Author: Robert Hyatt
Date: 06:57:10 09/22/01
Go up one level in this thread
On September 22, 2001 at 01:39:15, Miguel A. Ballicora wrote: >On September 22, 2001 at 00:52:06, Robert Hyatt wrote: > >>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. > >But I play g6xh5 first and you don't promote ;-) >I think we are talking about different things. You are setting a position >with only h6 and g5? then I have pawn less and has little to do with the game >itself. > OK... let's back up a bit. I have an a and c pawn, and a pawn at g5. You have pawns at g6/h7. That is the position in the game under discussion. Crafty was up a pawn, and had an eval of +2.something, although the game was later drawn. I am going to use my king to advance my a/c pawns. If you leave that area, I will promote easily. If you play h6, I am going to play gh and promote on the h file if your king isn't close enough, or on the a file if you try to stop the h pawn. That was the reason for setting up the kingside pawns so that you don't have any moves over there. With my queen-side pawns at (say) c4/a4 I don't see how your king is going to stop them. Wheneven you approach one, the other advances. If you "wait" I wait also by advancing my king. This was why I said it doesn't seem so easy to try to statically evaluate this, although I think I have some ideas of how to do this a bit more accurately by fixing what looks like a bug. >>> >>>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... > >Of course, but it is not the case of this game! >Ok it is late for me too, I better go to sleep... > >Miguel > >> >>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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