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Why does one-step TD strengthen only the last action of the sequence of actions that led to the high reward, while n-step TD the last n actions?

In the caption of figure 7.4 (p. 147) of Sutton & Barto's book (2nd edition), it's written The one-step method strengthens only the last action of the sequence of actions that led to the high ...
user529295's user avatar
6 votes
2 answers
874 views

How can the policy iteration algorithm be model-free if it uses the transition probabilities?

I'm actually trying to understand the policy iteration in the context of RL. I read an article presenting it and, at some point, a pseudo-code of the algorithm is given : What I can't understand is ...
Samuel Beaussant's user avatar
4 votes
1 answer
407 views

Is the minimax algorithm model-based?

Trying to get my head around model-free and model-based algorithms in RL. In my research, I've seen the search trees created via the minimax algorithm. I presume these trees can only be created with a ...
mason7663's user avatar
  • 633
5 votes
1 answer
2k views

Are model-free and off-policy algorithms the same?

In respect of RL, is model-free and off-policy the same thing, just different terminology? If not, what are the differences? I've read that the policy can be thought of as 'the brain', or decision ...
mason7663's user avatar
  • 633
5 votes
1 answer
2k views

Why are model-based methods more sample efficient than model-free methods?

Why do model-based methods use fewer samples than model-free methods? Here, I'm specifically referring to model-based methods in which we have to learn a policy and model. I can only think of two ...
Maybe's user avatar
  • 471
2 votes
1 answer
1k views

What is the relation between Monte Carlo and model-free algorithms?

Monte Carlo (MC) methods are methods that use some form of randomness or sampling. For example, we can use an MC method to approximate the area of a circle inside a square: we generate random 2D ...
nbro's user avatar
  • 41.4k
92 votes
6 answers
103k views

What's the difference between model-free and model-based reinforcement learning?

What's the difference between model-free and model-based reinforcement learning? It seems to me that any model-free learner, learning through trial and error, could be reframed as model-based. In ...
mynameisvinn's user avatar
  • 1,021