Author: Robert Hyatt
Date: 21:43:03 09/21/01
Go up one level in this thread
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 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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