# Questions tagged [sutton-barto]

For questions related to the book "Reinforcement Learning: An Introduction" (by Andrew Barto and Richard S. Sutton).

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### Why do we have two similar action selection strategies for UCB1?

In the literature, there are at least two action selection strategies associated with the UCB1's action selection strategy/policy. For example, in the paper Algorithms for the multi-armed bandit ...
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### Why is the fraction of time spent in state $s$, $\mu(s)$, not in the update rule of the parameters?

I am reading "Reinforcement Learning: An Introduction (2nd edition)" authored by Sutton and Barto. In Section 9, On-policy prediction with approximation, it first gives the mean squared ...
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### How to prove variance infinite of monte carlo ordinary importance sampling estimator

In example 5.5 of Sutton and Barto's book for proving infinite variance of first visit monte carlo ordinary importance sampling estimator, $\mathbb{E}[(\Pi_t\frac{\pi(A_t|S_t)}{b(A_t|S_t)}G_0)^2]$ is ...
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### Value Iteration failing to converge to optimal value function in Sutton-Barto's Gambler problem

In Example 4.3:Gambler's Problem of Sutton and Barto's book whose code is given here. In this code the value function array is initialized as np.zeros(states) where ...
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### Doubt regarding the proof of convergence of $\epsilon$ soft policies without exploring starts

In page 125 of Sutton and Barto (second last paragraph) the proof for equality of $v_{\pi}$ and $v_*$ for $\epsilon$ soft policies is given. But I could not understand the statement explaining the ...
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### What does the figure “Blackjack Value Function…” from Sutton represent?

I came across this graph in David Silver's youtube lecture and Sutton's book on reinforcement learning. Can anyone help me understand the graph? From the graph, for 10000 episodes what i see is ...
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### On-policy state distribution for episodic tasks on Sutton & Barto, page 199

In Sutton & Barto's "Reinforcement Learning: An Introduction", 2nd edition, page 199, they describe the on-policy distribution for episodic tasks in the following box: I don't understand how this ...
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### Counterexamples to the reward hypothesis

On Sutton and Barto's RL book, the reward hypothesis is stated as that all of what we mean by goals and purposes can be well thought of as the maximization of the expected value of the cumulative ...
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### Hashed Tile Coding vs Regular Tile Coding

In the book "Reinforcement Learning: An Introduction" (2018) Sutton and Barto explain at page 221 a form of tile coding using hashing, to reduce memory consumption. I have two questions about that: ...
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### Possible inconsistency in the Policy Improvement equation

I came across this formula in Sutton And Barto: RL an Intro (2nd Edition) equation number 4.7 (page number 78). If $\pi$ and $\pi'$ are deterministic policies and $q_\pi(s, \pi'(s)) \geq v_\pi(s)$ ...
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### How is the policy gradient calculated in REINFORCE?

Reading Sutton and Barto, I see the following in describing policy gradients: How is the gradient calculated with respect to an action (taken at time t)? I've read implementations of the algorithm, ...
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### What is the meaning of Model(s, a) in the prioritized sweeping algorithm?

I'm reading the book "Reinforcement Learning: An Introduction" (by Andrew Barto and Richard S. Sutton). The authors provide the pseudocode of the prioritized sweeping algorithm, but I do not know ...
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### How do we prove the n-step return error reduction property?

In section 7.1 (about the n-step bootstrapping) of the book Reinforcement Learning: An Introduction (2nd edition), by Andrew Barto and Richard S. Sutton, the authors write about what they call the "n-...
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### Understanding the notation in the definition of the expected reward

I am new to RL and I am trying to work through the book Reinforcement Learning: An Introduction I (Sutton & Barto, 2018). In chapter 3 on Finite Markov Decision Processes, the authors write the ...
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### Is my interpretation of the return correct?

Sutton and Barto 2018 define the discounted return $G_t$ the following way (p 55): Is my interpretation correct? Or should all "1" be in the same column?