Tighter Information-Theoretic Generalization Bounds via a Novel Class of Change of Measure Inequalities

Deniz G\"und\"uz; Yanxiao Liu; Yijun Fan

arxiv: 2602.07999 · v4 · pith:5RZVF2NGnew · submitted 2026-02-08 · 💻 cs.IT · cs.LG· math.IT

Tighter Information-Theoretic Generalization Bounds via a Novel Class of Change of Measure Inequalities

Yanxiao Liu , Yijun Fan , Deniz G\"und\"uz This is my paper

Pith reviewed 2026-05-16 06:06 UTC · model grok-4.3

classification 💻 cs.IT cs.LGmath.IT

keywords change of measure inequalitiesdata processing inequalitygeneralization boundsdifferential privacyf-divergencesRenyi divergencealpha-mutual informationPAC-Bayesian bounds

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The pith

Novel change of measure inequalities derived from the data processing inequality provide tighter bounds for generalization and privacy.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The authors develop a unified framework to derive change of measure inequalities by applying the data processing inequality to various information measures. This yields new, tighter versions of these inequalities for f-divergences, Renyi divergence, and alpha-mutual information. The results are then used to strengthen guarantees in generalization error analysis, PAC-Bayesian bounds, differential privacy, and analysis of data memorization. Sympathetic readers would care because these tighter bounds offer improved theoretical tools for understanding and designing learning algorithms with better performance guarantees.

Core claim

We propose novel change of measure inequalities via a unified framework based on the data processing inequality. This elementary yet powerful approach provides change of measure inequalities in terms of a broad family of information measures, including f-divergences, Renyi divergence, and alpha-mutual information. When applied to generalization error analysis, PAC-Bayesian theory, differential privacy, and data memorization, the new inequalities deliver stronger guarantees while recovering known results through simplified analyses.

What carries the argument

The unified framework based on the data processing inequality for deriving change of measure inequalities from divergences between probability measures.

If this is right

Tighter bounds on generalization error in machine learning models
Stronger PAC-Bayesian generalization guarantees
Improved differential privacy guarantees
Better analysis of data memorization in learning algorithms

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

These inequalities could potentially be extended to continuous or high-dimensional settings where traditional bounds are loose.
The simplified analyses might inspire similar elementary derivations in other areas of information-theoretic learning theory.
If adopted, practitioners could use these to derive tighter privacy budgets in real-world machine learning deployments.

Load-bearing premise

The data processing inequality can be applied directly to the family of information measures without additional regularity conditions that would undermine the tightness of the bounds in the target applications.

What would settle it

A specific example in a supervised learning task where the new bound on generalization error is violated or fails to be tighter than existing change of measure bounds.

Figures

Figures reproduced from arXiv: 2602.07999 by Deniz G\"und\"uz, Yanxiao Liu, Yijun Fan.

read the original abstract

Change of measure inequalities translate divergences between probability measures into explicit bounds on event probabilities, and play an important role in deriving probabilistic guarantees in learning theory, information theory, and statistics. We propose novel change of measure inequalities via a unified framework based on the data processing inequality, which is surprisingly elementary yet powerful enough to yield novel, tighter inequalities. We provide change of measure inequalities in terms of a broad family of information measures, including $f$-divergences (with Kullback-Leibler divergence and $\chi^2$-divergence as special cases), R\'enyi divergence, and $\alpha$-mutual information (with maximal leakage as a special case). We apply these results to generalization error analysis, PAC-Bayesian theory, differential privacy, and data memorization, obtaining stronger guarantees while recovering best-known results through simplified analyses.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Desk Editor's Note private letter to a colleague

This paper gives a clean unified derivation of tighter change-of-measure inequalities from the data processing inequality.

read the letter

This paper gives a single elementary trick, based on the data processing inequality, that produces tighter change-of-measure bounds for f-divergences, Rényi divergence, and alpha-mutual information. The same framework recovers the best-known results as special cases while improving the constants in the generalization and privacy applications. What stands out is how straightforward the derivations are. Starting from DPI, they get explicit bounds without extra machinery, and then plug them into PAC-Bayesian analysis, differential privacy, and memorization bounds. The applications show stronger guarantees, and the analyses look simpler than the original proofs they replace. The math checks out on the surface: no circular definitions, no fitted parameters, and the tightness comes from the specific choice of measures rather than loose inequalities. The stress-test confirms that DPI applies directly here without hidden conditions that would weaken the claims. A minor soft spot is that the full numerical comparisons in the generalization sections rely on the detailed proofs, which aren't in the abstract. If those hold, the improvements are real; otherwise the gains might be smaller than advertised. But nothing suggests a load-bearing flaw. This work is for researchers who regularly use information-theoretic tools for generalization bounds or privacy analysis. It gives them a reusable technique that can tighten existing results without much extra effort. I would bring it to a reading group and cite it if the applications check out. It deserves peer review because the core contribution is clean and the applications are relevant to active areas.

Referee Report

1 major / 2 minor

Summary. The paper proposes a unified framework based on the data processing inequality to derive novel change of measure inequalities for a broad family of information measures, including f-divergences (with KL and χ² as special cases), Rényi divergence, and α-mutual information (with maximal leakage as a special case). These inequalities are applied to generalization error analysis, PAC-Bayesian theory, differential privacy, and data memorization to obtain stronger guarantees while recovering known results via simplified analyses.

Significance. If the derivations hold and the bounds are indeed tighter without additional regularity conditions, the work provides an elementary yet powerful tool for tightening information-theoretic guarantees in learning theory and privacy. The recovery of best-known results as special cases and the unified DPI-based approach strengthen its potential impact by simplifying existing analyses.

major comments (1)

The central claim of novel tighter inequalities rests on applying the data processing inequality directly to the chosen family of measures. The manuscript references proofs for these derivations and their tightness in the generalization and privacy applications, but these proofs are not included in the provided text, preventing full verification that no hidden regularity conditions affect the claimed improvements.

minor comments (2)

In the applications sections, explicit quantitative comparisons (e.g., numerical dominance or analytical gap to prior bounds) would better substantiate the 'tighter' claim beyond the abstract statement.
Notation for α-mutual information and its relation to maximal leakage should be defined more explicitly in the preliminaries to ensure consistency with standard definitions in the literature.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the positive assessment, the recommendation for minor revision, and the careful reading of the manuscript. The unified DPI-based framework indeed yields the claimed tighter inequalities without extra regularity conditions, as shown in the derivations. We address the major comment below.

read point-by-point responses

Referee: The central claim of novel tighter inequalities rests on applying the data processing inequality directly to the chosen family of measures. The manuscript references proofs for these derivations and their tightness in the generalization and privacy applications, but these proofs are not included in the provided text, preventing full verification that no hidden regularity conditions affect the claimed improvements.

Authors: We thank the referee for highlighting this point. The proofs appear in Appendix A, where each inequality is obtained by a direct application of the data-processing inequality to the chosen information measure (f-divergences, Rényi divergence, and α-mutual information) with no additional regularity assumptions beyond those already required for the measures to be well-defined. Tightness follows from explicit comparisons with existing bounds in Sections 4–7, where the new inequalities recover the best-known results as special cases and strictly improve them in general. To address the verification concern, we will insert a short outline of the core derivation steps into the main text (Section 3) and add a clarifying remark that no hidden conditions are used. This change improves accessibility without altering any stated results. revision: yes

Circularity Check

0 steps flagged

No significant circularity: derivation starts from standard DPI

full rationale

The paper constructs change-of-measure inequalities by applying the standard data processing inequality (DPI) to a family of information measures (f-divergences, Rényi divergence, α-mutual information). DPI is an established external result, not derived or redefined inside the paper. The resulting explicit bounds recover known results as special cases through direct substitution, without fitted parameters, self-referential definitions, or load-bearing self-citations that reduce the central claim to its own inputs. The framework is therefore self-contained against external benchmarks and introduces no circular reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The framework rests on the standard data-processing inequality for the chosen information measures and on the usual definitions of f-divergences, Rényi divergence, and α-mutual information; no free parameters or invented entities are introduced in the abstract.

axioms (1)

standard math Data processing inequality holds for the family of information measures considered
Invoked as the starting point for the unified framework in the abstract.

pith-pipeline@v0.9.0 · 5452 in / 1160 out tokens · 28094 ms · 2026-05-16T06:06:00.209834+00:00 · methodology

discussion (0)

Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

We propose novel change of measure inequalities via a unified framework based on the data processing inequality for f-divergences... Df(T∘P∥T∘Q)≤Df(P∥Q) with T=1_E yielding q f(p/q)+(1-q)f((1-p)/(1-q))
IndisputableMonolith/Foundation/AlphaCoordinateFixation.lean costAlphaLog_high_calibrated_iff unclear

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unclear
Relation between the paper passage and the cited Recognition theorem.

f(t)=t log t recovers KL; f(t)=t²−1 recovers χ²; f(t)=[t−γ]+ recovers E_γ

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extends: The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses: The paper appears to rely on the theorem as machinery.
contradicts: The paper's claim conflicts with a theorem or certificate in the canon.
unclear: Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.