Double Null Move

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Double Null Move, a Null Move Pruning technique proposed by Vincent Diepeveen in 1997, that allows two consecutive null moves with common depth reduction R in a row. Provided that the depth or distance to the horizon is big enough to recognize a possible zugzwang 2R+2 plies shallower, and the first null move is refuted by the second one, its aim is to make NMH zugzwang aware. Double Null Move is used in Diep, and was widely discussed in computer chess forums , and overall recognized as a great idea. While likely too expensive in the middlegame where zugzwang is rare, and still not recommend for pawn endings, it might be well applied in other endgames.

=See also=
 * Fail-High Reductions
 * Internal Iterative Deepening
 * Null Move
 * Null Move Observation
 * Null Move Reductions
 * Null Move Test-Positions, where Null Move may fail due to zugzwang
 * Zugzwang
 * Zugzwang Verification

=Forum Posts=
 * Re: Null move? by Vincent Diepeveen, rgcc, October 11, 1997
 * Searching correctly with the Nullmove ==> no zugzwang problems anymore by Vincent Diepeveen, rgcc, October 23, 1997
 * Pseudo C code for double nullmove + PVS by Vincent Diepeveen, CCC, August 06, 2000
 * Double Nullmove by David Rasmussen, CCC, March 30, 2001
 * Double Null move? by Steve Maughan, CCC, July 13, 2001
 * Double Nullmove by Andreas Herrmann, CCC, April 25, 2002
 * double null move help by Daniel Shawul, CCC, July 04, 2004
 * Re: Search-algorithm by Vincent Diepeveen, CCC, August 01, 2009
 * Re: Search-algorithm by Don Dailey, CCC, August 01, 2009


 * Why not two consecutive null moves ? by Henk van den Belt, CCC, May 07, 2015

=References=

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