Author: Robert Hyatt
Date: 16:02:43 10/01/03
Go up one level in this thread
On October 01, 2003 at 14:01:52, Tord Romstad wrote: >On October 01, 2003 at 13:50:49, Robert Hyatt wrote: >> >>It seems to me that Chrilly's paper on null-move search included this >>idea as the "threat extension". > >It is not the same. The "deep search extension" (the term Chrilly used, >IIRC) extends in all positions where the null move fails low by a >sufficiently high margin, as you explain. The Botvinnik-Markoff >extension is different. It extends when the null move fails low at >ply n _for the same reason_ as the null move failed low at ply n-2. > >I have never seen this idea before. It seems original and interesting. > >Tord OK. It is just a restricted "singular extension". If a move is singular at two consecutive plies for the same side, it gets extended. The "for the same reason" seems wrong, since all you are looking at is the refutation move. Note that the _best_ move is not needed to produce a cutoff, just "a good enough move". That means it is more than just barely likely that two different moves will cutoff and cause the null-move search to fail low at two consecutive plies for the same side. This could happen when history totals change, killer arrays/counts change, one gets a hash hit the other doesn't, etc...
This page took 0.01 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.