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'''[[Main Page|Home]] * [[Search]] * [[Selectivity]] * [[Extensions]] * Capture Extensions'''
'''Capture Extensions''' were used early in [[Brute-Force|brute-force]] chess programs to minimize some [[Horizon Effect|horizon effects]]. Due to the self-restricting nature of [[Captures|captures]] in Chess (max. 30 pieces may be captured per game), one may consider this a good idea. However, extending every capture was discarded by most programmers, and some constrains or conditions were applied, i.e. to extend only forced [[Recapture Extensions|recaptures]] on the same [[Target Square|target square]].
[[Hans Berliner]] suggested to extend only those (re)captures, which restore the [[Material#Balance|material balance]] at the [[Root|root]]. Furthermore, capture extensions are often restricted to [[Node Types#PV|PV-nodes]], or some programs assign [[Extensions#FractionalExtensions|fractional extensions]] to different kinds of captures, considering [[Static Exchange Evaluation|SEE]], [[Distance|distance]] of target square to the opponent [[King|king]], recapturing on the same square, and material balance as mentioned.
A lot of todays programs, more focused on [[Reductions|reductions]] rather than extensions in the [[Scout]] part of their [[Principal Variation Search|PVS]], most often don't reduce captures, which makes it a kind of implicit extension relative to reduced late [[Quiet Moves|quiet moves]]. It also seems worth a try to reduce even captures with negative SEE while performing [[Late Move Reductions|LMR]].
However, it seems important to extend captures if a transition to certain late endgames occurs. [[Ed Schroder|Ed Schröder]] for instance extends '''three''' [[Ply|plies]] in [[Rebel]] if entering the [[Pawn Endgame|pawn endgame]], and the static, [[Incremental Updates|incremental updated]] [[Score|score]] dominated by [[Material|material]] is not outside a +-3 pawn window around zero: The extension is very powerful, it will often avoid REBEL entering a lost ending and vice versa <ref>[http://www.top-5000.nl/authors/rebel/chess840.htm Programmer Corner - How Rebel Plays Chess] by [[Ed Schroder|Ed Schröder]], Extension Techniques: Endgame, [http://members.home.nl/matador/Inside%20Rebel.pdf pdf reprint]</ref>.
=See also=
* [[Check Extensions]]
* [[Recapture Extensions]]
* [[Zwischenzug]]
=Publications=
* [[David Levy]], [[David Broughton]], [[Mark Taylor]] ('''1989'''). ''The SEX Algorithm in Computer Chess''. [[ICGA Journal|ICCA Journal]], Vol. 12, No. 1, pp. 10-21.
* [[Don Beal]] and [[Martin C. Smith]] ('''1995'''). ''Quantification of Search-Extension Benefits.'' [[ICGA Journal|ICCA Journal]], Vol. 18, No. 4, pp. 205-218.
* [[Yoshimasa Tsuruoka]], [[Daisaku Yokoyama]], [[Takashi Chikayama]] ('''2002'''). ''[http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.2.9258 Game-Tree Search Algorithm based on Realization Probability]''. [[ICGA Journal]], Vol. 25, No. 3, [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.2.9258&rep=rep1&type=pdf pdf], [http://www-tsujii.is.s.u-tokyo.ac.jp/~tsuruoka/papers/icga02.pdf pdf]
* [[David Levy]] ('''2002''') ''[http://ilk.uvt.nl/icga/journal/contents/content25-3.htm#SOME%20COMMENTS%20ON%20REALIZATION%20PROBABILITIES SOME COMMENTS ON REALIZATION PROBABILITIES AND THE SEX ALGORITHM]''. [[ICGA Journal]], Vol. 25, No. 3
=Forum Posts=
* [https://www.stmintz.com/ccc/index.php?id=35984 Capture/recapture extensions] by [[Andrew Williams]], [[CCC]], December 14, 1998
* [http://www.talkchess.com/forum/viewtopic.php?t=21403 Search extensions at promising trajectories] by [[Reinhard Scharnagl]], [[CCC]], May 28, 2008
=External Links=
* [http://web.archive.org/web/20070607151732/www.brucemo.com/compchess/programming/extensions.htm Search Extension] from [[Bruce Moreland|Bruce Moreland's]] [http://web.archive.org/web/20070607231311/www.brucemo.com/compchess/programming/index.htm Programming Topics]
* [http://www.top-5000.nl/authors/rebel/chess840.htm Programmer Corner - How Rebel Plays Chess] by [[Ed Schroder|Ed Schröder]], [http://members.home.nl/matador/Inside%20Rebel.pdf pdf reprint]
=References=
<references />
'''[[Extensions|Up one Level]]'''
'''Capture Extensions''' were used early in [[Brute-Force|brute-force]] chess programs to minimize some [[Horizon Effect|horizon effects]]. Due to the self-restricting nature of [[Captures|captures]] in Chess (max. 30 pieces may be captured per game), one may consider this a good idea. However, extending every capture was discarded by most programmers, and some constrains or conditions were applied, i.e. to extend only forced [[Recapture Extensions|recaptures]] on the same [[Target Square|target square]].
[[Hans Berliner]] suggested to extend only those (re)captures, which restore the [[Material#Balance|material balance]] at the [[Root|root]]. Furthermore, capture extensions are often restricted to [[Node Types#PV|PV-nodes]], or some programs assign [[Extensions#FractionalExtensions|fractional extensions]] to different kinds of captures, considering [[Static Exchange Evaluation|SEE]], [[Distance|distance]] of target square to the opponent [[King|king]], recapturing on the same square, and material balance as mentioned.
A lot of todays programs, more focused on [[Reductions|reductions]] rather than extensions in the [[Scout]] part of their [[Principal Variation Search|PVS]], most often don't reduce captures, which makes it a kind of implicit extension relative to reduced late [[Quiet Moves|quiet moves]]. It also seems worth a try to reduce even captures with negative SEE while performing [[Late Move Reductions|LMR]].
However, it seems important to extend captures if a transition to certain late endgames occurs. [[Ed Schroder|Ed Schröder]] for instance extends '''three''' [[Ply|plies]] in [[Rebel]] if entering the [[Pawn Endgame|pawn endgame]], and the static, [[Incremental Updates|incremental updated]] [[Score|score]] dominated by [[Material|material]] is not outside a +-3 pawn window around zero: The extension is very powerful, it will often avoid REBEL entering a lost ending and vice versa <ref>[http://www.top-5000.nl/authors/rebel/chess840.htm Programmer Corner - How Rebel Plays Chess] by [[Ed Schroder|Ed Schröder]], Extension Techniques: Endgame, [http://members.home.nl/matador/Inside%20Rebel.pdf pdf reprint]</ref>.
=See also=
* [[Check Extensions]]
* [[Recapture Extensions]]
* [[Zwischenzug]]
=Publications=
* [[David Levy]], [[David Broughton]], [[Mark Taylor]] ('''1989'''). ''The SEX Algorithm in Computer Chess''. [[ICGA Journal|ICCA Journal]], Vol. 12, No. 1, pp. 10-21.
* [[Don Beal]] and [[Martin C. Smith]] ('''1995'''). ''Quantification of Search-Extension Benefits.'' [[ICGA Journal|ICCA Journal]], Vol. 18, No. 4, pp. 205-218.
* [[Yoshimasa Tsuruoka]], [[Daisaku Yokoyama]], [[Takashi Chikayama]] ('''2002'''). ''[http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.2.9258 Game-Tree Search Algorithm based on Realization Probability]''. [[ICGA Journal]], Vol. 25, No. 3, [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.2.9258&rep=rep1&type=pdf pdf], [http://www-tsujii.is.s.u-tokyo.ac.jp/~tsuruoka/papers/icga02.pdf pdf]
* [[David Levy]] ('''2002''') ''[http://ilk.uvt.nl/icga/journal/contents/content25-3.htm#SOME%20COMMENTS%20ON%20REALIZATION%20PROBABILITIES SOME COMMENTS ON REALIZATION PROBABILITIES AND THE SEX ALGORITHM]''. [[ICGA Journal]], Vol. 25, No. 3
=Forum Posts=
* [https://www.stmintz.com/ccc/index.php?id=35984 Capture/recapture extensions] by [[Andrew Williams]], [[CCC]], December 14, 1998
* [http://www.talkchess.com/forum/viewtopic.php?t=21403 Search extensions at promising trajectories] by [[Reinhard Scharnagl]], [[CCC]], May 28, 2008
=External Links=
* [http://web.archive.org/web/20070607151732/www.brucemo.com/compchess/programming/extensions.htm Search Extension] from [[Bruce Moreland|Bruce Moreland's]] [http://web.archive.org/web/20070607231311/www.brucemo.com/compchess/programming/index.htm Programming Topics]
* [http://www.top-5000.nl/authors/rebel/chess840.htm Programmer Corner - How Rebel Plays Chess] by [[Ed Schroder|Ed Schröder]], [http://members.home.nl/matador/Inside%20Rebel.pdf pdf reprint]
=References=
<references />
'''[[Extensions|Up one Level]]'''
