Differentially Private Bilevel Optimization: Efficient Algorithms with Near-Optimal Rates

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Hauptverfasser: Lowy, Andrew, Liu, Daogao
Format: Preprint
Veröffentlicht: 2025
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author Lowy, Andrew
Liu, Daogao
author_facet Lowy, Andrew
Liu, Daogao
contents Bilevel optimization, in which one optimization problem is nested inside another, underlies many machine learning applications with a hierarchical structure -- such as meta-learning and hyperparameter optimization. Such applications often involve sensitive training data, raising pressing concerns about individual privacy. Motivated by this, we study differentially private bilevel optimization. We first focus on settings where the outer-level objective is convex, and provide novel upper and lower bounds on the excess empirical risk for both pure and approximate differential privacy. These bounds are nearly tight and essentially match the optimal rates for standard single-level differentially private ERM, up to additional terms that capture the intrinsic complexity of the nested bilevel structure. We also provide population loss bounds for bilevel stochastic optimization. The bounds are achieved in polynomial time via efficient implementations of the exponential and regularized exponential mechanisms. A key technical contribution is a new method and analysis of log-concave sampling under inexact function evaluations, which may be of independent interest. In the non-convex setting, we develop novel algorithms with state-of-the-art rates for privately finding approximate stationary points. Notably, our bounds do not depend on the dimension of the inner problem.
format Preprint
id arxiv_https___arxiv_org_abs_2506_12994
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Differentially Private Bilevel Optimization: Efficient Algorithms with Near-Optimal Rates
Lowy, Andrew
Liu, Daogao
Machine Learning
Cryptography and Security
Optimization and Control
Bilevel optimization, in which one optimization problem is nested inside another, underlies many machine learning applications with a hierarchical structure -- such as meta-learning and hyperparameter optimization. Such applications often involve sensitive training data, raising pressing concerns about individual privacy. Motivated by this, we study differentially private bilevel optimization. We first focus on settings where the outer-level objective is convex, and provide novel upper and lower bounds on the excess empirical risk for both pure and approximate differential privacy. These bounds are nearly tight and essentially match the optimal rates for standard single-level differentially private ERM, up to additional terms that capture the intrinsic complexity of the nested bilevel structure. We also provide population loss bounds for bilevel stochastic optimization. The bounds are achieved in polynomial time via efficient implementations of the exponential and regularized exponential mechanisms. A key technical contribution is a new method and analysis of log-concave sampling under inexact function evaluations, which may be of independent interest. In the non-convex setting, we develop novel algorithms with state-of-the-art rates for privately finding approximate stationary points. Notably, our bounds do not depend on the dimension of the inner problem.
title Differentially Private Bilevel Optimization: Efficient Algorithms with Near-Optimal Rates
topic Machine Learning
Cryptography and Security
Optimization and Control
url https://arxiv.org/abs/2506.12994