Crafty is a chess program written by Bob Hyatt. It is the "son" of Cray Blitz, winner of the 1983 and 1986 World Computer Chess Championships. Crafty is designed around bitboards (a 64-bit data structure) for reasons of speed of execution, ease of adding new knowledge, and a significantly cleaner overall design. Read more hot
Toga II is a derivative of the Fruit chess engine. It enhances on Fruit by offering greater chess knowledge and a better search algorithm. Read more hot
AICE is a C++/STL engine that is bitboard based. It uses alpha-beta (PVS) seaches, and has adaptive Null move pruning.
APIL chess is a fully distributed Alphabeta-search based, simple chess program.
Boo's Chess Engine (or BACE - Bowron Abernethy Chess Engine) is a text based chess engine that learns from experience using a temporal difference learning algorithm. It is compatible with WinBoard, Xboard and icsDrone.
Brutal Chess features full 3D graphics, an advanced particle engine, and several different levels of intelligent AI, inspired by the once popular "Battle Chess" released by Interplay circa 1988.
Bullucks is an experimental chess program. It's the re-incarnation of `Detolte'.
Cassandre is an extensible chess engine written in C++, it is Winboard/XBoard compliant.
CHEOPS (CHEss OPponent Simulator) is a fully-functional chess program capable of human-vs-human, human-vs-computer, and computer-vs-computer play. It uses a 64-square linear array board representation. The game tree search is alpha?beta, and the static evaluation function considers material, mobility, and motif features.
Chesley is a free software chess engine written in C++ targeting Unix-like platforms and the xboard GUI. Chesley implements a number of modern chess programming techniques, including bitboard move generation, transposition tables, etc.
Chispa is written in C++ and uses the STL library. It supports Fischer-Random Chess, and Shuffle Chess. Search features include: Minimax with Alpha-Beta pruning, Root aspiration windows, Negascout, Adaptive Null-Move pruning, Move ordering based on: SEE, History heuristic, Killer moves, and hash tables, and more.
CPP1 is an experimental OO chess program written in C++.
(commercial) Deep Sjeng is a professional chess playing and analysis engine. It plays above grandmaster level (more than 200 ELO stronger than 'Sjeng Free'), supports multiprocessors, different personalities which can simulate human errors, multivariation analysis, access to internet chess servers, a database, a professional hand-tuned openings book and all the other goodies you could want.
engendrov is a chess machine. Engendrov plays chess with an aprox ELO of 1800. It has a graphical interface for windows and linux.
Faile is a relatively strong (expert to master strength, ~ 2050 - 2250 ELO, depending on your computer).
(commercial) Fruit comes with a customised opening book and has many features which make it interesting especially for the engine enthusiast and serious correspondence player.
Gaia is a free amateur chess engine written in C++. It supports forward pruning, and internal iterative deepening.
GromitChess is a free xboard/WinBoard-chessengine for Linux and Windows. It finished 4th/18 at the World Microcomputer Chess Championships in Maastricht 2001 (see here), winning the amateur-title and being second in the single-processor category.
Gullydeckel Chess Program
The Gullydeckel chess playing program allows you to play a game of chess against a not too strong opponent. It has been written by Martin Borriss and is available free of charge on the terms of the GNU General Public License (GPL).
Hermann is a chess engine without an own graphical user interface.
Homer is written in C/C++ and runs on different hardware. Homer is a non bitboard based chess engine. Features include: Alpha/Beta search with PVS extension, 64 square board presentation, verified R 3 nullmove, hashtables, and static exchange evaluation.
KnightCap is a chess program written for the Fujitsu AP1000+ parallel computer (running AP/Linux). It will also run on most unixes, although you may need to tweak the includes.h file and Makefile. KnightCap is now starting to get reasonably competitive with some of the better known free chess programs. It beats gnuchess a reasonable percentage of the time (although I still think gnuchess is better) and has even been known to beat crafty on occasion.
Marvin features support for the UCI protocol, draw claim, resign option, hash tables with an opening book. It has built-in support for running testsuites.
Matheus is a chess engine compatible with Winboard, Xboard and UCI GUIs.
Modula2Chess is for one player versus computer programed in Modula2.
OliThink is a medium-high strength chess program, with an ELO about 2100.
Pepito features Bitboard infrastructure, Negascout search algorithm, Usual depth extensions to avoid horizon effect (i.e. check, recapture, pawn push...), Transposition tables, pawn hash tables & evaluation cache, Futility pruning at frontier and prefrontier nodes, razoring.
Phalanx is a chess playing engine. It does not have its own graphical interface, but can be used with general chess interface xboard. Phalanx is "wannabe Mikhail Tal", at least when compared to other programs. It looks at much more king safety terms than other programs. It counts numbers/types of attacks at squares near kings, number of safe checking moves available, etc.
pouetChess is a 3D and open source chess game for Linux with very few and basic dependencies. Moreover pouetChess has an embedded Artificial Intelligence so engines such as GNUChess are not even needed.
PyChess is a computer chess program for human vs. computer games. pythonchess is a complete chess program with alpha-beta search, hashing, pondering, iterative deepening, etc. implemented in Python programming language. Read more
Rzeznik is a bitboard engine, parametrized evaluation, search extensions, hash tables, null move, razoring, futility pruning, opening book, quiescence, static move evaluator (move ordering), killer moves, static capture evaluator, and Win/Xboard support.
Scid Vs PC
Scid Vs PC is a player vs. computer chess engine and database that was forked from Shane's Chess Information Database. It includes several well known engines, can be used to play on the Internet with FICS, and has extensive database and PGN file handling capabilities.
Shatranj is a bitboard based Python chess engine that uses a recursive alphabeta search. It does iterative deepening and can play a complete game. It is currently text based. The current evaluation function is rather weak, but you can expect about 6 ply on most moves with a relatively fast machine, which means about 4k-5k/nps.
Sjeng was an attempt to create a bughouse & crazyhouse playing program that can attain a level comparable to what the best human players are capable of. Newer versions of Sjeng also play standard, suicide, giveaway and losers chess.
Small Potato is a IETF protocol version 2 compliant chess engine, to be used with XBoard/WinBoard style interfaces. Sitting at around 1900 on 3-minute chess on FICS.
vcboard is a "non-intelligent" chess program that enables users to play chess over a network as well as enter, store, load, and view games.
vulcan lets you play against the computer a chess variant inspired by a certain well-known science fiction TV series.
Yace is an engine for WinBoard, Shredder and CB.
Zappa is a standard chess program, which is to say that is an alpha-beta searcher using nullmove forward pruning, various extensions, and a heuristical evaluation. It is written in C++, although it is not particularly object oriented, nor does it use a great deal of STL code, inheritance hierarchies, virtual functions, overloaded operators, or other C++ wizardry.