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Created page with "'''Home * Search * Alpha-Beta * Fail-Low''' FILE:Going down ?.jpg|border|right|thumb|Going down? <ref>[https://commons.wikimedia.org/wiki/File:Going_d..."
'''[[Main Page|Home]] * [[Search]] * [[Alpha-Beta]] * Fail-Low'''
[[FILE:Going down ?.jpg|border|right|thumb|Going down? <ref>[https://commons.wikimedia.org/wiki/File:Going_down_%3F.jpg Going down?)] [https://en.wikipedia.org/wiki/Camden_Fort_Meagher Camden Fort Meagher] by Twhelton, February 9, 2013, [https://en.wikipedia.org/wiki/Wikimedia_Commons Wikimedia Commons]</ref> ]]
There are two related semantics, if talking of a '''Fail-Low''' - inside the [[Search Tree|search tree]] or if using [[Aspiration Windows|aspiration windows]] at the [[Root|root]].
=Inside the Tree=
A '''Fail-low''' appears at so called [[Node Types#ALL|All-Nodes]] inside the [[Alpha-Beta|alpha-beta algorithm]], also called Fail-Low nodes. The score returned is a [[Upper Bound|upper bound]] on the [[Exact Score|exact score]] of the [[Node|node]].
Quote by [[Bruce Moreland]] <ref>[http://web.archive.org/web/20040512194831/brucemo.com/compchess/programming/glossary.htm#fail-high Programming - Glossary - Fail Low, Fail High] from [[Bruce Moreland|Bruce Moreland's]] [http://web.archive.org/web/20040403211728/brucemo.com/compchess/programming/index.htm Programming Topics Site]</ref>:
A fail-low indicates that this position was not good enough for us. We will not reach this position, because we have some other means of reaching a position that is better. We will not make the move that allowed the opponent to put us in this position.
=Root with Aspiration=
Another meaning of a '''Fail-Low''', is associated with [[Aspiration Windows|aspiration windows]] at the [[Root|root]], where one needs to re-search with wider windows to get the true score rather than an [[Upper Bound|upper bound]].
Bruce again:
You can also talk about failing high and failing low from the root position, if you use an aspiration window.
=See also=
* [[Fail-High]]
* [[Upper Bound]]
* [[Lower Bound]]
* [[Exact Score]]
* [[Move Ordering]]
* [[Null Window]]
=Forum Posts=
==1995 ...==
* [https://www.stmintz.com/ccc/index.php?id=23672 Failing low at the root] by [[Guido Schimmels]], [[CCC]], August 03, 1998
* [https://www.stmintz.com/ccc/index.php?id=84651 Question: Fail High then Low at Root] by [[William Bryant]], [[CCC]], December 28, 1999 » [[Fail-High]], [[Root]], [[Search Instability]]
==2000 ...==
* [https://www.stmintz.com/ccc/index.php?id=95710 Question: Fail low at root and time management] by [[William Bryant]], [[CCC]], February 08, 2000 » [[Root]], [[Time Management]]
* [https://www.stmintz.com/ccc/index.php?id=104748 Fail-Low ?] by [[Nobuhiro Yoshimura]], [[CCC]], April 05, 2000
* [https://www.stmintz.com/ccc/index.php?id=124884 Researching after a fail-low] by [[J. Wesley Cleveland]], [[CCC]], August 17, 2000
* [https://www.stmintz.com/ccc/index.php?id=126878 Fail highs..which subsequently fail low] by [[Tom King]], [[CCC]], August 27, 2000 » [[Fail-High]], [[Search Instability]]
* [https://www.stmintz.com/ccc/index.php?id=190179 Researching after a deep fail low] by [[José Carlos Martínez Galán|José Carlos]], [[CCC]], September 24, 2001
* [https://www.stmintz.com/ccc/index.php?id=311269 MTD, IID, fail-low, root-research] by Juergen Wolf, [[CCC]], August 14, 2003 » [[MTD(f)]], [[Internal Iterative Deepening]], [[Root]]
* [https://www.stmintz.com/ccc/index.php?id=353798 Search behavior in a case of root fail high/low] by [[Sergei Markoff|Sergei S. Markoff]], [[CCC]], March 10, 2004 » [[Fail-High]], [[MTD(f)]]
==2005 ...==
* [https://www.stmintz.com/ccc/index.php?id=480380 Fail-low pruning] by Tommi Rimpiläinen, [[CCC]], January 17, 2006
==2010 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=51284 Fail soft vs fail hard] by [[Sergei Markoff|Sergei S. Markoff]], [[CCC]], February 15, 2014 » [[Fail-Soft]], [[Fail-Hard]], [[Internal Iterative Deepening]]
* [http://www.talkchess.com/forum/viewtopic.php?t=54241 Solving a fail low situation at the root] by [[Alberto Sanjuan]], [[CCC]], November 03, 2014 » [[Aspiration Windows]]
* [http://www.open-chess.org/viewtopic.php?f=5&t=2754 What does "fail low at the root" mean?] by watersky33, [[Computer Chess Forums|OpenChess Forum]], December 24, 2014
==2015 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=55889 Fail low after fail high] by [[J. Wesley Cleveland]], [[CCC]], April 04, 2015 » [[Fail-High]], [[Search Instability]]
* [http://www.talkchess.com/forum/viewtopic.php?t=58542 Restarting iterative deepening] by [[Harm Geert Muller]], [[CCC]], December 09, 2015 » [[Aspiration Windows]], [[Iterative Deepening]]
* [http://www.talkchess.com/forum/viewtopic.php?t=64321 (I)ID and PV dropout] by [[Harm Geert Muller]], [[CCC]], June 17, 2017 » [[Internal Iterative Deepening]], [[Iterative Deepening]]
=External Links=
* [http://web.archive.org/web/20040512194831/brucemo.com/compchess/programming/glossary.htm#fail-high Programming - Glossary - Fail Low, Fail High] from [[Bruce Moreland|Bruce Moreland's]] [http://web.archive.org/web/20040403211728/brucemo.com/compchess/programming/index.htm Programming Topics Site]
* [[Videos#TheBeatles|The Beatles]] - [https://en.wikipedia.org/wiki/I%27m_Down I'm Down] (1966), [https://en.wikipedia.org/wiki/YouTube YouTube] Video
: {{#evu:https://www.youtube.com/watch?v=y_I8-FUdUWI|alignment=left|valignment=top}}
* [https://en.wikipedia.org/wiki/Stevie_Ray_Vaughan Stevie Ray Vaughan] <ref>[http://www.ryerson.ca/~nvempala/ Naresh Vempala], [http://ics.louisiana.edu/director.html Subrata Dasgupta] ('''2007'''). ''[http://dl.acm.org/citation.cfm?id=1254989 A Computational Model of the Music of Stevie Ray Vaughan]''. [http://www.ryerson.ca/~nvempala/SRV.pdf pdf]</ref> with [[Videos#JeffBeck|Jeff Beck]] and [[Videos#TerryBozzio|Terry Bozzio]] - [http://www.guitarworld.com/stevie-ray-vaughan-and-jeff-beck-perform-going-down-1989-video I'm Going Down] (1989), [https://en.wikipedia.org/wiki/YouTube YouTube] Video
: {{#evu:https://www.youtube.com/watch?v=AjnG5bVS76A|alignment=left|valignment=top}}
=References=
<references />
'''[[Alpha-Beta|Up one Level]]'''
[[FILE:Going down ?.jpg|border|right|thumb|Going down? <ref>[https://commons.wikimedia.org/wiki/File:Going_down_%3F.jpg Going down?)] [https://en.wikipedia.org/wiki/Camden_Fort_Meagher Camden Fort Meagher] by Twhelton, February 9, 2013, [https://en.wikipedia.org/wiki/Wikimedia_Commons Wikimedia Commons]</ref> ]]
There are two related semantics, if talking of a '''Fail-Low''' - inside the [[Search Tree|search tree]] or if using [[Aspiration Windows|aspiration windows]] at the [[Root|root]].
=Inside the Tree=
A '''Fail-low''' appears at so called [[Node Types#ALL|All-Nodes]] inside the [[Alpha-Beta|alpha-beta algorithm]], also called Fail-Low nodes. The score returned is a [[Upper Bound|upper bound]] on the [[Exact Score|exact score]] of the [[Node|node]].
Quote by [[Bruce Moreland]] <ref>[http://web.archive.org/web/20040512194831/brucemo.com/compchess/programming/glossary.htm#fail-high Programming - Glossary - Fail Low, Fail High] from [[Bruce Moreland|Bruce Moreland's]] [http://web.archive.org/web/20040403211728/brucemo.com/compchess/programming/index.htm Programming Topics Site]</ref>:
A fail-low indicates that this position was not good enough for us. We will not reach this position, because we have some other means of reaching a position that is better. We will not make the move that allowed the opponent to put us in this position.
=Root with Aspiration=
Another meaning of a '''Fail-Low''', is associated with [[Aspiration Windows|aspiration windows]] at the [[Root|root]], where one needs to re-search with wider windows to get the true score rather than an [[Upper Bound|upper bound]].
Bruce again:
You can also talk about failing high and failing low from the root position, if you use an aspiration window.
=See also=
* [[Fail-High]]
* [[Upper Bound]]
* [[Lower Bound]]
* [[Exact Score]]
* [[Move Ordering]]
* [[Null Window]]
=Forum Posts=
==1995 ...==
* [https://www.stmintz.com/ccc/index.php?id=23672 Failing low at the root] by [[Guido Schimmels]], [[CCC]], August 03, 1998
* [https://www.stmintz.com/ccc/index.php?id=84651 Question: Fail High then Low at Root] by [[William Bryant]], [[CCC]], December 28, 1999 » [[Fail-High]], [[Root]], [[Search Instability]]
==2000 ...==
* [https://www.stmintz.com/ccc/index.php?id=95710 Question: Fail low at root and time management] by [[William Bryant]], [[CCC]], February 08, 2000 » [[Root]], [[Time Management]]
* [https://www.stmintz.com/ccc/index.php?id=104748 Fail-Low ?] by [[Nobuhiro Yoshimura]], [[CCC]], April 05, 2000
* [https://www.stmintz.com/ccc/index.php?id=124884 Researching after a fail-low] by [[J. Wesley Cleveland]], [[CCC]], August 17, 2000
* [https://www.stmintz.com/ccc/index.php?id=126878 Fail highs..which subsequently fail low] by [[Tom King]], [[CCC]], August 27, 2000 » [[Fail-High]], [[Search Instability]]
* [https://www.stmintz.com/ccc/index.php?id=190179 Researching after a deep fail low] by [[José Carlos Martínez Galán|José Carlos]], [[CCC]], September 24, 2001
* [https://www.stmintz.com/ccc/index.php?id=311269 MTD, IID, fail-low, root-research] by Juergen Wolf, [[CCC]], August 14, 2003 » [[MTD(f)]], [[Internal Iterative Deepening]], [[Root]]
* [https://www.stmintz.com/ccc/index.php?id=353798 Search behavior in a case of root fail high/low] by [[Sergei Markoff|Sergei S. Markoff]], [[CCC]], March 10, 2004 » [[Fail-High]], [[MTD(f)]]
==2005 ...==
* [https://www.stmintz.com/ccc/index.php?id=480380 Fail-low pruning] by Tommi Rimpiläinen, [[CCC]], January 17, 2006
==2010 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=51284 Fail soft vs fail hard] by [[Sergei Markoff|Sergei S. Markoff]], [[CCC]], February 15, 2014 » [[Fail-Soft]], [[Fail-Hard]], [[Internal Iterative Deepening]]
* [http://www.talkchess.com/forum/viewtopic.php?t=54241 Solving a fail low situation at the root] by [[Alberto Sanjuan]], [[CCC]], November 03, 2014 » [[Aspiration Windows]]
* [http://www.open-chess.org/viewtopic.php?f=5&t=2754 What does "fail low at the root" mean?] by watersky33, [[Computer Chess Forums|OpenChess Forum]], December 24, 2014
==2015 ...==
* [http://www.talkchess.com/forum/viewtopic.php?t=55889 Fail low after fail high] by [[J. Wesley Cleveland]], [[CCC]], April 04, 2015 » [[Fail-High]], [[Search Instability]]
* [http://www.talkchess.com/forum/viewtopic.php?t=58542 Restarting iterative deepening] by [[Harm Geert Muller]], [[CCC]], December 09, 2015 » [[Aspiration Windows]], [[Iterative Deepening]]
* [http://www.talkchess.com/forum/viewtopic.php?t=64321 (I)ID and PV dropout] by [[Harm Geert Muller]], [[CCC]], June 17, 2017 » [[Internal Iterative Deepening]], [[Iterative Deepening]]
=External Links=
* [http://web.archive.org/web/20040512194831/brucemo.com/compchess/programming/glossary.htm#fail-high Programming - Glossary - Fail Low, Fail High] from [[Bruce Moreland|Bruce Moreland's]] [http://web.archive.org/web/20040403211728/brucemo.com/compchess/programming/index.htm Programming Topics Site]
* [[Videos#TheBeatles|The Beatles]] - [https://en.wikipedia.org/wiki/I%27m_Down I'm Down] (1966), [https://en.wikipedia.org/wiki/YouTube YouTube] Video
: {{#evu:https://www.youtube.com/watch?v=y_I8-FUdUWI|alignment=left|valignment=top}}
* [https://en.wikipedia.org/wiki/Stevie_Ray_Vaughan Stevie Ray Vaughan] <ref>[http://www.ryerson.ca/~nvempala/ Naresh Vempala], [http://ics.louisiana.edu/director.html Subrata Dasgupta] ('''2007'''). ''[http://dl.acm.org/citation.cfm?id=1254989 A Computational Model of the Music of Stevie Ray Vaughan]''. [http://www.ryerson.ca/~nvempala/SRV.pdf pdf]</ref> with [[Videos#JeffBeck|Jeff Beck]] and [[Videos#TerryBozzio|Terry Bozzio]] - [http://www.guitarworld.com/stevie-ray-vaughan-and-jeff-beck-perform-going-down-1989-video I'm Going Down] (1989), [https://en.wikipedia.org/wiki/YouTube YouTube] Video
: {{#evu:https://www.youtube.com/watch?v=AjnG5bVS76A|alignment=left|valignment=top}}
=References=
<references />
'''[[Alpha-Beta|Up one Level]]'''
