From 3a14c45f15db8e1cd61d8314b4882a651bdf0521 Mon Sep 17 00:00:00 2001 From: Ajay Dhangar <99037494+ajay-dhangar@users.noreply.github.com> Date: Mon, 11 Nov 2024 05:08:58 +0530 Subject: [PATCH] Update policy-gradient-visualization.md --- .../policy-gradient-visualization.md | 31 +++++++++---------- 1 file changed, 15 insertions(+), 16 deletions(-) diff --git a/docs/machine-learning/policy-gradient-visualization.md b/docs/machine-learning/policy-gradient-visualization.md index 9170d9e02..6b203d1c4 100644 --- a/docs/machine-learning/policy-gradient-visualization.md +++ b/docs/machine-learning/policy-gradient-visualization.md @@ -1,15 +1,16 @@ --- - -id: policy-gradient-visualization -title: Policy Gradient Methods Algorithm -sidebar_label: Policy Gradient Methods -description: "An introduction to policy gradient methods in reinforcement learning, including their role in optimizing policies directly for better performance in continuous action spaces." -tags: [machine learning, reinforcement learning, policy gradient, algorithms, visualization] - +id: policy-gradient-visualization +title: Policy Gradient Methods Algorithm +sidebar_label: Policy Gradient Methods +description: "An introduction to policy gradient methods in reinforcement learning, including their role in optimizing policies directly for better performance in continuous action spaces." +tags: [machine learning, reinforcement learning, policy gradient, algorithms, visualization] --- + + ### Definition: -**Policy Gradient Methods** are a class of algorithms in reinforcement learning that optimize the policy directly by updating its parameters to maximize the expected cumulative reward. Unlike value-based methods that learn a value function, policy gradient approaches adjust the policy itself, making them suitable for environments with continuous action spaces. + +**Policy Gradient Methods** are a class of reinforcement learning algorithms that optimize the policy directly by updating its parameters to maximize the expected cumulative reward. Unlike value-based methods that learn a value function, policy gradient approaches adjust the policy itself, making them suitable for environments with continuous action spaces. ### Characteristics: - **Direct Policy Optimization**: @@ -21,11 +22,11 @@ tags: [machine learning, reinforcement learning, policy gradient, algorithms, vi ### How It Works: Policy gradient methods operate by adjusting the policy parameters $\theta$ in the direction that increases the expected return $J(\theta)$. The update step typically follows this rule: -\[ +$$ \theta \leftarrow \theta + \alpha \nabla_\theta J(\theta) -\] +$$ -where $\alpha$ is the learning rate and $\nabla_\theta J(\theta)$ represents the gradient of the expected reward with respect to the policy parameters. +where $\alpha$ is the learning rate and $\nabla_\theta J(\theta)$ represents the gradient of the expected reward to the policy parameters. ### Problem Statement: Implement policy gradient algorithms as part of a reinforcement learning framework to enhance support for continuous action spaces and enable users to visualize policy updates and improvements over time. @@ -37,9 +38,9 @@ Implement policy gradient algorithms as part of a reinforcement learning framewo - **Score Function**: The gradient estimation used is known as the **likelihood ratio gradient** or **REINFORCE** algorithm, computed by: -\[ +$$ \nabla_\theta J(\theta) \approx \sum_{t=1}^{T} \nabla_\theta \log \pi_\theta(a_t | s_t) G_t -\] +$$ where $G_t$ is the discounted return after time step $t$. @@ -54,7 +55,7 @@ where $G_t$ is the discounted return after time step $t$. Combine policy gradient methods (actor) with a value function estimator (critic) to improve learning efficiency by using TD (Temporal-Difference) updates. 3. **Proximal Policy Optimization (PPO)**: - A popular policy gradient approach that prevents large updates to the policy by using a clipped objective function, enhancing stability. + A popular policy gradient approach prevents large updates to the policy by using a clipped objective function, enhancing stability. ### Steps Involved: 1. **Initialize Policy Parameters**: @@ -138,5 +139,3 @@ Implementing visualizations can help observe how the policy changes over time, w ### Conclusion: Policy gradient methods provide a robust framework for training reinforcement learning agents in complex environments, especially those involving continuous actions. By directly optimizing the policy, they offer a path to enhanced performance in various real-world applications. - ---- \ No newline at end of file