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Subject: Re: Nullmove: when to avoid it?

Author: Vincent Diepeveen

Date: 09:26:46 03/01/01

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On February 28, 2001 at 06:05:38, Severi Salminen 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?
>I avoid it also when it seems that this node is futile: material+MARGIN<=alpha.
>It saved a few nodes and it seems to be quite sound assumption.

I can save bunches of nodes by not nullmoving on the last ply before
qsearch. So if depthleft == 1 ply then not nullmoving reduces
for me the number of nodes considerably.

But diep is hell slower!

Are you sure that this futile prevention is working at big depths?
It never worked for me at big depths!

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