JustBot Chess Engine

JustBot is a competitive chess engine written in Rust, it's my attempt at learning the language while simultaneously working on something interesting to me; it has been a lot of fun and a huge learning experience and I hope to be able to continue working on it. This project has only been possible thanks to the wonderful open-source community. JustBot contains no LLM generated code.

Releases

Version	CCRL 40/15	CCRL Blitz
JustBot v0.3.0	3400*	3400*
JustBot v0.2.0	3124	3000*
JustBot v0.1.0	2400*	2400*

Note

*Elo is only an estimate

You can find precompiled binaries for Linux, Windows and macOS here

• avx512: The fastest build, only compatible with newer CPUs
• avx2: Usable on most modern CPUs
• generic: The slowest build, should run on any x86-64 CPU.

Building the project

To build the project, you need a working installation of Rust and Cargo, once the repository is cloned, you can run for a general build:

cargo build --release

For a targeted build you can run:

cargo rustc --release --bin justbot -- -C target-cpu=native

The binary should be located within ./target/release/

Features

Search

• Alpha-Beta Search
• Quiescence Search
  • Check Evasions
• Principal Variation Search
• Time management
  • Hard/Soft Bounds
• SEE Pruning
• Iterative Deepening
• Check Extensions
• Null Move Pruning
• Reverse Futility Pruning
• Aspiration Windows
• Late Move Reductions
• Late Move Pruning
• Futility Pruning
• Clustered Transposition Table
• Improving Modifier

Evaluation

• NNUE
  • Standard 768 Inputs
  • Dual Perspective
  • 512 HL
  • 8 Output Buckets

Move Ordering

• Noisy History
• Quiet History
• 1 and 2 Ply Continuation Histories

Supported UCI Options

Name	Default	Max	Description
Hash	16	1048576	Sets the size of the transposition table in MB
Clear Hash	---	---	Clears all entries in the transposition table
Threads	1	512	Sets the number of threads to use during search

Acknowledgments

• Chess Programming Wiki
• Maksim Korzh for helpful introductory videos, and where my magic numbers are from
• The very helpful members of the Stockfish Discord Server
• OpenBench as the testing framework, and for data generation
• Bullet for NNUE training
• Pawnocchio for converting PGNs to Viriformat

Additionally, the following engines have been huge sources of ideas and inspiration:

• Reckless
• Stockfish
• Stormphrax
• Viridithas
• Hobbes
• Potential
• Pawnocchio
• Icarus