Fail-Hard

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Fail-Hard is a term related to an Alpha-Beta like search, to make Alpha and Beta hard bounds of the returned value of the search. Even terminal nodes which indicate draw or mate scores are supposed to be adjusted on the hard alpha-beta bounds.

=Fail-Hard Condition= Alpha <= Score <= Beta

=See also=
 * Fail-Soft
 * Fail-High
 * Fail-Low
 * Principal Variation Search

=Forum Posts=

2000 ...

 * Fail-soft or Fail-hard ? by Teerapong Tovirat, CCC, November 04, 2000 » Fail-Soft
 * Fail-hard, fail-soft question by Dan Honeycutt, CCC, May 06, 2004

2005 ...

 * fail soft vs fail hard by cyberfish, CCC, November 19, 2008
 * Return eval or upper bound? by John Merlino, CCC, October 26, 2009

2010 ...

 * First post (and FailHigh question!) by Natale Galioto, CCC, June 14, 2013 » Fail-High, Fail-Soft
 * Fail soft vs fail hard by Sergei S. Markoff, CCC, February 15, 2014 » Fail-Soft, Fail-Low, Internal Iterative Deepening

2020 ...

 * Fail hard/soft by Philippe Chevalier, CCC, January 28, 2022

=External Links=
 * Alpha–beta pruning from Wikipedia
 * Lecture notes for February 2, 1999 Variants of Alpha-Beta Search by [[David Eppstein]

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