Geometry of the Loss Landscape in Invariant Deep Linear Neural Networks

27 Sept 2024 (modified: 05 Feb 2025)Submitted to ICLR 2025EveryoneRevisionsBibTeXCC BY 4.0
Keywords: Invariant Models, Data Augmentation, Deep Linear Networks, Low Rank Approximation, Regularization
TL;DR: We compare the optimization landscape of linear networks models made invariant via hard-wiring, regularization, and data augmentation.
Abstract: Equivariant and invariant machine learning models seek to take advantage of symmetries and other structures present in the data to reduce the sample complexity of learning. Empirical work has suggested that data-driven methods, such as regularization and data augmentation, may achieve a comparable performance as genuinely invariant models, but theoretical results are still limited. In this work, we conduct a theoretical comparison of three different approaches to achieve invariance: data augmentation, regularization, and hard-wiring. We focus on mean squared error regression with deep linear networks, which parametrize rank-bounded linear maps and can be hard-wired to be invariant to specific group actions. We show that the optimization problems resulting from hard-wiring and data augmentation have the same critical points, all of which are saddles except for the global optimum. In contrast, regularization leads to a larger number of critical points, again all of which are saddles except for the global optimum. The regularization path is continuous and converges to the hard-wired optimum.
Primary Area: learning theory
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Submission Number: 12114
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