A powerful chess engine written in C++ with support for the Universal Chess Interface (UCI) protocol.
- Features
- Building
- Usage
- UCI Options
- Testing
- Project Structure
- Technical Details
- Acknowledgments
- License
- Author
- Iterative Deepening with aspiration windows
- Principal Variation Search (PVS) / Alpha-Beta pruning
- Quiescence Search with quiet check generation
- Transposition Table with multi-bucket hashing
- Multi-Threading support (Lazy SMP)
- Move Ordering:
- Hash move / TT moves
- Captures ordered by MVV-LVA and SEE
- Killer moves (2 per ply)
- Counter move heuristic
- History heuristic
- Continuation history (1-ply and 2-ply)
- Null Move Pruning with verification search
- Late Move Reductions (LMR) with dynamic adjustments
- Late Move Pruning (LMP)
- Futility Pruning with depth-based margins
- Reverse Futility Pruning (Static Null Move)
- Razoring with depth-scaling margins
- SEE Pruning for captures and quiet moves
- Delta Pruning in quiescence search
- Multi-Cut Pruning
- ProbCut
- Internal Iterative Reductions (IIR)
- History-Based Pruning (Leaf, Counter, Followup)
- Check Extension
- In-Check Extension
- Singular Extension with multi-cut and double extensions
- Recapture Extension
- Passed Pawn Extension (7th rank)
- Capture Extension (SEE-based)
- PV Extension
- Mate Threat Extension
- Negative Extension for unexpected fail-highs
- Tapered Evaluation (Middlegame/Endgame interpolation with non-linear phase scaling)
- Material & Piece-Square Tables (incrementally updated)
- Pawn Structure:
- Passed pawns with connected bonus
- Candidate passed pawns
- Isolated, doubled, backward pawns
- Phalanx and connected pawns
- Pawn duo bonus
- King proximity to passed pawns (endgame)
- Blockaded passed pawn penalty
- Rook behind passed pawn bonus
- Rule of the Square bonus
- Piece Activity:
- Mobility for all pieces (contextual evaluation)
- Knight outposts
- Knight tropism (distance to enemy king)
- Bishop pair bonus
- Bad bishop detection
- Connected rooks bonus
- Rook on open/semi-open files
- Rook on 7th rank
- King Safety:
- Attack units table with weighted attackers
- Pawn shield evaluation
- King ring / inner king ring attacks
- Open/semi-open file penalties
- Threats Evaluation:
- Piece threats from pawns
- Minor piece and rook threats
- Hanging pieces detection
- Space Evaluation
- Tempo Bonus
- Lazy Evaluation for speedup in won/lost positions
- Pawn Hash Table for efficient pawn structure caching
- UCI Protocol full support
- Opening Book support (Polyglot format)
- Syzygy Tablebase support (via Fathom)
- Multi-PV analysis mode
- Pondering with ponderhit support
- Advanced Time Management with stability-based adjustment and panic mode
- Contempt and Dynamic Contempt options
- SPSA Tuning support for parameter optimization
- Texel Tuning support for evaluation tuning
- Built-in Profiler for performance analysis
- Benchmark command for reproducible testing
- C++17 compatible compiler:
- GCC 7+ (recommended: GCC 10+)
- Clang 5+
- MSVC 2017+
- GNU Make (or MinGW Make on Windows)
# Standard release build
mingw32-make
# Clean and rebuild
mingw32-make clean; mingw32-make all
# Build and run
mingw32-make run# Install dependencies (Ubuntu/Debian)
sudo apt-get update && sudo apt-get install -y g++ make
# Standard release build
make
# Clean and rebuild
make clean && make all# Debug build (no optimization, with symbols)
mingw32-make debug
# Build with PEXT/BMI2 support (Intel Haswell+, AMD Zen 3+)
mingw32-make pext
# Profile-Guided Optimization (PGO) - Step 1: Generate profile
mingw32-make pgo-generate
# Run benchmarks: ./output/main.exe bench
# Step 2: Use profile data
mingw32-make pgo-use
# PEXT + PGO for maximum performance
mingw32-make pext-pgo-generate
# Run benchmarks: ./output/main.exe bench
mingw32-make pext-pgo-use
# Internal profiling build (for performance analysis)
mingw32-make internal-profile
# Texel Tuner build
mingw32-make tuner| Platform | Executable Location |
|---|---|
| Windows | output/main.exe |
| Linux | output/main |
Run the engine and it will automatically start in UCI mode:
./output/main.exe| Command | Description |
|---|---|
uci |
Display engine info and available options |
isready |
Check if engine is ready |
ucinewgame |
Start a new game (clears hash table and history) |
position [fen | startpos] [moves ...] |
Set position |
go [options] |
Start search |
stop |
Stop current search |
ponderhit |
Opponent played the expected ponder move |
quit |
Exit engine |
| Option | Description |
|---|---|
depth N |
Search to depth N |
nodes N |
Search N nodes |
movetime N |
Search for N milliseconds |
wtime N |
White time remaining (ms) |
btime N |
Black time remaining (ms) |
winc N |
White increment per move (ms) |
binc N |
Black increment per move (ms) |
movestogo N |
Moves until next time control |
infinite |
Search until stopped |
ponder |
Start pondering |
| Command | Description |
|---|---|
perft N |
Run perft test to depth N |
divide N |
Run divided perft to depth N |
d |
Display current board position |
eval |
Show static evaluation of current position |
bench [depth] [threads] [hash] |
Run benchmark (default: depth 13, 1 thread, 16MB hash) |
# Test perft (move generation correctness)
echo "perft 5" | ./output/main.exe
# Test search
echo "go depth 10" | ./output/main.exe
# Run built-in benchmark
echo "bench" | ./output/main.exe
# Run benchmark with custom settings
echo "bench 15 4 256" | ./output/main.exe # depth 15, 4 threads, 256MB hash| Position | Depth | Nodes | Time |
|---|---|---|---|
| Starting | 5 | 4,865,609 | ~1.3s |
| Starting | 6 | 119,060,324 | ~74s |
| Kiwipete | 4 | 4,085,603 | ~0.4s |
The engine includes several test suites in the tests/ directory:
| File | Description |
|---|---|
wac.epd |
Win at Chess positions |
bratko_kopec.epd |
Bratko-Kopec test suite |
see-test.epd |
Static Exchange Evaluation tests |
Use the provided batch scripts for automated testing against other engines:
# Run gauntlet against multiple engines
./run_gauntlet.bat
# Run SPRT testing
./run_sprt.bat- Stockfish - Inspiration for many search techniques and algorithms
- Chess Programming Wiki - Invaluable resource for chess programming
- Fathom - Syzygy tablebase probing library
- Cutechess - Chess engine testing tool
This project is open source. Feel free to use, modify, and distribute.
Dhani - GC-Engine Development
Happy chess programming! ♟️