Distributionally-Constrained Adversaries in Online Learning

Fuente: arXiv
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Auteurs principaux: Blanchard, Moïse, Kpotufe, Samory
Format: Preprint
Publié: 2025
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author Blanchard, Moïse
Kpotufe, Samory
author_facet Blanchard, Moïse
Kpotufe, Samory
contents There has been much recent interest in understanding the continuum from adversarial to stochastic settings in online learning, with various frameworks including smoothed settings proposed to bridge this gap. We consider the more general and flexible framework of distributionally constrained adversaries in which instances are drawn from distributions chosen by an adversary within some constrained distribution class [RST11]. Compared to smoothed analysis, we consider general distributional classes which allows for a fine-grained understanding of learning settings between fully stochastic and fully adversarial for which a learner can achieve non-trivial regret. We give a characterization for which distribution classes are learnable in this context against both oblivious and adaptive adversaries, providing insights into the types of interplay between the function class and distributional constraints on adversaries that enable learnability. In particular, our results recover and generalize learnability for known smoothed settings. Further, we show that for several natural function classes including linear classifiers, learning can be achieved without any prior knowledge of the distribution class -- in other words, a learner can simultaneously compete against any constrained adversary within learnable distribution classes.
format Preprint
id arxiv_https___arxiv_org_abs_2506_10293
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Distributionally-Constrained Adversaries in Online Learning
Blanchard, Moïse
Kpotufe, Samory
Machine Learning
Statistics Theory
There has been much recent interest in understanding the continuum from adversarial to stochastic settings in online learning, with various frameworks including smoothed settings proposed to bridge this gap. We consider the more general and flexible framework of distributionally constrained adversaries in which instances are drawn from distributions chosen by an adversary within some constrained distribution class [RST11]. Compared to smoothed analysis, we consider general distributional classes which allows for a fine-grained understanding of learning settings between fully stochastic and fully adversarial for which a learner can achieve non-trivial regret. We give a characterization for which distribution classes are learnable in this context against both oblivious and adaptive adversaries, providing insights into the types of interplay between the function class and distributional constraints on adversaries that enable learnability. In particular, our results recover and generalize learnability for known smoothed settings. Further, we show that for several natural function classes including linear classifiers, learning can be achieved without any prior knowledge of the distribution class -- in other words, a learner can simultaneously compete against any constrained adversary within learnable distribution classes.
title Distributionally-Constrained Adversaries in Online Learning
topic Machine Learning
Statistics Theory
url https://arxiv.org/abs/2506.10293