# Minimalistic Gridworld Environment (MiniGrid)

There are other gridworld Gym environments out there, but this one is
designed to be particularly simple, lightweight and fast. The code has very few
dependencies, making it less likely to break or fail to install. It loads no
external sprites/textures, and it can run at up to 5800 FPS on a quad-core
laptop, which means you can run your experiments faster.

This environment has been built at the [MILA](https://mila.quebec/en/) as
part of the [Baby AI Game](https://github.com/maximecb/baby-ai-game) project.

## Installation

Clone this repository and install the other dependencies with `pip3`:

```
git clone https://github.com/maximecb/gym-minigrid.git
cd gym-minigrid
pip3 install -e .
```

Optionally, if you wish use the reinforcement learning code included
under [/basicrl](/basicrl), you can install its dependencies as follows:

```
cd basicrl

# PyTorch
conda install pytorch torchvision -c soumith

# OpenAI baselines
git clone https://github.com/openai/baselines.git
cd baselines
pip install -e .

# Other requirements
pip install -r requirements.txt
```

Note: the basicrl code is a custom fork of [this repository](https://github.com/ikostrikov/pytorch-a2c-ppo-acktr),
which was modified to work with this environment.

## Basic Usage

To run the standalone UI application, which allows you to manually control the agent with the arrow keys:

```
./standalone.py
```

The environment being run can be selected with the `--env-name` option, eg:

```
./standalone.py --env-name MiniGrid-Empty-8x8-v0
```

Basic reinforcement learning code is provided in the `basicrl` subdirectory.
You can perform training using the ACKTR algorithm with:

```
python3 basicrl/main.py --env-name MiniGrid-Empty-6x6-v0 --no-vis --num-processes 32 --algo acktr
```

You can view the result of training using the `enjoy.py` script:

```
python3 basicrl/enjoy.py --env-name MiniGrid-Empty-6x6-v0 --load-dir ./trained_models/acktr
```

## Included Environments

The environments listed below are implemented in the [gym_minigrid/envs](/gym_minigrid/envs) directory.

### Empty environment

Registered configurations:
- `MiniGrid-Empty-8x8-v0`
- `MiniGrid-Empty-6x6-v0`

This environment is an empty room, and the goal of the agent is to reach the
green goal square, which provides a sparse reward. A small penalty is
subtracted for the number of steps to reach the goal. This environment is
useful, with small rooms, to validate that your RL algorithm works correctly,
and with large rooms to experiment with sparse rewards.

### Door & key environment

Registered configurations:
- `MiniGrid-DoorKey-8x8-v0`
- `MiniGrid-DoorKey-16x16-v0`

<p align="center">
<img src="/figures/door-key-env.png">
</p>

This environment has a key that the agent must pick up in order to unlock
a goal and then get to the green goal square. This environment is difficult,
because of the sparse reward, to solve using classical RL algorithms. It is
useful to experiment with curiosity or curriculum learning.

### Multi-room environment

Registered configurations:
- `MiniGrid-MultiRoom-N6-v0`

<p align="center">
<img src="/figures/multi-room.gif" width=416 height=424>
</p>

This environment has a series of connected rooms with doors that must be
opened in order to get to the next room. The final room has the green goal
square the agent must get to. This environment is extremely difficult to
solve using classical RL. However, by gradually increasing the number of
rooms and building a curriculum, the environment can be solved.

### Fetch environment

Registered configurations:
- `MiniGrid-Fetch-8x8-v0`

<p align="center">
<img src="/figures/fetch-env.png" width=392 height=269>
</p>

This environment has multiple objects of assorted types and colors. The
agent receives a textual string as part of its observation telling it
which object to pick up. Picking up the wrong object produces a negative
reward.

### Four room question answering environment

Registered configurations:
- `MiniGrid-FourRoomQA-v0`

<p align="center">
<img src="/figures/fourroomqa-env.png">
</p>

This environment is inspired by the
[Embodied Question Answering](https://arxiv.org/abs/1711.11543) paper.
There are four colored rooms, and the agent is placed at a random position.
Multiple objects of different types and colors are also placed at random
positions in random rooms. A question and answer pair is generated, the
question is given to the agent as an observation, and the agent has a limited
number of time steps to explore the environment and produce a response.
