Winboard Message after Mating - Engine Problem?

[Charles Browne]

The below is with Winboard 4.4.0 and the recent 4.4.1.20091019 (don't know about earlier versions).


Playing a match with Reger 0.09 and Mustang 4.97 (Reger always set to play White) and in the games Mustang always won, after Mustang mated Winboard would kick up a box telling that White forfeited due to an illegal move or some such statement.

Also after Reger was mated, Reger's White clock would continue to run.

So trying to capture a debug file of this occurrence, this time though Reger won, but upon Reger mating, Winboard kicked up the message as seen in this Screenshot Here.


PGN as saved by Winboard

[Event "Computer Chess Game"]
[Site "SPORT"]
[Date "2009.10.20"]
[Round "-"]
[White "REGER 0.09"]
[Black "Mustang 4.97"]
[Result "1-0"]
[TimeControl "600+2"]

1. c4 c5 2. Nf3 Nf6 3. d4 cxd4 4. Nxd4 e6 5. Nc3 Bb4 6. g3 d5 7. Qa4+ Nc6
8. Nxc6 Bxc3+ 9. bxc3 bxc6 10. Qxc6+ Bd7 11. Qa6 Qc7 12. Rb1 O-O 13. Bg2
Bc8 14. Qa3 Qxc4 15. Rb4 Qc6 16. Bg5 Ne4 17. Bxe4 dxe4 18. O-O Ba6 19. Re1
Bc4 20. Be3 Rfc8 21. Rb2 Qc7 22. Reb1 Bd5 23. Rc1 Qd7 24. Bc5 Bc4 25. Be3
e5 26. Rd2 Qc7 27. Rcd1 a5 28. Rd7 Qb8 29. R7d2 Qc7 30. Qa4 f6 31. Rd7 Qb8
32. Qc2 Qb5 33. Qxe4 Bxa2 34. Qg4 g6 35. Qh4 Bf7 36. Qxf6 Qd5 37. Bh6 Qh1+
38. Kxh1 Bd5+ 39. R1xd5 Rxc3 40. Rg7+ Kh8 41. Rxg6#
{Xboard: Forfeit due to invalid move: a8c8 (a8c8) res=35} 1-0

Snippet of Winboard debug file. Perhaps if I could read debug files well I would already know what the problem is .

Code: Select all

2 ep=-3
1 ep=-3
0 ep=-4
time odds: 1 1
Interrupting second
1047320 >second: time 15290
1047320 >second: otim 19216
book hit = (NULL)
1047320 >second: g7g6
silence
1047430 <second: move a8c8
machine move 81, castling = -1 -1 -1 -1 0 -1
move to parse: a8c8
7 0 4 7 0 4 Legality test? a8c8
GameEnds(37, Xboard: Forfeit due to invalid move: a8c8 (a8c8) res=35, 4)
1047430 >first : result 1-0 {Xboard: Forfeit due to invalid move: a8c8 (a8c8) res=35}
Interrupting second
1047430 >second: result 1-0 {Xboard: Forfeit due to invalid move: a8c8 (a8c8) res=35}
1047430 >first : force
1047430 >first : ping 4
1047430 >second: force
1047650 <first : pong 4
GameEnds(37, Xboard: Forfeit due to invalid move: a8c8 (a8c8) res=35, 2)
1126580 >first : quit
1126580 >second: quit


[H.G.Muller]

The debug files are not that hard to read. Basically you see a time stamp, a < or > symbol to see if something came from the engine or went to it, and a first or second to indicate which engine. Finally you see what was sent. (Other lines you can ignore; they are info printed by WInBoard about its internal state or actions, which help me debugging if it really does something wrong.)

Here you see that the move "g7g6" was sent to the second engine, and that it replied with "move a8c8".

Now apparently you did not have WinBoard set for detecting mates by itself, or it would have printed "{XBoard adjudication: checkmate}" already after receiving "move g7g6" from "first". Without such detection, it just plays on until one of the engines sends it a result clam (like "1-0 {white mates}"). This could be either the engine that checkmated (after its move) or the one that was checkmated (before its move). It seems that neither of these engines does that. So WinBoard has no idea the game is finished. And in stead of admitting its loss, the second engine then plays a move while it is checkmated. Even without mate detection (but with legality testing on) WinBoard can see that this move is illegal, and so it forfeit the engine making it.

It could of course be that Mustang, due to a bug, already has another position internally here than WinBoard or its opponent, were it is not checkmated at all and where a8c8 is a legal move.

[Charles Browne]

Thank you for the explanation