Author: rasjid chan
Date: 08:33:48 12/06/03
Go up one level in this thread
On December 06, 2003 at 10:43:35, Alex Szabo wrote:
>On December 06, 2003 at 04:05:24, Daniel Shawul wrote:
>
>>hi
>>
>>here is my PVS code
>>
>> if(first move)
>> score=-search(-beta,-alpha,depth-1);
>> else
>> {
>> score=-search(-alpha-1,-alpha,depth-1);
>> if(score>alpha && score<beta)
>> score=-search(-score,-alpha,depth-1);
>> }
>>
>>should i use (-beta,-alpha) when search fails instead of (-score,-alpha).
>>can the algorithm handle search instablity correctly?
>>
>>regards
>>daniel
>
>I think you should use (-beta,-score). The zero-window search failed high
>improving alpha.
Even (-beta,-score) may be wrong as score may be > alpha + 1 and
cannot be used.
His pvs wnd is (alpha, alpha + 1)
On any score > alpha, ie any improvement ina alpha,
should use new wnd (alpha + 1, beta).
correct code is :-
if(first move)
score=-search(-beta,-alpha,depth-1);
else
{
score=-search(-alpha-1,-alpha,depth-1);
if(score>alpha)// ignore how much > than alpha
score=-search(-beta,-alpha - 1,depth-1);
}
score should never be used.
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