Eleeye

ElephantEye is an open source engine for xiangqi, the Chinese form of chess. It searches and evaluates positions to choose moves and to analyze a board for a human player, and it is distributed from the Chinese Chess Encyclopedia site, which publishes board software, opening theory, game archives and engine documentation alongside it. The engine is designed to be driven by a graphical board program rather than used on its own. It implements version 3.0 of the UCCI engine protocol and is normally paired with the companion board editor and game program published on the same site, which runs on Windows, Android, iPhone, iPad and Mac. Configurable options include the opening book, which ships with ten thousand symmetrical positions, thinking time or a fixed search depth, transposition table size with a default of 16 MB, how aggressively the search prunes, how much positional knowledge the evaluation uses, and four levels of randomness so the engine varies its play in repeated positions. From version 2.0 it also judges perpetual check and perpetual chase as losses, and it accepts a command that forbids specific moves when a user disagrees with its handling of a repetition. ElephantEye is free. It is released under version 2.1 of the GNU Lesser General Public License, with source code published on GitHub, so it can be used, studied and modified without a fee. The same site also distributes Pikafish, a more recent xiangqi engine that it lists first among its downloads, so ElephantEye is best understood as a long standing and unusually well documented reference implementation rather than the strongest engine on offer there.