Fail-High

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There are two related semantics, if talking of a **Fail-High** - inside the search tree or if using aspiration windows at the root.

=Inside the Tree= A **Fail-High** is associated with a Beta-Cutoff in the alpha-beta algorithm, which appears at so called Cut-Nodes, also called Fail-High nodes. The score returned is a lower bound on the exact score of the node.

Quote by Bruce Moreland :

=Root with Aspiration= Another meaning of a **Fail-High**, is associated with Aspiration Windows at the Root, where one needs to re-search with wider windows to get the true score rather than a lower bound.

Quote by Bruce again:

=See also=
 * Fail-Hard
 * Fail-High Reductions
 * Fail-Low
 * Fail-Soft
 * Upper Bound
 * Lower Bound
 * Exact Score
 * Move Ordering
 * Null Window

=Forum Posts=

1995 ...

 * [|Question: Fail High then Low at Root] by William Bryant, CCC, December 28, 1999 » Fail-Low, Root, Search Instability

2000 ...

 * [|"Percentage of fail-highs" question] by Daniel Clausen, CCC, January 03, 2000
 * [|Fail highs..which subsequently fail low] by Tom King, CCC, August 27, 2000 » Fail-Low, Search Instability
 * [|Q: Fail High percentage] by Peter Fendrich, CCC, December 08, 2000
 * [|What means lazy/plain alpha bounding?] by Severi Salminen, CCC, February 06, 2001 » Root
 * [|About False Fail Highs, professionals, and MTD searches] by Gian-Carlo Pascutto, CCC, April 12, 2002 » MTD(f)
 * [|what does "fail high" mean?] by Scott Farrell, CCC, November 29, 2002
 * [|what does "fail high" mean? In the context of iterative deepening] by Scott Farrell, CCC, November 30, 2002 » Iterative Deepening
 * [|Hash and first Fail High] by Peter Fendrich, CCC, August 14, 2003
 * [|Search behavior in a case of root fail high/low] by Sergei S. Markoff, CCC, March 10, 2004 » Fail-Low, MTD(f)
 * [|Fail-high on first move stat (86%)] by Michael Henderson, CCC, July 29, 2004 » Move Ordering

2005 ...

 * [|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-Hard, Fail-Soft
 * [|Why lower bound in fail-high?] by grandsmaster, OpenChess Forum, September 20, 2014

2015 ...

 * [|Fail low after fail high] by J. Wesley Cleveland, CCC, April 04, 2015 » Fail-Low, Search Instability
 * [|cut nodes] by Folkert van Heusden, CCC, October 18, 2017 » Cut-Nodes

=External Links= > media type="youtube" key="Qj0o22ClDTU" width="560"
 * [|Programming - Glossary - Fail Low, Fail High] from Bruce Moreland's [|Programming Topics Site]
 * [|Mop Mop] - So High, [|Ritual of the Savage] (2010),  [|YouTube] Video

=References= =What links here?= include page="Fail-High" component="backlinks" limit="100"
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