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A strong dotnet UCI Chess engine - My leaf nodes are growing

Play it here -> https://iblunder.com/

Or challenge it on Lichess -> https://lichess.org/@/sapling-bot

Rating pool Version ELO
CCRL 40/15 1.1.2 3378
Lichess Bullet 1.2.2 2890
Lichess Blitz 1.2.2 2786
Lichess Rapid 1.2.2 2797
Lichess Chess960 1.2.2 2209
Tournament Version Result
CCRL 112th Amateur Series Division 5 1.1.8 drawed 3rd place
Blitz Tournament 3'+2" (48th Edition) 1.2.0 Division 4 6th place
FRC Tournament (35th Edition) 1.2.2 TBD

Releases

You can browse all windows, linux or mac releases here

Latest Release v1.2.2 13/10/2024

Requirements

  • Sapling makes use of hardware intrinsics to improve performance. Currently your CPU must support: Avx2, Bmi1, Bmi2, Popcnt, Sse. Most modern hardware shipped after 2013 should be supported.
  • The releases come with a bundled version of the dotnet runtime, however if you want to run from source you'll need the dotnet 8 SDK installed.

Running from source

cd ./scripts

// Windows
./build_windows_avx256.bat
./build_windows_avx512.bat

// Linux
./build_linux_avx256.sh
./build_linux_avx512.sh

// Osx
./build_osx_avx256.sh
./build_osx_avx512.sh

Commands

  • quit : exit the program
  • setoption name threads value 8 : sets the number of threads to use
  • ucinewgame : initializes a new game
  • position startpos : sets the engine to the starting chess position
  • position startpos moves a2a3 a7a6 : sets the engine to the starting position then applies a set of moves
  • position fen rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1 : sets the engine to the position given by the fen string
  • d : outputs a diagram of the current position
  • go perft 6 : Runs a pert test to a specific depth
  • go depth 10 : Returns the best move after searching for the given depth
  • go wtime 10000 btime 10000 winc 100 binc 100 : returns the best move after searching with the given time control
  • go see a2a3 : [Dev] returns a the result of static exchange evaluation for a given move
  • go eval : [Dev] returns the static evaluation of the current position
  • datagen : [Dev] starts generating data in the bullet format, used when training a new NNUE network

Features

General
  • Bitboards
  • NNUE (768 -> 1024)x2 -> 8
  • Horizontal mirroring
  • Output buckets x8
  • Transposition table
  • Lazy SMP
  • Pondering
Search
  • Negamax
  • Quiescence
  • Alpha-Beta pruning
  • Iterative Deepening
  • Asperation windows
  • Null move pruning
  • Late Move Pruning
  • Futility Pruning
  • Razoring
  • Principal Variation Search
  • Check extensions
  • Internal Iterative Reduction
  • Late Move Reductions
  • Cuckoo filter repetition detection
Move generation / ordering
  • Pseudo-legal movegen
  • Static exchange evaluation
  • Killer move heuristic
  • Counter move heuristic
  • History heuristic with malus
  • Incremental sorting
  • Magic bitboards
  • PEXT bitboards

SPRT

After any changes to the engine a SPRT test must be ran to ensure that the changes have a positive effect.

There is a script sprt.bat which contains the command to run a cutechess-cli SPRT test. Ensure that you've configured CuteChess to point to both dev and base engines before hand, and also update the opening book + endgame table base to point to one on your system.

NNUE

I'm in the process of training a (768x8->1024)x2-8 network starting from random weights using self play data generation and bullet trainer. Expect the engine to get much stronger as I improve the network. Check here to see the sequence of networks starting from scratch and the training logs.

Resources: