Author: Robert Hyatt
Date: 06:55:45 10/24/98
Go up one level in this thread
On October 23, 1998 at 21:07:34, James Robertson wrote: >On October 23, 1998 at 20:40:03, Robert Hyatt wrote: > >>On October 23, 1998 at 00:45:33, James Robertson wrote: >> >>>On October 22, 1998 at 23:14:56, Robert Hyatt wrote: >>> >>>>On October 22, 1998 at 21:45:54, jonathan Baxter wrote: >>>> >>>>>How do chess programs detect perpetual check? Do they just extend on sequences >>>>>of checks or do they have specific features to detect likely perpetual >>>>>situations? >>>>> >>>>>Jon >>>> >>>> >>>>I don't do anything special other than checking for repetitions in the usual >>>>way. I extend on checks, and again if there is only one legal move to get >>>>out of check. Other than that, nothing special in my code at all... >>> >>>Wasn't Deep Blue unable to detect perpetual check in the second game of it's >>>Kasparov return match? And Kasparov then made the foolish mistake of believing >>>the computer wouldn't miss something like that? >>> >>>James >> >> >>Kasparov didn't see it either. It was a full 60 plies of search to see >>the repetition... > >I suppose it is obvious he didn't see it; he didn't play it. :) >Many perpetual check positions require many many plies to see them to their >conclusion (draw), and yet humans spot them all the time..... > >James this is a problem. And we solve it differently. IE I don't search for a repeated position, I search for a way *out* of the checks. And if I don't find it, I call this a draw. Crafty has to do it the other way, and sometimes the draw is so deep it wouldn't see it in a year, while a human would see it instantly. IE a position where white's queen is at a1, a white pawn at a2, and the king + black king/queen anywhere on the board where the black king isn't already in check... the black queen will run the white king all over the board before the position is repeated. But a human would look and say "no way to build a place to hide here, so there is no way to escape the queen checks... this is a draw" Computers just don't handle this very well...
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