Endgame Bitbases

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Endgame Bitbases, are compact endgame tablebases with game theoretical values of one or two bits per position stored. They are sufficient for various material configurations to reside inside RAM for short probing access time, intended to use deep inside the search. The boolean or four valued ranges are either {won, not_won} or {won, draw, loss, invalid}. While WDL information is sufficient to guide the search into won positions, it lacks any sense of progress in won positions. Therefor, programs either probe full tablebases at the root to reveal the number of moves until conversion or mate, or combine WDL-scores with heuristic evaluation scores, considering material, ply-distance to the root, pawn closeness to promotion, distance of pieces to opponent king, etc.. Endgame Bitbases were described in 1999 by Ernst A. Heinz in Knowledgeable Encoding and Querying of Endgame Databases, as applied with 4-men in DarkThought.

=Bitbase Implementations=
 * Gaviota Tablebases
 * Scorpio Bitbases
 * Shredder Bases
 * Syzygy Bases

=See also=
 * Interior Node Recognizer
 * KPK
 * Retrograde Analysis

=Publications=
 * Ken Thompson (1996). 6-Piece Endgames. ICCA Journal, Vol. 19, No. 4
 * Ernst A. Heinz (1999). Knowledgeable Encoding and Querying of Endgame Databases. ICCA Journal, Vol. 22, No. 2, ps
 * Ren Wu, Don Beal (2001). Fast, Memory-efficient Retrograde Algorithms. ICGA Journal, Vol. 24, No. 3

=Forum Posts=

2000

 * EGTB: Better algorithm by Urban Koistinen, CCC, April 07, 2001
 * Generating egtbs ICGAJ by Tony Werten, CCC, December 04, 2001
 * Wu/Beal predates Koistinen by Guy Haworth, CCC, December 04, 2001


 * EGTB generation with 1 bit per position? by Martin Fierz, CCC, March 25, 2003
 * Any programs besides Yace and Patzer that can use bitbase files by Dann Corbit, CCC, June 17, 2004 » Patzer, Yace

2005

 * Bitbases - yace, scorpio, gambitfruit by Bernhard Bauer, CCC, December 06, 2005
 * Open Source bitbase program by Peter Fendrich, CCC, April 09, 2007
 * KQKB and KQKN heuristic for bitbases?! by Jesper Nielsen, CCC, May 01, 2007
 * bitbases and Linux by Charles Roberson, CCC, June 26, 2007
 * Question about bitbases by Thomas Gaksch, CCC, February 02, 2008
 * How to generate a "simple" bitbase? by Alessandro Scotti, CCC, February 12, 2008
 * How much are bitbases worth? by Tord Romstad, CCC, May 22, 2008
 * Bitbases by Frank Phillips, CCC, May 03, 2009
 * Endgame bitbase / tablebase compromise? by clgd, CCC, July 13, 2009
 * Bitbase indexing and en passant by Tord Romstad, CCC, August 14, 2009

2010

 * Gaviota TBs [0.1.6.1, bitbase-like interface] by Miguel A. Ballicora, CCC, February 22, 2010
 * Gaviota TBs Probing Code (v0.2) UPDATE, Bitbases on the fly by Miguel A. Ballicora, CCC, March 20, 2010
 * hard-wired bitbases by Ben Stoker, CCC, April 13, 2010
 * Stockfish bitbase by kongsian, CCC, June 01, 2010
 * Search with bitbase by Pham Hong Nguyen, CCC, September 05, 2012
 * KPK bitbase by Maarten Bults, CCC, January 16, 2013 » KPK
 * What happens using egbb by Kai Laskos, CCC, October 12, 2013
 * Scorpio 6men EGBB Now available by Joshua Shriver, CCC, January 14, 2014 » Scorpio Bitbases

2015 ...

 * Yet another KPK endgame table generator: pfkpk by Marcel van Kervinck, CCC, September 05, 2015 » KPK

=External Links= =References=
 * Endgame tablebase | Computer chess - Wikipedia
 * Computing endgames with few men by Urban Koistinen
 * dshawul/Scorpio · GitHub includes Six men egbb code » Scorpio Bitbases
 * kervinck/pfkpk · GitHub » KPK Bitbase by Marcel van Kervinck

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