Author: Ricardo Gibert
Date: 23:53:30 09/21/99
Go up one level in this thread
On September 21, 1999 at 09:59:01, Robert Hyatt wrote: >On September 20, 1999 at 18:36:42, Howard Exner wrote: > >>On September 20, 1999 at 14:42:27, Robert Hyatt wrote: >> >>> >>>Here are a couple of examples: >>> >>> +---+---+---+---+---+---+---+---+ >>> 8 | | | | | | | *K| | >>> +---+---+---+---+---+---+---+---+ >>> 7 | *P| *P| | | | *P| *P| *P| >>> +---+---+---+---+---+---+---+---+ >>> 6 | | | | | | | | | >>> +---+---+---+---+---+---+---+---+ >>> 5 | | | | | | | | | >>> +---+---+---+---+---+---+---+---+ >>> 4 | | | | | | | | | >>> +---+---+---+---+---+---+---+---+ >>> 3 | | | | | | | P | | >>> +---+---+---+---+---+---+---+---+ >>> 2 | P | P | P | | | | P | | >>> +---+---+---+---+---+---+---+---+ >>> 1 | | | | | | | K | | >>> +---+---+---+---+---+---+---+---+ >>> a b c d e f g h >>> >>> >>>(fen 6k1/pp3ppp/8/8/8/6P1/PPP3P1/6K1/ w) >>> >>>old (16.18 crafty) evaluates this as -36 (black is better) because of >>>those two doubled kingside pawns. new crafty says +.36 because white has >>>a potential outside passer on the c file, black can't force a passer without >>>the king helping. Better... >> >>Black can force a passer here without the king's help. >> > >Of course but he also gives black one in return, which was the point. My >eval doesn't give anyone credit here. But the search returns a mate in 14 >almost instantly. (mate in 14 for black winning) I think you got the colors mixed up above. BTW could you post the mate in 14? > >Remember, I am simply trying to recognize (positionally) winning positions. I >don't think it is physically possible to force crafty into such a position with >the king totally blocked behind a bishop that is totally blocked, etc. I'll >accept that kind of error to get the real positions mostly right. :) > >Even an outside passed pawn doesn't always win. But it does most of the time, >so that the eval term I have had for years has always been pretty accurate... > > > >>Try the below artificial (and illegal) example on crafty. It will test >>whether black can force a passer without the king's help. It has that same pawn >>configuration on the king's side. >> >>1kb5/1p1p1ppp/1P1P4/8/8/1p1p2P1/1P1P2P1/K1B5 w The position appears legal to me. Perhaps you left off W: Pa3; B: Pa6? With white or black to move black wins (You can start the white K on b1 if you like. It makes no difference.). Black temporizes if necessary to make sure the white K is on a1 before sacrificing a pawn, then since he Qs 1st Qxc1 will mate. Note black does not even need the mate if he moves first. After h5 he will have 2 tempos to spare. > > >if you try to win the position I originally gave, if anybody wins, white >wins, and white winning is pretty likely. Because my first moves as white >will not have to worry about a black pawn running in, since the white king >will stop it easily. I'm pretty sure it's a draw. Black must wait patiently before "coming alive" on the K-side. It is also important to keep at least one black pawn on the Q-side, though in some variations, it is not a necessity. With black to move, the draw is definite.
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.