Home * Search * Depth Reduction R
R is a common name for a constant or variable signifying depth reduction used in the Null Move Pruning 1, Null Move Reductions and independently in Multi-Cut 2. 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 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 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
Chrilly Donninger. (1993). Null Move and Deep Search: Selective-Search Heuristics for Obtuse Chess Programs. ICCA Journal, Vol. 16, No. 3↩︎
Yngvi Björnsson, Tony Marsland (2001). Multi-cut Alpha-Beta Pruning in Game Tree Search. Theoretical Computer Science, Vol. 252↩︎
Ernst A. Heinz. (1999). Adaptive null-move pruning. ICCA Journal, Vol. 22, No 3↩︎
Rethinking r in null move by Michael Sherwin, CCC, August 18, 2017↩︎