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AI competitions don’t produce useful models

lukeoakdenrayner.wordpress.com

21–30 of 64 posts

Re: AI competitions don’t produce useful models

#21

Earlier quoted context omitted.

I think the point is we are left with uncertainty. Your prior should be that we don't know which competitor is best, and after the competition we are still unsure.

Isn't that the same thing as "not producing useful models"? Like, sure, some of the models may work, but unless you know which ones you can't make use of them.

Yes, very true, but if we're still unsure it may be worth testing them more, while if we've proven they don't work we can abandon them.

Re: AI competitions don’t produce useful models

#22
I guess the calculator he used is https://select-statistics.co.uk/calculators/sample-size-calc.... The calculator includes this caveat:

> "If one or both of the sample proportions are close to 0 or 1 then this approximation is not valid and you need to consider an alternative sample size calculation method."

0.86 is fairly close to 1. And they're not proportions but rather averages of Dice coefficients. The statistics used here seem very suspicious. I'd like to see a Monte Carlo simulation or at least the assumptions / derivation of the formula used.

Re: AI competitions don’t produce useful models

#24

I guess the calculator he used is https://select-statistics.co.uk/calculators/sample-size-calc... . The calculator includes this caveat: > "If one or both of the sample proportions are close to 0 or 1 then this approximation is not valid and you need to consider an alternative sample size calculation method." 0.86 is fairly close to 1. And they're not proportions but rather averages of Dice coefficients. The statisti…

Hi, author here. There are a range of ways the estimates can be improved, although many require data that isn't available. The main point is that having a ballpark idea of how reliable your results are is good, and you can achieve that with this sort of simple napkin maths.

No statistician would do what I did for a formal publication, but I think what I did gets the point across.

Re: AI competitions don’t produce useful models

#25

I guess the calculator he used is https://select-statistics.co.uk/calculators/sample-size-calc... . The calculator includes this caveat: > "If one or both of the sample proportions are close to 0 or 1 then this approximation is not valid and you need to consider an alternative sample size calculation method." 0.86 is fairly close to 1. And they're not proportions but rather averages of Dice coefficients. The statisti…

You're spot on - the calculations in the post are totally wrong. For instance, a Dice coefficient is itself the average of hundreds of thousands of observations (each pixel in an image), so you can't just treat the coefficient as a single data point. However you also can't just take a standard error, since the points are highly spatially correlated.

The post also doesn't draw on any actual reported experiences of either competitors or hosts of competitions. Generally in post competition wrap-ups there's a lot of information sharing and very significant development of understanding that comes about.

To take the imagenet example that's claimed in the post as being a likely example of over-fitting: each year's imagenet results led to very significant advances in our understanding of image classification, which are today very widely used in industry and research.

Re: AI competitions don’t produce useful models

#27

> Now imagine you aren’t flipping coins. Imagine you are all running a model on a competition test set. Instead of wondering if your coin is magic, you instead are hoping that your model is the best one, about to earn you $25,000. > Of course, you can’t submit more than one model. That would be cheating. One of the models could perform well, the equivalent of getting 8 heads with a fair coin, just by chance. > Good t…

while there is variance in how my models do against a test set, its highly unlikely my rank 10 model is going to dethrone a #1 rank model, nor a rank 1k model going to beat mine. Its possible, but only because I over fit the public leader board, and good ML practices help prevent that (such as if your cross validation improves a model but it does worse on the public leader board, be inclined to trust your cross validation).

Re: AI competitions don’t produce useful models

#28
If the problem is getting "lucky" on a test set, then it seems like you could do several rounds of splitting test/training set, retraining from scratch each time, and then take the median performance. Not great if training takes a long time, but it would at least conclusively answer the question.

Re: AI competitions don’t produce useful models

#29
https://www.lesswrong.com/posts/5gQLrJr2yhPzMCcni/the-optimi...

The competition and test set will still have hidden biases due to the ontology you use.

Sufficient optimization pressure always eventually overcomes your bias control metrics, in the context of actual utility rather than other metrics.

It's well known in cryptography and security that all abstractions are leaky.

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