#
Advantage Actor Critic (A2C) using Robotics Simulations with Panda-Gym 🤖

Now that you’ve studied the theory behind Advantage Actor Critic (A2C), you’re ready to train your A2C agent using Stable-Baselines3 in a robotic environment. And train a:

- A robotic arm 🦾 to move to the correct position.

We’re going to use

- panda-gym

To validate this hands-on for the certification process, you need to push your two trained models to the Hub and get the following results:

- `PandaReachDense-v3` get a result of >= -3.5.

To find your result, go to the leaderboard and find your model, the result = mean_reward - std of reward

For more information about the certification process, check this section 👉 https://huggingface.co/deep-rl-course/en/unit0/introduction#certification-process

To start the hands-on click on Open In Colab button 👇 :

#
Unit 6: Advantage Actor Critic (A2C) using Robotics Simulations with Panda-Gym 🤖

###
🎮 Environments:

- Panda-Gym

###
📚 RL-Library:

- Stable-Baselines3

We’re constantly trying to improve our tutorials, so if you find some issues in this notebook, please open an issue on the GitHub Repo.

##
Objectives of this notebook 🏆

At the end of the notebook, you will:

- Be able to use Panda-Gym, the environment library.
- Be able to train robots using A2C.
- Understand why we need to normalize the input.
- Be able to push your trained agent and the code to the Hub with a nice video replay and an evaluation score 🔥.

##
Prerequisites 🏗️

Before diving into the notebook, you need to:

🔲 📚 Study Actor-Critic methods by reading Unit 6 🤗

#
Let’s train our first robots 🤖

##
Set the GPU 💪

- To accelerate the agent’s training, we’ll use a GPU. To do that, go to `Runtime > Change Runtime type`

- `Hardware Accelerator > GPU`

##
Create a virtual display 🔽

During the notebook, we’ll need to generate a replay video. To do so, with colab, we need to have a virtual screen to be able to render the environment (and thus record the frames).

The following cell will install the librairies and create and run a virtual screen 🖥

    %%capture
    !apt install python-opengl
    !apt install ffmpeg
    !apt install xvfb
    !pip3 install pyvirtualdisplay

    # Virtual display
    from pyvirtualdisplay import Display

    virtual_display = Display(visible=0, size=(1400, 900))
    virtual_display.start()

###
Install dependencies 🔽

We’ll install multiple ones:

- `gymnasium`
- `panda-gym`: Contains the robotics arm environments.
- `stable-baselines3`: The SB3 deep reinforcement learning library.
- `huggingface_sb3`: Additional code for Stable-baselines3 to load and upload models from the Hugging Face 🤗 Hub.
- `huggingface_hub`: Library allowing anyone to work with the Hub repositories.

    !pip install stable-baselines3[extra]
    !pip install gymnasium
    !pip install huggingface_sb3
    !pip install huggingface_hub
    !pip install panda_gym

##
Import the packages 📦

    import os

    import gymnasium as gym
    import panda_gym

    from huggingface_sb3 import load_from_hub, package_to_hub

    from stable_baselines3 import A2C
    from stable_baselines3.common.evaluation import evaluate_policy
    from stable_baselines3.common.vec_env import DummyVecEnv, VecNormalize
    from stable_baselines3.common.env_util import make_vec_env

    from huggingface_hub import notebook_login

##
PandaReachDense-v3 🦾

The agent we’re going to train is a robotic arm that needs to do controls (moving the arm and using the end-effector).

In robotics, the end-effector is the device at the end of a robotic arm designed to interact with the environment.

In `PandaReach`, the robot must place its end-effector at a target position (green ball).

We’re going to use the dense version of this environment. It means we’ll get a dense reward function that will provide a reward at each timestep (the closer the agent is to completing the task, the higher the reward). Contrary to a sparse reward function where the environment return a reward if and only if the task is completed.

Also, we’re going to use the End-effector displacement control, it means the action corresponds to the displacement of the end-effector. We don’t control the individual motion of each joint (joint control).

This way the training will be easier.

###
Create the environment

####
The environment 🎮

In `PandaReachDense-v3` the robotic arm must place its end-effector at a target position (green ball).

    env_id = "PandaReachDense-v3"

    # Create the env
    env = gym.make(env_id)

    # Get the state space and action space
    s_size = env.observation_space.shape
    a_size = env.action_space

    print("_____OBSERVATION SPACE_____ \n")
    print("The State Space is: ", s_size)
    print("Sample observation", env.observation_space.sample()) # Get a random observation

The observation space is a dictionary with 3 different elements:

- `achieved_goal`: (x,y,z) position of the goal.
- `desired_goal`: (x,y,z) distance between the goal position and the current object position.
- `observation`: position (x,y,z) and velocity of the end-effector (vx, vy, vz).

Given it’s a dictionary as observation, we will need to use a MultiInputPolicy policy instead of MlpPolicy.

    print("\n _____ACTION SPACE_____ \n")
    print("The Action Space is: ", a_size)
    print("Action Space Sample", env.action_space.sample()) # Take a random action

The action space is a vector with 3 values:

- Control x, y, z movement

###
Normalize observation and rewards

A good practice in reinforcement learning is to normalize input features.

For that purpose, there is a wrapper that will compute a running average and standard deviation of input features.

We also normalize rewards with this same wrapper by adding `norm_reward = True`

You should check the documentation to fill this cell

    env = make_vec_env(env_id, n_envs=4)

    # Adding this wrapper to normalize the observation and the reward
    env = # TODO: Add the wrapper

####
Solution

    env = make_vec_env(env_id, n_envs=4)

    env = VecNormalize(env, norm_obs=True, norm_reward=True, clip_obs=10.)

###
Create the A2C Model 🤖

For more information about A2C implementation with StableBaselines3 check: https://stable-baselines3.readthedocs.io/en/master/modules/a2c.html#notes

To find the best parameters I checked the official trained agents by Stable-Baselines3 team.

    model = # Create the A2C model and try to find the best parameters

####
Solution

    model = A2C(policy = "MultiInputPolicy",
                env = env,
                verbose=1)

###
Train the A2C agent 🏃

- Let’s train our agent for 1,000,000 timesteps, don’t forget to use GPU on Colab. It will take approximately ~25-40min

    model.learn(1_000_000)

    # Save the model and  VecNormalize statistics when saving the agent
    model.save("a2c-PandaReachDense-v3")
    env.save("vec_normalize.pkl")

###
Evaluate the agent 📈

- Now that’s our agent is trained, we need to check its performance.
- Stable-Baselines3 provides a method to do that: `evaluate_policy`

    from stable_baselines3.common.vec_env import DummyVecEnv, VecNormalize

    # Load the saved statistics
    eval_env = DummyVecEnv([lambda: gym.make("PandaReachDense-v3")])
    eval_env = VecNormalize.load("vec_normalize.pkl", eval_env)

    # We need to override the render_mode
    eval_env.render_mode = "rgb_array"

    #  do not update them at test time
    eval_env.training = False
    # reward normalization is not needed at test time
    eval_env.norm_reward = False

    # Load the agent
    model = A2C.load("a2c-PandaReachDense-v3")

    mean_reward, std_reward = evaluate_policy(model, eval_env)

    print(f"Mean reward = {mean_reward:.2f} +/- {std_reward:.2f}")

###
Publish your trained model on the Hub 🔥

Now that we saw we got good results after the training, we can publish our trained model on the Hub with one line of code.

📚 The libraries documentation 👉 https://github.com/huggingface/huggingface_sb3/tree/main#hugging-face—x-stable-baselines3-v20

By using `package_to_hub`, as we already mentionned in the former units, you evaluate, record a replay, generate a model card of your agent and push it to the hub.

This way:

- You can showcase our work 🔥
- You can visualize your agent playing 👀
- You can share with the community an agent that others can use 💾
- You can access a leaderboard 🏆 to see how well your agent is performing compared to your classmates 👉 https://huggingface.co/spaces/huggingface-projects/Deep-Reinforcement-Learning-Leaderboard

To be able to share your model with the community there are three more steps to follow:

1️⃣ (If it’s not already done) create an account to HF ➡ https://huggingface.co/join

2️⃣ Sign in and then, you need to store your authentication token from the Hugging Face website.

- Create a new token (https://huggingface.co/settings/tokens) with write role

- Copy the token
- Run the cell below and paste the token

    notebook_login()
    !git config --global credential.helper store

If you don’t want to use a Google Colab or a Jupyter Notebook, you need to use this command instead: `huggingface-cli login`

3️⃣ We’re now ready to push our trained agent to the 🤗 Hub 🔥 using `package_to_hub()` function. For this environment, running this cell can take approximately 10min

    from huggingface_sb3 import package_to_hub

    package_to_hub(
        model=model,
        model_name=f"a2c-{env_id}",
        model_architecture="A2C",
        env_id=env_id,
        eval_env=eval_env,
        repo_id=f"ThomasSimonini/a2c-{env_id}", # Change the username
        commit_message="Initial commit",
    )

##
Some additional challenges 🏆

The best way to learn is to try things by your own! Why not trying `PandaPickAndPlace-v3`?

If you want to try more advanced tasks for panda-gym, you need to check what was done using TQC or SAC (a more sample-efficient algorithm suited for robotics tasks). In real robotics, you’ll use a more sample-efficient algorithm for a simple reason: contrary to a simulation if you move your robotic arm too much, you have a risk of breaking it.

PandaPickAndPlace-v1 (this model uses the v1 version of the environment): https://huggingface.co/sb3/tqc-PandaPickAndPlace-v1

And don’t hesitate to check panda-gym documentation here: https://panda-gym.readthedocs.io/en/latest/usage/train_with_sb3.html

We provide you the steps to train another agent (optional):

1. Define the environment called “PandaPickAndPlace-v3”
2. Make a vectorized environment
3. Add a wrapper to normalize the observations and rewards. Check the documentation
4. Create the A2C Model (don’t forget verbose=1 to print the training logs).
5. Train it for 1M Timesteps
6. Save the model and VecNormalize statistics when saving the agent
7. Evaluate your agent
8. Publish your trained model on the Hub 🔥 with `package_to_hub`

###
Solution (optional)

    # 1 - 2
    env_id = "PandaPickAndPlace-v3"
    env = make_vec_env(env_id, n_envs=4)

    # 3
    env = VecNormalize(env, norm_obs=True, norm_reward=True, clip_obs=10.)

    # 4
    model = A2C(policy = "MultiInputPolicy",
                env = env,
                verbose=1)
    # 5
    model.learn(1_000_000)

    # 6
    model_name = "a2c-PandaPickAndPlace-v3";
    model.save(model_name)
    env.save("vec_normalize.pkl")

    # 7
    from stable_baselines3.common.vec_env import DummyVecEnv, VecNormalize

    # Load the saved statistics
    eval_env = DummyVecEnv([lambda: gym.make("PandaPickAndPlace-v3")])
    eval_env = VecNormalize.load("vec_normalize.pkl", eval_env)

    #  do not update them at test time
    eval_env.training = False
    # reward normalization is not needed at test time
    eval_env.norm_reward = False

    # Load the agent
    model = A2C.load(model_name)

    mean_reward, std_reward = evaluate_policy(model, eval_env)

    print(f"Mean reward = {mean_reward:.2f} +/- {std_reward:.2f}")

    # 8
    package_to_hub(
        model=model,
        model_name=f"a2c-{env_id}",
        model_architecture="A2C",
        env_id=env_id,
        eval_env=eval_env,
        repo_id=f"ThomasSimonini/a2c-{env_id}", # TODO: Change the username
        commit_message="Initial commit",
    )

See you on Unit 7! 🔥

##
Keep learning, stay awesome 🤗

< > Update on GitHub