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Subject: Re: CB vs. DT2 analysis of 27...c5! and resulting eval

Author: Gian-Carlo Pascutto

Date: 03:37:57 09/10/01

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On September 09, 2001 at 21:05:23, Dave Gomboc wrote:

>Is this a won position for Black?  DJ6 doesn't seem to think so, but it might
>just be wrong...

Cray Blitz - Deep Thought II
[D]4k3/7R/3p2p1/4bpB1/8/3R2PK/r6P/r7 b - - 0 1

Analysis by Crafty 18.08:

49...Rb1 50.Rd2 Rxd2 51.Bxd2 Rb3 52.Bg5 f4 53.Re7+ Kf8 54.Re6 f3 55.Rxg6 Kf7
56.Rh6 f2 57.Kg2 Rb2
  -+  (-2.06)   depth: 14/31   00:02:11  84431kN, tb=113
49...Rb1 50.Rd2 Rxd2 51.Bxd2 Rb3 52.Bg5 f4 53.Re7+ Kf8 54.Re6 f3 55.Rxg6 Rb1
56.Be3 Kf7 57.Rh6 Rb2
  -+  (-1.89)   depth: 15/35   00:02:44  105884kN, tb=245
49...Rb1 50.Rd2 Rxd2 51.Bxd2 Rb3 52.Bg5 f4 53.Re7+ Kf8 54.Re6 f3 55.Rxg6 Kf7
56.Rh6 f2 57.Kg2 Rb2 58.Be3 Kg7
  -+  (-2.00)   depth: 16/37   00:05:46  217826kN, tb=1256
49...Rb1 50.Rd2 Rxd2 51.Bxd2 Rb3 52.Bg5 f4 53.Re7+ Kf8 54.Re6 f3 55.Rxg6 Kf7
56.Rh6 Rb2 57.Rh4 d5 58.Rh7+ Ke6 59.Re7+ Kf5
  -+  (-2.14)   depth: 17/39   00:11:33  428732kN, tb=4302
49...Rb1 50.Rd2 Rxd2 51.Bxd2 Rb3 52.Rh4 Kf7 53.Bg5 Ke6 54.Rc4 Kd5 55.Rh4 Kc5
56.Ra4 Rb2 57.Be3+ Kb5 58.Ra8 Kc4 59.Rd8
  -+  (-2.29)   depth: 18/41   00:31:10  1133497kN, tb=15025

I tend to prefer Crafty over Hiarcs in endgames, but I have
no idea whose assesement is better here. But note that Crafty
is already heavy in the tablebases here, and the score is
going up for black...

Hiarcs is around -1.55 in all these positions, but doesn't
hit tablebases yet.

>Back to 47.Kg1 Ra1+ 48.Kf2 R6a2+ 49.Rd2 Bf6 50.Bh6 g5

Instead of 50. .. g5, 50. .. d5!  and I get -2.26 in
favor of black.

>I suspect that 46.Re7+ Kf8 47.Rb3 Ra8 48.Rxh7 Rxa2 49.g3 is about the same.

Hiarcs d5 with -1.9, Crafty -2.2

>42.Bh6 Bg7 43.Bxg7 Kxg7 might just be a draw, though.  Hmm, 42...Rcxa4, I guess, then it's similar to before.

Yes

>I don't know, GCP, I don't think these pawn up endings deserve +2.25.  But in
>order for DT2 to settle on that kind of score, if it got to these variations it
>must have assessed them as such.

Crafty obviously disagrees with you, as does Hiarcs in some of the positions
(although its score is usually more around -1.6, it drops down the lines).

The question is of course whose assesement is more correct.

I do think this shows that DT's assesement wasn't bogus or due to
a bug. But perhaps we need to relax the requirement for the starting
position a bit and require that c5 is found within 7 seconds with
a score lesser than 2.x.

--
GCP



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