[Retros] Bug in Natch?!

[Joost de Heer]

> I recently came across this old proofgame by Myllyniemi. I noticed that

> Natch cannot find the solution. I cross-checked with Kostas Prentos, who

> also experienced issues in trying to test it. He wrote that he managed in

> the end, after reboots and certain tricks, but he didn't mention details in

> his email.

> 

> I tried two versions : v2.2 solves it fine, v2.4 exits after few seconds

> without giving any solution. Btw, Euclide solves it in seconds.

> 

> Matti Myllyniemi

> 3 Pr Die Schwalbe 1965 (correction : Die Schwalbe 1983)

> 

> rsbR1Ssr/pp2kppp/8/8/8/8/PP3P1P/RSbQKqSR

> 22 single moves


Natch 2.4 finds a solution on Linux, no tricks whatsoever.

Natch 2.4      Copyright (C) 1997,98,99,2001-2005 Pascal Wassong

+---+---+---+---+---+---+---+---+

|*R |*S |*B | R |   | S |*S |*R |

+---+---+---+---+---+---+---+---+

|*P |*P | . |   |*K |*P |*P |*P |

+---+---+---+---+---+---+---+---+

|   | . |   | . |   | . |   | . |

+---+---+---+---+---+---+---+---+

| . |   | . |   | . |   | . |   |

+---+---+---+---+---+---+---+---+

|   | . |   | . |   | . |   | . |

+---+---+---+---+---+---+---+---+

| . |   | . |   | . |   | . |   |

+---+---+---+---+---+---+---+---+

| P | P |   | . |   | P |   | P |

+---+---+---+---+---+---+---+---+

| R | S |*B | Q | K |*Q | S | R |

+---+---+---+---+---+---+---+---+
rsbR1Ssr/pp2kppp/8/8/8/8/PP3P1P/RSbQKqSR
22 single moves.        12 + 13

The resolution begins at Fri Apr  6 20:49:04 2007

Solution 1 (position 20)
1.Pd2-d4   Pe7-e5   2.Bc1-f4   Pe5xf4   3.Pd4-d5   Pf4-f3
4.Pd5-d6   Pf3xg2   5.Pd6xc7   Pd7-d5   6.Pe2-e4   Pd5-d4
7.Pe4-e5   Pd4-d3   8.Pe5-e6   Pd3xc2   9.Pe6-e7   Pc2-c1=B
10.Pe7xf8=S Ke8-e7   11.Pc7xd8=R Pg2xf1=Q

The resolution ends at Fri Apr  6 20:49:52 2007
Resolution time : 29.48 s.

Joost