arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2202.04690stat.MLcs.LG
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平滑的在线学习就像统计学习一样简单

Smoothed Online Learning is as Easy as Statistical Learning

MIT(麻省理工学院)

Adam Block, Yuval Dagan, Noah Golowich, Alexander Rakhlin

摘要:

大部分现代学习理论都分为两种模式:经典的离线设置,数据独立到达,在线设置,数据以对抗方式到达。虽然前一种模型通常在计算和统计上都易于处理,但后者不需要分布假设。为了实现两全其美,以前的工作提出了平滑在线设置,其中每个样本都是从一个相反选择的分布中提取的,该分布是平滑的,即,它有一个有界密度相对于一个固定的支配措施。我们提供了严格的界限上的极小极大遗憾学习的非参数函数类,与近最佳的依赖于地平线和平滑参数。此外,我们提供了第一个甲骨文高效,无悔的算法在这种情况下。特别是,我们提出了一个预言高效的不当算法,其遗憾实现最佳依赖的地平线和一个适当的算法,只需要一个单一的预言调用每轮的遗憾具有最佳的地平线依赖的分类设置,一般是次线性的。这两种算法对对手的平滑参数的依赖性指数比极大极小率差。然后,我们证明了任何适当的学习算法,它匹配的甲骨文有效的上限到多项式因子的甲骨文复杂性的下限,从而证明了在平滑的在线学习的计算差距的存在。最后,我们将我们的研究结果的上下文强盗设置表明,如果一个函数类是可学习的经典设置,然后有一个预言机的高效,没有遗憾的算法上下文强盗的情况下,上下文顺利到达。

英文摘要:

Much of modern learning theory has been split between two regimes: the classical offline setting, where data arrive independently, and the online setting, where data arrive adversarially. While the former model is often both computationally and statistically tractable, the latter requires no distributional assumptions. In an attempt to achieve the best of both worlds, previous work proposed the smooth online setting where each sample is drawn from an adversarially chosen distribution, which is smooth, i.e., it has a bounded density with respect to a fixed dominating measure. We provide tight bounds on the minimax regret of learning a nonparametric function class, with nearly optimal dependence on both the horizon and smoothness parameters. Furthermore, we provide the first oracle-efficient, no-regret algorithms in this setting. In particular, we propose an oracle-efficient improper algorithm whose regret achieves optimal dependence on the horizon and a proper algorithm requiring only a single oracle call per round whose regret has the optimal horizon dependence in the classification setting and is sublinear in general. Both algorithms have exponentially worse dependence on the smoothness parameter of the adversary than the minimax rate. We then prove a lower bound on the oracle complexity of any proper learning algorithm, which matches the oracle-efficient upper bounds up to a polynomial factor, thus demonstrating the existence of a statistical-computational gap in smooth online learning. Finally, we apply our results to the contextual bandit setting to show that if a function class is learnable in the classical setting, then there is an oracle-efficient, no-regret algorithm for contextual bandits in the case that contexts arrive in a smooth manner.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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