Author: Robert Hyatt
Date: 05:57:04 02/11/98
Go up one level in this thread
On February 11, 1998 at 02:52:29, Bernhard Bauer wrote: >On February 10, 1998 at 12:09:49, Bruce Moreland wrote: > >>Cool bug. If you want to see other bugs of this type, try setting up >>positions where each side has only one minor piece, but there is a mate >>in one. >> >>For instance something like >> >>5Bbk/8/7K/8/8/8/8/8 w - - 0 1 >> > >Crafty gives: > > White(1): Bg7# > time used: 0.18 > > Crafty offers a draw. > >So after mating Crafty offers a draw. > >>When I tried this a few years ago I found that several programs called >>this a draw. Maybe they still do. >> > >Looks like you are right. > >>Regarding 5-piece endgame databases, I have a whole bunch of them, but I >>don't actually use very many on ICC, since the Alpha doesn't have enough >>disk. >> >>One of the ones I put on the Alpha, almost as a lark, was KP vs KNN, and >>it has come in handy twice, which was twice more than I expected. >> > >I think it's a good idea to do things in a proper way. Crippling down a >program for speed reasons may be a bad idea and may give the customers >a bad feeling. It would be better to insert a line of code like: > you are assuming facts not in evidence. The reason *I* do what I did is to win games that are winnable. IE imagine a position where there are 7 pieces on the board. White has a king, two knights and a pawn. Black has a king knight and bishop. Crafty finds a way to win one of black's pieces for a pawn, and concludes "hey, I have two pieces vs one piece for my opponent, that's +3, so I'm going for it since the current score is only + 1. But the resulting position ends up a draw. Since it is impossible to determine which are winnable and which are drawable by search, I have to either say "draw or +3". DRAW is right 99.99999 percent of the time. It isn't a speed issue at all. IE imagine intentionally heading into these +3 types of position tactically, only to find out 50 moves later there was no way to win. It happened many times until I fixed this. I'd rather win 100 and draw 1, than draw 100 and win 1. >XXX will not handle this position properly due to speed reasons. STOP. > >Here are 2 positions from V. Albillo's home page that cause difficulties >to crafty. > >8/1k1K4/8/8/1pN5/1N6/8/8 w - - bm Nc5+; id "VA19: 6mate"; >8/8/8/5K2/7k/7p/7N/7N w - - bm Nf2; id "VA20: 9mate"; > >Now I know why. > >Regards >Bernhard >>bruce
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