Author: Vincent Diepeveen
Date: 07:45:18 12/27/99
Go up one level in this thread
On December 27, 1999 at 00:07:47, William Bryant wrote:
>If your search fails low on the root PV move.
>(IE. the full alpha beta window for the PV move returns a score <= alpha
>and nothing is backed up into the PV array).
>
>Do you?
>
>1) Stop PVS and search the rest of the root moves for this iteration with a
> full alpha beta window?
>
>2) Stop PVS until at least one move for this iteration falls into the alpha
> beta window. If no moves fall into the window, research the whole
> iteration with a lower window. (fail low). This means that you may end up
> searching every move with a full alpha beta window which would take more
> time before the fail low occurs.
>
>3) Stop now and lower the window and research with PVS.
>
>4) Do Nothing?
> Continue the rest of the root moves within the -alpha-1, -alpha PVS window.
> Only search moves outside the PVS window for the rest of this iteration
> if they return a score > alpha on the PVS search. Hope that if the
> every root move is going to fail low, that this will speed up the
> search until the window is lower.
>
>5) Suggest something better.
I'm not having this problem too much in DIEP.
I'm searching using PVS, so i start with -infinite, infinite window.
I don't have any problems with PV arrays, as i simply don't have
a PV array. I only have 1 variable called: bestmove.
The rest of the PV i get out of hashtable.
How pvs works:
search:
alfabeta(-inf,inf);
alfabeta(int alfa,int beta,...
firstmove:
alfabeta(alfa,beta...);
other moves:
t = alfabeta(alfa,alfa+1...
if( t > alfa && t < beta )
t = alfabeta(t,beta,...);
>Fail low on the root move seem to bring my search to a crawl and I'm looking
>for a way to be more efficient.
>
>Thanks in advance.
>
>William
>wbryant@ix.netcom.com
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