Last Layer Empirical Bayes

Fuente: arXiv
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Autores principales: Villecroze, Valentin, Wang, Yixin, Loaiza-Ganem, Gabriel
Formato: Preprint
Publicado: 2025
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author Villecroze, Valentin
Wang, Yixin
Loaiza-Ganem, Gabriel
author_facet Villecroze, Valentin
Wang, Yixin
Loaiza-Ganem, Gabriel
contents The task of quantifying the inherent uncertainty associated with neural network predictions is a key challenge in artificial intelligence. Bayesian neural networks (BNNs) and deep ensembles are among the most prominent approaches to tackle this task. Both approaches produce predictions by computing an expectation of neural network outputs over some distribution on the corresponding weights; this distribution is given by the posterior in the case of BNNs, and by a mixture of point masses for ensembles. Inspired by recent work showing that the distribution used by ensembles can be understood as a posterior corresponding to a learned data-dependent prior, we propose last layer empirical Bayes (LLEB). LLEB instantiates a learnable prior as a normalizing flow, which is then trained to maximize the evidence lower bound; to retain tractability we use the flow only on the last layer. We show why LLEB is well motivated, and how it interpolates between standard BNNs and ensembles in terms of the strength of the prior that they use. LLEB performs on par with existing approaches, highlighting that empirical Bayes is a promising direction for future research in uncertainty quantification.
format Preprint
id arxiv_https___arxiv_org_abs_2505_15888
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Last Layer Empirical Bayes
Villecroze, Valentin
Wang, Yixin
Loaiza-Ganem, Gabriel
Machine Learning
Artificial Intelligence
The task of quantifying the inherent uncertainty associated with neural network predictions is a key challenge in artificial intelligence. Bayesian neural networks (BNNs) and deep ensembles are among the most prominent approaches to tackle this task. Both approaches produce predictions by computing an expectation of neural network outputs over some distribution on the corresponding weights; this distribution is given by the posterior in the case of BNNs, and by a mixture of point masses for ensembles. Inspired by recent work showing that the distribution used by ensembles can be understood as a posterior corresponding to a learned data-dependent prior, we propose last layer empirical Bayes (LLEB). LLEB instantiates a learnable prior as a normalizing flow, which is then trained to maximize the evidence lower bound; to retain tractability we use the flow only on the last layer. We show why LLEB is well motivated, and how it interpolates between standard BNNs and ensembles in terms of the strength of the prior that they use. LLEB performs on par with existing approaches, highlighting that empirical Bayes is a promising direction for future research in uncertainty quantification.
title Last Layer Empirical Bayes
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2505.15888