Author: Robert Hyatt
Date: 20:48:58 01/05/01
Go up one level in this thread
On January 05, 2001 at 14:11:59, David Rasmussen wrote: >On January 05, 2001 at 09:45:47, Robert Hyatt wrote: > >>On January 05, 2001 at 08:05:26, David Rasmussen wrote: >> >>>What is the best way to sort moves at the root after each iteration? >> >>My approach is to (a) put the PV move from the previous iteration first. >>Sort the remainder of the moves based on the number of nodes in the subtree >>produced by each of the other moves... >> >> > >OK. I do this too already. > >>> >>>What is the best way adjust alpha and beta at the root after each iteration? >> >>center it around the value returned by the previous iteration. Look at your >>output carefully to find your "swing" value. This is the amount of score >>"swing" caused only by even/odd ply searching. If yours happens to be zero, >>then just center the score on the last iteration value. If you notice that >>your odd ply searches have a score about .15 higher than even ply searches for >>the same move, then factor that in. >> >> > >OK. > >> >>One problem if you do null-move, is to watch for cases where a root move fails >>high, then fails low on the re-search. In that case I do _not_ make that move >>a PV move. > >What do you do then? OK.. let's take the root. The first move is searched. I then use the PVS null-window on the remainder of the ply=1 moves. If one fails high on the null-window search, I re-search with the correct PVS beta value. If this search fails low, I pretend the fail-high didn't happen and keep right on searching without replacing the PV move. If it fails high on the re-search, It does become a PV move even if it then fails low on the 4th re-search... The bad case is failing high on the null-window search then failing low on the first re-search... that can make you play lemon moves...
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.