Depth Reduction R

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R is a common name for a constant or variable signifying depth reduction used in the Null Move Pruning, Null Move Reductions and independently in Multi-Cut. In many null move implementations it is either 2 or 3, the exact formula being depth - R - 1.

=Variable Reduction= When R becomes a variable, then we say that a program uses adaptive null move pruning, first described by Ernst A. Heinz, 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.

=Forum Posts=

1997 ...

 * Null move depth reductions by Tom King, rgcc, February 02, 1997
 * Null move reductions by Roberto Waldteufel, CCC, October 04, 1998

2000 ...

 * Null move R=2 vs Null move R=2/3 by Tom King, CCC, August 09, 2001
 * Null-Move: Difference between R = 2 and R = 3 in action by Omid David, CCC, July 11, 2002
 * Smooth scaling -- an explanation by Dann Corbit, CCC, December 30, 2009

2010 ...

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

=References=

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