Optimization Dynamics of Equivariant and Augmented Neural Networks

Fuente: arXiv
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Autores principales: Nordenfors, Oskar, Ohlsson, Fredrik, Flinth, Axel
Formato: Preprint
Publicado: 2023
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author Nordenfors, Oskar
Ohlsson, Fredrik
Flinth, Axel
author_facet Nordenfors, Oskar
Ohlsson, Fredrik
Flinth, Axel
contents We investigate the optimization of neural networks on symmetric data, and compare the strategy of constraining the architecture to be equivariant to that of using data augmentation. Our analysis reveals that that the relative geometry of the admissible and the equivariant layers, respectively, plays a key role. Under natural assumptions on the data, network, loss, and group of symmetries, we show that compatibility of the spaces of admissible layers and equivariant layers, in the sense that the corresponding orthogonal projections commute, implies that the sets of equivariant stationary points are identical for the two strategies. If the linear layers of the network also are given a unitary parametrization, the set of equivariant layers is even invariant under the gradient flow for augmented models. Our analysis however also reveals that even in the latter situation, stationary points may be unstable for augmented training although they are stable for the manifestly equivariant models.
format Preprint
id arxiv_https___arxiv_org_abs_2303_13458
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Optimization Dynamics of Equivariant and Augmented Neural Networks
Nordenfors, Oskar
Ohlsson, Fredrik
Flinth, Axel
Machine Learning
Optimization and Control
68T07, 20C35, 37N40
We investigate the optimization of neural networks on symmetric data, and compare the strategy of constraining the architecture to be equivariant to that of using data augmentation. Our analysis reveals that that the relative geometry of the admissible and the equivariant layers, respectively, plays a key role. Under natural assumptions on the data, network, loss, and group of symmetries, we show that compatibility of the spaces of admissible layers and equivariant layers, in the sense that the corresponding orthogonal projections commute, implies that the sets of equivariant stationary points are identical for the two strategies. If the linear layers of the network also are given a unitary parametrization, the set of equivariant layers is even invariant under the gradient flow for augmented models. Our analysis however also reveals that even in the latter situation, stationary points may be unstable for augmented training although they are stable for the manifestly equivariant models.
title Optimization Dynamics of Equivariant and Augmented Neural Networks
topic Machine Learning
Optimization and Control
68T07, 20C35, 37N40
url https://arxiv.org/abs/2303.13458