Lean Formalization of Generalization Error Bound by Rademacher Complexity and Dudley's Entropy Integral

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Main Authors: Sonoda, Sho, Kasaura, Kazumi, Mizuno, Yuma, Tsukamoto, Kei, Onda, Naoto
Format: Preprint
Published: 2025
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author Sonoda, Sho
Kasaura, Kazumi
Mizuno, Yuma
Tsukamoto, Kei
Onda, Naoto
author_facet Sonoda, Sho
Kasaura, Kazumi
Mizuno, Yuma
Tsukamoto, Kei
Onda, Naoto
contents Understanding and certifying the generalization performance of machine learning algorithms -- i.e. obtaining theoretical estimates of the test error from the training error -- is a central theme of statistical learning theory. Among the many complexity measures used to derive such guarantees, Rademacher complexity yields sharp, data-dependent bounds that apply well beyond classical VC-dimension theory. In this study, we formalize the generalization error bound by Rademacher complexity in Lean 4, building on measure-theoretic probability theory available in the Mathlib library. Our development provides a mechanically-checked pipeline from the definitions of empirical and expected Rademacher complexity, through a formal symmetrization argument and a bounded-differences analysis, to high-probability uniform deviation bounds via a formally proved McDiarmid inequality. A key technical contribution is a reusable mechanism for lifting results from countable hypothesis classes (where measurability of suprema is straightforward in Mathlib) to separable topological index sets via a reduction to a countable dense subset. As worked applications of the abstract theorem, we mechanize standard empirical Rademacher bounds for linear predictors under $\ell_2$ and $\ell_1$ regularizations, and we also formalize a Dudley-type entropy integral bound based on covering numbers and a chaining construction.
format Preprint
id arxiv_https___arxiv_org_abs_2503_19605
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Lean Formalization of Generalization Error Bound by Rademacher Complexity and Dudley's Entropy Integral
Sonoda, Sho
Kasaura, Kazumi
Mizuno, Yuma
Tsukamoto, Kei
Onda, Naoto
Machine Learning
Computation and Language
Statistics Theory
Understanding and certifying the generalization performance of machine learning algorithms -- i.e. obtaining theoretical estimates of the test error from the training error -- is a central theme of statistical learning theory. Among the many complexity measures used to derive such guarantees, Rademacher complexity yields sharp, data-dependent bounds that apply well beyond classical VC-dimension theory. In this study, we formalize the generalization error bound by Rademacher complexity in Lean 4, building on measure-theoretic probability theory available in the Mathlib library. Our development provides a mechanically-checked pipeline from the definitions of empirical and expected Rademacher complexity, through a formal symmetrization argument and a bounded-differences analysis, to high-probability uniform deviation bounds via a formally proved McDiarmid inequality. A key technical contribution is a reusable mechanism for lifting results from countable hypothesis classes (where measurability of suprema is straightforward in Mathlib) to separable topological index sets via a reduction to a countable dense subset. As worked applications of the abstract theorem, we mechanize standard empirical Rademacher bounds for linear predictors under $\ell_2$ and $\ell_1$ regularizations, and we also formalize a Dudley-type entropy integral bound based on covering numbers and a chaining construction.
title Lean Formalization of Generalization Error Bound by Rademacher Complexity and Dudley's Entropy Integral
topic Machine Learning
Computation and Language
Statistics Theory
url https://arxiv.org/abs/2503.19605