A Proximal Augmented Lagrangian Method Based on Quadratic Approximations for Weakly Convex Optimization

Fuente: arXiv
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Autores principales: Zhang, Yule, Liu, Benqi, Xiao, Xiantao, Zhang, Liwei
Formato: Preprint
Publicado: 2026
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author Zhang, Yule
Liu, Benqi
Xiao, Xiantao
Zhang, Liwei
author_facet Zhang, Yule
Liu, Benqi
Xiao, Xiantao
Zhang, Liwei
contents This paper proposes QPALM, a proximal augmented Lagrangian method based on quadratic approximations, for solving nonlinear programming problems with weakly convex objective and constraint functions. The algorithm is constructed by incorporating quadratic approximations of both the objective and constraint functions into a proximal Lagrangian framework. We establish its non-asymptotic convergence rate in terms of the total number of subproblems solved. The convergence of QPALM is characterized by three metrics associated with the $\varepsilon$-KKT conditions: the squared norm of the gradient of the Moreau envelope of the Lagrangian, the average constraint violation, and the average complementarity violation. All three metrics are shown to converge at a rate of $O(T^{-1/3})$ after $T$ iterations. Preliminary numerical results demonstrate the practical efficiency of the proposed method. These results are established under two mild conditions: (i) weak convexity of all problem functions, and (ii) the existence of a strictly feasible point. The proposed QPALM is a sequentially strongly convex programming method that is readily implementable.
format Preprint
id arxiv_https___arxiv_org_abs_2605_03415
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle A Proximal Augmented Lagrangian Method Based on Quadratic Approximations for Weakly Convex Optimization
Zhang, Yule
Liu, Benqi
Xiao, Xiantao
Zhang, Liwei
Optimization and Control
90C30
This paper proposes QPALM, a proximal augmented Lagrangian method based on quadratic approximations, for solving nonlinear programming problems with weakly convex objective and constraint functions. The algorithm is constructed by incorporating quadratic approximations of both the objective and constraint functions into a proximal Lagrangian framework. We establish its non-asymptotic convergence rate in terms of the total number of subproblems solved. The convergence of QPALM is characterized by three metrics associated with the $\varepsilon$-KKT conditions: the squared norm of the gradient of the Moreau envelope of the Lagrangian, the average constraint violation, and the average complementarity violation. All three metrics are shown to converge at a rate of $O(T^{-1/3})$ after $T$ iterations. Preliminary numerical results demonstrate the practical efficiency of the proposed method. These results are established under two mild conditions: (i) weak convexity of all problem functions, and (ii) the existence of a strictly feasible point. The proposed QPALM is a sequentially strongly convex programming method that is readily implementable.
title A Proximal Augmented Lagrangian Method Based on Quadratic Approximations for Weakly Convex Optimization
topic Optimization and Control
90C30
url https://arxiv.org/abs/2605.03415