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Subject: Re: Correct values if all moves are pruned?

Author: Bas Hamstra

Date: 08:53:49 01/06/01

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On January 06, 2001 at 03:52:18, Severi Salminen wrote:

>On January 05, 2001 at 17:20:09, Bas Hamstra wrote:
>
>>In such a situation you assume that that are no good captures. So you return the
>>score of the evaluation for that node IF it is above Alpha. Otherwise just
>>Alpha.
>
>You mean the 2. case? I think that if all captures are pruned and standpat score
>is <alpha I should return that instead of alpha. My point for this was that
>returning something lower than alpha might improve all the researches. I just
>didn't know how much lower value I could safely return.

That is also possible. But since pruning captures will make errors, I think
"safest" is to return Alpha. In case of doubt it might not be best to return
values outside [alpha, beta]. Same problem with lazy eval: I choose the
"conservative" approach.

Ciao!
Bas.
>
>>>Hi!
>>>
>>>1.If I prune a move in normal search: if(material+gain(move)+FMARGIN<=alpha)
>>>what should I assign to the best score so far? Material+gain, material+FMARGIN,
>>>material+gain+FMARGIN or material only? Now I'm using material+FMARGIN but it
>>>can't be right. Material+gain sounds right because that would be returned from
>>>qsearch if stand pat fails high?
>>>
>>>2.I'm using now SEE and I wonder what is the "correct" value to return from
>>>qsearch if I prune all captures: if(eval()+seescore(move)+MARGIN<=alpha)? Now I
>>>just return alpha. If all moves result a score<=alpha should I return
>>>eval+seescore or something else.
>>>
>>>I ask this because PVS or aspiration window search doesn't seem to like "wrong
>>>values"
>>>
>>>Severi



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