Betafish

Betafish - An amalgamation of AlphaZero and Stockfish.

Play it here.

Read more about it on my blog.

Introduction

Betafish is a chess engine and AI move finder written in Javascript, based on the Negamax algorithm. It beats Stockfish Level 6 on Lichess, and I estimate its around 1800-2000 Elo, depending on the thinking time afforded.

Features

• Negamax algorithm with alpha-beta pruning
• Move ordering using the MVV-LVA heuristic
• Principal variation search
• Quiescence search
• Iterative deepening
• Piece-square tables
• Tapered evaluation

This enables Betafish to search to a depth of 7-8 plies and around ~1mil possible nodes, given a thinking time of around 1-2 seconds.

Possible Improvements

• Transposition tables
• Zobrist hashing
• Opening tables

Of course, re-writing this in a compiled language like C++ would be a huge improvement. I wrote it in Javacript as I wanted to deploy it as a web app, as what fun would a game be without letting your friends challenge it? However, I quickly realised the limitations, as JS is definitely not suited for these computing-intensive tasks.

Changelogs

• 1.1 - Changed evaluation function from Simplified Eval to PeSTO's Eval Function. Major improvements ~ 200 elo.

Credits

• Chess Engines: A Zero to One - The article that jumpstarted my journey into chess programming.
• WukongJS - A JS chess engine, written by Maksim Korzh, who was patient enough to answer my questions, give me pointers and point me in the right direction in this journey.
• Bluefever Software's YouTube series - A 63-part series on chess programming, which was an absolute gold mine and served as inspiration for the bulk of the chess engine.
• Chess Programming Wiki - A great resource for chess programming.
• CM Chessboard - The library I used for the GUI.