Double Null Move

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Double Null Move,
a Null Move Pruning technique proposed by Vincent Diepeveen in 1997 ¹, 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 ², and was widely discussed in computer chess forums ³, and overall recognized as a great idea ⁴ . While likely too expensive in the middlegame where zugzwang is rare, and still not recommend for pawn endings ⁵, 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