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Subject: Re: Using null move to adjust alpha?

Author: Stuart Cracraft

Date: 13:12:53 09/20/04

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Excellent explanation. Thanks.

On September 20, 2004 at 04:07:40, martin fierz wrote:

>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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