Questions tagged [q-learning]

For questions related to the Q-learning algorithm, which is a model-free and temporal-difference reinforcement learning algorithm that attempts to approximate the Q function, which is a function that, given a state s and an action a, returns a real number that represents the return (or value) of state s when action a is taken from s. Q-learning was introduced in the PhD thesis "Learning from Delayed Rewards" (1989) by Watkins.

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3
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1answer
102 views

Why is the reward function $\text{reward} = 1/{(\text{cost}+1)^2}$ better than $\text{reward} =1/(\text{cost}+1)$?

I have implemented a simple Q-learning algorithm to minimize a cost function by setting the reward to the inverse of the cost of the action taken by the agent. The algorithm converges nicely, but ...
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1answer
65 views

Is it possible to prove that the target policy is better than the behavioural policy based on learned Q values?

I have retrospective data for a sort of "behaviour policy" which I will use to train a deep q network to learn a target greedy policy. After learning the Q values for this target policy, can we make ...
10
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1answer
578 views

Are Q-learning and SARSA the same when action selection is greedy?

I'm currently studying reinforcement learning and I'm having difficulties with question 6.12 in Sutton and Barto's book. Suppose action selection is greedy. Is Q-learning then exactly the same ...
1
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1answer
78 views

Q table not converging for an arbitrary experiment

This is an experiment in order to understand the working of Q table and Q learning. I have the states as states = [0,1,2,3] I have an arbitrary value for each ...
3
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1answer
91 views

Does Q Learning learn from an opponent playing random moves?

I've created a Q Learning algorithm to play Connect Four against an opponent who just chooses a random free column. My Q Agent is currently only winning about 0.49 games on average (30,000 episodes). ...
1
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1answer
37 views

Applying Eligibility Traces to Q-Learning algorithm does not improve results (And might not function well)

I am trying to apply Eligibility Traces to a currently working Q-Learning algorithm. The reference code for the Q-Learning algorithm was taken from this great blog ...
1
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1answer
39 views

Should I just use exploitation after I have trained the Q agent?

When using a trained Q-learning algorithm in an actual game, would I just use exploitation and no longer use exploration? Should I use exploration only during the training phase?
2
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1answer
60 views

Adversarial Q Learning should use the same Q Table?

I'm creating a RF Q-Learning agent for a two player fully-observable board game and wondered, if I was to train the Q Table using adversarial training, should I let both 'players' use, and update, the ...
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0answers
37 views

Is Q-Learning suitable for time-dependent spaces?

Many Q-learning techniques have been developed to capture discrete state(observation), actions like a robot in a grid world, and even continuous (state or action) spaces. But I am wondering how we can ...
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0answers
20 views

Why is expected sarsa algorithm an off-policy learning? [duplicate]

I am not able to understand why expected sarsa algorithm is an off-policy learning method? How is it that behaviour and target policies can be different? Also please tell under what situation and ...
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0answers
31 views

Why are Dueling Q Networks not used more often to approximate Q-values in reinforcement learning algorithms?

I've just learned about Dueling Network Architectures to estimate $Q$-values and am wondering why this architecture is not used more often in deep RL algorithms? DDPG and TD3 estimate the $Q$-function ...
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3answers
1k views

What is the target Q-value in DQNs?

I understand that in DQNs, the loss is measured by taking the MSE of outputted Q-values and target Q-values. What does the target Q-values represent? And how is it obtained/calculated by the DQN?
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0answers
30 views

Relationship between the reward rate and the sampled reward in a Semi-Markov Decision Process

In the paper: Reinforcement learning methods for continuous-time Markov decision problems, the authors provide the following update rule for the Q-learning algorithm, when applied to Semi-Markov ...
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2answers
193 views

Is my understanding of the value function, Q function, policy, reward and return correct?

I'm a beginner in the RL field, and I would like to check that my understanding of certain RL concepts. Value function: How good it is to be in a state S following policy π. ...
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2answers
56 views

Why does the policy $\pi$ affect the Q value?

From my understanding, the policy $\pi$ is basically how the agent acts (i.e. the actions it will take in each state). However, I am confused about the Q value and how it is "affected" by a policy. ...
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2answers
288 views

Is the Q value the same as the state-action pair value?

Am I right to say that the Q value of a particular state and action is the same as the state-action pair value of that same state and action?
2
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2answers
350 views

How does Monte Carlo Exploring Starts work?

I'm having trouble understanding the 5th step in the flowchart. For the 5th step, the 'update the Q function by taking the average of returns' is confusing. From what I understand, the Q function ...
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0answers
38 views

How are n-dimensional vectors state vectors represented in Q-learning?

Using this code: ...
4
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1answer
137 views

Are Q values estimated from a DQN different from a duelling DQN with the same number of layers and filters?

I am confused about the Q values of a duelling deep Q network (DQN). As far as I know, duelling DQNs have 2 outputs Advantage: how good it is to be in a particular state $s$ Value: the advantage of ...
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1answer
291 views

Can this be a possible deep q learning pseudocode?

I am not using replay here. Can this be a possible deep q learning pseudocode? ...
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0answers
94 views

Do RNN solves the need for LSTM and/or multiple states in Deep Q-Learning?

Introduction I am trying to setup a Deep Q-Learning agent. I have looked that the papers Playing Atari with Deep Reinforcement Learning as well as Deep Recurrent Q-Learning for Partially Observable ...
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2answers
82 views

Non-Neural Network algorithms for large state space in zero sum games

I was reading online that tic-tac-toe has a state space of $3^9 = 19,683$. From my basic understanding, this sounds too large to use tabular Q-learning, as the Q table would be huge. Is this correct? ...
2
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0answers
115 views

Whats the correct loss function to use during deep Q-learning (discrete action space)

After playing around with normal Q-learning I have decided to switch to deep Q-learning and I have encountered this problem. As I understand, for a task with discrete action space, where there are 4 ...
5
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2answers
297 views

What are some online courses for deep reinforcement learning?

What are some (good) online courses for deep reinforcement learning? I would like the course to be both programming and theoretical. I really liked David Silver's course, but the course dates from ...
2
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1answer
36 views

How to use convolution neural network in Deep-Q?

I currently have a grid of pixels 20x20. Each pixel can be red green blue or black. So I have one hot-encoded the pixels giving a 20x20x4 array for each screen. For my Deep-Q Network, I have ...
2
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1answer
46 views

Intutitive explanation of why Experience Replay is used in a Deep Q Network?

I understand that Experience Replay is used for data efficiency reasons and to remove correlations in sequences of data. How exactly do these sequences of correlated data affect the performance of the ...
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0answers
56 views

How should I define the state space for this life science problem?

I would like to ask for a piece of advice with regard to Q-learning. I am studying RL and would like to do a basic project applied to life science and calculate the reward. I have been trying to get ...
2
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1answer
194 views

How is the expected value in the loss function of DQN approximated?

In Deep Q Learning the parametrized Q-functions $Q_i$ are optimised by performing gradient descent on the series of loss functions $L_i(\theta_i)= E_{(s,a)\sim p}[(y_i-Q(s,a;\theta_i))^2]$ , where ...
2
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1answer
331 views

Is there an advantage in decaying $\epsilon$ during Q-Learning?

If the agent is following an $\epsilon$-greedy policy derived from Q, is there any advantage to decaying $\epsilon$ even though $\epsilon$ decay is not required for convergence ?
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0answers
47 views

Understanding V- and Q-functions

Assume the existence of a Markov Decision Process consisting of: State space $S$ Action space $A$ Transition model $T: S \times A \times S \to [0,1]$ Reward function $R: S \times A \times S \to \...
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0answers
50 views

Evaluation a policy learned using Q - learning

I have been reading literature on reinforcement learning in healthcare. I am slightly confused between the policy evaluation for both SARSA and Q-learning. To my knowledge, I believe that SARSA is ...
2
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1answer
213 views

Taxi-v3 help. What is meant exactly by convergence of the algo, the highest reward and optimal action for every state?

I started learning about Q table from this blog post Introduction to reinforcement learning and OpenAI Gym, by Justin Francis, which has a line as below - After so many episodes, the algorithm will ...
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0answers
85 views

How to represent a state in a card game environment? (Wizard)

We are attempting to build an AI that manages to play the cardgame Wizard. So far er have a working network (based on the YOLO object-detection) that is abled to detect which cards are played. When ...
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1answer
46 views

Q-learning problem wrong policy

I am coding out a simple 4x4 grid game whereby the agent starts at a particular state and his aim is to reach the terminal state. The agent is supposed to avoid traps along the way and reach the end ...
2
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1answer
48 views

Do we need an explicit policy to sample $A'$ in order to compute the target in SARSA or Q-learning?

I would much appreciate if you could point me in the right direction regarding this question about targets for SARSA and Q-learning (notation: $S$ is the current state, $A$ is the current action, $R$ ...
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1answer
2k views

What is the difference between the $\epsilon$-greedy and softmax policies?

Could someone explain to me which is the key difference between the $\epsilon$-greedy policy and the softmax policy? In particular, in the contest of SARSA and Q-Learning algorithms. I understood the ...
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0answers
190 views

Expected SARSA, SARSA and Q-learning

I would much appreciate if you could point me in the right direction regarding this question about targets for approximate ...
3
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1answer
131 views

Why Monte Carlo epsilon-soft approach cannot compute $\max Q(s,a)$?

I am new to Reinforcement learning and am currently reading up on the estimation of Q $\pi(s, a)$ values using MC epsilon-soft approach and chanced upon this algorithm. The link to the algorithm is ...
4
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1answer
328 views

How can a DQN backpropagate its loss?

I'm currently trying to take the next step in deep learning. I managed so far to write my own basic feed-forward network in python without any frameworks (just numpy and pandas), so I think I ...
3
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1answer
109 views

Is the Q value updated at every episode?

I trying to understand the Bellman equation for updating the Q table values. The concept of initially updating the value is clear to me. What is unclear is the subsequent updates to the value. Is the ...
1
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0answers
39 views

N-tuple based tic tac toe diverges in temporal difference learning

I have n-tuple based tic tac toe. I already have perfect minimax player and perfectly trained table-based player. My n-tuple network consists of 8 different rows of 3 of the board as triplets having ...
2
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0answers
81 views

Q-learning: How to include a terminal state in updating rule? [duplicate]

I use Q-learning in order to determine the optimal path of an agent. I know in advance that my path is composed of exactly 3 states (so after 3 states I reach a terminal state). I would like to know ...
1
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0answers
71 views

Reinforcement learning for a 2D game involving two players

I'd like to create an AI for a 2D game involving two players fighting against each other. The map look something like this (The map is a NxN array somehow randomly generated): Basically the players ...
1
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1answer
43 views

Is the following the correct implementation of the Q learning algorithm for a neural network?

I just wanted to confirm that my understanding of Q learning was correct (with respect to a neural network). ...
6
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2answers
1k views

Does using the softmax function in Q learning not defeat the purpose of Q learning?

It is my understanding that, in Q-learning, you are trying to mimic the optimal $Q$ function $Q*$, where $Q*$ is a measure of the predicted reward received from taking action $a$ at state $s$ so that ...
2
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0answers
68 views

How would one develop an action space for a game that is proprietary?

I'm currently trying to develop an RL that will teach itself to play the popular fighting game "Tekken 7". I initially had the idea of teaching it to play generally- against actual opponents with ...
3
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1answer
112 views

Can Google's patented ML algorithms be used commercially?

I just find that Google patents some of the widely used machine learning algorithms. For example: System and method for addressing overfitting in a neural network (Dropout?) Processing images using ...
2
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0answers
38 views

What is the complexity of policy gradient algorithms compared to discrete action space algorithms?

I am using a policy gradient algorithm (actor-critic) for wireless networks. The policy gradient-based algorithm helps because it considers continuous action space. But how much does a policy ...
2
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1answer
59 views

Why feed actions in later layer in Q network?

I read the DDPG paper, in which the authors state that the actions are fed only later to their Q network: Actions were not included until the 2nd hidden layer of Q. (Sec 7, Experiment Details) So ...

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