Cascade of phase transitions in the training of Energy-based models

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Main Authors: Bachtis, Dimitrios, Biroli, Giulio, Decelle, Aurélien, Seoane, Beatriz
Format: Preprint
Published: 2024
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author Bachtis, Dimitrios
Biroli, Giulio
Decelle, Aurélien
Seoane, Beatriz
author_facet Bachtis, Dimitrios
Biroli, Giulio
Decelle, Aurélien
Seoane, Beatriz
contents In this paper, we investigate the feature encoding process in a prototypical energy-based generative model, the Restricted Boltzmann Machine (RBM). We start with an analytical investigation using simplified architectures and data structures, and end with numerical analysis of real trainings on real datasets. Our study tracks the evolution of the model's weight matrix through its singular value decomposition, revealing a series of phase transitions associated to a progressive learning of the principal modes of the empirical probability distribution. The model first learns the center of mass of the modes and then progressively resolve all modes through a cascade of phase transitions. We first describe this process analytically in a controlled setup that allows us to study analytically the training dynamics. We then validate our theoretical results by training the Bernoulli-Bernoulli RBM on real data sets. By using data sets of increasing dimension, we show that learning indeed leads to sharp phase transitions in the high-dimensional limit. Moreover, we propose and test a mean-field finite-size scaling hypothesis. This shows that the first phase transition is in the same universality class of the one we studied analytically, and which is reminiscent of the mean-field paramagnetic-to-ferromagnetic phase transition.
format Preprint
id arxiv_https___arxiv_org_abs_2405_14689
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Cascade of phase transitions in the training of Energy-based models
Bachtis, Dimitrios
Biroli, Giulio
Decelle, Aurélien
Seoane, Beatriz
Machine Learning
Disordered Systems and Neural Networks
Statistical Mechanics
In this paper, we investigate the feature encoding process in a prototypical energy-based generative model, the Restricted Boltzmann Machine (RBM). We start with an analytical investigation using simplified architectures and data structures, and end with numerical analysis of real trainings on real datasets. Our study tracks the evolution of the model's weight matrix through its singular value decomposition, revealing a series of phase transitions associated to a progressive learning of the principal modes of the empirical probability distribution. The model first learns the center of mass of the modes and then progressively resolve all modes through a cascade of phase transitions. We first describe this process analytically in a controlled setup that allows us to study analytically the training dynamics. We then validate our theoretical results by training the Bernoulli-Bernoulli RBM on real data sets. By using data sets of increasing dimension, we show that learning indeed leads to sharp phase transitions in the high-dimensional limit. Moreover, we propose and test a mean-field finite-size scaling hypothesis. This shows that the first phase transition is in the same universality class of the one we studied analytically, and which is reminiscent of the mean-field paramagnetic-to-ferromagnetic phase transition.
title Cascade of phase transitions in the training of Energy-based models
topic Machine Learning
Disordered Systems and Neural Networks
Statistical Mechanics
url https://arxiv.org/abs/2405.14689