickelson and anchor Walter Cronkite thought the claim was a load of baloney but figured it would at least be entertaining to try it on the air.

    On election night, the 16,000-pound Univac remained at its home in Philadelphia. In the TV studio, CBS set up a fake computer -- a panel embedded with blinking Christmas lights and a teletype machine. Cronkite sat next to it. Correspondent Charles Collingwood and a camera crew set up in front of the real Univac.

    By 8:30 p.m. ET -- long before news organizations of the era knew national election outcomes -- Univac spit out a startling prediction. It said Eisenhower would get 438 electoral votes to Stevenson's 93 -- a landslide victory. Because every poll had said the race would be tight, CBS didn't believe the computer and refused to air the prediction.

    Under pressure, Woodbury rejigged the algorithms. Univac then gave Eisenhower 8-to-7 odds over Stevenson. At 9:15 p.m., Cronkite reported that on the air. But Woodbury kept working and found he'd made a mistake. He ran the numbers again and got the original results -- an Eisenhower landslide.

    Late that night, as actual results came in, CBS realized Univac had been right. Embarrassed, Collingwood came back on the air and confessed to millions of viewers that Univac had predicted the results hours earlier.

    In fact, the official count ended up being 442 electoral votes for Eisenhower and 89 for Stevenson. Univac had been off by less than 1%. It had missed the popular vote results by only 3%. Considering that the Univac had 5,000 vacuum tubes that did 1,000 calculations per second, that's pretty impressive. A musical Hallmark card has more computing power.

    --
    Free Martian Whores!
  5. Predictions are only as good as the models... by divisionbyzero · · Score: 3, Insightful

    The only way to validate the model is to apply it and see if it works. The problem with hish risk disasters is that they don't happen all that often so it's hard to validate the model. I mean sure you can special case it to death to get it to predict "the Columbia disaster, Hurricane Katrina and the World Trade Center collapse" but if you special case it too much it loses predictive ability for similar but not identical events.

    The reason there is so much "uncertainty" (not for me but many others) around climate change is that it is practically a singular event that'll occur 50-100 years in the future. Of course the models can be validated as we go but how much validation is enough? When it's too late?

  6. Scepticism... by shic · · Score: 4, Insightful

    I like supercomputers in the same way I like architectural monuments - there's an element of beauty in stretching technology to ever more extreme goals, but I'm far from convinced that there's an objective, practical, point to any of the calculations they make.

    I'm very sceptical about climate change prediction - because, without any calculation, it's blindingly obvious that climate will change (all evidence suggests vast changes throughout history) and - because mankind is significant among life on earth - obviously we should assume a fair chunk to be 'man made'. I seldom see the questions that matter addressed... for example, in what ways can we expect climate change to be beneficial to mankind? When we ask the wrong questions, no matter how large-scale or accurate our computation, it will be worthless. Don't get me wrong, I see immense value in forecasting... but I don't see available computational power as a limiting factor... in my opinion there are two critical issues for forecasting: (1) collecting relevant data accurately; (2) establishing the right kind of summaries and models. While some models are computationally expensive - in my opinion - the reason for attempting to brute-force these models has far less to do with objective research and far more to do with political will to have a concrete answer irrespective of its relevance... The complexity of extensive computation is exploited to lend an air of credibility, in most cases, IMHO.

    "Don't worry about the future. Or worry, but know that worrying is as effective as trying to solve an algebra equation by chewing bubble gum. The real troubles in your life are apt to be things that never crossed your worried mind, the kind that blindside you at 4 p.m. on some idle Tuesday."

    The reason is simple: avoidable disasters occur not because we haven't done enough calculations - but because the calculations we do are done for the wrong reasons and produce irrelevant results. If we want to move forwards, we need more observation and more intelligent consideration. Iterating existing formulas beyond the extent possible with off-the-shelf technology, IMHO, is unlikely to yield anything significant.

  7. The title is misleading by Anonymous Coward · · Score: 2, Interesting

    The title is misleading and not really correct, because it doesn't describe the main thrust of the project. What the group at Texas is trying to do is change the way computer models make predictions, because they recognize that predicting events like Katrina or 9/11 with any kind of accuracy, based on essentially no data, is basically impossible, and that even when prediction is possible, it's still full of uncertainty.

    They don't want the models to spit out a single answer (e.g. "There will be a sea level rise of 10 centimeters within 20 years"), but rather a probability distribution ("The sea level rise over the next twenty years can be modeled as a normal distribution with a mean of 10 centimeters and a standard deviation of 5 centimeters"). The distribution is supposed to be based on uncertainties that arise at various stages in the process of modeling, such as model assumptions and data collection.

    Personally, I think in certain cases these techniques are great, and in other cases they are worse than useless. If you have a model that's supposed to predict terrorist attacks, it will happily tell you that with 90% confidence the probability of a terrorist attack in Location X in the next year is between 1 and 3 percent. This may be perfectly correct, but highly misleading, because fundamentally the event is not probabilistic, and the only reason it appears to be is that a key piece of data is missing. As such, what the computer should really do is say the following. "Dear DHS: I don't know whether the terrorists are planning the attack. If they are, it is very likely to occur. If they aren't, it won't happen. Please do your job and go find out whether they are or not, and let me do more interesting things. Sincerely, Computer."

    1. Re:The title is misleading by statdr · · Score: 2, Interesting

      That doesn't make much sense. Models don't just spit out one answer. Models will report estimates and estimates of the uncertainty (typically standard errors) of the estimates. These uncertainty estimates define the probabilistic distribution from which the events being modeled derive. Of course, there can be quite complex underlying probabilistic distributions; not just the simple case of a one-dimensional distribution defined by one parameter. Computers are useful when the number of dimensions of the underlying probabilistic distribution is large and also when the form of the underlying distribution is not some convenient structure. However, while a supercomputer can handle models with complex underlying probabilistic distributions, this doesn't mean that you'll get anything useful out of the modeling exercise. You still need to have lots of data on events (and non-events) to try and predict the events with any degree of accuracy and precision.

  8. (No subject) by spirito · · Score: 2

    This is a topic of great interest in aerodynamics. Aim is to understand how uncertainties in the input data (flow conditions, geometric imperfections, ....) affect the predicted aircraft performances. Some research has already taken place in Europe, for example see the project nodesim (http://www.nodesim.eu).