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Deep Double Descent: Where Bigger Models and More Data Hurt

Preetum Nakkiran, Gal Kaplun, Yamini Bansal

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Tristan Yang, Boaz Barak, Ilya Sutskever

2019 · arXiv

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From the abstract

We show that a variety of modern deep learning tasks exhibit a "double-descent" phenomenon where, as we increase model size, performance first gets worse and then gets better. Moreover, we show that double descent occurs not just as a function of model size, but also as a function of the number of training epochs. We unify the above phenomena by defining a new complexity measure we call the effective model complexity and conjecture a generalized double descent with respect to this measure. Furthermore, our notion of model complexity allows us to identify certain regimes where increasing (even quadrupling) the number of train samples actually hurts test performance.

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6 selected excerpts · 6 total mentions

noosphr
Neutral mention · rule
>For example, getting good performance on a dataset with deep learning also involves a lot of guesswork. But, if your training loss is way lower than your test loss, you're in the "overfitting" regime, and you're wasting your time if you try to increase the capacity of your model. https://arxiv.org/abs/1912.02292
rndphs
Neutral mention · rule
https://arxiv.org/pdf/1912.02292 "We show that a variety of modern deep learning tasks exhibit a "double-descent" phenomenon where, as we increase model size, performance first gets worse and then gets better." That is the first sentence of the abstract. The first graph shown in the paper backs it up. Looking into it further, it seems that typical LLMs are in the first descent regime anyway though so my original point is not too relevant for them anyway it seems. Also it looks like the second descent region doesn't always reach a lower loss than the first, it appears to depend on other factors as well.
cs702
Neutral mention · rule
> ... all DNNs face the issue of overfitting as they learn, which is when performance on one data set increases but the network's performance fails to generalize (often measured by the divergence of performance on training vs testing data sets). This ubiquitous problem in DNNs is often solved by experimenters via "noise injections" in the form of noisy or corrupted inputs. The goal of this paper is to argue that the brain faces a similar challenge of overfitting, and that nightly dreams evolved to combat the brain's overfitting during its daily learning. Actually, there's compelling evidence that overfitting is a necessary step for achieving state-of-the-art performance…
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with DNNs! Many state-of-the-art deep learning models today are trained until they achieve ~100% accuracy on the training data, and then we continue to train them because once they go past this "interpolation threshold" they continue learning to generalize better to unseen data. This is known as the "double descent" phenomenon. See, for example: https://openai.com/blog/deep-double-descent/ https://arxiv.org/abs/1912.02292 https://arxiv.org/abs/1903.08560 The author makes no mention of double descent and the need for overfitting. In fact, he seems completely unaware of it. -- EDIT: Also, see this comment https://news.ycombinator.com/item?id=23957501 elsewhere on this page.
preetum
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Hi, we define the interpolation threshold in Section 2 of the full paper (https://arxiv.org/abs/1912.02292) as the point when the "Effective Model Complexity" = # of train samples. Where the "Effective Model Complexity (EMC)" of a model + training procedure (w.r.t an input distribution) is the maximum number of samples from the distribution that the model+training can fit to ~0 train error. Our experiments are consistent with the hypothesis that the double-descent peak occurs when EMC = n; that is, when the model+training is just barely able to fit the train set.

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