Department of Applied Mathematics & Physics, Kyoto University

Technical Report 2022-001 (February 3, 2022)

An accelerated proximal gradient method for multiobjective optimization
by Hiroki Tanabe, Ellen H. Fukuda, and Nobuo Yamashita

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Many researchers have studied descent methods for multiobjective optimization problems in recent years. For example, Fliege and Svaiter proposed the steepest descent method for differentiable multiobjective optimization problems. Afterward, a proximal gradient method, which can solve non-differentiable problems, was also considered. However, their accelerated versions are not sufficiently studied. Recently, El Moudden and El Mouatasim proposed a natural extension of Nesterov's accelerated method for multiobjective optimization problems. They proved the global convergence rate of the algorithm ($O(1/k^2)$) under the assumption that the sequence of the Lagrangian multipliers of the subproblems is eventually fixed. However, this assumption is restrictive because it means that the method is regarded as the Nesterov's method for the weighting problem. In this paper, we propose a new accelerated algorithm, in which we solve subproblems with terms that only appear in the multiobjective case. We also show the proposed method's global convergence rate ($O(1/k^2)$) under a more natural assumption, using a merit function to measure the complexity. Moreover, we present an efficient way to solve the subproblem in the proposed method via its dual, and we confirm the validity of the proposed method through numerical experiments.