Early Classification of Time Series in Non-Stationary Cost Regimes

Fuente: arXiv
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Autores principales: Renault, Aurélien, Bondu, Alexis, Cornuéjols, Antoine, Lemaire, Vincent
Formato: Preprint
Publicado: 2026
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author Renault, Aurélien
Bondu, Alexis
Cornuéjols, Antoine
Lemaire, Vincent
author_facet Renault, Aurélien
Bondu, Alexis
Cornuéjols, Antoine
Lemaire, Vincent
contents Early Classification of Time Series (ECTS) addresses decision-making problems in which predictions must be made as early as possible while maintaining high accuracy. Most existing ECTS methods assume that the time-dependent decision costs governing the learning objective are known, fixed, and correctly specified. In practice, however, these costs are often uncertain and may change over time, leading to mismatches between training-time and deployment-time objectives. In this paper, we study ECTS under two practically relevant forms of cost non-stationarity: drift in the balance between misclassification and decision delay costs, and stochastic realizations of decision costs that deviate from the nominal training-time model. To address these challenges, we revisit representative ECTS approaches and adapt them to an online learning setting. Focusing on separable methods, we update only the triggering model during deployment, while keeping the classifier fixed. We propose several online adaptations and baselines, including bandit-based and RL-based approaches, and conduct controlled experiments on synthetic data to systematically evaluate robustness under cost non-stationarity. Our results demonstrate that online learning can effectively improve the robustness of ECTS methods to cost drift, with RL-based strategies exhibiting strong and stable performance across varying cost regimes.
format Preprint
id arxiv_https___arxiv_org_abs_2602_00918
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Early Classification of Time Series in Non-Stationary Cost Regimes
Renault, Aurélien
Bondu, Alexis
Cornuéjols, Antoine
Lemaire, Vincent
Machine Learning
Early Classification of Time Series (ECTS) addresses decision-making problems in which predictions must be made as early as possible while maintaining high accuracy. Most existing ECTS methods assume that the time-dependent decision costs governing the learning objective are known, fixed, and correctly specified. In practice, however, these costs are often uncertain and may change over time, leading to mismatches between training-time and deployment-time objectives. In this paper, we study ECTS under two practically relevant forms of cost non-stationarity: drift in the balance between misclassification and decision delay costs, and stochastic realizations of decision costs that deviate from the nominal training-time model. To address these challenges, we revisit representative ECTS approaches and adapt them to an online learning setting. Focusing on separable methods, we update only the triggering model during deployment, while keeping the classifier fixed. We propose several online adaptations and baselines, including bandit-based and RL-based approaches, and conduct controlled experiments on synthetic data to systematically evaluate robustness under cost non-stationarity. Our results demonstrate that online learning can effectively improve the robustness of ECTS methods to cost drift, with RL-based strategies exhibiting strong and stable performance across varying cost regimes.
title Early Classification of Time Series in Non-Stationary Cost Regimes
topic Machine Learning
url https://arxiv.org/abs/2602.00918