# Tag Info

23

The notation I'll be using is from two different lectures by David Silver and is also informed by these slides. The expected Bellman equation is $$v_\pi(s) = \sum_{a\in \cal{A}} \pi(a|s) \left(\cal{R}_s^a + \gamma\sum_{s' \in \cal{S}} \cal{P}_{ss'}^a v_\pi(s')\right) \tag 1$$ If we let \cal{P}_{ss'}^\pi = \sum\limits_{a \in \cal{A}} \pi(a|s)\cal{P}_{ss'}^a ...

2

There's not much to derive here it's simply a definition of Bellman operator, it comes from Bellman equation. If you're wondering why $$Q^{\pi} = (I - \gamma P^{\pi})^{-1}r \tag{1}$$ they state that $Q^{\pi}$ is a fixed point which means if you apply Bellman operator to it you get the same value T^{\pi}(Q^{\pi}) = ...

2

The inequality \begin{align} \left\|T^{\pi} V-T^{\pi} U\right\|_{\infty} & \leq \gamma\|V-U\|_{\infty} \label{1}\tag{1}, \end{align} where $U$ and $V$ are two value functions, follows from the definition of Bellman policy operator (at slide 16) \begin{align} T^{\pi} V(s) &\triangleq R(s, a)+\gamma \sum_{s^{\prime}} \operatorname{Pr}\left(s^{\prime}...

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