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Journal of Scientific Computing
Article . 2025 . Peer-reviewed
License: Springer Nature TDM
Data sources: Crossref
https://dx.doi.org/10.48550/ar...
Article . 2024
License: arXiv Non-Exclusive Distribution
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Single-Loop Projection-Free and Projected Gradient-Based Algorithms for Nonconvex-Concave Saddle Point Problems with Bilevel Structure

Authors: Mohammad Mahdi Ahmadi; Erfan Yazdandoost Hamedani;

Single-Loop Projection-Free and Projected Gradient-Based Algorithms for Nonconvex-Concave Saddle Point Problems with Bilevel Structure

Abstract

In this paper, we explore a broad class of constrained saddle point problems with a bilevel structure, wherein the upper-level objective function is nonconvex-concave and smooth over compact and convex constraint sets, subject to a strongly convex lower-level objective function. This class of problems finds wide applicability in machine learning, encompassing robust multi-task learning, adversarial learning, and robust meta-learning. Our study extends the current literature in two main directions: (i) We consider a more general setting where the upper-level function is not necessarily strongly concave or linear in the maximization variable. (ii) While existing methods for solving saddle point problems with a bilevel structure are projection-based algorithms, we propose a one-sided projection-free method employing a linear minimization oracle. Specifically, by utilizing regularization and nested approximation techniques, we introduce a novel single-loop one-sided projection-free algorithm, requiring $\cO(ε^{-4})$ iterations to attain an $ε$-stationary solution, moreover, when the objective function in the upper-level is linear in the maximization component, our result improve to $\cO(ε^{-3})$. Subsequently, we develop an efficient single-loop fully projected gradient-based algorithm capable of achieving an $ε$-stationary solution within $\cO(ε^{-5})$ iterations. This result improves to $\cO(ε^{-4})$ when the upper-level objective function is strongly concave in the maximization component. Finally, we tested our proposed methods against the state-of-the-art algorithms for solving a robust multi-task regression problem to showcase the superiority of our algorithms.

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Keywords

Optimization and Control (math.OC), FOS: Mathematics, Mathematics - Optimization and Control

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
1
Average
Average
Average
Green