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Chess engine: Catto 0.5.2

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Catto - UCI chess engine
Author: Phu Minh  Rating CEDR=2316

 What do we currently have?
The engine
Negamax search algorithm with Alpha-Beta pruning.
Move ordering:
MVV-LVA heuristic.
Killer heuristic.
History heuristic.
Countermove heuristic.
Checkmate and stalemate detection.
Quiescence search.
Evalution:
PeSTO evaluation.
Pawn structure.
UCI.

v.0.5.2:
Fixed LMR: if moves with reduced depth can raise alpha, we would have to do full search again. Otherwise, a move that has a high score in low depth might not have a high score in high depth, and we potentially miss a better move too.
Fixed Zobrist hashing: hash piece color as well. FEN string is removed too.
Reduced depth to 4, increase search extension to 2. This is not fast, but not terribly slow like the previous version.



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