Implementation of MILO, a model-based, offline imitation learning algorithm.

Link to pdf: https://arxiv.org/abs/2106.03207

After cloning this repository and installing the requirements, please run

cd milo && pip install -e .

cd mjrl && pip install -e .

The experiments are run using MuJoCo physics, which requires a license to install. Please follow the instructions on MuJoCo Website

The milo package contains our imitation learning, model-based environment stack, and boilerplate code. We modified the mjrl package to interface with our cost functions when doing model-based policy gradient. This modification can be seen in mjrl/mjrl/algos/batch_reinforce.py. Note that we currently only support NPG/TRPO as our policy gradient algorithm; however, in principle one could replace this with other algorithms/repositories.

This repository supports 5 modified MuJoCo environments that can be found in milo/milo/gym_env. They are

1. Hopper-v4
2. Walker2d-v4
3. HalfCheetah-v4
4. Ant-v4
5. Humanoid-v4

If you would like to add an environment, register the environment in /milo/milo/gym_env/__init__.py according to OpenAI Gym instructions.

Please download the datasets from this google drive link. Each environment will have 2 datasets: [ENV]_expert.pt and [ENV]_offline.pt.

In the data directory, place the expert and offline datasets in the data/expert_data and data/offline_data direcotires respectively.

We provide an example run script for Hopper, example_run.sh, that can be modified to be used with any other registered environment. To view all the possible arguments you can run please see the argparse in milo/milo/utils/arguments.py.

To cite this work, please use the following citation. Note that this repository builds upon MJRL so please also cite any references noted in the README here.

@misc{chang2021mitigating,
      title={Mitigating Covariate Shift in Imitation Learning via Offline Data Without Great Coverage}, 
      author={Jonathan D. Chang and Masatoshi Uehara and Dhruv Sreenivas and Rahul Kidambi and Wen Sun},
      year={2021},
      eprint={2106.03207},
      archivePrefix={arXiv},
      primaryClass={cs.LG}
}