Reductions

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Reductions (as opposed to pruning),
a class of search heuristics that decrease the depth to which a certain branch of the tree is searched, also interpreted as negative extension.

Recursive Reductions

• Late Move Reductions - LMR
• Fail-High Reductions - FHR
• Null Move Reductions
• RankCut

Near the Tips

• Razoring

Pruning after a reduced Search

Some dynamic pruning techniques base their pruning decision on a reduced search by factor R, also applied recursively:

• Null Move Pruning
• Multi-Cut

A none recursive pruning based on reduction at some fixed depth is applied by:

• ProbCut

See also

• Pruning
• Extensions

Forum Posts

1998 ...

• A new selective heuristic? by Frank Schneider, CCC, June 21, 1998

2000 ...

• Evaluation-based Reductions and/or Extensions by Tom Likens, CCC, December 28, 2003 » Extensions
• extensions + reductions + pruning = confusion by Johan de Koning, CCC, March 24, 2004 (was Shredder 8 secret: search depth?)

2005 ...

• Reductions and null move refutations by Tord Romstad, Winboard Forum, April 18, 2005  » Null Move Pruning
• Has anyone tested Gambit Fruit with Rebel Reductions on? by Ryan B., CCC, November 15, 2005 » Rebel, Gambit Fruit
• Reducing King Moves? by mjlef, Winboard Forum, January 03, 2007
• Toga/Glaurung/Strelka Prunings/Reductions by Edsel Apostol, CCC, January 31, 2008 » Toga, Glaurung, Strelka, Pruning

2010 ...

• Reducing/Pruning Bad Captures (SEE < 0) by Edsel Apostol, CCC, August 19, 2011 » SEE
• Reductions from internal iterative deepening by Evert Glebbeek, CCC, August 20, 2012 » Internal Iterative Deepening
• Houdini 3 reducing the depth feature by Maurizio Maglio, CCC, October 17, 2012 » Houdini
• Pruning in PV nodes by Sergei S. Markoff, CCC, January 14, 2014 » Root, Node Types
• variable reductions by Robert Hyatt, CCC, June 22, 2014

2015 ...

• Ratio reduction by Steven Edwards, CCC, September 20, 2015 » Late Move Reductions, Symbolic
• Reduction Research Question by Dennis Sceviour, CCC, September 25, 2015
• Reductions by Harm Geert Muller, CCC, May 22, 2016
• EMR & EMP by Michael Sherwin, CCC, July 19, 2016
• Floating Move Reduction by Dennis Sceviour, CCC, September 14, 2016
• EMR based on Null Move threat by Michael Sherwin, CCC, October 30, 2017

2020 ...

• Pruning / reduction depending on king safety by Vivien Clauzon, CCC, February 02, 2020 » King Safety
• An alternative to IID by Ed Schröder, CCC, August 13, 2020 » IID
• Futility reductions by Jost Triller, CCC, July 05, 2021 » Futility Pruning

External Links

• Reduction from Wikipedia
• Programmer Corner - How Rebel Plays Chess - Reductions by Ed Schröder (Wayback Machine), pdf reprint

References

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