Current state

Development of Luna has ceased in favor of my new NNUE engine Illumina.

About

Luna is an alpha-beta pruning based chess engine that uses traditional evaluation methods. It currently supports UCI protocol, so it is possible to embed it into a GUI.

Features

• Move generation

  • Magic bitboards based move-generation
  • Staged movegen

• Search features

  • Principal Variation Search w/ QSearch
  • Iterative deepening with Transposition Tables
  • SEE + MVV-LVA ordering for captures
  • Killer move heuristic
  • Late move reductions
  • History heuristic
  • Null move pruning
  • Futility pruning
  • Delta pruning
  • Aspiration Windows
  • Check extensions
  • Singular extensions
  • Static null move pruning
  • Countermove heuristic
  • SEE Pruning
  • Razoring
  • Internal iterative deepening

• Evaluation features

  • Tapered eval
  • Material
  • Mobility
  • Tapered Non-pawns PSTs
  • Tapered Pawn PSTs w/ King Buckets
  • King safety
  • Passed pawns
  • Isolated pawns
  • Doubled pawns
  • Bishop pair
  • Knight outposts
  • Endgame specific evaluations (ex: KBN vs K)

Project Structure

• /src - Source code

  • /luna - Static library that contains all of Luna's core logic, but no entry point.

  • /lunacli - Command line application that runs Luna beneath a UCI protocol layer.

  • /lunatest - Executable for unit tests.

  • /lunatuner - Tuner application for evaluation parameters.

• /ext - External dependencies.

• /scripts - Useful scripts related to testing, datagen, tuning or any other required task.

Building Prerequisites

• C++17 compliant compiler
• CMake 3.12 or higher (build system generator)

Building

Once you are done cloning this repository and all submodules located on the ext/ folder, you can follow the steps below to build Luna, according to the plaftorm you're using.

• Unix based terminal + Makefile

Use one of the following command while in the root of the repository to setup the build system:

For debug builds: cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug

For release builds: cmake -S . -B build -DCMAKE_BUILD_TYPE=Release

After that, cd onto build and call make. This will generate binaries for Luna.

• Visual Studio 2019/2022

First, make sure 'C++ Cmake tools for Windows' is installed. If not, it is possible to do so in the Visual Studio Installer.

With Visual Studio running, go to File > Open > Cmake... and select the CMakeLists.txt file at the root of this repository. Visual Studio should then load the project accordingly, and you'll be able to compile and run it within the IDE.

Usage

Luna is a command line application that follows the UCI protocol. A documentation for the protocol can be found here.

Note that, by using the UCI protocol, Luna is designed to be easily integrated with existing chess graphical interfaces.

Besides existing UCI commands, Luna also provides the following extensions:

• domoves <move1> [<move2> ...] Makes the specified moves on the current position.

• takeback [<n>] Retracts the last n moves. 'n' defaults to 1.

• getfen Outputs the FEN string for the current position.

• getpos Outputs the current position in a human comprehensible format.

• perft <depth> [--alg] [--pseudo] Calculates and outputs the perft results for the current position.

  • --alg If set, displays moves in algebraic notation (ex. e4, Nf6, O-O).
  • --pseudo If set, displays 'pseudo-legal' moves (moves that follow the patterns pieces move, but don't care if their resulting position is illegal)