Journal of the Operations Research Society of China ›› 2026, Vol. 14 ›› Issue (2): 632-652.doi: 10.1007/s40305-024-00540-5

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An Alternating Gradient Projection Algorithm with Momentum for Nonconvex-Concave Minimax Problems

Jue-You Li1, Tao Xie2   

  1. 1 School of Mathematical Sciences, Chongqing Normal University, Chongqing 401331, China;
    2 Big Data & Intelligence Engineering School, Chongqing College of International Business and Economics, Chongqing 401520, China
  • Received:2023-05-09 Revised:2024-03-05 Online:2026-06-30 Published:2026-07-06
  • Contact: Jue-You Li E-mail:lijueyou@cqnu.edu.cn
  • Supported by:
    This work was partially supported by the National Key R&D Program of China (No. 2023YFA1011303), the National Natural Science Foundation of China (Nos. 11971083 and 11991024), the Team Project of Innovation Leading Talent in Chongqing (No. CQYC20210309536), and the Contract System Project of Chongqing Talent Plan (No. cstc2022ycjh-bgzxm0147).

Abstract: The growing interest in addressing minimax optimization problem has been fueled by recent applications in machine learning. Although extensively studied in the convex-concave regime, where a global solution can be efficiently computed, this paper delves into the minimax problem within the nonconvex-concave setup. We propose an alternating gradient projection algorithm with momentum (M-AGP), belonging to single-loop algorithms that not only are easier to implement but also require only the computation of gradient projection updates. We demonstrate that the proposed algorithm identifies an ε-stationary point of the nonconvex-strongly concave minimax problem in O(ε-2) iterations, representing the best-known rate in the literature. Finally, we utilize two test problems, namely robust nonlinear regression and an image classification problem, to showcase the efficacy of the proposed algorithm.

Key words: Minimax optimization, Alternating gradient projection algorithm, Gradient descent–ascent algorithm, Iteration complexity

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