Home *Search * Depth Reduction R

R is a common name for a constant or variable signifyingdepth reduction used in theNull Move Pruning^[1],Null Move Reductions and independently inMulti-Cut^[2]. In many null move implementations it is either 2 or 3, the exact formula beingdepth - R - 1.

Variable Reduction

WhenR becomes a variable, then we say that a program usesadaptive null move pruning, first described byErnst A. Heinz^[3], using R=3 when normal search depth exceeds 6 plies and R=2 otherwise, while more recently most engines account increased search depth with greater reductions^[4].

Forum Posts

1997 ...

• Null move depth reductions byTom King,rgcc, February 02, 1997
• Null move reductions byRoberto Waldteufel,CCC, October 04, 1998

2000 ...

• Null move R=2 vs Null move R=2/3 byTom King,CCC, August 09, 2001
• Null-Move: Difference between R = 2 and R = 3 in action byOmid David,CCC, July 11, 2002
• Smooth scaling -- an explanation byDann Corbit,CCC, December 30, 2009

2010 ...

• Figuring out the R factor byMichael Sherwin,CCC, January 03, 2010
• How much to reduce ? byHenk van den Belt,CCC, October 03, 2013 »Late Move Reductions
• Reductions byHarm Geert Muller,CCC, May 22, 2016 »Late Move Reductions
• Calculating R value for Null Move byAndrew Grant,CCC, June 23, 2016
• Rethinking r in null move byMichael Sherwin,CCC, August 18, 2017
• Update on null move and LMR byMichael Sherwin,CCC, October 01, 2017 »RomiChess

References

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