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Subject: Re: nullmoving - an idea...

Author: Robert Hyatt

Date: 07:39:22 10/30/03

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On October 29, 2003 at 22:16:59, macaroni wrote:

>I don't know if this has been done, probobly has, but here goes anyway. Lets say
>the computer gets to this position somewhere in it's search.
>
>[D]2k2q2/pp4pp/2p5/2p1p3/5n2/1NP4P/PP3PP1/2Q3K1 w - -
>
>white to move is ok, but when the search nullmoves, black wins with Ne2+!!. Ok,
>my idea (and probobly loads of other peoples), is to store this move, Ne2+,
>since for alot of whites possible moves, Ne2+ still wins the queen. I'm not
>quite sure how the code would work, or how effective this would be. Maybe you
>wouldn't want to store it if it were a capture? as they are checked early
>anyway. You could possibly store it as a killer move? I don't know. If it has
>already been done, can people tell me how effective it is? if at all.

Your idea is known as a "killer move" as explained by Slate/Atkin in chess
4.x...  If you use killer moves, you will quickly find that Ne2+ "kills"
almost all white moves except for moves that move the king, move the queen,
or defend the e2 square.

That is really independent of the null-move search completely, except that you
might say that you learned about the "killer move" quicker.  But if you do a
normal killer move ordering approach, you get this for free...


>
>I have heard of mate threat extensions...does that use null move to?

Yes.  If you do a null-move, and you get mated as a result, your opponent has
a very strong mate threat, since you have to do something to avoid getting
mated.  It makes sense to search a little deeper along that particular line.




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