Natural Hypergradient Descent: Algorithm Design, Convergence Analysis, and Parallel Implementation

Fuente: arXiv
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Autores principales: Kong, Deyi, Chen, Zaiwei, Zhang, Shuzhong, Mou, Shancong
Formato: Preprint
Publicado: 2026
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author Kong, Deyi
Chen, Zaiwei
Zhang, Shuzhong
Mou, Shancong
author_facet Kong, Deyi
Chen, Zaiwei
Zhang, Shuzhong
Mou, Shancong
contents In this work, we propose Natural Hypergradient Descent (NHGD), a new method for solving bilevel optimization problems. To address the computational bottleneck in hypergradient estimation--namely, the need to compute or approximate Hessian inverse--we exploit the statistical structure of the inner optimization problem and use the empirical Fisher information matrix as an asymptotically consistent surrogate for the Hessian. This design enables a parallel optimize-and-approximate framework in which the Hessian-inverse approximation is updated synchronously with the stochastic inner optimization, reusing gradient information at negligible additional cost. Our main theoretical contribution establishes high-probability error bounds and sample complexity guarantees for NHGD that match those of state-of-the-art optimize-then-approximate methods, while significantly reducing computational time overhead. Empirical evaluations on representative bilevel learning tasks further demonstrate the practical advantages of NHGD, highlighting its scalability and effectiveness in large-scale machine learning settings.
format Preprint
id arxiv_https___arxiv_org_abs_2602_10905
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Natural Hypergradient Descent: Algorithm Design, Convergence Analysis, and Parallel Implementation
Kong, Deyi
Chen, Zaiwei
Zhang, Shuzhong
Mou, Shancong
Machine Learning
Optimization and Control
In this work, we propose Natural Hypergradient Descent (NHGD), a new method for solving bilevel optimization problems. To address the computational bottleneck in hypergradient estimation--namely, the need to compute or approximate Hessian inverse--we exploit the statistical structure of the inner optimization problem and use the empirical Fisher information matrix as an asymptotically consistent surrogate for the Hessian. This design enables a parallel optimize-and-approximate framework in which the Hessian-inverse approximation is updated synchronously with the stochastic inner optimization, reusing gradient information at negligible additional cost. Our main theoretical contribution establishes high-probability error bounds and sample complexity guarantees for NHGD that match those of state-of-the-art optimize-then-approximate methods, while significantly reducing computational time overhead. Empirical evaluations on representative bilevel learning tasks further demonstrate the practical advantages of NHGD, highlighting its scalability and effectiveness in large-scale machine learning settings.
title Natural Hypergradient Descent: Algorithm Design, Convergence Analysis, and Parallel Implementation
topic Machine Learning
Optimization and Control
url https://arxiv.org/abs/2602.10905