Author: Robert Hyatt
Date: 10:05:02 09/01/02
Go up one level in this thread
On September 01, 2002 at 06:19:33, Alvaro Jose Povoa Cardoso wrote: >>>Difference is that Crafty used alpha instead of value when it re-searches. >>>Is there any reason to use alpha instead of value? >>>Using value which is greater than alpha seems to cause more cutoffs than using >>>alpha. >>> >>>Thanks in advance. >> >>I do this only because it is possible to fail low on the re-search, and now you >>have the question of whether this fail-high/fail-low means anything. I choose >>to go to the full window so that if it fails low, I know it is not good and I >>can ignore the fail high. This is a null-move / hashing artifact that simply >>happens to anyone doing PVS, null-move and hashing, all together... > > >Just curious, if we removed null-move, would that artifact still happen? >In other words, would PVS+hashing cause that? Yes. Say you do a really deep search while pondering, and store position X with a big depth and a score>x.xx type lower bound. Now your opponent plays a different move, you start the search over. But many times, you reach position X via transpositions, and you pop out that score>x.xx and it causes you to fail high. But on the re-search, you fail low because now you are on your own, and can't use that big-depth table entry to help because alpha and beta have been raised. This is not terribly common, but it can obviously happen... It can also happen without the big pondering search, just because of how the hash table works.. > >Regards, >Alvaro Cardoso
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.