Houdini

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Houdini, a chess engine by Robert Houdart, which appeared in 2010 as closed source engine, free for non-commercial use. In January 2011, Houdini 1.5 was leading Ingo Bauer's IPON rating list. Houdini 2, released in September 2011, is commercial and bundled with a number of ChessOK products, such as Aquarium, Chess Assistant, and since December 2011, Chess King. Houdini 1.5a remains available as a free download. Houdini 3, released in October 2012, has further improved by more than 50 Elo points. According to its author, Houdini 3 applies a accelerated principal variation search, also dubbed "Smart" Fail-High. If a different move becomes best at very high search depths at the root, re-searches to determine its exact score and the new principal variation are done faster due to a reduced search depth, presumably in conjunction with extensions along the PV. Since November 2012, Houdini 3 is available as ChessBase engine. Houdini 4, released in November 2013, was about 50 Elo stronger than its predecessor, and features 6-men Syzygy bases. =Houdini 5= Released about three years after the previous version, in November 2016, Houdini 5 is vastly improved being about 200 Elo stronger than Houdini 4. It has a completely rewritten evaluation with more aggressive king safety and sophisticated piece mobility, features a more selective search, exploring critical variations significantly deeper, and for hardware with multiple processors, Lazy SMP. Houdini 5 Pro supports up to 128 threads, up to 128 GiB of hash memory, large memory pages, NUMA-architecture, and Nalimov tablebases to find the shortest path to mate.

A development version of Houdini 5 qualified for TCEC Season 9 Superfinal, and even won the TCEC Season 9 Rapid tournament. The final release version of Houdini 5 is about 30 Elo stronger than the engine that played in the TCEC tournament so far. But that was apparently not enough for Stockfish 8 in long time control matches - Houdini 5 lost the 100 game Superfinal with 45½ - 54½. =Houdini 6= Released in September 2017, Houdini 6 again improved in search and evaluation to add another 50-60 Elo in strength, which roughly corresponds to doubling the computational power of the computer. Houdini 6.03 won the TCEC Season 10 Superfinal versus Komodo 1970.00, a successor of Komodo 11, with 53 - 47 (+15=76-9).

=Houdini's Origin= Robert Houdart claims his engine is original, and admits taking ideas from the open source programs Ippolit/Robbolito, Stockfish and Crafty. Other programmers and forum members raised suspicions that Robert took ideas from the controversial Ippolit/Robbolito source code too literally as initial base of his program.

Sources of Inspiration
Robert Houdart on the origins of Houdini in CCC, June 08, 2010 From the start I have very clearly acknowledged the different sources of inspiration for Houdini (Ippo/Robbo, Stockfish and Crafty) and have shown every respect for the hard work of others, be it on my web site, in the readme file, or in this forum ...

Houdini and the Ippo family have lots of high-level similarities, but zillions of low-level subtle differences. Claims have been made that I "just changed a couple of resource strings", "made a cheap compile" or "grabbed some free code", but, in truth, none of you have any clue about the effort that was invested in Houdini.

It is funny that I would not be called a "real" chess engine author, when I am both a professional software developer and a reasonably strong chess player (peak 2280 rating), who has been writing chess engines for over 25 years now in a variety of programming languages.

It is sad that on the one hand you request that everybody demonstrates respect for the hard work of others, but on the other hand you seem to be unable to extend the same courtesy (or even the benefit of the doubt) to Houdini.

Material Table
The idea to index the material table in the same manner as Robbolito, with combined counters of queens, rooks, light and dark bishops, knights and pawns, and to calculate piece counters from that table-index by a sequence of mod/div operations by {2,2,3,3,2,2,2,2,3,3,9,9} might be considered obvious after studying the mentioned source code, and if applying that scheme, there is hardly anything to avoid a sequence of almost identical x86 machine code with same constants for reciprocal multiplication.

Strelka 5
Robert Houdart on Strelka 5, December 04, 2011 Strelka 5 is Houdini 1.5 RE, not Houdini 2. I share your fears, any #1 engine will be RE'd in a matter of months. For Houdini 1.5 it's taken about 6 months.

Reply by Richard Vida You mean 6 months until Strelka has been released to public. You do not know how much time did Yuri Osipov spent on RE, neither when he did start his RE project. For me it took barely one week. As Milos S. pointed out, you made RE very very easy because of starting your project from Robbolito codebase... Personally I see no problem with that (other than you not telling the truth).

Stockfish
In March 2020, an anonymous poster who came into possession of Houdini 6's source code, apparently due to access to a subversion server owned by Robert Houdart, claimed Houdini 5 and 6 were Stockfish derivatives. In summer 2021, the Stockfish team filed a lawsuit against ChessBase to enforce the consequences of the accused license termination concerning Fat Fritz 2 and the allegedly Stockfish derivative Houdini 6 sold by ChessBase.

=Release Dates= =Publications=
 * Houdini 1.0 : May 15, 2010
 * Houdini 1.5 : December 15, 2010
 * Houdini 2.0 : September 01, 2011
 * Houdini 3 : October 15, 2012
 * Houdini 4 : November 25, 2013
 * Houdini 5: November 09, 2016
 * Houdini 6: September 17, 2017

Chess Engine

 * Diogo R. Ferreira (2012). Determining the Strength of Chess Players based on actual Play. ICGA Journal, Vol. 35, No. 1 » Playing Strength
 * Arno Nickel (2012). Die schöne neue Welt der Schachengines. SCHACH 2,3,5,6 2012, pdf (German)
 * Matej Guid, Ivan Bratko (2012). Detecting Fortresses in Chess. Elektrotehniški vestnik, Vol. 79, Nos. 1-2, pdf » Fortress, Rybka, Houdini
 * Diogo R. Ferreira (2013). The Impact of the Search Depth on Chess Playing Strength. ICGA Journal, Vol. 36, No. 2 » Depth, Diminishing Returns, Match Statistics, Playing Strength

Harry Houdini

 * Harry Houdini, et al. (1906, 2012). The Right Way to Do Wrong: An Exposé of Successful Criminals. CreateSpace, amazon.com
 * Harry Houdini (2007). The Right Way to Do Wrong. Librivox audio recording from the Internet Archive


 * Harry Houdini, Harry Houdini Collection (1908). The unmasking of Robert-Houdin. New York : Publishers Printing Co.
 * Walter Brown Gibson, Morris N. Young (1953). Houdini on Magic. Dover Publications

=Postings=

2010 ...
2011
 * Re: Costeff Study 1979 by Robert Houdart, CCC, May 16, 2010
 * Introducing Houdini, a new, strong UCI chess engine by Robert Houdart, CCC, May 16, 2010
 * Houdini - a cheap compile of Ippo/Robo by Lance Perkins, CCC - Computer Chess Club: Engine Origins, May 29, 2010 (requires login)
 * Re: question on draw evaluation by Robert Houdart, CCC, June 07, 2010 » Draw Evaluation
 * Houdini 1.03 is available by Robert Houdart, CCC, July 15, 2010
 * Re: Mate in 17 revisited by Robert Houdart, CCC, July 16, 2010 » Zugzwang
 * Houdini 1.03a bug-fix is available by Robert Houdart, CCC, July 17, 2010
 * Houdini 1.03a tests by Harun Taner, CCC, July 18, 2010
 * Why Is Houdini Not Entered In The WCCC?? by Sean Evans, Open Chess Forum, August 03, 2010
 * Re: Plain and fancy magic on modern hardware by Robert Houdart, CCC, August 26, 2010 » Magic Bitboards
 * Gaviota EGTB in Houdini 1.5 + contacting Eugene Nalimov by Robert Houdart, CCC, December 01, 2010
 * Houdini 1.5 is released by Robert Houdart, CCC, December 15, 2010
 * Houdini 1.5 with Large Page support and 8-cores for w32 by Robert Houdart, CCC, December 19, 2010
 * Houdini 1.5: one mystery/question by Jouni Uski, CCC, December 21, 2010
 * Houdini and Chessbase GUI engine matches by Robert Houdart, CCC, December 27, 2010
 * Houdini Engine Origins by Jeremy Bernstein, OpenChess Forum, January 18, 2011
 * a Telltale position by Larry Kaufman, CCC, 12 February, 2011
 * Re: Why are the Ippo derivative stronger than Stockfish? by Richard Vida, CCC, 25 February, 2011
 * Re: Hash usage percent display (in Arena) by Robert Houdart, CCC, March 24, 2011
 * Re: Houdini, Fire, IvanHoe, (and Rybka?) are 'clones'...? by Jury Osipov, CCC, May 12, 2011
 * Some news about Houdini 2.0 by Robert Houdart, CCC, July 22, 2011
 * Houdini 2 is released by Robert Houdart, CCC, September 02, 2011
 * Houdini 2 Aquarium released by Robert Houdart, CCC, October 09, 2011
 * Computer Chess Biggest Liar by kingliveson, OpenChess Forum, October 09, 2011
 * how far is too far: houdini for sell? by Joseph, CCC, October 11, 2011
 * Houdini with 1:1 Robbolito-code? by Dr. Alexander Schmidt, CCC, October 12, 2011
 * Re: Houdini with 1:1 Robbolito-code? by Norman Schmidt, CCC, October 12, 2011

2012 2013 2014
 * Strelka 5 by Yuriy Osipov by Slavik Pavloff, CCC, October 15, 2011 » Strelka
 * New:Houdini 2 Chess Benchmarks are Acceptable! by Sedat Canbaz, CCC, November 26, 2011
 * Re: Any plans for Houdini 3? by Robert Houdart, CCC, December 03, 2011
 * Re: Komodo 4 on long time control by Richard Vida, CCC, December 04, 2011 » Komodo, Strelka
 * Houdini 2.0c - Mate in 1 bug by Árpád Rusz, CCC, December 08, 2011
 * Re: Interesting poll by Rebel, Rybka Forum, July 15, 2012
 * Houdini 3 reducing the depth feature by Maurizio Maglio, CCC, October 17, 2012
 * Houdini 3 does not behave the same in 64-bit and 32-bit by Ernest Bonnem, CCC, October 23, 2012
 * houdini3 search and mate scores by Uri Blass, CCC, October 29, 2012 » Mate Scores
 * Houdini 3 update does behave the same in 64-bit and 32-bit by Ernest Bonnem, CCC, November 01, 2012
 * What is stronger than Houdini 3 for what? by S.Taylor, CCC, November 11, 2012
 * Houdini 3 tests (8cpu) by Harun Taner, CCC, November 12, 2012
 * The scaling of Houdini 3 and Komodo 5 by Kai Laskos, CCC, November 16, 2012 » Komodo
 * Houdini 3-Houdini 3: Nutzen der Bedenkzeitverlängerung by Patrick Götz, CSS-Forum, December 07, 2012 (German) » Diminishing Returns
 * Houdini 3 the same in 64-bit and 32-bit: well, not quite? by Ernest Bonnem, CCC, November 28, 2012
 * 10 Lessons to be Learned from todays Top Engines by Josef, Rybka Forum, January 03, 2013 » Komodo, Stockfish
 * eval scale in Houdini by Rein Halbersma, CCC, January 14, 2013 » Evaluation
 * Scaling at 2x nodes (or doubling time control) by Kai Laskos, CCC, July 23, 2013 » Doubling TC, Diminishing Returns, Playing Strength, Houdini
 * Houdini 4 has been released by Robert Houdart, CCC, November 25, 2013
 * Houdini, much weaker engines, and Arpad Elo by Kai Laskos, CCC, November 29, 2013 » Match Statistics, Pawn Advantage, Win Percentage, and ELO
 * IPON results for Houdini 4 by Robert Houdart, CCC, December 02, 2013 » IPON
 * Be careful where you buy Houdini 4, or you could get burned by Tom Likens, CCC, December 05, 2013
 * Houdini 3/4? by Jason Coombs, CCC, January 30, 2014
 * Threads factor: Komodo, Houdini, Stockfish and Zappa by Andreas Strangmüller, CCC, May 17, 2014 » Thread, Komodo, Houdini, Stockfish, Zappa

2015 ...
2016 2017 2018
 * Empirical results with Lazy SMP, YBWC, DTS by Kai Laskos, CCC, April 16, 2015 » Lazy SMP, YBWC, DTS
 * Houdini 5 in TCEC by John Wentworth, CCC, April 13, 2016 » TCEC Season 9
 * Houdini 5 dev in TCEC by Jouni Uski, CCC, September 08, 2016 » TCEC Season 9
 * New Houdini by Dann Corbit, CCC, October 05, 2016
 * Houdini 5 has been released by Robert Houdart, CCC, November 09, 2016
 * chessbase houdini is out but... by Stavros Atmatzidis, CCC, December 03, 2016
 * Houdini 6 has been released by Robert Houdart, CCC, September 18, 2017
 * Scaling from FGRL results with top 3 engines by Kai Laskos, CCC, September 26, 2017 » FGRL, Komodo, Stockfish
 * Re: Houdini 6.02 by Robert Houdart, CCC, October 02, 2017
 * Houdini 6.03 released by Christian Goralski, CCC, November 20, 2017
 * Whatever happened to Houdini for Android? by Ted Summers, CCC, November 21, 2017
 * Houdini 6 - Initial position until depth 50 by Andreas Strangmüller, CCC, April 13, 2018 » Initial Position

2020 ...

 * Houdini is a Stockfish Derivative (and started life as a Robbolito derivative) by cucumber, CCC (Engine Origins requires registration), March 22, 2020
 * Houdini is a clone of Stockfish 8 by c9publice...@gmail.com, FishCooking, March 26, 2020
 * An Old Engine by MikeB, CCC, April 11, 2020
 * Re: Is cloning a hobby? by Andrew Grant, CCC, September 17, 2020
 * Our lawsuit against ChessBase, The Stockfish team, Stockfish Blog, July 20, 2021

=External Links=

Chess Engine

 * Houdini Chess Engine
 * Houdini Chess Engine (Wayback Machine, May 19, 2010)
 * Houdini (chess) from Wikipedia

Purchase

 * Houdini 6 Pro ChessBase Shop, September 17, 2017
 * Houdini 5 Pro ChessBase Shop, December 02, 2016
 * Houdini 6 and Aquarium 2018, ChessOK » Aquarium

Interviews

 * Interview of Robert Houdart, the Creator of the Strongest Chess Engine in the world: Houdini (pdf), chess-king.com
 * Houdini 3 – the world's strongest chess engine in the Fritz interface - Interview with Robert Houdart, author of Houdini, ChessBase News, October 29, 2012
 * Robert Houdart on Houdini 5 dev in TCEC, Chessdom, August 25, 2016 » TCEC Season 9
 * Interview with Robert Houdart, Mark Lefler and GM Larry Kaufman by Nelson Hernandez, Chessdom, November 23, 2017 » TCEC Season 10
 * Interview with Robert Houdart, author of the champion engine Houdini, Chessdom, December 08, 2017

Reports

 * New: Houdini 6 | ChessBase, ChessBase News, October 18, 2017
 * Houdini 3: the new king of the block (part one) by Albert Silver, ChessBase News, November 13, 2012
 * Houdini 3: Analyzing in the cloud (part two) by Albert Silver, ChessBase News, November 17, 2012
 * Houdini 4: the 800-pound gorilla, ChessBase News, December 07, 2013
 * One chess champion per laptop by Roberto Perez-Franco, MIT's The Tech, January 15, 2014 » TCEC Season 5
 * Houdini 5 to participate in TCEC Season 9, Chessdom, April 13, 2016 » TCEC Season 9
 * Houdini 5's Tactical Mode: Releasing the Kraken by Albert Silver, ChessBase News, December 08, 2016
 * Fair play in engine chess, ChessBase News, December 30, 2016 » Houdini 5, Komodo 10
 * TCEC: Superfinal Houdini vs Komodo by Stephan Oliver Platz, ChessBase News, November 23, 2017 » TCEC Season 10
 * Houdini is TCEC Season 10 champion!, Chessdom, December 07, 2017
 * Houdini wins TCEC Superfinal by Stephan Oliver Platz, ChessBase News, December 13, 2017 » TCEC Season 10
 * 10 years Houdini by Stephan Oliver Platz, ChessBase News, June 30, 2020

Rating Lists

 * Houdini in CCRL 40/40
 * Houdini 6 64-bit 4CPU in CCRL 40/40

Harry Houdini

 * Harry Houdini from Wikipedia
 * Harry Houdini - The Life of Harry Houdini
 * Harry Houdini Collection
 * Harry Houdini Biography - Facts, Birthday, Life Story - Biography.com

=References= Up one level