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Subject: Re: Using null move to adjust alpha?

Author: martin fierz

Date: 01:07:40 09/20/04

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On September 19, 2004 at 23:58:28, Stuart Cracraft wrote:

>I use null move only to return the null move search
>value if >= beta, otherwise fall through to everything else
>
>But I hear that one can use the null to adjust alpha.
>
>When I try to adjust alpha this way:
>
>    nullmovestuff
>    alpha = MAX(alpha,nullmovescore);
>
>my results drop precipitously.
>
>Perhaps my method is wrong or adjusting alpha has fallen
>out of favor.
>
>Comments anyone?
>
>Stuart

as michael said, you normally do the nullmove search with a minimal window, i.e.
any score you get will be a bound and therefore useless.
i expect that you could use an infinite window and use the returned exact value
to adjust alpha if it is larger than alpha. but i'd be very surprised if that
helped overall!
the reason is that most of the time in your search, the search windows will be
very small anyway, and it will be very unlikely that you can adjust alpha based
on this technique.

cheers
  martin



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