Reinforcement Learning as Classification: Leveraging Modern Classifiers

The basic tools of machine learning appear in the inner loop of most reinforcement learning algorithms, typically in the form of Monte Carlo methods or function approximation techniques. To a large extent, however, current reinforcement learning algorithms draw upon machine learning techniques that are at least ten years old and, with a few exceptions, very little has been done to exploit recent advances in classification learning for the purposes of reinforcement learning. We use a variant of approximate policy iteration based on rollouts that allows us to use a pure classification learner, such as a support vector machine (SVM), in the inner loop of the algorithm. We argue that the use of SVMs, particularly in combination with the kernel trick, can make it easier to apply reinforcement learning as an "out-of-the-box" technique, without extensive feature engineering. Our approach opens the door to modern classification methods, but does not preclude the use of classical methods. We present experimental results in the pendulum balancing and bicycle riding domains using both SVMs and neural networks for classifiers.