Author: Uri Blass
Date: 10:36:03 04/08/04
Go up one level in this thread
On April 08, 2004 at 12:22:15, Ed Schröder wrote:
>On April 08, 2004 at 09:04:15, Harald Lüßen wrote:
>
>>On April 08, 2004 at 07:10:29, Daniel Shawul wrote:
>>
>>>Hi
>>>Here are some questions
>>>
>>>2.In Ed's paper there are some tricks done at horizon.
>>> trick one if(score - (margin + largest hanging piece) > beta)
>>> don't do quiescence
>>> trick two if(score - 900 > beta)
>>> don't do quiescence
>>> My question is every body does
>>> score=eval()
>>> if(score > beta)
>>> don't do quiescence;
>>> So i don't see how the tricks work?
>
>
>>His alpha is our beta and vice versa.
>
>Really?
>
>If true I need to re-read some papers :)
>
>To clarify, suppose an aspiration search with a 0.50 window and a best move with
>a 0.20 score then going to the next iteration I get a window of:
>
>ALPHA = -0.30
>BETA = 0.70
>
>Your comment suggests:
>
>ALPHA = 0.70
>BETA = -0.30
>
>Ed
No
suppose that we start with position of big advantage for white and you have
alpha=3.00 beta=4.00
His point is that the meaning of alpha and beta is different.
Search is a recursive function so alpha=3.00 beta=4.00 turns out to be
alpha=--4.00 beta=-3.00 after a recursive call.
You try to prune moves before calling search so you may use
alpha=3.00 beta=4.00 when most programmer try to prune moves after calling
search so they have alpha=-4.00 beta=-3.00
Your pruning trick when it is white to move is
if(score - (margin + largest hanging piece) > 4.00 pawns)
don't do quiescence
It is translated after calling search to
if (score+margin+largest hanging piece<-4.00 pawns
don't do qsearch.
I guess also that your score is not from the same side to move like other
programmers.
Uri
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