Author: Robert Hyatt
Date: 21:52:06 09/21/01
Go up one level in this thread
On September 22, 2001 at 00:43:03, Robert Hyatt wrote: >On September 21, 2001 at 23:45:54, Miguel A. Ballicora wrote: > >>On September 21, 2001 at 23:01:29, Robert Hyatt wrote: >> >>>On September 21, 2001 at 17:01:35, Miguel A. Ballicora wrote: >>> >>>>On September 21, 2001 at 16:45:44, Robert Hyatt wrote: >>>> >>>>>On September 21, 2001 at 16:27:01, Gian-Carlo Pascutto wrote: >>>>> >>>>>>On September 21, 2001 at 14:57:20, Robert Hyatt wrote: >>>>>> >>>>>>>I don't mind that kind of mis-evaluation so much. If anybody wins, white >>>>>>>wins. What I would not like is to see that kind of evaluation and then lose >>>>>>>the game... >>>>>> >>>>>>The problem is when crafty prefers the 1.8 from this ending over the 1.7 from >>>>>>another ending that _is_ won for white. >>>>>> >>>>>>That'll cost you half a point. >>>>>> >>>>>>-- >>>>>>GCP >>>>> >>>>> >>>>>I don't disagree. But it is just as important to not lose when you can win >>>>>or draw. The not drawing when you can win is another level of tuning. I need >>>>>to study the ending because a pawn on the a and c file becomes very hard for >>>>>a lone king to stop... it might have simply made a mistake and drawn a won >>>>>position in this case.. I didn't look at it very carefully (yet). >>>> >>>>It looks drawn. As you already know, the advantage of the outside passer is that >>>>you can sacrifice it and the king can go and eat up the opponent pawns on the >>>>other side. In this case it is impossible (that's the problem here). For >>>>instance, place the pawns in g6,h5,g4. How can the white king capture them? it >>>>can't because as soon as you capture g6 black plays h4 and promotes. On the >>>>other hand, two passers cannot beat a king on the Q side, they need the help of >>>>the wKing. however, the wK cannot go to the Q side because black promotes. >>>> >>>>Regards, >>>>Miguel >>> >>> >>>I don't believe it is quite that simple. If the pawns are zugged on the >>>kingside, the two passers on the queenside can easily win. This is the >>>attraction of "wild 7" on ICC, which is what the "mini game" is all about. >> >>I am not sure what you mean by zugged pawns. Anyway, white cannot capture the >>pawns in any case, so how can white win? two passers, if they are not separated >>enough, cannot win without king support. >>The only chance is a race, when white king rush to the Q side to support them >>letting a black pawn to promote. >> >> >>>In this zug-less position (at present) things aren't so clear, of course, >>>but >>>put the black pawns at g5 and h6 and the white pawn at g4, and this turns >>>into a simple white win... >> >>Black plays h5 and it is a draw. I think I did not understand. >> >>Regards, >>Miguel > > >You are assuming that a KQ vs KQPP is a draw? IE after h5, I play gxh5 and I >promote first. > >To understand the rp and bp vs a lone king, requires a bit of thought. But >once you understand that this is all about zugzwang, you realize that if the >tempo is mine, and you have _no_ move to make but king moves, you can't stop >the two pawns. Just visualize the two pawns side by side at a4/c4, with your >king at b6. It is your move and you have to stop the two pawns. If you play >Kc5, I play a5 and you can't take the c pawn. If you play Ka5, I play c5 and >you can't take the a pawn. So you retreat, I advance, and we reach this >position one rank further up. It's a cute position that once caused a lot >of interest on ICC until most everyone figured out how to win (white starts >off with pawns at a2/b2/c2, king at d1. Black has pawns at h7/g7/f7, king >at e8. White moves and wins every time if he plays right. One wrong move > Part of the above is right. Part is wrong. Too late at night to correct it now... Depends on how far the pawns are advanced... Bob and black draws or wins. > >So calling this a draw or a win or a loss is not so easy for a static eval. >If black has one "passing" move (wild 7 has white playing a4/c5/a5/c5 until >the black king stops the pawns, then using the b pawn to gain the necessary >tempo to win the game) then this doesn't work. In the position I started with >above, if white has to move, either pawn move loses, as black can then capture >that pawn and catch the other before it can promote... > >That's why I said this was a hard one to evaluate without a lot of searching >or specific pattern analysis. I don't want to include the specific knowledge >for the above analysis in Crafty as it would be slower, and it would hardly >ever be used... > >But I do plan to look at the position and see if the eval can be tweaked some >as it _does_ know that black has a majority. I am probably incorrectly giving >credit to white for two "distant passers" when there is really only one. And >black has a distant passer himself that it does know about...
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