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 eff...
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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 gradientprojection updates. We demonstrate that the proposed algorithm identifies an epsilon\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varepsilon $$\end{document}-stationary point of the nonconvex-strongly concave minimax problem in O(epsilon-2)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$O(\varepsilon <^>{-2})$$\end{document} 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.
Much recent research effort has been directed to the development of efficient algo-rithms for solving minimax problems with theoretical convergence guarantees due to the relevance of these problems to a few emergent a...
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Much recent research effort has been directed to the development of efficient algo-rithms for solving minimax problems with theoretical convergence guarantees due to the relevance of these problems to a few emergent applications. In this paper, we propose a unified single-loop alternatinggradientprojection (AGP) algorithm for solving smooth nonconvex-(strongly) concave and (strongly) convex-nonconcave minimax problems. AGP employs simple gradientprojection steps for updating the primal and dual variables alternatively at each iteration. We show that it can find an epsilon-stationary point of the objective function in O (epsilon(-2)) (resp. O (epsilon(-4))) iterations under nonconvex-strongly concave (resp. nonconvex-concave) setting. Moreover, its gradi-by O (epsilon(-2)) (resp., O (epsilon(-4))) under the strongly convex-nonconcave (resp., convex- ent complexity to obtain an epsilon-stationary point of the objective function is bounded nonconcave) setting. To the best of our knowledge, this is the first time that a simple and unified single-loop algorithm is developed for solving both nonconvex-(strongly) concave and (strongly) convex-nonconcave minimax problems. Moreover, the complexity results for solving the latter (strongly) convex-nonconcave minimax problems have never been obtained before in the literature. Numerical results show the efficiency of the proposed AGP algorithm. Furthermore, we extend the AGP algorithm by presenting a block alternating proximal gradient (BAPG) algorithm for solving more general multi-block nonsmooth nonconvex-(strongly) concave and (strongly) convex-nonconcave minimax problems. We can similarly establish the gradient complexity of the proposed algorithm under these four different settings.
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