Author: José Carlos
Date: 01:28:07 10/27/02
Go up one level in this thread
On October 27, 2002 at 04:14:25, Nagendra Singh Tomar wrote:
>On October 27, 2002 at 04:05:19, José Carlos wrote:
>
>>On October 26, 2002 at 19:04:33, Nagendra Singh Tomar wrote:
>>
>>>On October 26, 2002 at 12:27:46, José Carlos wrote:
>>>
>>>>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".
>>>
>>>That <beta check is needed because if the score is >beta, then also we are not
>>>interested in the score because we know that this is too good a score for
>>>us for the opponent to allow .. so the opponent will not let us lead to
>>>the board where we can play this move.. thats why we ignore for >alpha and >beta cases.
>>
>> Wrong. In the root you consider every move. There's no way for your opponent
>>to avoid any of your root moves ;)
>>
>> José C.
>>
>>
>
>You are right .. But I meant the non-root case !!
Sorry then. I though you were still asking for root nodes.
In non root nodes, of course you need beta.
José C.
>>>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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