A Position That Stumps Computers

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Fernando
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Post by Fernando »

Weird all what you say...my Gambit challenger, a cheap version of chess challenger 8, solved this one in 6 minutes...

Life is full of marvels regards
Fern
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rlsuth
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Post by rlsuth »

Peter Grayson wrote:
Feel free to refute 27.Bb3 #13 and I'll get back to you.

PeterG
Seeing as I am still using an abacus as a computer, I would need to see your mating line to be able to manually check it and understand it. Feel free to post it and I will endeavor to refute it.
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Peter Grayson
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Post by Peter Grayson »

rlsuth wrote:
Peter Grayson wrote:
Feel free to refute 27.Bb3 #13 and I'll get back to you.

PeterG
Seeing as I am still using an abacus as a computer, I would need to see your mating line to be able to manually check it and understand it. Feel free to post it and I will endeavor to refute it.
Here's the line for the #13 with Black's Re7 confirmed by my Chafitz Sargon 2.5 ;-)

When engines are outside their search horizon for a Zugswang they fail to see the problem. This can be quite shallow with some.

White's rook on f1 together with bishop on h6 is the bind. Once White's bishop goes to d1 the e6 pawn is untouchable because if it is captured white freely captures black's piece and the major black piece on the back rank must stay there because of Rf8#.

There is no single #13 but that is the longest line to mate. Once the conditions above are established, White just plays a waiting game until Black runs out of moves and eventually must play a losing move. Because of this White's queen side pawn majority is also a winning threat so there are a number of ways to finish black off . White's eventual Rf7 and exchange means Black is helpless to stop the C pawn advancing because of the faster mate by e6-e7+ if Black's remaining active major piece moves off e7.

[Event "Moscow, 1951"]
[Site "?"]
[Date "2014.06.03"]
[Round "?"]
[White "Gusev"]
[Black "Averbakh, Bad ..Re7"]
[Result "1-0"]
[ECO "B70"]
[Annotator "Grayson,Peter"]
[SetUp "1"]
[FEN "4q1kr/p6p/1prQPppB/4n3/4P3/2P5/PP2B2P/R5K1 w - - 0 24"]
[PlyCount "77"]

24. Qxe5 fxe5 25. Rf1 Rc7 $2 26. Bd1 b5 (26... Re7 $2 27. Bb3 {#13} a6 28. Bd5
b5 29. Kh1 a5 30. Kg2 b4 31. c4 Qb8 32. Rf7 Qe8 33. Rxe7 Qxe7 34. Kh3 g5 35.
Kg4 a4 36. a3 bxa3 37. bxa3 Qb7 38. e7+ Qxd5 39. e8=Q#) 27. Bb3 Rc4 (27... Re7
28. Bd5 {#12} a5 29. Kg2 {#10} a4 30. a3 {#9} Qd8 31. Rf7 {#7} Qe8 32. Rxe7
Qxe7) 28. a4 a6 {Houdini 4 Pro x64:} 29. Ba2 Qe7 (29... Qd8 30. b4 {#21}) 30.
b4 Qg7 31. Bxg7 Kxg7 32. Bxc4 bxc4 33. Rf7+ Kh6 34. e7 Re8 35. a5 Kh5 36. Rxh7+
Kg4 37. Rf7 g5 38. Kg2 Kh5 39. Rf6 Rxe7 40. Rxa6 Rf7 41. Re6 Kg4 42. Rxe5 Rd7
43. Rd5 Ra7 44. Rf5 Ra6 45. h3+ Kh4 46. Kf3 Rd6 47. Rd5 Ra6 48. Ke3 Kg3 49.
Rxg5+ Kh4 50. Rg4+ Kxh3 51. Rg5 Rd6 52. Rd5 Ra6 53. Kd4 Kg4 54. e5 Kf5 55. Rd6
Ra7 56. a6 Rg7 57. Rf6+ Kg5 58. b5 Ra7 59. Kxc4 Ra8 60. Kd4 Rd8+ 61. Kc5 Re8
62. a7 {[%eval 703,31]} 1-0
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