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'''[[Main Page|Home]] * [[Knowledge]] * [[Endgame Tablebases]] * Edwards' Tablebases'''
'''Edwards' Tablebases''',
are three-, four and some five-piece tablebases constructed by [[Steven Edwards]] in the early 90s, initially for his chess program [[Spector]]. Edwards' Tablebases rely on [[Endgame Tablebases#DTM|Depth to Mate]] and the complete coverage for both sides, using one [[Byte|byte]] per [[Chess Position|position]], with evaluations of the forms "mate in N", "lose (get mated) in N", "draw", and "illegal". Values for the number N (measured in fullmoves, not [[Ply|ply]]) for mates range from mate in 1 upto mate in 126 and for losses in 0 (lose in 0 means [[Checkmate|checkmated]]) to lose in 125 moves. Each file is for a given class (e.g., KBNK) and for a given [[Side to move|side to move]] (e.g., White) <ref>[https://www.stmintz.com/ccc/index.php?id=11493 Steve Edward's Endgame Tablebase generator is now available for WIN95] by [[Michael Byrne|Mike Byrne]], [[CCC]], November 01, 1997</ref>. After finishing the construction procedure in 1994, Steven Edwards made the whole data, documentation and a test program written in [[C|ANSI-C]] publicly available on the Internet. Until the advent of the compressed [[Nalimov Tablebases]], Edwards' Tablebases were quite popular and used in several chess programs, such as [[Crafty]], [[Gromit]], and the commercial [[MChess|MChess Pro]], to name a few.
=Index Scheme=
The index scheme for pawn-less endgames exploits the fourfold symmetry of the [[Chessboard|chessboard]] to restrict the last identified piece to the a1-d1-d4 triangle by [[Horizontal Mirroring|horizontal]], [[Vertical Flipping|vertical]], or [[Diagonal Mirroring|diagonal reflections]], and features vertical symmetry by confining one pawn to the queen-side flank for endgames with one pawn. Other schemes as applied for instance in [[Thompson's Databases]], enumerating all legal positions of both kings as combined index and considering pawns can't reside on the first or eighth rank, feature denser index ranges than Edwards' <ref>[[Ernst A. Heinz]] ('''1999'''). ''Endgame Databases and Efficient Index Schemes for Chess.'' [[ICGA Journal#22_1|ICCA Journal, Vol. 22, No. 1]], [http://people.csail.mit.edu/heinz/ps/edb_index.ps.gz ps]</ref>.
=See also=
* [[Endgame Bitbases|Bitbases]]
* [[Gaviota Tablebases]]
* [[Lomonosov Tablebases]]
* [[Nalimov Tablebases]]
* [[Scorpio Bitbases]]
* [[Syzygy Bases]]
* [[Thompson's Databases]]
=Publications=
* [[Steven Edwards]] and the Editorial Board ('''1995'''). ''An Examination of the Endgame KBNKN''. [[ICGA Journal#18_3|ICCA Journal, Vol. 18, No. 3]], [http://arno.uvt.nl/show.cgi?fid=106843 pdf]
* [[Steven Edwards]] ('''1996'''). ''An Examination of the Endgame KBBKN.'' [[ICGA Journal#19_1|ICCA Journal, Vol. 19, No. 1]]
=Forum Posts=
==1990 ...==
* [https://groups.google.com/d/msg/rec.games.chess/RN3yWuteQQ4/9G7rH4pFVKMJ Announcing forced mates: a poll] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], July 21, 1994
* [https://groups.google.com/d/msg/rec.games.chess/PZV47lZr2jE/xxZIRd4q4vIJ KBBK tablebases: attempt #2] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], August 13, 1994
* [https://groups.google.com/d/msg/comp.archives/XSXGunhIhjM/VsWof-hiBaoJ Updated tablebase documentation] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], October 14, 1994
* [https://groups.google.com/d/msg/comp.archives/806Mshtacxc/rBvnTLgJxqUJ KPK tablebases now available via ftp] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], October 14, 1994
==1995 ...==
* [https://groups.google.com/d/msg/alt.chess.ics/E_3_8Z7sPT8/ufKMjWjxM80J Re: FICS vs. ICS: No, really, which is better?] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|alt.chess.ics]], June 01, 1995
* [https://groups.google.com/d/msg/rec.games.chess.computer/8AKVzXG7Efw/ieMDuzaJjY4J MCP6 Endgame Tablebase. Thanks mr.Hirsch!] by H.Pieters, [[Computer Chess Forums|rgcc]], November 11, 1996
* [https://www.stmintz.com/ccc/index.php?id=11493 Steve Edward's Endgame Tablebase generator is now available for WIN95] by [[Michael Byrne|Mike Byrne]], [[CCC]], November 01, 1997
* [https://www.stmintz.com/ccc/index.php?id=14970 EGTB] by [[Frank Phillips]], [[CCC]], February 10, 1998
==2000 ...==
* [http://www.open-aurec.com/wbforum/viewtopic.php?f=18&t=34259 Tablebases Edwards] by RR, [[Computer Chess Forums|Winboard Forum]], July 25, 2001
==2010 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=53244 A different tablebase encoding format] by [[Steven Edwards]], [[CCC]], August 10, 2014
=Downloads=
<ref>Courtesy [[Steven Edwards]]</ref>
* [[File:tbgen.zip]]
* [[File:Spector.zip]]
=References=
<references />
'''[[Endgame Tablebases|Up one level]]'''
'''Edwards' Tablebases''',
are three-, four and some five-piece tablebases constructed by [[Steven Edwards]] in the early 90s, initially for his chess program [[Spector]]. Edwards' Tablebases rely on [[Endgame Tablebases#DTM|Depth to Mate]] and the complete coverage for both sides, using one [[Byte|byte]] per [[Chess Position|position]], with evaluations of the forms "mate in N", "lose (get mated) in N", "draw", and "illegal". Values for the number N (measured in fullmoves, not [[Ply|ply]]) for mates range from mate in 1 upto mate in 126 and for losses in 0 (lose in 0 means [[Checkmate|checkmated]]) to lose in 125 moves. Each file is for a given class (e.g., KBNK) and for a given [[Side to move|side to move]] (e.g., White) <ref>[https://www.stmintz.com/ccc/index.php?id=11493 Steve Edward's Endgame Tablebase generator is now available for WIN95] by [[Michael Byrne|Mike Byrne]], [[CCC]], November 01, 1997</ref>. After finishing the construction procedure in 1994, Steven Edwards made the whole data, documentation and a test program written in [[C|ANSI-C]] publicly available on the Internet. Until the advent of the compressed [[Nalimov Tablebases]], Edwards' Tablebases were quite popular and used in several chess programs, such as [[Crafty]], [[Gromit]], and the commercial [[MChess|MChess Pro]], to name a few.
=Index Scheme=
The index scheme for pawn-less endgames exploits the fourfold symmetry of the [[Chessboard|chessboard]] to restrict the last identified piece to the a1-d1-d4 triangle by [[Horizontal Mirroring|horizontal]], [[Vertical Flipping|vertical]], or [[Diagonal Mirroring|diagonal reflections]], and features vertical symmetry by confining one pawn to the queen-side flank for endgames with one pawn. Other schemes as applied for instance in [[Thompson's Databases]], enumerating all legal positions of both kings as combined index and considering pawns can't reside on the first or eighth rank, feature denser index ranges than Edwards' <ref>[[Ernst A. Heinz]] ('''1999'''). ''Endgame Databases and Efficient Index Schemes for Chess.'' [[ICGA Journal#22_1|ICCA Journal, Vol. 22, No. 1]], [http://people.csail.mit.edu/heinz/ps/edb_index.ps.gz ps]</ref>.
=See also=
* [[Endgame Bitbases|Bitbases]]
* [[Gaviota Tablebases]]
* [[Lomonosov Tablebases]]
* [[Nalimov Tablebases]]
* [[Scorpio Bitbases]]
* [[Syzygy Bases]]
* [[Thompson's Databases]]
=Publications=
* [[Steven Edwards]] and the Editorial Board ('''1995'''). ''An Examination of the Endgame KBNKN''. [[ICGA Journal#18_3|ICCA Journal, Vol. 18, No. 3]], [http://arno.uvt.nl/show.cgi?fid=106843 pdf]
* [[Steven Edwards]] ('''1996'''). ''An Examination of the Endgame KBBKN.'' [[ICGA Journal#19_1|ICCA Journal, Vol. 19, No. 1]]
=Forum Posts=
==1990 ...==
* [https://groups.google.com/d/msg/rec.games.chess/RN3yWuteQQ4/9G7rH4pFVKMJ Announcing forced mates: a poll] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], July 21, 1994
* [https://groups.google.com/d/msg/rec.games.chess/PZV47lZr2jE/xxZIRd4q4vIJ KBBK tablebases: attempt #2] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], August 13, 1994
* [https://groups.google.com/d/msg/comp.archives/XSXGunhIhjM/VsWof-hiBaoJ Updated tablebase documentation] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], October 14, 1994
* [https://groups.google.com/d/msg/comp.archives/806Mshtacxc/rBvnTLgJxqUJ KPK tablebases now available via ftp] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|rgc]], October 14, 1994
==1995 ...==
* [https://groups.google.com/d/msg/alt.chess.ics/E_3_8Z7sPT8/ufKMjWjxM80J Re: FICS vs. ICS: No, really, which is better?] by [[Steven Edwards|Steven J. Edwards]], [[Computer Chess Forums|alt.chess.ics]], June 01, 1995
* [https://groups.google.com/d/msg/rec.games.chess.computer/8AKVzXG7Efw/ieMDuzaJjY4J MCP6 Endgame Tablebase. Thanks mr.Hirsch!] by H.Pieters, [[Computer Chess Forums|rgcc]], November 11, 1996
* [https://www.stmintz.com/ccc/index.php?id=11493 Steve Edward's Endgame Tablebase generator is now available for WIN95] by [[Michael Byrne|Mike Byrne]], [[CCC]], November 01, 1997
* [https://www.stmintz.com/ccc/index.php?id=14970 EGTB] by [[Frank Phillips]], [[CCC]], February 10, 1998
==2000 ...==
* [http://www.open-aurec.com/wbforum/viewtopic.php?f=18&t=34259 Tablebases Edwards] by RR, [[Computer Chess Forums|Winboard Forum]], July 25, 2001
==2010 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=53244 A different tablebase encoding format] by [[Steven Edwards]], [[CCC]], August 10, 2014
=Downloads=
<ref>Courtesy [[Steven Edwards]]</ref>
* [[File:tbgen.zip]]
* [[File:Spector.zip]]
=References=
<references />
'''[[Endgame Tablebases|Up one level]]'''
