Welcome to my AI experimentation repository!

In this repo I want to test different approaches to using AI to play games at a high skill level; mostly using different reinforcement learning techniques.

At the time of writing, this repo is a Python port of my Tic-Tac-Clojure repo. I created this port because I want to use Google's JAX library to experiment with neural networks.

This codebase was written with Python 3.8 and so may use some slightly older features with the Typing module and lacks support for pattern matching.

I may create more game environments to experiment with in the future, we will see...

Requirements

This repo should be compatible with any version of Python 3.

Shell scripts

The shell scripts provided are mostly to help myself remember how to do certain things in the Python ecosystem.

Although the scripts are just references, I do recommend using run-tests.sh however. See Run unit tests.

Setup

I run this project using Python's virtual environments to isolate the dependencies for this project from the rest of the system.

1. Create a Python virtual environment

I name mine .venv, using the following command from the root directory:

python3 -m venv .venv

The generated .venv folder is already added to .gitignore

2. Activate virtual environment in current shell

From the root directory:

source .venv/bin/activate

3. Install project dependencies

python -m pip install --requirement requirements.txt

4. Run unit tests

I would recommend using run-tests.sh because the script will make sure that you provide a specific directory/project, run tests with a coverage report and clean up the .coverage report that would otherwise be left behind by pytest-cov.

Example usage:

./run-tests.sh tictactoe
./run-tests.sh mcts

Running games

Some example usage of setting up a Monte Carlo Tree Search agent vs a random move agent is provided in play-tic-tac-toe.py:

python play-tic-tac-toe.py

Artificial Intelligence Agents

At the moment there is an agent that uses Monte Carlo Tree Search (MCTS) to intelligently pick the best move for a given state. I have abstracted implementation details to be as game-agnostic as possible and should be able to be used for other games given that you can provide the following functions that have the following shapes:

• get_valid_moves_list :: (State) -> list[Move]
• is_terminal :: (State) -> bool
• apply_move_to_state :: (State, Move) -> State
• check_win :: (State) -> int | None

Performance

Below compare the performance of the Python code in this repo to that of my naïve Clojure version, where "naïve" means I wrote the code once, with no attempt at optimisation and have not written any concurrent processing.

Initially I translated the Clojure code straight into Python, including preserving the paradigm where functional programming languages use recursion for all looping. However when running large numbers of Monte Carlo simulations, I needed to incorporate the tail_recursive library to prevent stack overflows. This actually slowed down the performance significantly - 30% slower!

I found this initial naïve Python code to be extremely slow, and so rewrote the tail-call recursive loop in the main Monte Carlo Tree Search loop into a range-based for loop and also compared against using a while loop. Both increased the speed approximately 2.5×.

To see if I could get additional performance gains, I then rewrote the rest of the tail-call recursive loops in the Monte Carlo Tree Search code into for/while loops. I would say that the performance improvement was negligible in this case.

The results below are from running 1,000 games of an agent that picks random moves vs a MCTS agent with exploration = 1.2 and number of iterations = 1,000. This was run on an Apple M1 Max processor:

Optimisation	Speed
Clojure naïve	48s
Python naïve	7m 19s
Python naïve with tail_recursive	9m 29s
Python MCTS main loop = while loop	3m 49s
Python MCTS main loop = for loop	3m 46s
Python All MCTS loops = for/while loops	3m 22s

To-Do

• Add linting
• See if there are better test-coverage reporting libraries
• Parallelise MCTS AI
• Get around to to-do's in code