Version 1.6.0

A bitboard-based chess engine with advanced search techniques and evaluation.

• Bitboard Representation: 64-bit bitboards for efficient move generation

• Magic Bitboards: Fast sliding piece attack generation using magic numbers

• Search Algorithm:

  • Negamax with alpha-beta pruning
  • Iterative deepening
  • Aspiration windows
  • Principal Variation Search (PVS)
  • Null Move Pruning (NMP) with adaptive reduction
  • Late Move Reductions (LMR)
  • Late Move Pruning (LMP)
  • Reverse Futility Pruning (RFP)
  • Futility Pruning (FP)
  • Static Exchange Evaluation (SEE) pruning
  • Internal Iterative Reductions (IIR)
  • Check extensions
  • Quiescence search with SEE filtering
  • Repetition / draw detection in search
  • Soft/Hard time management
  • Transposition Table

• Move Ordering:

  • TT move first
  • Good captures (SEE ≥ threshold) with MVV-LVA scoring
  • Killer moves
  • History + continuation history for quiet moves (Bad quiets are penalized)
  • Bad captures ordered last

• Evaluation:

  • Tuned MG/EG piece values (not default PeSTO values)
  • Tuned PSTs (PeSTO-initialized, then engine-tuned)
  • Tapered evaluation (midgame/endgame interpolation)
  • Piece mobility (Knight, Bishop, Rook, Queen) with MG/EG terms
  • King-zone attack pressure from mobility
  • Double pawn penalty
  • Isolated pawn penalty
  • Passed pawn bonuses (MG/EG tables)
  • King shield bonus
  • Precomputed passed-pawn masks for faster eval hot path

The Makefile automatically detects your operating system.

# Automatic detection (recommended)
make

# Or specify your OS explicitly
make windows
make linux
make mac

# Clean build artifacts
make clean

Output: Executable will be created as Solo.exe (Windows) or Solo (Linux/Mac)

If you don't have Make:

g++ -O3 -mavx2 -std=c++23 -ffast-math -pthread main.cpp board.cpp movegen.cpp search.cpp evaluation.cpp bitboard.cpp history.cpp -o Solo.exe -static -static-libgcc -static-libstdc++

g++ -O3 -std=c++23 -ffast-math -pthread main.cpp board.cpp movegen.cpp search.cpp evaluation.cpp bitboard.cpp history.cpp -o Solo -lm

clang++ -O3 -std=c++23 -ffast-math -march=armv8-a -pthread main.cpp board.cpp movegen.cpp search.cpp evaluation.cpp bitboard.cpp history.cpp -o Solo -lm

./Solo

# Example UCI commands:
uci
setoption name Hash value 64
position startpos moves e2e4 e7e5
go depth 10

./Solo bench

Runs a built-in benchmark on 12 positions at depth 8.

• Estimated ELO: ~2300+ (based on SPRT testing)
• Lichess ELO: ~2200

• Multi-threading support (Lazy SMP)
• NNUE evaluation
• Continuation history
• Singular extensions

├── bitboard.cpp/h      # Magic bitboards & attack generation
├── board.cpp/h         # Board representation & move make/unmake
├── evaluation.cpp/h    # Tuned tapered evaluation & mobility
├── history.cpp/h       # History heuristic for move ordering
├── movegen.cpp         # Legal move generation
├── search.cpp/h        # Negamax search, pruning & reductions
├── uci.cpp/h           # UCI protocol handler
├── types.h             # Basic types & constants
├── main.cpp            # Entry point
└── Makefile            # Build system

• Author: xsolod3v
• Inspired by: Patricia engine by Adam Kulju, Potential Engine by ProgramciDusunur
• Evaluation Base: PeSTO piece-square tables by Ronald Friederich (further tuned)
• Resources: Chess Programming Wiki, Potential source code, Ethereal source code

MIT License - Do whatever you want with it!

See LICENSE for full details.

Want to contribute? Feel free to open issues or pull requests!