Hardness of Learning Fixed Parities with Neural Networks
- URL: http://arxiv.org/abs/2501.00817v2
- Date: Wed, 08 Jan 2025 10:42:53 GMT
- Title: Hardness of Learning Fixed Parities with Neural Networks
- Authors: Itamar Shoshani, Ohad Shamir,
- Abstract summary: Learning parity functions is a canonical problem in learning theory.
For any fixed parity of some minimal size, using it as a target function to train one-hidden-layer ReLU networks will fail to produce anything meaningful.
- Score: 33.84710024813985
- License:
- Abstract: Learning parity functions is a canonical problem in learning theory, which although computationally tractable, is not amenable to standard learning algorithms such as gradient-based methods. This hardness is usually explained via statistical query lower bounds [Kearns, 1998]. However, these bounds only imply that for any given algorithm, there is some worst-case parity function that will be hard to learn. Thus, they do not explain why fixed parities - say, the full parity function over all coordinates - are difficult to learn in practice, at least with standard predictors and gradient-based methods [Abbe and Boix-Adsera, 2022]. In this paper, we address this open problem, by showing that for any fixed parity of some minimal size, using it as a target function to train one-hidden-layer ReLU networks with perturbed gradient descent will fail to produce anything meaningful. To establish this, we prove a new result about the decay of the Fourier coefficients of linear threshold (or weighted majority) functions, which may be of independent interest.
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