The Space Between: On Folding, Symmetries and Sampling

Fuente: arXiv
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Hauptverfasser: Lewandowski, Michal, Heinzl, Bernhard, Pisoni, Raphael, Moser, Bernhard A.
Format: Preprint
Veröffentlicht: 2025
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author Lewandowski, Michal
Heinzl, Bernhard
Pisoni, Raphael
Moser, Bernhard A.
author_facet Lewandowski, Michal
Heinzl, Bernhard
Pisoni, Raphael
Moser, Bernhard A.
contents Recent findings suggest that consecutive layers of neural networks with the ReLU activation function \emph{fold} the input space during the learning process. While many works hint at this phenomenon, an approach to quantify the folding was only recently proposed by means of a space folding measure based on Hamming distance in the ReLU activation space. We generalize this measure to a wider class of activation functions through introduction of equivalence classes of input data, analyse its mathematical and computational properties and come up with an efficient sampling strategy for its implementation. Moreover, it has been observed that space folding values increase with network depth when the generalization error is low, but decrease when the error increases. This underpins that learned symmetries in the data manifold (e.g., invariance under reflection) become visible in terms of space folds, contributing to the network's generalization capacity. Inspired by these findings, we outline a novel regularization scheme that encourages the network to seek solutions characterized by higher folding values.
format Preprint
id arxiv_https___arxiv_org_abs_2503_08502
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Space Between: On Folding, Symmetries and Sampling
Lewandowski, Michal
Heinzl, Bernhard
Pisoni, Raphael
Moser, Bernhard A.
Machine Learning
Neural and Evolutionary Computing
Recent findings suggest that consecutive layers of neural networks with the ReLU activation function \emph{fold} the input space during the learning process. While many works hint at this phenomenon, an approach to quantify the folding was only recently proposed by means of a space folding measure based on Hamming distance in the ReLU activation space. We generalize this measure to a wider class of activation functions through introduction of equivalence classes of input data, analyse its mathematical and computational properties and come up with an efficient sampling strategy for its implementation. Moreover, it has been observed that space folding values increase with network depth when the generalization error is low, but decrease when the error increases. This underpins that learned symmetries in the data manifold (e.g., invariance under reflection) become visible in terms of space folds, contributing to the network's generalization capacity. Inspired by these findings, we outline a novel regularization scheme that encourages the network to seek solutions characterized by higher folding values.
title The Space Between: On Folding, Symmetries and Sampling
topic Machine Learning
Neural and Evolutionary Computing
url https://arxiv.org/abs/2503.08502