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Subject: Re: aspiration search question

Author: Robert Hyatt

Date: 08:09:32 05/13/04

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On May 13, 2004 at 03:35:00, Daniel Shawul wrote:

>Hello
>
>My search is fail soft(i return the actual score)
>when i fail high at the root i widen the window by 3 pawns (300).
>
>                 if(score<=r_alpha)
>		 {
>			  r_beta=r_alpha;
>			  r_alpha=score-300; //r_alpha = -MATESCORE;
>		 }
>		 else if(score>=r_beta)
>		 {
>			  r_alpha=r_beta;
>			  r_beta=score + 300; //r_beta = MATESCORE;
>		 }
>If the search fail's high at 1.75 score but the real score was 10
>i get a score of 4.75 (1.75 + 3) in the next iteration. Why? my search is fail
>soft and the score returned should be independent of beta. If i change the 200
>to 300,score returned is 4.75??


There is much more to fail-soft that just returning a score outside the bound
window.  Normally at the front of search, your alpha value is passed in and even
if a search call returns a value < alpha, you still maintain alpha as the "best"
value.  That is not fail-soft..




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