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Finite-Sample Analysis of GTD Algorithms
Proceedings of the 31st Conference on Uncertainty in Artificial Intelligence, PMLR R13:89-98, 2015.
Abstract
In this paper, we conduct the finite-sample analysis of the gradient temporal difference learning (GTD) family of algorithms. Previous analyses of this class of algorithms use ODE techniques to show their asymptotic convergence, and to the best of our knowledge, no finite-sample analysis has been done. Moreover, there has been very little sample complexity analysis for reinforcement learning algorithms in off-policy learning scenarios. In this paper, we formulate the GTD methods as stochastic gradient algorithms w.r.t. a primal-dual saddle-point objective function, and then conduct a saddle-point error bound analysis to obtain finite-sample error bounds of GTD algorithms family. Two revised algorithms are also proposed as projected GTD2 and GTD2-MP for better convergence guarantee and acceleration, respectively. The results of our theoretical analysis show that the GTD algorithms are indeed comparable to the existing LSTD methods in off-policy learning scenarios.