Author: Robert Hyatt
Date: 13:52:05 02/28/01
Go up one level in this thread
On February 28, 2001 at 14:49:19, Miguel A. Ballicora wrote: >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? Sorry. I am white, you are black trying to stop both of my pawns. > 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). That only makes it worse. So I have a bishop and two pawns threatening to promote. You have the bishop as above. You are _still_ zugged. I don't see why you would limit null move based on _both_ sides. You should only limit it if the side on move can be zugged. But in any case, it still fails if we both have a bishop. > >Regards, >Miguel
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