Author: Nagendra Singh Tomar
Date: 16:13:21 10/27/02
Go up one level in this thread
On October 27, 2002 at 04:33:23, José Carlos wrote:
>On October 26, 2002 at 19:14:57, Nagendra Singh Tomar wrote:
>
>>On October 26, 2002 at 05:17:12, Severi Salminen wrote:
>>
>>>>score = -alphabeta(board, -alpha-1, -alpha, depth-1);
>>>>
>>>>if(score > alpha && score < beta)
>>>>{
>>>> score = -alphabeta(board, -beta, -score, depth-1);
>>>> OR
>>>> score = -alphabeta(board, -beta, -score+1, depth-1);
>>>>}
>>>
>>>-score+1 is correct.
>>>
>>>Severi
>>
>>thanx, its a relief to read such a small and to the point answer after such a
>>"long debate".
>>I than Antonio and Jose to get me such nice ideas.. But Jose beta is still
>>useful..
>
>Sorry. I read this:
>
>**************
>If we are using PVS search and assume that at the root, the 2nd move (searched
> ^^^^^^^^^^^
>with a zero window) turns out to be the best move. Since we are passing a zero
> ^^^^^^^^^^^^^^^^^^^^^
>window down to that subtree, at all the plys below, it will either fail-low or
>^^^^^^^^^^^^^^^^^^^^^^^^^^^
>fail-high, so none of the plies will update the PV. In this case we will get a
>pv length of 1 (with only the root move in the PV).
>Is this true whenever any move other than the first move tried at the root lies
>on the PV.
>How do we fill the PV in such cases ? using trans table ?
>**************
>
> and I was trying to answer it. Note your words: We are at the root, searching
>a zero window, passing it down to the subtree. So, in that subtree, all nodes
>are searched with a zero window, so it's certainly impossible to get a score
>between alpha and beta (beta is alpha+1 everywhere).
>
> José C.
>
>
>>remember that opponent will never let you grwo more than beta .. It is
>>his value we cannot do anything about it .. we can always try to increase alpha
>>but never beyond beta ..
>>
>>tomar
Jose, if I am not mistaken i never conveyed that we are at the root. Moreover we
will not get a PV if we do a sero window search, but the idea of the zero win
search is to prove that this is worse than the PV move. if it turns out to be
better (fail-high) then anyway we are trying with a wide window and then we will
be able to collect PV.
My question was simply asking whether for thos wide window search we use -score
or -score+1 for beta .
Of which now I got the answer <-score+1>
regds
tomar
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