High-Order Error Bounds for Markovian LSA with Richardson-Romberg Extrapolation

arXiv:2508.05570 · stat.ML, cs.LG, math.OC, math.ST, stat.TH · Submitted 2025-08-07 · Read on arXiv

stat.ML, cs.LG, math.OC, math.ST, stat.TH

Submitted: 2025-08-07

Updated: 2026-10-12

Comments: Revised the proofs of Proposition 7 and Corollary 6. The dependence on $α$ and $n$ remains unchanged, while the dependence on $τ_{\text{mix}}$ and $p$ is now less favorable

License: http://creativecommons.org/licenses/by/4.0/

The gist: In this paper, we study the bias and high-order error bounds of the Linear Stochastic Approximation (LSA) algorithm with Polyak-Ruppert (PR) averaging under Markovian noise.

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Abstract

In this paper, we study the bias and high-order error bounds of the Linear Stochastic Approximation (LSA) algorithm with Polyak-Ruppert (PR) averaging under Markovian noise. We focus on the version of the algorithm with constant step size α and propose a novel decomposition of the bias via a linearization technique. We analyze the structure of the bias and show that the leading-order term is linear in α and cannot be eliminated by PR averaging. To address this, we apply the Richardson-Romberg (RR) extrapolation procedure, which effectively cancels the leading bias term. We derive high-order moment bounds for the RR iterates and show that the leading error term aligns with the asymptotically optimal covariance matrix of the vanilla averaged LSA iterates.

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