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Lishex (codename 1F98A)

A UCI chess-engine built in C++.

Features

Universal Chess Interface (UCI) compatible.
Hybrid board representation
- Bitboard representation for move generation and evaluation
- Square centric 8x8 board for quick piece-lookup during move making
Iterative deepening Negamax framework
- Alpha-Beta pruning
- Principal variation search
- Aspiration windows with PVS
- Quiescence search
- Most Valuable Victim Least Valuable Attacker (MVV-LVA) heuristic
- Killer move heuristic
- History heuristic
- Null-move pruning
- Transposition tables to store results of previously performed searches (based on Zobrist hashes)
- Late move reduction
- Futility pruning
- Razoring
- Basic king safety (king danger zone, pawn shield, pawn storm)
- Check extension
Tapered PeSTO's Piece-square tables for static position evaluation interpolated between different game stages
Static Exchange Evaluation (SEE) to detect losing captures
Mobility scores
Parameter fine-tuning (based on Texel's tuning method) - stochastically optimized with a basic implementation of Adam (in mini-batch mode)
Doxygen-generated documentation

How to

Lishex does not come with its own grapical user interface (GUI). Instead, it implements the UCI protocol making it compatible with most popular chess GUIs such as:

Arena Chess GUI (free)
Chessbase (paid)
Cutechess (free)
BanksiaGUI (free)
Nibbler (free).

TODOs

Lishex is a work in progress and there are many features that I would like to implement in the future. These include:

More search extensions: extending search depth in specific subtrees to combat the horizon effect
LazySMP for parallel searching on multiple threads
More sophisticated king safety (including queen distance, tropism)
Endgame tablebase probing
Extension limiting
Smarter time control logic, estimated time to finish search
Chess960 (Fisher Random Chess) support
NNUE

Source code

You can find the project repository here.