stable-baselines3

PyTorch version of Stable Baselines, reliable implementations of reinforcement learning algorithms.

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Quick Overview

Stable Baselines3 (SB3) is a set of reliable implementations of reinforcement learning algorithms in PyTorch. It is the next major version of Stable Baselines, a fork of OpenAI Baselines, and aims to provide clean code, good documentation, and quality implementations of popular RL algorithms.

Pros

Well-documented and easy to use for both beginners and experienced researchers
Implements various popular RL algorithms with consistent interfaces
Actively maintained with regular updates and bug fixes
Integrates well with OpenAI Gym environments and provides tools for custom environment creation

Cons

Limited to PyTorch, which may not suit users preferring other frameworks
Some advanced RL algorithms or recent innovations might not be included
Performance may not always match specialized implementations of specific algorithms
Requires understanding of reinforcement learning concepts for effective use

Code Examples

Training a PPO agent on the CartPole environment:

from stable_baselines3 import PPO
from stable_baselines3.common.env_util import make_vec_env

# Create environment
env = make_vec_env("CartPole-v1", n_envs=4)

# Initialize and train the agent
model = PPO("MlpPolicy", env, verbose=1)
model.learn(total_timesteps=25000)

# Save the trained model
model.save("ppo_cartpole")

Loading a pre-trained model and evaluating it:

from stable_baselines3 import PPO
from stable_baselines3.common.evaluation import evaluate_policy
import gym

# Load pre-trained model
model = PPO.load("ppo_cartpole")

# Create environment for evaluation
env = gym.make("CartPole-v1")

# Evaluate the agent
mean_reward, std_reward = evaluate_policy(model, env, n_eval_episodes=10)
print(f"Mean reward: {mean_reward:.2f} +/- {std_reward:.2f}")

Using a custom policy network:

import gym
import torch as th
from torch import nn
from stable_baselines3 import A2C
from stable_baselines3.common.torch_layers import BaseFeaturesExtractor

class CustomCNN(BaseFeaturesExtractor):
    def __init__(self, observation_space: gym.spaces.Box, features_dim: int = 256):
        super().__init__(observation_space, features_dim)
        n_input_channels = observation_space.shape[0]
        self.cnn = nn.Sequential(
            nn.Conv2d(n_input_channels, 32, kernel_size=8, stride=4, padding=0),
            nn.ReLU(),
            nn.Conv2d(32, 64, kernel_size=4, stride=2, padding=0),
            nn.ReLU(),
            nn.Flatten(),
        )

        # Compute shape by doing one forward pass
        with th.no_grad():
            n_flatten = self.cnn(
                th.as_tensor(observation_space.sample()[None]).float()
            ).shape[1]

        self.linear = nn.Sequential(nn.Linear(n_flatten, features_dim), nn.ReLU())

    def forward(self, observations: th.Tensor) -> th.Tensor:
        return self.linear(self.cnn(observations))

policy_kwargs = dict(
    features_extractor_class=CustomCNN,
    features_extractor_kwargs=dict(features_dim=128),
)
model = A2C("CnnPolicy", "BreakoutNoFrameskip-v4", policy_kwargs=policy_kwargs, verbose=1)
model.learn(total_timesteps=1000)

Getting Started

To get started with Stable Baselines3, follow these steps:

Install the library:
```
pip install stable-baselines3[extra]
```

Import the desired algorithm and create an environment:

from stable_baselines3 import PPO
import gym

env = gym.make("CartPole

Competitor Comparisons

baselines

15,725

OpenAI Baselines: high-quality implementations of reinforcement learning algorithms

Pros of baselines

Developed by OpenAI, a leading AI research organization
Includes a wider variety of RL algorithms
More established and battle-tested in research environments

Cons of baselines

Less actively maintained and updated
Documentation is less comprehensive and user-friendly
Code structure is more complex and harder to understand for beginners

Code Comparison

baselines:

from baselines import deepq
from baselines.common.atari_wrappers import wrap_deepmind

env = wrap_deepmind(gym.make("PongNoFrameskip-v4"))
model = deepq.learn(env, network='conv_only', total_timesteps=100000)

stable-baselines3:

from stable_baselines3 import DQN
from stable_baselines3.common.env_util import make_atari_env

env = make_atari_env("PongNoFrameskip-v4", n_envs=1, seed=0)
model = DQN("CnnPolicy", env, verbose=1)
model.learn(total_timesteps=100000)

The code comparison shows that stable-baselines3 offers a more streamlined and intuitive API, making it easier for users to implement and train RL agents. baselines, while powerful, requires more setup and configuration.

stable-baselines

4,141

A fork of OpenAI Baselines, implementations of reinforcement learning algorithms

Pros of stable-baselines

More established and mature project with a longer history
Supports a wider range of algorithms and environments
Better documentation and more extensive examples

Cons of stable-baselines

Uses older TensorFlow 1.x, which is less performant and harder to maintain
Less active development and slower updates
Lacks some modern features and optimizations found in PyTorch-based implementations

Code Comparison

stable-baselines:

from stable_baselines import PPO2
model = PPO2('MlpPolicy', 'CartPole-v1', verbose=1)
model.learn(total_timesteps=10000)

stable-baselines3:

from stable_baselines3 import PPO
model = PPO('MlpPolicy', 'CartPole-v1', verbose=1)
model.learn(total_timesteps=10000)

The code structure is similar, but stable-baselines3 uses updated import statements and slightly different class names. The core functionality remains largely the same, making migration between the two libraries relatively straightforward for most use cases.

agents

2,788

TF-Agents: A reliable, scalable and easy to use TensorFlow library for Contextual Bandits and Reinforcement Learning.

Pros of TF-Agents

Built on TensorFlow, offering seamless integration with TensorFlow ecosystem
Provides a wider range of algorithms and environments
Better support for distributed training and deployment

Cons of TF-Agents

Steeper learning curve, especially for those new to TensorFlow
Less user-friendly documentation compared to Stable Baselines3
Slower development cycle and community updates

Code Comparison

Stable Baselines3 (PPO implementation):

from stable_baselines3 import PPO

model = PPO("MlpPolicy", "CartPole-v1", verbose=1)
model.learn(total_timesteps=10000)

TF-Agents (PPO implementation):

from tf_agents.agents.ppo import ppo_agent
from tf_agents.networks import actor_distribution_network, value_network

actor_net = actor_distribution_network.ActorDistributionNetwork(
    obs_spec, action_spec, fc_layer_params=(200, 100))
value_net = value_network.ValueNetwork(obs_spec, fc_layer_params=(200, 100))

agent = ppo_agent.PPOAgent(
    time_step_spec, action_spec, actor_net, value_net,
    optimizer=tf.compat.v1.train.AdamOptimizer(learning_rate=1e-3))

ray

33,421

Ray is a unified framework for scaling AI and Python applications. Ray consists of a core distributed runtime and a set of AI Libraries for accelerating ML workloads.

Pros of Ray

Broader scope: Ray is a general-purpose distributed computing framework, offering more versatility beyond reinforcement learning
Scalability: Designed for large-scale distributed computing, making it suitable for bigger projects and clusters
Ecosystem: Includes libraries for various tasks like hyperparameter tuning (Ray Tune) and reinforcement learning (RLlib)

Cons of Ray

Steeper learning curve: More complex to set up and use due to its broader feature set
Overhead: May introduce unnecessary complexity for smaller projects focused solely on reinforcement learning
Documentation: Can be overwhelming due to the wide range of features and use cases

Code Comparison

Ray (RLlib) example:

import ray
from ray import tune
from ray.rllib.agents import ppo

ray.init()
tune.run(ppo.PPOTrainer, config={"env": "CartPole-v0"})

Stable-Baselines3 example:

from stable_baselines3 import PPO
from stable_baselines3.common.env_util import make_vec_env

env = make_vec_env("CartPole-v1", n_envs=4)
model = PPO("MlpPolicy", env, verbose=1)
model.learn(total_timesteps=25000)

PARL

3,257

A high-performance distributed training framework for Reinforcement Learning

Pros of PARL

Built on PaddlePaddle, offering better integration with Baidu's AI ecosystem
Supports distributed training out-of-the-box
Includes a wider range of algorithms, including multi-agent reinforcement learning

Cons of PARL

Less extensive documentation compared to Stable-baselines3
Smaller community and fewer third-party resources
Steeper learning curve for those not familiar with PaddlePaddle

Code Comparison

PARL example:

import parl
from parl import layers

class Model(parl.Model):
    def __init__(self, act_dim):
        self.fc1 = layers.fc(size=128, act='relu')
        self.fc2 = layers.fc(size=act_dim)

Stable-baselines3 example:

from stable_baselines3 import PPO

model = PPO("MlpPolicy", "CartPole-v1", verbose=1)
model.learn(total_timesteps=10000)

Both libraries offer easy-to-use APIs for implementing reinforcement learning algorithms. PARL provides more flexibility in defining custom models, while Stable-baselines3 focuses on simplicity and quick implementation of common algorithms.

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README

Stable Baselines3

Stable Baselines3 (SB3) is a set of reliable implementations of reinforcement learning algorithms in PyTorch. It is the next major version of Stable Baselines.

You can read a detailed presentation of Stable Baselines3 in the v1.0 blog post or our JMLR paper.

These algorithms will make it easier for the research community and industry to replicate, refine, and identify new ideas, and will create good baselines to build projects on top of. We expect these tools will be used as a base around which new ideas can be added, and as a tool for comparing a new approach against existing ones. We also hope that the simplicity of these tools will allow beginners to experiment with a more advanced toolset, without being buried in implementation details.

Note: Despite its simplicity of use, Stable Baselines3 (SB3) assumes you have some knowledge about Reinforcement Learning (RL). You should not utilize this library without some practice. To that extent, we provide good resources in the documentation to get started with RL.

Main Features

The performance of each algorithm was tested (see Results section in their respective page), you can take a look at the issues #48 and #49 for more details.

Features	Stable-Baselines3
State of the art RL methods	:heavy_check_mark:
Documentation	:heavy_check_mark:
Custom environments	:heavy_check_mark:
Custom policies	:heavy_check_mark:
Common interface	:heavy_check_mark:
`Dict` observation space support	:heavy_check_mark:
Ipython / Notebook friendly	:heavy_check_mark:
Tensorboard support	:heavy_check_mark:
PEP8 code style	:heavy_check_mark:
Custom callback	:heavy_check_mark:
High code coverage	:heavy_check_mark:
Type hints	:heavy_check_mark:

Planned features

Please take a look at the Roadmap and Milestones.

Migration guide: from Stable-Baselines (SB2) to Stable-Baselines3 (SB3)

A migration guide from SB2 to SB3 can be found in the documentation.

Documentation

Documentation is available online: https://stable-baselines3.readthedocs.io/

Integrations

Stable-Baselines3 has some integration with other libraries/services like Weights & Biases for experiment tracking or Hugging Face for storing/sharing trained models. You can find out more in the dedicated section of the documentation.

RL Baselines3 Zoo: A Training Framework for Stable Baselines3 Reinforcement Learning Agents

RL Baselines3 Zoo is a training framework for Reinforcement Learning (RL).

It provides scripts for training, evaluating agents, tuning hyperparameters, plotting results and recording videos.

In addition, it includes a collection of tuned hyperparameters for common environments and RL algorithms, and agents trained with those settings.

Goals of this repository:

Provide a simple interface to train and enjoy RL agents
Benchmark the different Reinforcement Learning algorithms
Provide tuned hyperparameters for each environment and RL algorithm
Have fun with the trained agents!

Github repo: https://github.com/DLR-RM/rl-baselines3-zoo

Documentation: https://rl-baselines3-zoo.readthedocs.io/en/master/

SB3-Contrib: Experimental RL Features

We implement experimental features in a separate contrib repository: SB3-Contrib

This allows SB3 to maintain a stable and compact core, while still providing the latest features, like Recurrent PPO (PPO LSTM), Truncated Quantile Critics (TQC), Quantile Regression DQN (QR-DQN) or PPO with invalid action masking (Maskable PPO).

Documentation is available online: https://sb3-contrib.readthedocs.io/

Stable-Baselines Jax (SBX)

Stable Baselines Jax (SBX) is a proof of concept version of Stable-Baselines3 in Jax, with recent algorithms like DroQ or CrossQ.

It provides a minimal number of features compared to SB3 but can be much faster (up to 20x times!): https://twitter.com/araffin2/status/1590714558628253698

Installation

Note: Stable-Baselines3 supports PyTorch >= 1.13

Prerequisites

Stable Baselines3 requires Python 3.8+.

Windows 10

To install stable-baselines on Windows, please look at the documentation.

Install using pip

Install the Stable Baselines3 package:

pip install stable-baselines3[extra]

Note: Some shells such as Zsh require quotation marks around brackets, i.e. pip install 'stable-baselines3[extra]' (More Info).

This includes an optional dependencies like Tensorboard, OpenCV or ale-py to train on atari games. If you do not need those, you can use:

pip install stable-baselines3

Please read the documentation for more details and alternatives (from source, using docker).

Example

Most of the code in the library tries to follow a sklearn-like syntax for the Reinforcement Learning algorithms.

Here is a quick example of how to train and run PPO on a cartpole environment:

import gymnasium as gym

from stable_baselines3 import PPO

env = gym.make("CartPole-v1", render_mode="human")

model = PPO("MlpPolicy", env, verbose=1)
model.learn(total_timesteps=10_000)

vec_env = model.get_env()
obs = vec_env.reset()
for i in range(1000):
    action, _states = model.predict(obs, deterministic=True)
    obs, reward, done, info = vec_env.step(action)
    vec_env.render()
    # VecEnv resets automatically
    # if done:
    #   obs = env.reset()

env.close()

Or just train a model with a one liner if the environment is registered in Gymnasium and if the policy is registered:

from stable_baselines3 import PPO

model = PPO("MlpPolicy", "CartPole-v1").learn(10_000)

Please read the documentation for more examples.

Try it online with Colab Notebooks !

All the following examples can be executed online using Google Colab notebooks:

Implemented Algorithms

Name	Recurrent	`Box`	`Discrete`	`MultiDiscrete`	`MultiBinary`	Multi Processing
ARS¹	:x:	:heavy_check_mark:	:heavy_check_mark:	:x:	:x:	:heavy_check_mark:
A2C	:x:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:
DDPG	:x:	:heavy_check_mark:	:x:	:x:	:x:	:heavy_check_mark:
DQN	:x:	:x:	:heavy_check_mark:	:x:	:x:	:heavy_check_mark:
HER	:x:	:heavy_check_mark:	:heavy_check_mark:	:x:	:x:	:heavy_check_mark:
PPO	:x:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:
QR-DQN¹	:x:	:x:	:heavy_check_mark:	:x:	:x:	:heavy_check_mark:
RecurrentPPO¹	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:
SAC	:x:	:heavy_check_mark:	:x:	:x:	:x:	:heavy_check_mark:
TD3	:x:	:heavy_check_mark:	:x:	:x:	:x:	:heavy_check_mark:
TQC¹	:x:	:heavy_check_mark:	:x:	:x:	:x:	:heavy_check_mark:
TRPO¹	:x:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:
Maskable PPO¹	:x:	:x:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:	:heavy_check_mark:

1: Implemented in SB3 Contrib GitHub repository.

Actions gym.spaces:

Box: A N-dimensional box that contains every point in the action space.
Discrete: A list of possible actions, where each timestep only one of the actions can be used.
MultiDiscrete: A list of possible actions, where each timestep only one action of each discrete set can be used.
MultiBinary: A list of possible actions, where each timestep any of the actions can be used in any combination.

Testing the installation

Install dependencies

pip install -e .[docs,tests,extra]

Run tests

All unit tests in stable baselines3 can be run using pytest runner:

make pytest

To run a single test file:

python3 -m pytest -v tests/test_env_checker.py

To run a single test:

python3 -m pytest -v -k 'test_check_env_dict_action'

You can also do a static type check using pytype and mypy:

pip install pytype mypy
make type

Codestyle check with ruff:

pip install ruff
make lint

Projects Using Stable-Baselines3

We try to maintain a list of projects using stable-baselines3 in the documentation, please tell us if you want your project to appear on this page ;)

Citing the Project

To cite this repository in publications:

@article{stable-baselines3,
  author  = {Antonin Raffin and Ashley Hill and Adam Gleave and Anssi Kanervisto and Maximilian Ernestus and Noah Dormann},
  title   = {Stable-Baselines3: Reliable Reinforcement Learning Implementations},
  journal = {Journal of Machine Learning Research},
  year    = {2021},
  volume  = {22},
  number  = {268},
  pages   = {1-8},
  url     = {http://jmlr.org/papers/v22/20-1364.html}
}

Maintainers

Stable-Baselines3 is currently maintained by Ashley Hill (aka @hill-a), Antonin Raffin (aka @araffin), Maximilian Ernestus (aka @ernestum), Adam Gleave (@AdamGleave), Anssi Kanervisto (@Miffyli) and Quentin GallouÃ©dec (@qgallouedec).

Important Note: We do not provide technical support, or consulting and do not answer personal questions via email. Please post your question on the RL Discord, Reddit, or Stack Overflow in that case.

How To Contribute

To any interested in making the baselines better, there is still some documentation that needs to be done. If you want to contribute, please read CONTRIBUTING.md guide first.

Acknowledgments

The initial work to develop Stable Baselines3 was partially funded by the project Reduced Complexity Models from the Helmholtz-Gemeinschaft Deutscher Forschungszentren, and by the EU's Horizon 2020 Research and Innovation Programme under grant number 951992 (VeriDream).

The original version, Stable Baselines, was created in the robotics lab U2IS (INRIA Flowers team) at ENSTA ParisTech.

Logo credits: L.M. Tenkes

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