title: What is the difference between value iteration and policy iteration?
body: <p>In reinforcement learning, what is the difference between <em>policy iteration</em> and <em>value iteration</em>? </p>
  
  <p>As much as I understand, in value iteration, you use the Bellman equation to solve for the optimal policy, whereas, in policy iteration, you randomly select a policy π, and find the reward of that policy. </p>
  
  <p>My doubt is that if you are selecting a random policy π in PI, how is it guaranteed to be the optimal policy, even if we are choosing several random policies.</p>