Author: Richard Pijl
Date: 01:38:28 10/06/04
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On October 05, 2004 at 16:43:38, Gerd Isenberg wrote: >What, if best move after null is the reverse previous move, >like doing three alternated null moves in a row. >What can we conclude then? > >Thanks, >Gerd Assume for arguments sake that white plays a move, black nullmoves and white reverses his move. Then I think there are two possibilities: Either that the first move by white was really bad (worse than nullmove), and black is likely to get a nullmove cutoff, e.g. a position with a back-rank mate threat. Moving a rook off the back-rank is clearly about the worst move on the board, so after an opponent nullmove it is moved back. Or that white is in zugzwang (and does the reverse move to do a nullmove himsel), in which case the nullmove (the real one) will fail to produce a cutoff as playing a move is better, or, when it does produce a cutoff, playing a move is even better, so the cutoff is ok anyway. There may be some horizon effects with the reductions used though (as effectively white nullmoved with R=normalR+2, but I guess this is normally not a problem as we expect this 'nullmove' to fail low. Adjusting the score (or even not considering the reverse move) can be dangerous as the scores propagated to the parent nodes will be hashed, increasing search instability. Hope this helps Richard.
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