Author: José Carlos
Date: 09:27:46 10/26/02
Go up one level in this thread
On October 26, 2002 at 12:07:16, Antonio Dieguez wrote:
>>>score = -alphabeta(board, -alpha-1, -alpha, depth-1);
>>>
>>>if(score > alpha && score < beta)
>> ^^^^^^^^^^^^^^^
>>
>> Don't use beta there. You just want to know you're above the pv score (which
>>is alpha now).
>
>if I am not mistaken it depends on the exact writing.
>
>he can write
>
>make...
>score = -alphabeta(board, -alpha-1, -alpha, depth-1);
>if(score > alpha && score < beta)
>{
> unmake & make(depends on the program)
> score = -alphabeta(board, -beta, -alpha+1, depth-1);
>}
>
>unmake
>
>if (score>alpha)
>{
> blabla
> if (score>=beta)
> { update killer; update hash; etc. }
>}
>
>-------------------
>or he can write something like this?
>
>make
>score = -alphabeta(board, -alpha-1, -alpha, depth-1);
>if(score > alpha)
>{
> if (score>=beta)
> { unmake; update killer; update hash; return beta; }
> unmake & make(depends on the program)
> score = -alphabeta(board, -beta, -alpha+1, depth-1);
> unmake
> if (score>alpha) // 'cause it could fail low right?
> {
> if (score>=beta)
> { update killer; update hash; return beta; }
> etc.
> }
>}
>
>I have written the first option, I think I can't make it prettier with the
>second option or something else but may be you can write it better off corse.
>
>Ah if the search always return alpha or beta then that can change things.
>
>
>antonio's usefull post.
I don't quite follow. He's talking about the null window searches after the
pv. He's searching [alpha,alpha+1] so he might fail high with alpha+1 or
alpha+500, and beta isn't useful here at all. All you know if you fail high is
"I've found a move that seems to be better than my current pv". So you open the
window and research to get a true score (note that you can also forget about the
true score and keep searching the other moves with [alpha,alpha+1] hoping no
other move fails high and trust your fh and go to the next ply).
Beta only matters if you search [alpha,beta], this is, if it is one of the
bounds.
José C.
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