Author: Robert Hyatt
Date: 10:03:46 01/24/01
Go up one level in this thread
On January 24, 2001 at 11:49:55, Ricardo Gibert wrote: >On January 24, 2001 at 10:38:28, Robert Hyatt wrote: > >>On January 24, 2001 at 01:19:45, Uri Blass wrote: >> >>>On January 24, 2001 at 00:24:23, Robert Hyatt wrote: >>> >>>>On January 23, 2001 at 13:45:24, Gerrit Reubold wrote: >>>> >>>>>On January 22, 2001 at 16:02:56, Robert Hyatt wrote: >>>>> >>>>><big snip> >>>>> >>>>>>The problem is endgame knowledge. A program _ought_ to know that if you have >>>>>>a passer, then trade pieces to reach a won ending. Only in this case, that >>>>>>heuristic back-fires as it is black who ends up winning. This is a _tough_ >>>>>>exception to handle... >>>>>> >>>>>>although a GM would tell you instantly "No I won't trade queens..." >>>>> >>>>>Hello all, >>>>> >>>>>I think stating that a GM would know instantly that trading queens lose is >>>>>misguiding. One tempo decides whether the queen exchange loses or wins. Both a >>>>>GM and a chess engine should calculate here and not simply trust their >>>>>evaluation. Of course, "tell you instantly" could mean that the GM did the >>>>>calculations unconsciuosly and super-fast, but I don't think it was meant this >>>>>way. >>>>> >>>> >>>> >>>>I calculated it like this: >>>> >>>>1. remove queens. it is now white's move. Can white force those connected >>>>passers in? not quickly. >>> >>>You need to calculate to find that not quickly enough. >>> >>>look at this position when the king is in h2 and not in h1: >>> >>>[D]6k1/2p5/4P3/p3PP2/1p1P4/7P/P6K/8 b - - 0 1 >> >>OK. Black is going to get a queen in 4 moves. a4, b3, b2 and b1, or >>a4, b3, bxa2 a1, or if white wastes one tempo, a4, b3 axb3 b2 and b1. IE >>if white ignores it, 4 moves, if white wastes one move, it takes 5, but that >>is still 4 moves effectively. >> >>Now for black. >> >>Here I don't see any way for white to make a queen in 4 moves, or to make >>moves that force black to move his king and delay his queening plan. What am >>I overlooking? > >d4-d5-d6-d7-d8 makes 4 effective moves for White. You are right... I didn't look closely enough. Black can't stop the white pawn(s) from promoting... > >I set the position up with white having the three pawns and >>king exactly as in your position, but black having a pawn on b5, which leaves >>it with the same number of moves. Crafty can't find a way for white to win >>this... >> >> >> >> >>> >>>In this case white can force the connected pawns quickly enough because the >>>passed pawns queens with check. >>>> >>>>2. what about black's b-pawn? Can white stop it? no. >>>> >>>>moral: don't trade queens _yet_. >>>> >>>>Crafty understands how to 'count squares' to see if a pawn can be caught or >>>>not. It just doesn't yet know how to apply that to 'candidate passers' since >>>>it costs a couple of tempi to make the passer, then more to run it in. >>>> >>>> >>>> >>>>>Consider the following changes to the position after blacks 45.th move: >>>>> >>>>>(a) if the black a-pawn were on a6 instead of a5: 46. Qe6+ wins, but it is not >>>>>obvious. >>>>>(b) if the white King were on g2 instead on h1: 46. Qe6+ wins, even less >>>>>obvious. >>>> >>>>these are easy (obvious) to me. just ask "can the king reach the queening >>>>square of the b pawn or not?" >>> >>> >>>The king cannot reach the b pawn from g2 but white wins because black does not >>>force a new queen with check and can do it only without check so white can >>>promote one of the passed pawn to be a new queen and we get again a queen >>>endgame. >>> >>>I think that programs should see that black has unstoppable passed pawn but >>>should also see that white has unstoppable passed pawn and the only way to know >>>which pawn is winning is by caculating. >>> >>>Uri
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.