Nonsmooth Projection-Free Optimization with Functional Constraints

Fuente: arXiv
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Autores principales: Asgari, Kamiar, Neely, Michael J.
Formato: Preprint
Publicado: 2023
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author Asgari, Kamiar
Neely, Michael J.
author_facet Asgari, Kamiar
Neely, Michael J.
contents This paper presents a subgradient-based algorithm for constrained nonsmooth convex optimization that does not require projections onto the feasible set. While the well-established Frank-Wolfe algorithm and its variants already avoid projections, they are primarily designed for smooth objective functions. In contrast, our proposed algorithm can handle nonsmooth problems with general convex functional inequality constraints. It achieves an $ε$-suboptimal solution in $\mathcal{O}(ε^{-2})$ iterations, with each iteration requiring only a single (potentially inexact) Linear Minimization Oracle (LMO) call and a (possibly inexact) subgradient computation. This performance is consistent with existing lower bounds. Similar performance is observed when deterministic subgradients are replaced with stochastic subgradients. In the special case where there are no functional inequality constraints, our algorithm competes favorably with a recent nonsmooth projection-free method designed for constraint-free problems. Our approach utilizes a simple separation scheme in conjunction with a new Lagrange multiplier update rule.
format Preprint
id arxiv_https___arxiv_org_abs_2311_11180
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle Nonsmooth Projection-Free Optimization with Functional Constraints
Asgari, Kamiar
Neely, Michael J.
Optimization and Control
Machine Learning
Systems and Control
65K05, 65K10, 65K99, 90C25, 90C15, 90C25, 90C30
This paper presents a subgradient-based algorithm for constrained nonsmooth convex optimization that does not require projections onto the feasible set. While the well-established Frank-Wolfe algorithm and its variants already avoid projections, they are primarily designed for smooth objective functions. In contrast, our proposed algorithm can handle nonsmooth problems with general convex functional inequality constraints. It achieves an $ε$-suboptimal solution in $\mathcal{O}(ε^{-2})$ iterations, with each iteration requiring only a single (potentially inexact) Linear Minimization Oracle (LMO) call and a (possibly inexact) subgradient computation. This performance is consistent with existing lower bounds. Similar performance is observed when deterministic subgradients are replaced with stochastic subgradients. In the special case where there are no functional inequality constraints, our algorithm competes favorably with a recent nonsmooth projection-free method designed for constraint-free problems. Our approach utilizes a simple separation scheme in conjunction with a new Lagrange multiplier update rule.
title Nonsmooth Projection-Free Optimization with Functional Constraints
topic Optimization and Control
Machine Learning
Systems and Control
65K05, 65K10, 65K99, 90C25, 90C15, 90C25, 90C30
url https://arxiv.org/abs/2311.11180