Houdini (chess)

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Developer(s) Robert Houdart
Initial release May 15, 2010; 7 years ago (2010-05-15)
Stable release
5 / November 7, 2016; 7 months ago (2016-11-07)
Development status Active
Written in C++
Operating system Microsoft Windows
Type Chess engine
License Proprietary
Website www.cruxis.com/chess/houdini.htm

Houdini is a UCI chess engine developed by Belgian programmer Robert Houdart. It is influenced by open source engines IPPOLIT/RobboLito, Stockfish, and Crafty. Earlier versions are free for non-commercial use (up to version 1.5a), but later versions (2.0 and onwards) are commercial. As of January 2017, Houdini 5 is the second top-rated chess engines on major chess engine rating lists between Stockfish and Komodo.[1][2][3][4][5]

Playing style[edit]

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.[6]

Version history[edit]

Version Release date Features[7]
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.

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)

November 7, 2016 (2016-11-07)

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

November 15, 2016 (2016-11-15)

Maintenance update with some interface corrections and improvements.

The latest stable release of Houdini comes in two versions: Houdini 5 Standard and Houdini 5 Pro. Houdini 5 Pro supports up to 128 processor cores, 128 GB of RAM (hash) and is NUMA-aware, Houdini 5 Standard only supports up to 6 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.[7]

Controversial origins[edit]

Robert Houdart describes his engine as original and admits taking ideas from the open source programs IPPOLIT/Robbolito, Stockfish and Crafty.[8][9] However, some chess programmers raised suspicions that Houdart may have taken ideas from the controversial Ippolit/Robbolito source-code "too literally" as the initial base of his program.[8][10]

Competition results[edit]

Houdini has won top honors in the TCEC tournament, which is often regarded as the Unofficial World Computer Chess Championship. Houdini has won three seasons to date, and narrowly failed to qualify for the finals in nTCEC Season 2, having lost out to Komodo and Stockfish.[11]

Notable games[edit]

"Houdini Immortal"
Rybka - Houdini
a b c d e f g h
h8 black rook
d7 black bishop
e7 black pawn
f7 black king
g7 black bishop
a5 black rook
f5 black pawn
a4 black knight
d3 white king
f3 white pawn
a2 white pawn
b2 white pawn
c2 white knight
f2 white knight
g2 white pawn
h2 white pawn
a1 white rook
c1 white bishop
h1 white rook
7 7
6 6
5 5
4 4
3 3
2 2
1 1
a b c d e f g h
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 to lose a piece 7 moves later.


  1. ^ "CCRL 40/40 Rating List — All engines (best versions only)". computerchess.org.uk. Retrieved January 25, 2017. 
  2. ^ "IPON Rating List". inwoba.de. Retrieved January 25, 2017. 
  3. ^ "SWCR chess engine ratings list". amateurschach.de. Retrieved January 25, 2017. 
  4. ^ "CEGT Best Versions". husvankempen.de. Retrieved January 25, 2017. 
  5. ^ "CCRL 40/4 Rating List". CCRL. Retrieved 25 January 2017. 
  6. ^ "Houdini with Black pieces in the Thoresen Chess Engines Competition. Game shows Houdini playing style from 6:23" on YouTube
  7. ^ a b Cruxis, Retrieved 16 June 2012
  8. ^ a b "kingliveson: Houdini is a modified and improved RobboLito.", 25 October 2013
  9. ^ "Houdart: Why Houdini has never entered in a WCCC.", 25 October 2013
  10. ^ "kingliveson: Again, Houdini is RobboLito modified.", 25 October 2013
  11. ^ TCEC Official page, 25 October 2013
  12. ^ Video annotation by Kingscrusher on YouTube
  13. ^ Monokroussos, Dennis. "Houdini 1.5a defeats Rybka 4: 23.5-16.5". Retrieved 25 October 2013. 
  14. ^ Video annotation by Kingscrusher on YouTube
  15. ^ "Free Houdini beats commercial Rybka 23.5-16.5". Chessvibes. 10 February 2010. Retrieved 25 October 2013. 

External links[edit]