[Retros] Natch-2.5Beta

Mario Richter mri_two at t-online.de
Thu Jul 9 06:35:43 EDT 2009

Hello Pascal,

> rs1q1bsr/1ppkpppp/4p3/1K1b4/p7/8/PPPP1PPP/RSBQ1BSR

> 14 single moves. 15 + 16


> The problem is caused by the moves Bc8-d7-c6-d5, necessary because of

> Pd7xe6, colliding with the move Ke8-d7.


> If you play 7.Qd7 (or 7.Nd7) instead of 7.Kd7, there is no problem.

> The problem also disappears if the bK plays another move after passing

> by d7. By adding 8.Bc4 Kd6, Natch finds again the solution.

Interestingly, if you raise the ply count to 16:

Natch 2.4 Copyright (C) 1997,98,99,2001-2005 Pascal Wassong
16 single moves. 15 + 16

the first solution given by Natch 2.4 is:

Solution 1 (position 1)
1.Pe2-e3 Pa7-a6 2.Pe3-e4 Pa6-a5 3.Pe4-e5 Pa5-a4
4.Pe5-e6 Pd7xe6 5.Ke1-e2 Bc8-d7 6.Ke2-d3 Bd7-c6
7.Kd3-c4 Bc6-d5 8.Kc4-b5 Ke8-d7

> The complete and technical explanation of this bug is a bit longer.

so I'm just wondering, if divisibilty by 4 or something similiar
did play a role ...



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