Houdini is a UCI

chess engine In computer chess, a chess engine is a computer program that analyzes chess or chess variant positions, and generates a move or list of moves that it regards as strongest. A chess engine is usually a back end with a command-line interface wit ...

developed by

Belgian Belgian may refer to: * Something of, or related to, Belgium * Belgians, people from Belgium or of Belgian descent * Languages of Belgium, languages spoken in Belgium, such as Dutch, French, and German *Ancient Belgian language, an extinct languag ...

programmer A computer programmer, sometimes referred to as a software developer, a software engineer, a programmer or a coder, is a person who creates computer programs — often for larger computer software. A programmer is someone who writes/creates ...

Robert Houdart. It is influenced by

open-source Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...

engines

IPPOLIT IPPOLIT is an open-source chess program released by authors using pseudonyms, Yakov Petrovich Golyadkin, Igor Igorovich Igoronov, Roberto Pescatore, Yusuf Ralf Weisskopf, Ivan Skavinsky Skavar, and Decembrists. The program is a console applicat ...

/RobboLito,

Stockfish Stockfish is unsalted fish, especially cod, dried by cold air and wind on wooden racks (which are called "hjell" in Norway) on the foreshore. The drying of food is the world's oldest known preservation method, and dried fish has a storage lif ...

, and

Crafty Crafty is a chess program written by UAB professor Dr. Robert Hyatt, with continual development and assistance from Michael Byrne, Tracy Riegle, and Peter Skinner. It is directly derived from Cray Blitz, winner of the 1983 and 1986 World Compu ...

. Versions up to 1.5a are available for non-commercial use, while 2.0 and later are commercial only.

Playing style

Chess commentator and video annotator CM Tryfon Gavriel compared Houdini's playing style to that of the Romantic Era of chess, where an attacking, sacrificial style was predominant. According to Robert Houdart, Houdini's advantage against other top engines is in its handling of piece mobility, which is why it "favors aggressive play that tries to win the game".

Version history

The latest stable release of Houdini comes in two versions: ''Houdini 6 Standard'' and ''Houdini 6 Pro''. ''Houdini 6 Pro'' supports up to 128 processor cores, 128 GB of

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

(hash) and is

NUMA Nuclear mitotic apparatus protein 1 is a protein that in humans is encoded by the ''NUMA1'' gene. Interactions Nuclear mitotic apparatus protein 1 has been shown to interact with PIM1, Band 4.1, GPSM2 and EPB41L1 Band 4.1-like protein 1 is a pro ...

-aware, ''Houdini 5 Standard'' only supports up to 8 processor cores, 4 GB of hash and is not NUMA-aware. As with many other UCI engines, Houdini comes with no

GUI The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

, so a chess GUI is needed for running the engine. Houdini 5 uses calibrated evaluations in which engine scores correlate directly with the win expectancy in the position.

Controversies

Houdini has had a history of allegations against it that it contains code from other engines. Houdini 1.0 has been alleged to be an

derivative, and to have plagiarized from

Rybka Rybka is a computer chess engine designed by International Master Vasik Rajlich. Around 2011, Rybka was one of the top-rated engines on chess engine rating lists and won many computer chess tournaments. After Rybka won four consecutive World ...

, which initially lead to Houdini 1.0 to not be tested in any rating lists such as

CCRL Computer chess includes both hardware (dedicated computers) and software capable of playing chess. Computer chess provides opportunities for players to practice even in the absence of human opponents, and also provides opportunities for analysi ...

and

CEGT Chess Engines Grand Tournament, also known as CEGT, is an organization that tests computer chess software by playing chess engines against one another and publishing a ratings table. CEGT routinely tests chess engines in various time controls suc ...

. Houdini 5.0 and Houdini 6.0 have been alleged to be Stockfish 8 derivatives without providing the sources on request, and thus, violating the GPL license. This has resulted in

TCEC Top Chess Engine Championship, formerly known as Thoresen Chess Engines Competition (TCEC or nTCEC), is a computer chess tournament that has been run since 2010. It was organized, directed, and hosted by Martin Thoresen until the end of Season 6; f ...

revoking Houdini's championship results, and disallowing Houdini from competing. Leaked source code has seemingly been shown to produce almost identical play to Houdini 5.0 and Houdini 6.0, while containing direct references to Stockfish in the code documentation. On 20 July 2021, the Stockfish team announced legal action against ChessBase alleging that Houdini 6 and Fat Fritz 2 were in violation of the

GNU General Public License The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the Four Freedoms (Free software), four freedoms to run, study, share, and modify the software. The license was th ...

license. As part of the settlement agreement, ChessBase has conceded the allegations. Houdini 6.0 is also no longer available on ChessBase's website due to it being a Stockfish derivative.

Competition results

Houdini used to be one of the most successful engines in

, with three championship wins to date, but since season 18 it no longer participates in TCEC due to it allegedly containing plagiarized code (see

Controversies Controversy is a state of prolonged public dispute or debate, usually concerning a matter of conflicting opinion or point of view. The word was coined from the Latin ''controversia'', as a composite of ''controversus'' – "turned in an opposite d ...

Notable games

TCEC Houdini - Rybka Match 2011 · Queen Pawn Game: London System (D02) · 1–0
Houdini plays a pawn sacrifice on move 43.

References

External links

*
Interview with Houdart
about the genesis and strengths of his program {{Chess, state=collapsed Chess engines 2010 software