Author: Amir Ban
Date: 02:44:48 11/26/98
Go up one level in this thread
On November 25, 1998 at 21:38:16, Howard Exner wrote: >On November 25, 1998 at 19:15:45, Amir Ban wrote: > >>On November 25, 1998 at 17:49:38, blass uri wrote: >> >>> >>>On November 24, 1998 at 19:13:05, Robert Hyatt wrote: >>> >>> >>>>I'll wait on Bruce to comment as he may have saved this analysis... But I >>>>believe that this was one of several "defenses" we analyzed on ICC and >>>>chess.net last year. And while I don't remember the specifics, I do remember >>>>that we still ended at draw... And I notice his eval slipped again... As I >>>>said, "rumor" has it that axb5 and Qb6 lead to the same position... we'll >>>>see... >>>Bruce, did you analyze the position after 36.Qb6 Rd8 37.Be4 a5 38.axb5 axb4 >>>39.Rxa8 Rxa8 40.Ra6 on ICC? >>> >>>Uri >> >>This variation was discussed last October here on CCC, shortly after it was >>founded. We were discussing the same subject as now, DB's thoughts on move 36. >>Someone, Rob Jojodyne I think, suggested 36...Rd8 as an obvious improvement to >>DB's 36...Qe7, if white plays 37.axb5. I pointed out that 37.Be4 refutes Rd8, >>and he came up with a5 followed by the piece sacrifice axb4. We analyzed the >>continuation for a few days and concluded it draws. > >I remember this thread also. He was using Lang's Genius program and said >that it played this sacrificial line. You and I posed lines where we thought >that white could win but there always seemed to be a perpetual lurking for >black as countered by Rob J. There were many interesting twists and turns in our >group efort to analyse this. > Here's a repost of my summary of it. Amir -------------------------------------- Subject: Move 36 analysis summary From: Amir Ban E-mail: amirban@m-sys.com Message Number: 10968 Date: October 21, 1997 at 11:55:20 In Reply to: Re: Let's analyze move 36 Message ID: 10947 Posted by: Bruce Moreland At: brucemo@seanet.com On: October 20, 1997 at 13:19:31 On October 20, 1997 at 13:19:31, Bruce Moreland wrote: >This discussion died out. Did you guys arrive at any conclusions, or >did you just beat on each other until you became exhausted? > >Did DB cheat in that game? > >bruce We discussed the PV's and evaluations given in the printouts. The object was to see if they are reasonable. We did reach some conclusions, yes, and also discovered some interesting things about that position. Here is a summary: The PV given by DB up to ply 10 starting with 36.Qb6 Qe7 37.axb5 Rab8 38.Qxa6 e4 39.Bxe4 Qe5 evaluated +0.74: We found no tactical insights for this line. Positionally, mainstream opinion is that the eval is way off. Rebel 9.0 evaluates it at +2.00. Junior at +1.36, Hiarcs somewhere in between. CSTal is a dissenting opinion with an eval of about +0.50. At ply 11 the eval was +0.48 with no PV. If the same line was considered then the eval is even further off. Rob investigated lines other than 36...Qe7 that may match the eval more closely, and came up with this: 36. Qb6 Rd8! Now the continuation as in the PV is much better for black because Bd6 is protected. Say: 37.axb5 Rab8 38.Qxa6 e4 39.b6 Qe5 40.Qxc4 e3. This position is still unclear and evaluated as positive for white on my computer, but I would feel very uncomfortable as white and would take an eval of +0.48 as natural. However: It took Junior only a few seconds to switch from 37.axb5 to 37.Be4!, which locks the position, wins a pawn, evals as +1.4 and looks dead lost for black. However Rob found this interesting line: 36.Qb6 Rd8 37.Be4 a5! 38.axb5 axb4! 39.Rxa8 Rxa8 40.Rxa8 Qxa8 41.Qxd6 Qa1+ 42.Kh2 Qf1. There's an echo of the final position here, and the result is the same, although this position is much more complicated. E.g.: 43.g3 bxc3 44.Bg2 Qd3! 45.b6 c2 draws, since 46.b7?? c1Q 47.b8Q+ Kh7 48.Qe6 Qxg3+! 49.Kxg3 Qf4# or: 43.Qc5! Qf4+ 44.Kh1 Qxe4 45.cxb4 Qe1+ 46.Kh2 c3 47.Qc4! Qd2 48.b6 c2 49.b7 c1Q 50.b8Q+ Kh7 51.Qxc1 Qxc1 will draw. Neither 52.Qb6 nor 52.Qb5 work since white cannot both guard against the perpetual and stop the e-pawn. This variation is very interesting and maybe shows that Qb6 indeed does not win, but since it's not credible that DB saw that far, I don't think it's relevant. My conclusion: 1. The DB choice was based on evaluation. 2. That evaluation was "non-standard" for our field. 3. The analysis does not prove cheating, but is no great help in disproving it either. The status quo remains. Amir
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