In-Person Oral presentation / top 25% paper

Multi-Objective Online Learning

Jiyan Jiang · Wenpeng Zhang · Shiji Zhou · Lihong Gu · Xiaodong Zeng · Wenwu Zhu

[ Abstract ] [ Livestream: Visit Oral 5 Track 2: Optimization ]
Wed 3 May 1:50 a.m. — 2 a.m. PDT

This paper presents a systematic study of multi-objective online learning. We first formulate the framework of Multi-Objective Online Convex Optimization, which encompasses a novel multi-objective regret. This regret is built upon a sequence-wise extension of the commonly used discrepancy metric Pareto suboptimality gap in zero-order multi-objective bandits. We then derive an equivalent form of the regret, making it amenable to be optimized via first-order iterative methods. To motivate the algorithm design, we give an explicit example in which equipping OMD with the vanilla min-norm solver for gradient composition will incur a linear regret, which shows that merely regularizing the iterates, as in single-objective online learning, is not enough to guarantee sublinear regrets in the multi-objective setting. To resolve this issue, we propose a novel min-regularized-norm solver that regularizes the composite weights. Combining min-regularized-norm with OMD results in the Doubly Regularized Online Mirror Multiple Descent algorithm. We further derive the multi-objective regret bound for the proposed algorithm, which matches the optimal bound in the single-objective setting. Extensive experiments on real-world datasets verify the effectiveness of the proposed algorithm.

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