Author: Will Singleton
Date: 13:04:51 10/03/05
Go up one level in this thread
On October 03, 2005 at 11:43:22, Robert Hyatt wrote: >On October 02, 2005 at 13:49:37, Will Singleton wrote: > >>White wins easily by promoting and exchanging queens, but most comps can't see >>it. >> >>[d]8/5p1P/8/8/6K1/5P2/1k6/q7 w - - >> >>Amateur failed to exchange queens, and drew the game. I'm not quite sure why, >>seems like a simple search should be enough to handle this. Oddly, if the >>exchange is forced, the win is seen immediately. This happens with other progs >>as well. I thought I had taken steps to eliminate root-position dependencies in >>the search, but maybe something else is happening. >> >>Will > > >Here is what you need: > >Your program probably understands that if you remove the black queen, white is >winning because of the "outside passed pawn"??? (ignore the fact that the pawn >promotes instantly for now). If so, you need one more critical piece of >knowledge. > >Your program needsd to realize that if things are not obvious, no pawn to >promote, no distant passer on the board, but its king is closer to the remaining >pawns than the enemy king, the game is _still_ won. > >Set up a position like white/black pawns locked up at a4/a5, white passer at h2, >both kings near the center of the board. The easiest way to win is to push the >h-pawn. Black has to go over and stop it, and once it is gone, white is too >close to the remaining black a-pawn and the game is over. > >If you don't catch this case, you will play for a distant passer, but then >refuse to give it up, and once your king gets to the distant passer to defend >it, you can't force the promotion, and when you wait too long, as your king >finally gives up the passer, black eats it and then follows you across the board >and hems in your king on the a-file or else black gets to the a-file and the >game is a draw. But if you just push and get the black king too far away, you >win easily... > >Crafty plays this move instantly with no endgame tables of any kind, and shows a >big +score for white immediately, due to the above... > > Thanks for the info, it will be helpful in other situations. This one is different. After h8=Q a1=Q, we get this position: [d]7Q/5p2/8/8/6K1/5P2/k7/q7 w - - From here, Crafty takes 15 ply (over a minute on my comp) to see the exchange, then another ply to get a winning score. This is the problem I was referring to, albeit clumsily. Will
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.