Questions tagged [reinforcement-learning]

For questions related to learning controlled by external positive reinforcement or negative feedback signal or both, where learning and use of what has been thus far learned occur concurrently.

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6 views

Are the final states not being updated in this $n$-step Q-Learning algorithm?

I am reading this paper and in algorithm 3 they describe an $n$-step Q-Learning algorithm. Below is the pseudo-code. $n$-step q-learning"> From this pseudo-code, it looks as though the final tuples ...
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1answer
22 views

What is meant by the rank of the scoring function here?

I've been reading this paper on Knowledge Graph Reasoning for Explainable Recommendation lately, and I don't understand a particular section: Specifically, the scoring function $f((r,e)|u)$ maps ...
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1answer
27 views

Is there any programming practice website for beginners in Reinforcement Learning [closed]

I am doing an online course on Reinforcement Learning from university of Alberta. It focus too much on theory. I am engineering and I am interested towards applying RL to my applications directly. ...
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23 views

Calculating the advantage 'gain' of actions in model-free reinforcement learning

I have a simple question about model-free reinforcement. In a model I'm writing about, I want to know the value 'gain' we'd get for executing an action, relative to the current state. That is, what ...
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Learning to select a subgraph via reinforcement learning?

I have the following problem: I am given a graph with a lot (>30000) nodes. Nodes are associated with a low (<10)-dimensional feature vector, and edges are associated with a low (<10)-...
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1answer
24 views

Can the agent wait until the end of the episode to determine the reward in SARSA?

From Sutton and Barto's book Reinforcement Learning (Adaptive Computation and Machine Learning series) (p. 99), the following definition for first-visit MC prediction, for estimating $V \sim V_\pi$ is ...
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1answer
67 views

What is a RAM state in the gym's breakout-ram environment?

I have encountered the gym environment and decided to create AI that plays breakout. Here is the link: https://gym.openai.com/envs/Breakout-ram-v0/. The documentation says that the state is ...
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1answer
51 views

Can Q-learning converge even if it doesn't explore all state-action pairs?

My understanding of Q-learning is that it essentially builds a dictionary of state-action pairs, so as to maximize the Markovian (i.e., step-wise, history-agnostic?) reward. This incremental update of ...
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28 views

Actor-Critic implementation not learning

I've implemented a vanilla actor-critic and have run into a wall. My model does not seem to be learning the optimal policy. The red graph below shows its performance in cartpole, where the algorithm ...
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28 views

How to prevent deep Q-learning algorithms to overfit?

I have recently solved the Cartpole problem using double deep Q-learning. When I saw how the agent was doing, it used to go right every time, never left, and it did similar actions all the time. Did ...
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1answer
33 views

If deep Q-learning starts to choose only one action, is this a sign that the algorithm diverged?

I'm working on a deep q-learning model in an infinite horizon problem, with a continous state space and 3 possible actions. I'm using a neural network to approximate the action-value function. ...
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1answer
52 views

Is the distribution of state-action pairs from sample based planning accurate for small experience sets?

From the David Silver's lecture 8: Integrating Learning and Planning - based on Sutton and Barto - he talks about using sample-based planning to use our model to take a sample of a state and then use ...
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1answer
30 views

Why is learning $s'$ from $s,a$ a kernel density estimation problem but learning $r$ from $s,a$ is just regression?

In David Silver's 8th lecture he talks about model learning and says that learning $r$ from $s,a$ is a regression problem whereas learning $s'$ from $s,a$ is a kernel density estimation. His ...
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2answers
295 views

Is there any good reference for double deep Q-learning?

I am new in reinforcement learning, but I already know deep Q-learning and Q-learning. Now, I want to learn about double deep Q-learning. Do you know any good references for double deep Q-learning? ...
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1answer
22 views

What are finite horizon look-ahead policies in reinforcement learning?

I was reading the paper How to Combine Tree-Search Methods in Reinforcement Learning published in AAAI Conference 2019. It starts with the sentence Finite-horizon lookahead policies are abundantly ...
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1answer
37 views

How should I decay $\epsilon$ in Q-learning?

How should I decay the $\epsilon$ in Q-learning? Currently, I am decaying epsilon as follows. I initialize $\epsilon$ to be 1, then, after every episode, I multiply it by some $C$ (let it be $0.999$)...
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35 views

Understanding the role of the target network in this DQN algorithm

I've found online this interesting algorithm: From what I understand reading this algorithm, I can't figure out why I should "perform the opposite action" and consequently storing that second ...
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1answer
112 views

Is this proof of $\epsilon$-greedy policy improvement correct?

The text book being referred to, in this question is "Reinforcement Learning: An introduction" by Richard Sutton and Andrew Barto (second edition, 2018). For your convenience, I have enclosed the ...
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2answers
114 views

Is there any good source for when the pole actually starts all the way at the bottom, in the cartpole problem?

There are a lot of examples of balancing a pole (see image below) using reinforcement learning, but I find that almost all examples start close to the upright position. Is there any good source (or ...
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36 views

Using a model-based method to build an accurate day trading environment model

There are several different angles we can classify Reinforcement Learning methods from. We can distinguish three main aspects : Value-based and policy-based On-policy and off-policy Model-free and ...
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18 views

Can you find another reason for sample inefficiency of model-free on-policy Deep Reinforcement Learning?

The following mindmap gives an overview of multiple reasons for sample inefficiency. The list is definitely not complete. Can you see another reason not mentioned so far? Some related links: ...
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19 views

Why do we also need to normalize the action's values on continuous action spaces?

I was reading here tips & tricks for training in DRL and I noticed the following: always normalize your observation space when you can, i.e., when you know the boundaries normalize your ...
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35 views

Can weighted importance sampling be applied to off-policy evaluation for continuous state space MDPs?

Can weighted importance sampling (WIS) and importance sampling (IS) be applied to off-policy evaluation for continuous state spaces MDPs? Given that I have trajectories of $(s_t,a_t)$ pairs and the ...
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1answer
68 views

How do I convert an MDP with the reward function in the form $R(s,a,s')$ to and an MDP with a reward function in the form $R(s,a)$?

The AIMA book has an exercise about showing that an MDP with rewards of the form $r(s, a, s')$ can be converted to an MDP with rewards $r(s, a)$, and to an MDP with rewards $r(s)$ with equivalent ...
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1answer
93 views

Handle non-existing states in q-learning

I am using Q-learning to solve an engineering problem. The objective is to generate a Q-table associating state to Q-values. I created a State vector ...
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39 views

How to create MDP (RL) environment for custom problem?

I am trying to solve the scheduling of resources problems using RL/GA. I am stuck on how to create a custom environment for the problem and actually carry out some tests. I read and implemented Q-...
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1answer
49 views

How would researchers determine the best deep learning model if every run of the code yields different results?

There are many factors that cause the results of ML models to be different for every run of the same piece of code. One factor could be different initialization of weights in the neural network. ...
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2answers
174 views

Why is the policy not a part of the MDP definition?

I'm reading an article on reinforcement learning, and I don't understand why the agent's policy $\pi$ is not part of definition of Markov Decision process(MDP): Bu, Lucian, Robert Babu, and ...
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1answer
34 views

What is the relation between multi-agent learning and reinforcement learning?

What is the relation between multi-agent learning and reinforcement learning? Is one a sub-field of the other? For instance, would it make sense to state that your research interest are multi-agent ...
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0answers
28 views

How can I perform policy update in python? [closed]

I'm using Python and tensorflow to implement a Deep Q-learning with experience replay in a continous action and state spaces and I have used two neural networks to approximate both the policy function ...
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1answer
83 views

What made your DDPG implementation on your environment work?

I am working on scheduling problem that has inherent randomness. The dimensions of action and state spaces are 1 and 5 respectively. I am using DDPG, but it seems extremely unstable, and so far it ...
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42 views

Convergence of a delayed policy update Q-learning

I thought about an algorithm that twists the standard Q-learning slightly, but I am not sure whether convergence to the optimal Q-value could be guaranteed. The algorithm starts with an initial ...
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31 views

Policy Gradient on Tic-Tac-Toe not working

I wanted to implement the Policy Gradient on Tic-Tac-Toe. I tried to use the code that worked for any environment like CartPole-v0 to my Tic-Tac-To game. But it is not learning. There are no errors. ...
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1answer
26 views

In vanilla policy gradient is the baseline lagging behind the policy?

Vanilla policy gradient algorithm (using baseline to reduce variance) acc to here (page 16) Initialize policy parameter θ, baseline b for iteration=1, 2, . . . do Collect a set of ...
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Pytorch XLA to solve the spawn problems in a Colab Env [migrated]

It seems that torch.multiprocessing.set_start_method("spawn") can't be used in an Colab Env. Only 'fork' is allowed. I have implemented A3C - data parallelism to ...
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1answer
38 views

Can we increase the speed of training a reinforcement learning algorithm?

I am new in reinforcement learning. I started reading the PyTorch's documentation about the cart pole control. Whenever an agent fails, they restart the environment. When I run the code, the time in ...
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2answers
57 views

What is the intuition behind importance sampling for off-policy value evaluation?

The technique for off-policy value evaluation comes from importance sampling, which states that $$E_{x \sim q}[f(x)] \approx \frac{1}{n}\sum_{i=1}^n f(x_i)\frac{q(x_i)}{p(x_i)},$$ where $x_i$ is ...
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1answer
24 views

Do we have two Q-learning update formulas?

I have seen two deep Q-learning formulas: $$Q\left(S_{t}, A_{t}\right) \leftarrow Q\left(S_{t}, A_{t}\right)+\alpha\left[R_{t+1}+\gamma \max _{a} Q\left(S_{t+1}, a\right)-Q\left(S_{t}, A_{t}\right)\...
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1answer
34 views

Learning policy where action involves discrete and continuous parameters

Typically it seems like reinforcement learning involves learning over either a discrete or a continuous action space. An example might be choosing from a set of pre-defined game actions in Gym Retro ...
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1answer
62 views

What are the conditions of convergence of temporal-difference learning?

In reinforcement learning, temporal difference seem to update the value function in each new iteration of experience absorbed from the environment. What would be the conditions for temporal-...
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19 views

How can I increase the exploration in the Proximal Policy Optimation algorithm?

How can I increase the exploration in the Proximal Policy Optimation reinforcement learning algorithm? Is there a variable assigned for this purpose? I'm using the stable-baseline implementation: ...
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1answer
60 views

Can deep reinforcement learning algorithms be deterministic in their reproducibility in results?

I ran a deep q learning algorithm (DQN) for $x$ number of epochs and got policy $\pi_1$. I reran the same script for the same $x$ number of epochs and got policy $\pi_2$. I expected $\pi_1 $ and $\...
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2answers
287 views

How can we compute the ratio between the distributions if we don't know one of the distributions?

Here is my understanding of importance sampling. If we have two distributions $p(x)$ and $q(x)$, where we have a way of sampling from $p(x)$ but not from $q(x)$, but we want to compute the expectation ...
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0answers
44 views

How do I set up rewards to account for unmanned aerial vehicle crashes?

I am working on a project to implement a collision avoidance algorithm on a real unmanned aerial vehicle (UAV). I'm interested in understanding the process to set up a negative reward to account for ...
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1answer
28 views

How to add more than 1 agent in one generation with Q Learning

Sometimes the agent learns a bit slow and you want to have multiple agents in one generation. And at each episode you'll draw on the screen only the best of them or all of them. How is that possible? ...
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1answer
33 views

How can I model and solve the Knight Tour problem with reinforcement learning?

I've read about the Knight Tour problem. And I wanted to try to solve it with a reinforcement learning algorithm with OpenAI's gym. So, I want to make a bot that can move on the chess table like the ...
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0answers
29 views

What should the action space for the card game Crib be?

I'm working on creating an environment for a card game, which the agent chooses to discard certain cards in the first phase of the game, and uses the remaining cards to play with. (The game is Crib if ...
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1answer
98 views

Why is update rule of the value function different in policy evaluation and policy iteration?

In the textbook "Reinforcement Learning: An Introduction", by Richard Sutton and Andrew Barto, the pseudo code for Policy Evaluation is given as follows: The update equation for $V(s)$ comes from the ...
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1answer
69 views

How do I derive the gradient with respect to the parameters of the softmax policy?

The gradient of the softmax eligibility trace is given by the following: \begin{align} \nabla_{\theta} \log(\pi_{\theta}(a|s)) &= \phi(s,a) - \mathbb E[\phi (s, \cdot)]\\ &= \phi(s,a) - \sum_{...
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1answer
31 views

If agent chooses an action that the environment can't operate, how should I handle this situation?

I'm building a really simple experiment, letting an agent move from the bottom-left corner to the upper-right corner on a 3x3 squared paper. I plan to use DQN to do this. I'm having trouble handling ...

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