Author: Dave Gomboc
Date: 21:47:12 11/08/02
Go up one level in this thread
On November 07, 2002 at 11:42:57, Robert Hyatt wrote: >On November 06, 2002 at 15:42:14, martin fierz wrote: > >>On November 06, 2002 at 14:51:50, Robert Hyatt wrote: >> >>>On November 06, 2002 at 13:58:24, martin fierz wrote: >>> >>>>On November 06, 2002 at 11:15:43, Robert Hyatt wrote: >>>> >>>>>On November 06, 2002 at 03:43:58, martin fierz wrote: >>>>> >>>>>>On November 06, 2002 at 00:02:57, Robert Hyatt wrote: >>>>>> >>>>>>>On November 05, 2002 at 14:17:55, martin fierz wrote: >>>>>>> >>>>>>>>On November 05, 2002 at 01:18:07, Jouni Uski wrote: >>>>>>>> >>>>>>>>>There is interesting and quite long analysis about game 2. which Kramnik won. >>>>>>>>>They claim, that after whites 35. Rc5, there is no need for black to lose: >>>>>>>>> >>>>>>>>>[D]r7/3k1ppp/8/p1R1p3/Pp2P3/5PP1/1P5P/4K3 b - - >>>>>>>>> >>>>>>>>>According to analysis 35.-Rc8 draws! Really? >>>>>>>> >>>>>>>>Rc8 is obviously the best move in this position. shortly after the game i posted >>>>>>>>this position asking if any program can find this move - only bob answered >>>>>>>>saying that if a position is lost it doesnt matter what move you make (hmm, >>>>>>>>sounds rather stupid to me...). >>>>>>> >>>>>>> >>>>>>>Sorry to sound "stupid" but my point was that trying to find a "good" move >>>>>>>after the game is lost is not very interesting. Much better to try to find >>>>>>>a good move _prior_ to things going south. >>>>>>> >>>>>>>Rc8 might be good enough to draw. I'm not so sure being a pawn down with an >>>>>>>active rook is that great if your opponent has a rook that is causing problems >>>>>>>as well. I would rather try to find something _earlier_ in the game... >>>>>> >>>>>>that still sounds a bit stupid to me :-) every chess player gets into positions >>>>>>where he wishes he had done something different earlier in the game. but then >>>>>>the right reaction is not to kick yourself for the earlier mistake, but instead >>>>>>to fight as well as you still can and make things hard for your opponent. >>>>>> >>>>>>you can also just see it as a test position which has no reference to what >>>>>>happened earlier in the game. black to move and fight for the draw! the >>>>>>discussion then was whether kramnik was playing specifically anti-fritz or not, >>>>>>i.e. whether it was really such a big help that he got the *exact* copy before >>>>>>the match. i still dont't think so, and this position is one of the reasons. >>>>>>which computer will play Rc8 here? my guess: not one. which means that kramnik's >>>>>>strategy (as seen in games 1-4, but no more later) would have worked against >>>>>>most other computers too... >>>>>> >>>>>>aloha >>>>>> martin >>>>> >>>>> >>>>>I suspect it _would_ have worked. I'm not particularly worried by this >>>>>position, because >>>>>it requires dumping a pawn for a little activity, which is not going to be easy >>>>>to implement. >>>> >>>>this is really a standard idea in rook endings. it's not like this is a "one in >>>>a million" position... >>>> >>>>>The work spent on getting a program to do that in the right way will be _far_ >>>>>greater than >>>>>the work required to avoid the entire sub-tree earlier in the game, which was my >>>>>point. This >>>>>is about "economy of effort" more than anything else. >>>> >>>>which may be right for this particular game. but rook endings are the most >>>>common endings, and this is a very common theme in rook endings. >>>> >>>>aloha >>>> martin >>> >>> >>>It's a common theme, but it is also very "special-case". For every position >>>where giving >>>up a pawn for activity is right, there are cases where it is also wrong. >>that may be true, but then the challenge is obviously to find an evaluation >>function which knows which case is which... >> >>>That's the problem I was talking about. And once you choose to give up the >>>pawn, you are >>>committed, right or wrong. Until then you have options. >> >>not true. in this position, after ...Rc8 Rxsome pawn Rc2, the white king is >>trapped on the back rank. which is surely a big help for the defending side. you >>cannot wait until white has activated his king - you don't have the option of >>saccing that pawn any time you like. >> >>aloha >> martin > >Of course not, but at that point I have a choice. After I sac I have no choice >whatsoever... > >If the sac loses more times than it wins, then it turns out to be bad. This is >one >of many such cases where a human's intuition and experience will help, but >trying >to transform that into an evaluation function is nowhere near easy. But Bob, the rules for R+P endings is "1. activity. 2. activity. 3. activity.". I've read that in these endings, rook activity takes priority over the pawn count 9 times out of 10. Nothing worthwhile is easy. ;-) Dave
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