Computer Chess Club Archives


Search

Terms

Messages

Subject: Re: Aspiration search, PVS

Author: Russell Reagan

Date: 11:50:00 12/28/02

Go up one level in this thread


On December 28, 2002 at 14:01:24, Tony Werten wrote:

>If a move is better than score it means it is somewhere between x and y (
>probably between score and y ) and you have to check if this is true.

Thanks Tony. Let me see if I understand now.

In PVS, you search with a window of (alpha,alpha+1). If the score from that
search is in the range (alpha,beta) that means that move is better, and you have
to re-search to find out how much better. This same concept applies at the root.
If you search with an aspiration window, and the score comes back between alpha
and beta, then you know that this move is better, but not how much better. If
this happens in the middle of a search (like in PVS) you have to re-search. But
if this happens at the root, you can set that as your new "move to play", even
though you don't know how much better the move is until you finish re-searching.
The advantage is that you will play the "better" move if the re-search doesn't
finish in time.

Or more generally: If you search with an aspiration window, and the score is
between alpha and beta, you must re-search. The exception is at the root where
you could play the move, knowing it is better than what you had, without having
to re-search.

Do I understand correctly?

Russell



This page took 0 seconds to execute

Last modified: Thu, 15 Apr 21 08:11:13 -0700

Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.