Sparse gradient-based direct policy search

Reinforcement learning is challenging if state and action spaces are continuous. The discretization of state and action spaces and real-time adaptation of the discretization are critical issues in reinforcement learning problems. In our contribution we consider the adaptive discretization, and introduce a sparse gradient-based direct policy search method. We address the issue of efficient states/actions selection in the gradient-based direct policy search based on imposing sparsity through the L 1 penalty term. We propose to start learning with a fine discretization of state space and to induce sparsity via the L 1 norm. We compare the proposed approach to state-of-the art methods, such as progressive widening Q-learning which updates the discretization of the states adaptively, and to classic as well as sparse Q-learning with linear function approximation. We demonstrate by our experiments on standard reinforcement learning challenges that the proposed approach is efficient.