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		Critter, an UCI compatible cross-platform chess engine by Richard Vida, executables freely available for personal use to run under Windows, Linux, Android and Mac OS [1] . Starting in late 2008, Critter was first written in Object Pascal compiled with Delphi, now available as open source engine [2] [3] , and was ported to C / C++ in 2009 [4] . It consistently evolved through various board representations from 0x88 to bitboards, as acknowledged by Richard Vida, also incorporating ideas from strong open source programs like Ippolit [5] , to a world class engine which achieved top five of most engine rating lists [6] .In 2012, Critter had its over the board debut at the ICT 2012, where it became strong runner-up behind the Rybka cluster.
Critter Country [7]

Description

Critter applies a principal variation search with aspiration windows, null move pruning ^[8] and other state of the art forward pruning, reduction and extension techniques, such as the Botvinnik-Markoff extensions ^[9] . It can search in parallel with up to eight threads ^[10] , supports Gaviota tablebases ^[11] , and is able to play Chess960 ^[12] . Critter features a tapered eval with a score pair class and overloaded operators ^{[13] [14]} , and blockage detection in late endgames ^[15] .

Selected Games

ICT 2012, round 7, Rybka - Critter ^{[16] [17]}

[Event "ICT12"]
[Site "Leiden"]
[Date "2012.05.13"]
[Round "7"]
[White "Rybka"]
[Black "Critter"]
[Result "1/2-1/2"]
 
1.d4 d5 2.c4 e6 3.Nf3 c6 4.e3 Bd6 5.b3 f5 6.Bd3 Nf6 7.O-O Qe7 8.Bb2 O-O
9.Qc1 b6 10.Ba3 Bb7 11.Bxd6 Qxd6 12.Nc3 dxc4 13.Bxc4 Nbd7 14.Re1 b5
15.Bd3 b4 16.Na4 c5 17.Nxc5 Bxf3 18.gxf3 Rfc8 19.Bc4 Nxc5 20.dxc5 Rxc5
21.a3 bxa3 22.Qxa3 Nd5 23.Red1 Qc7 24.Kg2 Rd8 25.Bxd5 Rdxd5 26.Qa4 Qe7
27.Rxd5 Rxd5 28.Qxa7 Qxa7 29.Rxa7 Rb5 30.Re7 Rb6 31.Kg3 Kf8 32.Rd7 Rxb3
33.Kf4 Rb5 34.h4 h6 35.Kg3 Rb8 36.h5 Re8 37.Rb7 Re7 38.Rb5 Kf7 39.e4 Kf6
40.exf5 exf5 41.Kf4 Re2 42.Rxf5+ Ke6 43.Rb5 Rxf2 44.Rb6+ Kf7 45.Rb7+ Kf6
1/2-1/2

Release Dates

• Critter 0.38 : 2009-05
• Critter 0.39a : 2009-06
• Critter 0.42 : 2009-10
• Critter 0.52 : 2010-01
• Critter 0.52b : 2010-02
• Critter 0.60 : 2010-04
• Critter 0.70 : 2010-05
• Critter 0.80 : 2010-07
• Critter 0.90 : 2010-11
• Critter 1.0 : 2011-03
• Critter 1.01 : 2011-03
• Critter 1.2 : 2011-06
• Critter 1.4 : 2011-12
• Critter 1.4a : 2012-01
• Critter 1.6 : 2012-06
• Critter 1.6a : 2012-06

See also

• Fiction
• Mammal

Publications

• Arno Nickel (2012). Die schöne neue Welt der Schachengines. SCHACH 2,3,5,6 2012, pdf (German) ^[18]

Forum Posts

2009

• Critter 0.34 : 2146 by Patrick Buchmann, CCC, April 18, 2009
• Critter 0.38 : 2330 by Patrick Buchmann, CCC, May 22, 2009
• Critter 0.40 released by Richard Vida, CCC, July 26, 2009
• Critter 0.40 : 2471 by Patrick Buchmann, CCC, August 01, 2009
• Critter: Pascal vs C by Richard Vida, CCC, August 27, 2009 » C, Pascal
• Critter 0.42 available by Richard Vida, CCC, October 08, 2009 » Pascal
• Critter 0.42 : 2649 by Patrick Buchmann, CCC, October 11, 2009

2010

• Critter 0.52 available by Richard Vida, CCC, Jan 25, 2010 » C
• Critter 0.52b added to the IPON list ... by Ingo Bauer, CCC, February 04, 2010
• Strange knight underpromotion by Critter by Richard Vida, CCC, March 04, 2010
• Critter goes SMP (version 0.60 is released) by Richard Vida,CCC, April 13, 2010
• Critter 0.60: 2718 by Patrick Buchmann, CCC, April 14, 2010
• Critter 0.70 is out by Richard Vida, CCC, May 23, 2010
• Critter 0.80 by Richard Vida, CCC, July 24, 2010
• Critter 0.90 released by Richard Vida, CCC, November 29, 2010
• Critter - looking at static evaluation by Richard Vida, CCC, December 11, 2010

2011

• Critter 1.0 available by Richard Vida, CCC, March 16, 2011
• Critter 1.0 for Linux by Richard Vida, CCC, March 22, 2011 » Linux
• My experience with Linux/GCC by Richard Vida, CCC, March 23, 2011
• Critter bugfix update by Richard Vida, CCC, March 28, 2011 ^[19]
• Critter 1.2 update + new homepage by Richard Vida, CCC, June 25, 2011 » Android
• Critter 1.2 SEEMS to be a member of the Ippo family by Kai Laskos, CCC, July 02, 2011
• for Pascal fans: Critter by Richard Vida, CCC, September 16, 2011

2012 ...

• Re: World Computer Chess Championship ? by Richard Vida, CCC, June 11, 2012
• Re: Critter 1.6 released! by Richard Vida, CCC, June 15, 2012
• Continuation of Critter would be very appreciated by Mike Scheidl, CCC, May 15, 2013

External Links

Chess Engine

• Critter for win32/64, linux and android platforms hosted by Emil Vlasák
• SourceForge.net: Critter Chess - Project Web Hosting - Open Source Software (Pascal Version)
• Critter (chess) from Wikipedia
• Critter at CCRL 40/40

Misc

• Critter (disambiguation page) from Wikipedia
• Little Critter from Wikipedia
• Critter Country from Wikipedia
• Critters (film series) from Wikipedia
• Critters animatronic critter hand puppet replica by Andy Wright

References

1. ^ Critter for win32/64, linux and android platforms hosted by Emil Vlasák, Mac OS version compiled by Jeremy Bernstein
2. ^ for Pascal fans: Critter by Richard Vida, CCC, September 16, 2011
3. ^ SourceForge.net: Critter Chess - Project Web Hosting - Open Source Software
4. ^ Critter: Pascal vs C by Richard Vida, CCC, August 27, 2009
5. ^ Re: World Computer Chess Championship ? by Richard Vida, CCC, June 11, 2012
6. ^ Critter (chess) from Wikipedia
7. ^ Critter Country from Wikipedia run by The Walt Disney Company
8. ^ Interview with Richard Vida by Frank Quisinsky, February 20, 2010
9. ^ Re: World Computer Chess Championship ? by Richard Vida, CCC, June 11, 2012
10. ^ Critter goes SMP (version 0.60 is released) by Richard Vida, CCC, April 13, 2010
11. ^ Critter 0.70 is out by Richard Vida, CCC, May 23, 2010
12. ^ Critter 0.80 by Richard Vida, CCC, July 24, 2010
13. ^ Re: talk about IPP's evaluation by Richard Vida, CCC, November 07, 2009 » Ippolit, SIMD and SWAR Techniques
14. ^ My experience with Linux/GCC by Richard Vida, CCC, March 23, 2011
15. ^ Chiron 1.1 bug? by Richard Vida, CCC, December 24, 2011
16. ^ Leiden Round 7: Rybka vs Critter by Ray, Rybka Forum, May 13, 2012
17. ^ ICT 12 - PGN download, CSVN
18. ^ Part 1 covers Houdini, Rybka, Komodo, Stockfish, Critter, Naum, Chiron and Spike
19. ^ Difficult position to Critter by Jouni Uski, CCC, March 24, 2011

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