Author: Amir Ban
Date: 08:55:20 10/21/97
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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.cxb4 Qf4+ 44.Kh1 Qxe4 45.Qc5! 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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