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Subject: Re: Nullmove: when to avoid it?

Author: Robert Hyatt

Date: 13:55:52 02/28/01

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On February 28, 2001 at 13:32:34, Josť Carlos 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 don't use null move, so this could be nonsense, but maybe mobility (number
>of available moves) could be used as a threashold for null-move use. For
>example, don't do null-move unless you have at least 10 available moves.
>
>  Josť C.


That isn't quite good enough.  In the position I gave the bishop has that many
available squares.  Except that most lose...



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