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Subject: Re: Double Null move?

Author: Uri Blass

Date: 14:12:54 07/13/01

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On July 13, 2001 at 12:28:01, Steve Maughan wrote:

>I'm thinking of implementing double null move in my program.  Now as far as I
>know the most conventional way is to do the normal null move search and if there
>is a cutoff follow it with a normal search at reduced depth to confirm no
>zugwag.  However I do remember that someone here (Vincent?) outlined a different
>way of doing double null move.  Is there another way?  If there is, what are the
>pros and cons of each?
>
>Thanks,
>
>Steve

I think that the idea is simply to search in the following way:

The first move that you search is always null if it is a legal move(it is
illegal to play 3 nulls in a row).

null is considered as more plies then a regular move so even if null does not
produce a cutoff you did not waste a lot of time about it and this is the reason
that it is a good order of moves to start with null.

If you think that you waste too much time about searching lines with
null null you can decide that the second null in 2 consecurtive nulls is even
more plies.

By this way you can avoid zunzwang if you search deep enough without the problem
of being significantly slower.

Uri



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