# Questions tagged [reward-functions]

For questions about rewards functions (e.g. in the context of reinforcement learning, which may be denoted as $R(s, a)$).

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### How to encourage the reinforcement-learning agent to reach the goal as quickly as possible, and what's the effect of discount factor?

I am trying to use reinforcement learning to solve a task and compare its performance to humans. The task is to find a single target in a fixed number of locations. At each step, the agent will pick ...
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### How do I compute the value function when the reward is only at the end in the context of actor-critic algorithms?

Consider the actor-critic reinforcement learning setting (actor and critic parameterized by a neural network). The reward is given only at the end of the episode (or when there is a timeout there is ...
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### How are rewards calculated for episodic tasks like playing chess or tic-tac-toe?

I am new to Reinforcement Learning and trying to understand the concept of reaping rewards during episodic tasks. I think in games like tic-tac-toe, rewards will be in terms of a win or lose. But does ...
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### In addition to the reward function, which other functions do I need to implement Q-learning?

In general, $Q$ function is defined as $$Q : S \times A \rightarrow \mathbb{R}$$ $$Q(s_t,a_t) = Q(s_t,a_t) + \alpha[r_{t+1} + \gamma \max\limits_{a} Q(s_{t+1},a) - Q(s_t,a_t)]$$ $\alpha$ and $\gamma$...
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### How would you shape a reward function if there was four quantities to optimize?

I found this article quite useful on how to shape a reward function in RL. However, the example they gave is quite simple, where the goal is to minimize only two quantities (velocity and distance). ...
99 views

### How do we get the value of this state of an MDP, at time-step $h-2$, using dynamic programming?

I am trying to understand the problem below, represented as an MDP with four states (PU, PF, RU, and RF) and two actions (AS). Let's consider V(RF), the value of the state RF. At time-step $h$, V(RF) ...
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### What happens with policy gradient methods if rewards are differentiable?

I would like some help with understanding why there is no explicit flow of information from the reward gradient to the parameters of the policy in policy gradient methods. What I mean is the following,...
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### How to scale all positive continuous reward?

My RL project has all positive continuous rewards for every step and the goal is to have the maximum cumulative reward (episodic reward). The problem is that the rewards are too close and all between ...
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### How to define a reward function in POMDPs?

How do I define a reward function for my POMDP model? In the literature, it is common to use one simple number as a reward, but I am not sure if this is really how you define a function. Because this ...
### Why is the equation $r(s', a, s') =\sum_{r \in \mathcal{R}} r \frac{p\left(s^{\prime}, r \mid s, a\right)}{p\left(s^{\prime} \mid s, a\right)}$true?
I am referring to eq. 3.6 (page 49) based on Sutton's online book and can be found in an image below. I could not make sense of the final derivation of the equation $r(s, a, s')$. My question is ...