Concentration bounds for two time scale stochastic approximation

Abstract

Viewing a two time scale stochastic approximation scheme as a noisy discretization of a singularly perturbed differential equation, we obtain a concentration bound for its iterates that captures its behavior with quantifiable high probability. This uses Alekseev's nonlinear variation of constants formula and a martingale concentration inequality and extends the corresponding results for single time scale stochastic approximation.

8 pages