Logarithmic Regret and Polynomial Scaling in Online Multi-step-ahead Prediction

Fuente: arXiv
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Autores principales: Qian, Jiachen, Zheng, Yang
Formato: Preprint
Publicado: 2025
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author Qian, Jiachen
Zheng, Yang
author_facet Qian, Jiachen
Zheng, Yang
contents This letter studies the problem of online multi-step-ahead prediction for unknown linear stochastic systems. Using conditional distribution theory, we derive an optimal parameterization of the prediction policy as a linear function of future inputs, past inputs, and past outputs. Based on this characterization, we propose an online least-squares algorithm to learn the policy and analyze its regret relative to the optimal model-based predictor. We show that the online algorithm achieves logarithmic regret with respect to the optimal Kalman filter in the multi-step setting. Furthermore, with new proof techniques, we establish an almost-sure regret bound that does not rely on fixed failure probabilities for sufficiently large horizons $N$. Finally, our analysis also reveals that, while the regret remains logarithmic in $N$, its constant factor grows polynomially with the prediction horizon $H$, with the polynomial order set by the largest Jordan block of eigenvalue 1 in the system matrix.
format Preprint
id arxiv_https___arxiv_org_abs_2511_12467
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Logarithmic Regret and Polynomial Scaling in Online Multi-step-ahead Prediction
Qian, Jiachen
Zheng, Yang
Machine Learning
Systems and Control
This letter studies the problem of online multi-step-ahead prediction for unknown linear stochastic systems. Using conditional distribution theory, we derive an optimal parameterization of the prediction policy as a linear function of future inputs, past inputs, and past outputs. Based on this characterization, we propose an online least-squares algorithm to learn the policy and analyze its regret relative to the optimal model-based predictor. We show that the online algorithm achieves logarithmic regret with respect to the optimal Kalman filter in the multi-step setting. Furthermore, with new proof techniques, we establish an almost-sure regret bound that does not rely on fixed failure probabilities for sufficiently large horizons $N$. Finally, our analysis also reveals that, while the regret remains logarithmic in $N$, its constant factor grows polynomially with the prediction horizon $H$, with the polynomial order set by the largest Jordan block of eigenvalue 1 in the system matrix.
title Logarithmic Regret and Polynomial Scaling in Online Multi-step-ahead Prediction
topic Machine Learning
Systems and Control
url https://arxiv.org/abs/2511.12467