Houdini (chess)

Houdini is a UCI chess engine developed by Belgian programmer Robert Houdart. It is influenced by open-source engines IPPOLIT/RobboLito, Stockfish, and Crafty. Versions up to 1.5a are available for non-commercial use, while 2.0 and later are commercial only. As of October 2019, Houdini 6 is the fourth highest-rated chess engine on major chess engine rating lists, behind Stockfish, Leela Chess Zero and Komodo.[1]

Houdini
Developer(s)Robert Houdart
Initial releaseMay 15, 2010 (2010-05-15)
Stable release
6.03 / November 20, 2017 (2017-11-20)
Operating systemMicrosoft Windows
TypeChess engine
LicenseProprietary
Websitewww.cruxis.com/chess/houdini.htm

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.[2] 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".[3]

Version history
Version Release date Features[4]
1.0 May 15, 2010 (2010-05-15) First release
1.01 June 1, 2010 (2010-06-01) Bug fixes, improved search algorithm
1.02 June 18, 2010 (2010-06-18) SMP and hash collision bug fixes. Work-around for Shredder GUI.
1.03 July 15, 2010 (2010-07-15) Multi-PV, searchmove and large page support. Improved evaluation function.
1.03a July 17, 2010 (2010-07-17) Bug fix for Multi-PV
1.5 December 15, 2010 (2010-12-15) Improved search and evaluation. Gaviota Table Base Support.
1.5a January 15, 2011 (2011-01-15) Maintenance update with work-arounds for Fritz GUI and other minor improvements.
2.0 September 1, 2011 (2011-09-01) First commercial release. Improved analysis capabilities, enhanced search and evaluation. Houdini Pro version for high-end users with powerful hardware (multi-core support). Chess960 support. Strength limit feature. Position learning. Save hash to file, load hash from file, never clear hash.
2.0b November 7, 2011 (2011-11-07) Maintenance update with minor bug corrections and Nalimov EGTB support.
2.0c November 20, 2011 (2011-11-20) Maintenance update with minor bug corrections and new analysis options. MultiPV_cp option to limit multi-PV analysis to moves within a range of the best move. FiftyMoveDistance option to make the 50-move rule kick in earlier. UCI_Elo and UCI_LimitStrength options as UCI standard-compliant alternative to Strength option. Exit on detection with GUI exit.
3.0 October 15, 2012 (2012-10-15) Major new version. Improved search and evaluation (+50 Elo), Tactical Mode, Scorpio bitbases, accelerated Principal Variation Search "Smart Fail-High", optimized hash usage.
4.0

November 25, 2013 (2013-11-25)

 Major new version. Improved search and evaluation (+50 Elo), 6-men Syzygy table bases (coding provided by Ronald de Man)
5.0

November 7, 2016 (2016-11-07)

 Major new version, about 200 Elo stronger. Rewritten evaluation function, deeper search.
5.01

November 15, 2016 (2016-11-15)

 Maintenance update with some interface corrections and improvements.
6.0

September 15, 2017 (2017-09-15)

 Major new version. Improved search and evaluation (+50-60 Elo), enhanced multi-threading.
6.01

September 24, 2017 (2017-09-24)

 Maintenance update with Nalimov EGTB correction and new output option.
6.02

October 1, 2017 (2017-10-01)

 Maintenance update with Polyglot book support.
6.03

November 20, 2017 (2017-11-20)

 Correction for incorrect detection of stalemate in positions with white pawn capture moves.

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 (hash) and is NUMA-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, 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.[4]

Competition results

Houdini is one of the most successful engines in the TCEC tournament, which is often regarded as the Unofficial World Computer Chess Championship, with three championship wins to date.[5] The fourth championship win has been revoked (see Controversy).

Controversy

Houdini 6 has been alleged to be a Stockfish 8 derivative without providing the sources on request, and thus, violating the GPL license. The allegations have been confirmed by the Stockfish maintainers.[6] This has resulted in TCEC revoking the championship results of Houdini 6.[7] A technical overview of the allegations is available in.[8]

Notable games
"Houdini Immortal"
Rybka - Houdini
abcdefgh
8
8
77
66
55
44
33
22
11
abcdefgh
Position after the 24th move. Houdini (Black) is three pawns down but has very active pieces and White's king is exposed. White couldn't avoid losing a piece 7 moves later.

See also

References
  1. "CCRL 40/40". Retrieved 16 October 2019.
  2. "Houdini with Black pieces in the Thoresen Chess Engines Competition. Game shows Houdini playing style from 6:23" on YouTube
  3. "Interview with Robert Houdart, Mark Lefler and GM Larry Kaufman". chessdom.com. November 23, 2017. Retrieved November 24, 2017.
  4. Cruxis, Retrieved 16 June 2012
  5. "Houdini is TCEC Season 10 champion!". 7 December 2017.
  6. VandeVondele, Joost (Apr 6, 2020). "Houdini is a clone of Stockfish 8". Fishcooking forums. Retrieved Dec 23, 2020.
  7. Grant, Andrew (Dec 21, 2020). "A Thank You, to TCEC". TalkChess.com. Retrieved Dec 23, 2020.
  8. Williams, Aaron (Apr 12, 2020). "Is Houdini 6 a Stockfish clone? (answer)". Retrieved Dec 23, 2020.
  9. Video annotation by Kingscrusher on YouTube
  10. Monokroussos, Dennis. "Houdini 1.5a defeats Rybka 4: 23.5-16.5". Retrieved 25 October 2013.
  11. Video annotation by Kingscrusher on YouTube
  12. "Free Houdini beats commercial Rybka 23.5-16.5". Chessvibes. 10 February 2010. Retrieved 25 October 2013.
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