Author: Miguel A. Ballicora
Date: 11:49:19 02/28/01
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On February 28, 2001 at 13:22:41, Robert Hyatt wrote: >On February 28, 2001 at 11:10:30, Miguel A. Ballicora wrote: > >>On February 28, 2001 at 05:56:36, Leen Ammeraal wrote: >> >>>I am not sure about when to avoid nullmoves. >>>I omit it: >>>a. when in check >>>b. when there are less than 5 pieces (including pawns) on the board >>>c. when the last move was a nullmove >>>d. at the root node >>>Should I also omit it in some other cases, >>>for example, when any hashmove (even with a low draft) was found, >>>or when beta = alpha + 1? >>>Thanks in advance for any help. >>>Leen >> >>Hi Leen, >> >>Regarding b, I do not know whether what I am doing now is correct but I think >>that works for me: >>When either black or white had no "long range" pieces (bishop, rook or queen) >>I disable null move. The rationale is that one side cannot waste >>a tempo in a given position having pawns, king and/or knights making the >>position prone to have a zugswang. >> >>Miguel > > >That seems dangerous. you are white, with a bishop on d5. I am black and I >have a pawn on a7 and g7. The bishop is zugged here. If your king can't move, >you lose even though you have a long-range slider on the board. And null move >will fail high here naturally as not moving is better than having to move and >lose. I think that you meant a3 and g3? If that's so I got your point and you're right. However, I disable nullmove when _either_ side lacks a long-range slider. In your example, it will be disabled because you do not have a bishop. If you do have a bishop, it won't be disabled (both sides got a slider) but at least I don't have "mutual" zugswangs which are the nastiest (I think). At least, with a slider per side the mutual zugswangs are more difficult (of course not impossible but I have to draw a line somewhere). Regards, Miguel
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