Credits

Chess Challenge Engine stands on the work of other free-software authors.

Obsidian — search

The search algorithm and its 42 SPSA-tuned search parameters (LmrBase, NmpBase, RfpDepthMul, …) are adapted from Obsidian by gab8192, licensed under the GNU GPL v3. The parameter values are taken verbatim from Obsidian's src/search.cpp; this engine is a Python translation, not an independent design.

Cheese — evaluation

The piece-square tables, tapered piece values and the bishop-pair, pawn-structure, rook, knight-mobility and king-attacker terms in eval_params.py are ported from the Cheese chess engine by Patrice Duhamel, Copyright (C) 2006-2025, licensed under the GNU GPL v3 (cheesechess.net).

python-chess — move generation

Move generation and board representation are provided by python-chess by Niklas Fiekas, licensed under GPL-3.0-or-later.

Copyright and licence

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3. It is distributed WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for details.