Exercise 4.3 What are the equations analogous to (4.3), (4.4), and (4.5) for the action-value function qπq_\piqπ and its successive approximation by a sequence of functions q0,q1,q2,...q_0, q_1, q_2, . . .q0,q1,q2,...?
According to the result of exercise 3.17, we have:
Qπ(s,a)=∑s′Rs,s′aPss′a+γ∑s′[∑a′Qπ(s′,a′)π(s′,a′)]Ps,s′a
Q_\pi(s,a) = \sum_{s'} R_{s,s'}^a P_{ss'}^a + \gamma \sum_{s'} \bigl[ \sum_{a'} Q_\pi(s',a') \pi(s',a') \bigr] P_{s,s'}^a
Qπ(s,a)=s′∑Rs,s′aPss′a+γs′∑[a′∑Qπ(s′,a′)π(s′,a′)]Ps,s′a
Let QkπQ_k^\piQkπ be the previous estimated value of QπQ_\piQπ and substitute it to the right side of the equation. For the next iteration, Qk+1πQ_{k+1}^\piQk+1π can be:
Qk+1π(s,a)=∑s′Rs,s′aPss′a+γ∑s′[∑a′Qkπ(s′,a′)π(s′,a′)]Ps,s′a
Q_{k+1}^\pi(s,a) = \sum_{s'} R_{s,s'}^a P_{ss'}^a + \gamma \sum_{s'} \bigl[ \sum_{a'} Q_k^\pi(s',a') \pi(s',a') \bigr] P_{s,s'}^a
Qk+1π(s,a)=s′∑Rs,s′aPss′a+γs′∑[a′∑Qkπ(s′,a′)π(s′,a′)]Ps,s′a