Author: Robert Hyatt
Date: 21:56:04 04/12/03
Go up one level in this thread
On April 12, 2003 at 22:01:10, Uri Blass wrote: >On April 12, 2003 at 21:45:13, Koundinya Veluri wrote: > >>On April 12, 2003 at 19:58:09, Uri Blass wrote: >> >>>On April 12, 2003 at 19:45:22, Koundinya Veluri wrote: >>> >>>>On April 12, 2003 at 06:13:05, Uri Blass wrote: >>>> >>>>>On April 12, 2003 at 05:46:08, Jeremiah Penery wrote: >>>>> >>>>>>On April 12, 2003 at 04:22:57, Uri Blass wrote: >>>>>> >>>>>>>On April 12, 2003 at 01:44:26, Robert Hyatt wrote: >>>>>>> >>>>>>>>That has to be part of the evaluation. IE you have to know that you can >>>>>>>>give the pawn up if your king is closer to the remaining pawns than the >>>>>>>>opposing king is... >>>>>>>> >>>>>>>>I do that obviously... >>>>>>> >>>>>>>This has nothing to do with the pawn. >>>>>>> >>>>>>>You have to evaluate correctly the following position that can happen >>>>>>>if you do not search deep enough >>>>>>> >>>>>>>[D]8/8/1K6/5p1p/4kP1P/6P1/8/8 w - - 0 6 >>>>>>> >>>>>>>I hope that movei will be able to see it after I add some knolwedge but the >>>>>>>knowledge that is needed is not about passed pawns because there are no passed >>>>>>>pawns in that position. >>>>>> >>>>>>Bob never said anything about passed pawns. >>>>> >>>>>He did in the post that started this thread: >>>>> >>>>>http://www.talkchess.com/forums/1/message.html?292975 >>>>> >>>>>"This seems to be an example of an engine that misses the power of the "distant >>>>>passed pawn". >>>>> >>>>>I agree that a lot of engines have problems in the evaluation but the problem >>>>>is about not evaluating correctly king relative to the pawns and has nothing to >>>>>do with evaluation of the "distant passed pawns". >>>>> >>>>>Uri >>>> >>>>It may take several moves for the white king to capture the passed pawn in some >>>>variations, so if the search can't see the capture from the initial position, >>>>then the "king relative to pawns" evaluation might not be sufficient to solve >>>>this. After the capture is made, the search can usually see the rest faily >>>>easily so I think the "distant passed pawns" evaluation is more important to >>>>solve these type of positions. >>>> >>>>Koundinya >>> >>>I disagree. >>> >>>A program without knowledge about distant passed pawns(but with some small bonus >>>for passed pawns) and with knowledge about king relative to pawns will >>>have no problem in that position. >>> >>>The *only* reason that a program with a bonus for passed pawns can fail here is >>>lack of knowledge about king relative to the pawns. >>> >>>There may be other positions when knowledge about distant passed pawns is >>>important but not the position that was posted. >>> >>>The point is that white has equality without trading rooks and can capture the >>>black passed pawn without trading the rooks so even a small bonus for passed >>>pawns is enough to avoid trading rooks unless the search can see that white can >>>win a pawn after trading rooks and it is exactly what happens to program that >>>trade the rooks. >>> >>>Uri >> >>For a program to see that Rd4 loses, it must also see the reply Rxd4. So >>consider the position after the rooks have been captured. >> >>8/8/1p4k1/5p1p/3K1P1P/6P1/8/8 b - - 0 2 >> >>For the "king relative to pawns" evaluation to come into play, the black king >>has to get closer to the white pawns than the white king. This doesn't happen >>until the white king is pulled away by the passed pawn. > >Yes but if the pawn is not captured the program in the search the program has no >reason to let the rook trade. > >simple evaluation that give bonus to every passed pawn is enough. You have _got_ to be a better chess player than that. You are saying all passed pawns are equal. They most definitely are not. Pawns on the a,b c file for both sides. My passer is on the h file. Yours is on the e file. You _still_ think that a bonus for a passer is enough? I have a passer already, you can trade rooks to create your passed e pawn. Smart move? I don't think so... > > > This takes approximately >>11 plies. Until that point, the "king relative to pawns" code won't even come >>into play. > >11 plies is a small depth in an endgame and program may get it even at blitz >time control. > >If the program does not see the capture of the pawn then it is going to be right >in giving black the advantage because of the passed pawn. > > Additionally, when the rooks are on the board, the program won't >>search as deeply as after the trade. > So from the initial position I think the >>"distant passed pawn" knowledge is more important here. Of course you will >>probably need both pieces of knowledge for the evaluation to be stable between >>plies, but the "king relative to pawns" evaluation only may not be sufficient if >>the program isn't a deep searcher. I do agree though that the evaluation you >>suggested is also necessary. >> >>Koundinya > >I agree that evaluation of distant passed pawn is necessary but the position was >not a good example because program with only small bonus for passed pawns and >knowledge to evaluate pawns relative to the king can also solve it. > >It is possible to have a case when evaluation of distant passed pawn is >important but I think that a case when both sides have passed pawns or a case >that you need to sacrifice a pawn in order to create the distant passed pawn can >be better. > >Uri
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