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Prove that a position is legal and reachable.
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Alex Brown



Joined: 02 Feb 2007
Posts: 609
Location: New Zealand
PostPost subject: Re: Prove that a position is legal and reachable.    Posted: Sat May 19, 2012 9:27 pm Reply to topic Reply with quote
George Tsavdaris wrote:
Sven Schüle wrote:
Cubeman wrote:
[d]6b1/ppp1pp1B/2k1p1p1/8/5P2/3PprP1/PPPrPqRP/RnK2nb1 w - -
   ::    ::    :: BB ::
BP BP BP    BP BP :: WB
   :: BK :: BP :: BP ::
::    ::    ::    ::    
   ::    ::    WP    ::
::    :: WP BP BR WP    
WP WP WP BR WP BQ WR WP
WR BN WK    :: BN BB    

Is a test position that George Tsavdaris posted a few years ago apparantly the position is a draw and you have to prove it.Could the program that was suggested earlier in topic http://natch.free.fr/Natch.html recreate this game?

If you say it is "apparently a draw" but Houdini and Stockfish both say that it were mated in 10, the only possible explanation could be that retro analysis would reveal it is a draw by 50 moves rule ...

Well Houdini and Stockfish should be more clever and claim a draw by "50-move" rule claiming(correctly) that black made a move that resulted in the previous 50 moves of both sides to not contain any Pawn moves or piece captures. Very Happy

Here is one such game.
The task here is to find(prove) that this position can't be reached in less than 50 moves of white and black that were not Pawns moves and captures.
I.e: it is true that in order this position to be reached, the 50-move rule will apply. So white can claim a draw after ...Nb1

[Event "?"]
[Site "?"]
[Date "2001.10.11"]
[Round "?"]
[White "George"]
[Black "Gromit 3.8.1"]
[Result "1/2-1/2"]
[PlyCount "236"]
[EventDate "2001.??.??"]

1. d3 Nf6 2. Nf3 Nc6 3. Ng5 Na5 4. Ne6 dxe6 5. Bg5 Nd5 6. Qd2 h6 7. Nc3 hxg5 8.
Qf4 gxf4 9. Kd1 Kd7 10. Kd2 Kd6 11. Kd1 Ke5 12. Kd2 Kf5 13. Kd1 Kg5 14. Kd2 Ne3
15. Nd5 Nd1 16. Ne3 fxe3+ 17. Kc1 Bd7 18. f4+ Kg4 19. Kb1 Rh3 20. Kc1 Rf3 21.
Kb1 Rf2 22. Kc1 Bc6 23. Kb1 Qd4 24. Kc1 Rd8 25. Kb1 Rd5 26. Kc1 Rh5 27. Kb1 Rh3
28. Kc1 Rhf3 29. g3 Be4 30. Bh3+ Kh5 31. Kb1 Bh7 32. Bf5 Bg8 33. Bh7 Kg4 34. Rg1
Kh3 35. Rh1 Rf1 36. Kc1 Re1 37. Kb1 Nb3 38. Rg1 Nd2+ 39. Kc1 Nf1 40. Kb1 Qe4 41.
Kc1 Qf5 42. Kb1 g6 43. Rh1 Bg7 44. Rg1 Bc3 45. Rh1 Bd2 46. Rg1 Bc1 47. Rh1 Nf2
48. Rg1 Ne4 49. Rh1 Nc5 50. Rg1 Nb3 51. Rh1 Kg2 52. Rg1+ Kf2 53. Rh1 Rd1 54. Rg1
Ke1 55. Rh1 Kd2 56. Rg1 Re1 57. Rh1 Kd1 58. Rg1 Bd2 59. Rh1 Nc1 60. Rg1 Bc3 61.
Rh1 Kd2 62. Rg1 Rd1 63. Rh1 Ke1 64. Rg1 Kf2 65. Rh1 Kg2 66. Rg1+ Kh3 67. Rh1 Be1
68. Rg1 Rd2 69. Rh1 Nb3 70. Rg1 Nc5 71. Rh1 Ne4 72. Rg1 Nf2 73. Rh1 Nd1 74. Rg1
Bf2 75. Rh1 Bg1 76. Kc1 Kg4 77. Kb1 Kh5 78. Kc1 Qh3 79. Kb1 Qg2 80. Kc1 Qf2 81.
Kb1 Qe1 82. Kc1 Bf2 83. Rg1 Kh6 84. Rg2 Kg7 85. Kb1 Bg1 86. Kc1 Qf2 87. Kb1 Kf8
88. Kc1 Ke8 89. Kb1 Kd7 90. Kc1 Kc6 91. Kb1 Nc3+ 92. Kc1 Nb1 {White clams a draw according to
50-move rule because black has made a move that resulted in the previous 50 moves of both sides
to not contain any Pawn moves or piece captures.} 1/2-1/2


Yes thanks for the game example, I remember trying to solve this but gave up after a few tries.
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Subject Author Date/Time
Prove that a position is legal and reachable. Dustin Yoder Wed May 16, 2012 11:23 am
      Re: Prove that a position is legal and reachable. Julien MARCEL Wed May 16, 2012 11:45 am
            Re: Prove that a position is legal and reachable. Arpad Rusz Wed May 16, 2012 1:22 pm
      Re: Prove that a position is legal and reachable. Uri Blass Wed May 16, 2012 1:28 pm
      Re: Prove that a position is legal and reachable. Ricardo Barreira Wed May 16, 2012 1:49 pm
            Re: Prove that a position is legal and reachable. Julien MARCEL Wed May 16, 2012 1:55 pm
                  Re: Prove that a position is legal and reachable. Sven Schüle Wed May 16, 2012 2:43 pm
                  Re: Prove that a position is legal and reachable. H.G.Muller Wed May 16, 2012 6:25 pm
                        Re: Prove that a position is legal and reachable. George Tsavdaris Sat May 19, 2012 2:22 pm
      Re: Prove that a position is legal and reachable. Edmund Moshammer Wed May 16, 2012 2:49 pm
            Re: Prove that a position is legal and reachable. George Tsavdaris Sat May 19, 2012 1:50 pm
      Re: Prove that a position is legal and reachable. Joona Kiiski Wed May 16, 2012 6:39 pm
            Re: Prove that a position is legal and reachable. H.G.Muller Wed May 16, 2012 6:50 pm
                  Re: Prove that a position is legal and reachable. Alex Brown Wed May 16, 2012 10:57 pm
                        Re: Prove that a position is legal and reachable. Sven Schüle Thu May 17, 2012 9:01 pm
                              Re: Prove that a position is legal and reachable. Sven Schüle Thu May 17, 2012 9:27 pm
                                    Re: Prove that a position is legal and reachable. Arpad Rusz Thu May 17, 2012 9:58 pm
                              Re: Prove that a position is legal and reachable. George Tsavdaris Sat May 19, 2012 2:40 pm
                                    Re: Prove that a position is legal and reachable. Sven Schüle Sat May 19, 2012 8:56 pm
                                    Re: Prove that a position is legal and reachable. Alex Brown Sat May 19, 2012 9:27 pm
                  Re: Prove that a position is legal and reachable. Uri Blass Thu May 17, 2012 2:55 am
                        Re: Prove that a position is legal and reachable. H.G.Muller Thu May 17, 2012 8:39 am
      Algorithm Ideas Dustin Yoder Wed May 16, 2012 6:48 pm
            Re: Algorithm Ideas fernando Sat May 19, 2012 5:12 pm
      Re: Prove that a position is legal and reachable. Robert Hyatt Thu May 17, 2012 9:59 pm
            Re: Prove that a position is legal and reachable. George Speight Fri May 18, 2012 2:34 am
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