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Статья

On the Stability of Random Matrix Product with Markovian Noise: Application to Linear Stochastic Approximation and TD Learning

Moulines E., Durmus A., Naumov A., Samsonov S., Wai H.

This paper studies the exponential stability of  random matrix products driven by a general (possibly unbounded) state space Markov chain. It is a  cornerstone in the analysis of stochastic algorithms in machine learning (e.g. for parameter tracking in online-learning or reinforcement learning). The existing results impose strong  conditions  such as uniform boundedness of the matrix-valued functions and uniform ergodicity of the Markov chains.  Our main contribution is an exponential stability result for the p-th moment of random matrix product, provided  that (i) the underlying Markov chain satisfies a super-Lyapunov drift condition, (ii) the growth of the matrix-valued functions is controlled by an appropriately defined function (related to the drift condition). Using this result, we give finite-time p-th moment bounds for constant and decreasing stepsize linear stochastic approximation schemes with Markovian noise on general state space. We illustrate these findings for linear value-function estimation in reinforcement learning. We provide finite-time p-th moment bound for various members of temporal difference (TD) family of algorithms.