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Learning in High Dimension Always Amounts to Extrapolation (arxiv.org)
1 point by tosh on Nov 7, 2023 | hide | past | pdf | 1 comment on HN

In plain words: A point counts as interpolation only if it lies inside the shape enclosing all training points. In data with over 100 dimensions that almost never happens, so learning is really always extrapolation, and this old distinction says nothing about how well a model generalizes.

Abstract

The notion of interpolation and extrapolation is fundamental in various fields from deep learning to function approximation. Interpolation occurs for a sample $x$ whenever this sample falls inside or on the boundary of the given dataset's convex hull. Extrapolation occurs when $x$ falls outside of that convex hull. One fundamental (mis)conception is that state-of-the-art algorithms work so well because of their ability to correctly interpolate training data. A second (mis)conception is that interpolation happens throughout tasks and datasets, in fact, many intuitions and theories rely on that assumption. We empirically and theoretically argue against those two points and demonstrate that on any high-dimensional ($>$100) dataset, interpolation almost surely never happens. Those results challenge the validity of our current interpolation/extrapolation definition as an indicator of generalization performances.

Randall Balestriero, Jerome Pesenti, Yann LeCun
arXiv:2110.09485 · cs.LG, cs.CV · submitted Oct 18, 2021 · updated Oct 29, 2021
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Also discussed: Oct 2023 (2 points, 0 comments)

If my memory serves me right, there was quite a bit of discussion about this paper on twitter and François Chollet pointed out that linear interpolation in these vector spaces is far from the conceptual interpolation and data points might not even land on the desired manifold. So this paper is not as deeply insightful/strongly relevant as it might sound.