在线优化多个子模函数,提升选择目标的平均收益
Online Two-Stage Submodular Maximization
- 在线逐个揭示子模函数,动态优化候选集以提升平均性能
- 在一般拟阵约束下实现(1-1/e)²的次线性后悔率,均匀拟阵下更优
- 适用于影响力传播、数据摘要等场景,适合在线决策应用
给定一组单调子模函数,两阶段子模最大化(2SSM)的目标是限制基础集,使得从集合中随机选取的任一目标函数在受限集上优化时,其最大值的平均表现尽可能高。本文提出在线两阶段子模最大化(O2SSM)问题,其中子模目标函数以在线方式逐步揭示。针对加权阈值势函数这一重要且广泛的单调子模函数类(包括影响力传播、数据摘要和设施选址等),设计了一种算法,在一般拟阵约束下实现(1 - 1/e)²的次线性后悔率,在秩为k的均匀拟阵情况下达到(1 - 1/e)(1-e^{-k}k^k/k!)的后悔率;后者也构成了离线2SSM问题的最先进界。通过真实数据集实验验证了该在线算法的有效性。
原文摘要 · Abstract (English)
Given a collection of monotone submodular functions, the goal of Two-Stage Submodular Maximization (2SSM) [Balkanski et al., 2016] is to restrict the ground set so an objective selected u.a.r. from the collection attains a high maximal value, on average, when optimized over the restricted ground set. We introduce the Online Two-Stage Submodular Maximization (O2SSM) problem, in which the submodular objectives are revealed in an online fashion. We study this problem for weighted threshold potential functions, a large and important subclass of monotone submodular functions that includes influence maximization, data summarization, and facility location, to name a few. We design an algorithm that achieves sublinear $(1 - 1/e)^2$-regret under general matroid constraints and $(1 - 1/e)(1-e^{-k}k^k/k!)$-regret in the case of uniform matroids of rank $k$; the latter also yields a state-of-the-art bound for the (offline) 2SSM problem. We empirically validate the performance of our online algorithm with experiments on real datasets.
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