Author: Dieter Buerssner
Date: 14:59:41 12/27/01
Go up one level in this thread
On December 27, 2001 at 11:13:40, Sune Larsson wrote:
> [D]8/3k2p1/4pp2/1p2PP2/1PpP2P1/8/4K3/8 w - - 0 35
>
> This position is from a game Rocha - Spraggett, 1999.
> White is worse here and there are several ways for him to
> lose this position. Hecht, in his commentaries, even thought
> that the key move is the only way for white to make the draw.
> This ending is tricky, so I'm not 100% sure that Hecht is correct.
> Anyway, white has a simple and straight forward way to secure the draw.
>
> Theme - pawn ending: One protected passer can hold his own vs two connected.
>
>
> Test: Programs with some of this knowledge should evaluate the position
> after 1.d5! as 0.00 or close to it.
This is an interesting sentence :-) I actually had looked at such positions, and
found it not totally easy ... What I fear, is that such a rule can fail, or
better formulated, that one can miss the restrictions under which it is valid.
What I think of for example: Can the base of the protected pawn be attacked by
another pawn. And of course the (at least to the human) obvious things, like:
are both - the protected passer and the connected passers stopped right now? Are
there more candidates for passers on the board?
From an engine point of view, one could also ask, how useful such a rule would
be. In this case, it seems Ke3 is also drawing - but I agree - not that
convincing. However, when all other ideas would be losing, the engine might see
this anyway by search. So, such a rule might be most useful when one trades into
a pawn endgame. But now there might be not much search depth, so the rule would
need to be pretty tight, to not heal one case and open another bigger trap. You
are welcome, to make a suggestion, for all restrictions such a rule needs :-)
I followed the lines you discussed with Miguel, and I allways get a draw
position, as you said already. I did not allways get a draw score, but in KPPKPP
with search depth 26 and only K moves in the PV, I found it pretty obvious. Also
some lines yielding Q endings with one pawn up for black showed draw score after
following the line.
Here is what Yace thinks of the position:
[-1.39 was the smallest score]
45373204 4:27.0 -1.39 14t 35. Ke3 Ke7 36. Ke4 g6 37. fxg6 fxe5 38. dxe5
Ke8 39. Kf4 Kf8 40. Ke3 Kg7 41. Kd2 Kxg6 42.
Ke3 Kg5H 43. Kd2H Kxg4H 44. Kc2H Kg3H 45. Kb1H
c3H 46. Kc2H Kf4H 47. Kxc3H Kxe5H 48. Kd2H Kf4H
49. Ke2H e5H 50. Kf2H {HT} {-80}
56908616 5:34.6 -1.39 14. 35. Ke3 Ke7 36. Ke4 g6 37. fxg6 fxe5 38. dxe5
Ke8 39. Kf4 Kf8 40. Ke3 Kg7 41. Kd2 Kxg6 42.
Ke3 Kg5 43. Kd2 Kxg4 44. Kc2 Kg3 45. Kb1 c3 46.
Kc2 Kf4 47. Kxc3 Kxe5 48. Kd2 Kf4 49. Ke2 e5
50. Kf2 {HT} {-80}
76441598 7:31.6 -0.99 15++ 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 Kf7 45. Kd7 c1=Q 46. e8=Q+
Kf6 {0}
95530206 9:26.7 -0.87 15t 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 {HT} {-80}
113043377 11:11.7 -0.87 15. 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 {HT} {-80}
171901814 17:15.4 -0.89 16t 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 47. Qe6+ Kg5 48. d6 {-80}
206952809 20:53.7 -0.89 16. 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 47. Qe6+ Kg5 48. d6 {-80}
342037206 34:43.7 -0.90 17t 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 47. Qe6+ Kg5 48. d6 g3 {-80}
418214286 42:11.2 -0.90 17. 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 47. Qe6+ Kg5 48. d6 g3 {-80}
671517913 1:06:22 -0.75 18t 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 47. Qe6+ Kg5 48. Qe5+ Kh4 49. d6 {-80}
819191465 1:20:37 -0.75 18. 35. Ke3 Ke7 36. Ke4 g6 37. exf6+ Kxf6 38. g5+
Kxg5 39. fxe6 Kf6 40. d5 g5 41. Kd4 g4 42. Kc5
c3 43. Kd6 c2 44. e7 c1=Q 45. e8=Q Qf4+ 46. Kd7
Qxb4 47. Qe6+ Kg5 48. Qe5+ Kh4 49. d6 {-80}
I wonder, how Crafty reaches such high search depth fast in this position
(Pavel's post). Queens are seen pretty soon, which will increase the branching
factor. Also, there are many pawn moves possible.
Regards,
Dieter
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