johan-gras/ MuZero
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Description
A structured implementation of MuZero
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MuZero
This repository is a Python implementation of the MuZero algorithm. It is based upon the
pre-print paper__ and the
pseudocode__ describing the Muzero framework. Neural computations are implemented with Tensorflow.
You can easily train your own MuZero, more specifically for one player and non-image based environments (such as
CartPole__). If you wish to train Muzero on other kinds of environments, this codebase can be used with slight modifications.
__ https://arxiv.org/abs/1911.08265 __ https://arxiv.org/src/1911.08265v1/anc/pseudocode.py __ https://gym.openai.com/envs/CartPole-v1/
DISCLAIMER: this code is early research code. What this means is:
- Silent bugs may exist.
- It may not work reliably on other environments or with other hyper-parameters.
- The code quality and documentation are quite lacking, and much of the code might still feel "in-progress".
- The training and testing pipeline is not very advanced.
Dependencies
We run this code using:
- Conda 4.7.12
- Python 3.7
- Tensorflow 2.0.0
- Numpy 1.17.3
Training your MuZero
This code must be run from the main function in
muzero.py(don't forget to first configure your conda environment).
Training a Cartpole-v1 bot
To train a model, please follow these steps:
1) Create or modify an existing configuration of Muzero in
config.py.
2) Call the right configuration inside the main of
muzero.py.
3) Run the main function:
python muzero.py.
Training on an other environment
To train on a different environment than Cartpole-v1, please follow these additional steps:
1) Create a class that extends
AbstractGame, this class should implement the behavior of your environment. For instance, the
CartPoleclass extends
AbstractGameand works as a wrapper upon
gym CartPole-v1__. You can use the
CartPoleclass as a template for any gym environment.
__ https://gym.openai.com/envs/CartPole-v1/
2) This step is optional (only if you want to use a different kind of network architecture or value/reward transform). Create a class that extends
BaseNetwork, this class should implement the different networks (representation, value, policy, reward and dynamic) and value/reward transforms. For instance, the
CartPoleNetworkclass extends
BaseNetworkand implements fully connected networks.
3) This step is optional (only if you use a different value/reward transform). You should implement the corresponding inverse value/reward transform by modifying the
loss_valueand
loss_rewardfunction inside
training.py.
Differences from the paper
This implementation differ from the original paper in the following manners:
- We use fully connected layers instead of convolutional ones. This is due to the nature of our environment (Cartpole-v1) which as no spatial correlation in the observation vector.
- We don't scale the hidden state between 0 and 1 using min-max normalization. Instead we use a tanh function that maps any values in a range between -1 and 1.
- We do use a slightly simple invertible transform for the value prediction by removing the linear term.
- During training, samples are drawn from a uniform distribution instead of using prioritized replay.
- We also scale the loss of each head by 1/K (with K the number of unrolled steps). But, instead we consider that K is always constant (even if it is not always true).