Summary

In this chapter, we introduced the most important RL concepts, focusing on the mathematical structure of an environment as a Markov Decision Process, and on the different kinds of policy and how they can be derived from the expected reward obtained by an agent. In particular, we defined the value of a state as the expected future reward considering a sequence discounted by a factor, γ. In the same way, we introduced the concept of the Q function, which is the value of an action when the agent is in a specific state.

These concepts directly employed the policy iteration algorithm, which is based on a Dynamic Programming approach assuming complete knowledge of the environment. The task is split into two stages; during the first one, the agent evaluates all the states given the current policy, while in the second one, the policy is updated in order to be greedy with respect to the new value function. In this way, the agent is forced to always pick the action that leads to a transition...