Author: Vincent Diepeveen
Date: 05:41:11 05/11/98
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On May 11, 1998 at 07:04:23, Amir Ban wrote: >On May 10, 1998 at 18:51:35, Vincent Diepeveen wrote: > > >>36. axb5! >> >>This is a brilliant move, which i can easily explain >>with DB kingsafety. There are several tens of pawns needed to make >>a program play axb5! instead of Qb6. If your kingsafety however gives >>white a huge penalty after the line given by GM Lubosh Kavalek >>(Qb6 Rd8 axb5 Rab8 Qxa6 e4 and the black queen gets into the white >>position driving white king to centre with queens on the board), then >>this move is easily explainable, supposing that DB has singular >>extensions >>and can see here line of about 15 half moves among which a lot of checks >>and forced moves. >> > >This position was analyzed much more deeply than this. > >After 36.Qb6, Rd8 is indeed best, but DB did not consider it but >36...Qe7 (I posted the complete analysis recently). After 36... Rd8 >37.axb5, a micro will quickly see that white is in trouble, but after >36...Qe7 37.axb5, black is a full pawn worse because of the need to >protect the bishop on d6. Justifying 36.axb5 if you do not consider Rd8 >is more than a few tenth of a pawn to justify, actually it's about a >full pawn. > >Why didn't DB consider Rd8 ? Probably it saw 36. Qb6 Rd8 37.Be4 ! and it >seems black is screwed. But black has a fantastic resource: 37... a5! >38.axb5 axb4!! sacing a piece, to get the queen to the first rank and >force a draw on perpetual threats (echo of the final position, but more >complicated). It is clear that DB didn't see the piece sac, because this line is way longer than the 23 ply (Diep needs) to see that Kf1? leads to a draw and Kh1! wins the game. In the line you posted i see that DB score doesn't get to zero, but just goes down few tens of a pawn. So that'll be some king safety, no doubt. >I showed this to Kasaprov last November, and was surprised to find that >he knows about this. Actually he treated it derisively. He says after >continuations of the sort axb5 Rab8 the queen should not take on a6 but >retreat to f2 or e3 and white looks good. >>24.b4? this move is a horrible positional concession. Lucky for DB >>most PC >> programs play it too. > >Kasparov disagrees. He says this move is necessary to avoid losing >material. I didn't check, but I remember that Junior would have played >it. This was raised when strategies for human intervention were >discussed and Kasparov mentioned 24.b4 as a move where second-guessing >the computer would be a bad mistake. I don't believe Kasparov, he first needs to give an analysis. Anyway, this move ain't interesting because PC programs play b4 too. More interesting is 2 moves further where DB plays b4-b5? which is not played by several PC programs after long analysis. I was surprised seeing in the lines you posted here that DB just got 11 ply. Although i admit that when i would search fullwidth with SE and all kind of check/threat extensions i doubt whether i would get more with around 70 Billion nodes. >Amir
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