[bug #48321] Strange "adjudication: Checkmate but bare king"

[Tim Mann]

Update of bug #48321 (project xboard):

  Status:None => Invalid
 Open/Closed:Open => Closed 

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Follow-up Comment #3:

H.G. explained a bit more in email at the time:

"Normally XBoard corrects all wins for a side with a bare King to a draw, and
then appends this "but bare king" phrase to the result message. This is mainly
meant for wins by forfeit (e.g. flagging), as in normal chess it should not be
possible to checkmate when you have only a king. (There was a problem in
variant atomic, where it actually quite usual that a king is the only piece
left after you explode the opponent king with your last pieces, but this was
fixed in 4.9.0.)"

The above produces confusing results in a case like this one, where black won
by checkmate, but (it seems) an engine bug caused the engine to send xboard a
message saying that white won by checkmate.  Correcting for engine bugs is a
bit above and beyond the requirements for xboard, though it does try to do so
sometimes.

Anyway, I am closing this as an engine bug, not xboard bug.



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Re: [Bug-XBoard] [bug #48321] Strange 'adjudication: Checkmate but bare king'

[Tim Mann]

...much much later...

It's not possible to tell exactly what happened from the PGN file. We would
need debug output from the engine. However, what almost certainly happened
was that an engine bug resulted in the engine issuing a message that said
White won by checkmate when actually Black won by checkmate. xboard didn't
handle this engine bug as well as it could have, but correcting for engine
bugs is a bit above and beyond the call of duty.



On Tue, Jun 28, 2016 at 5:17 PM Tim Mann  wrote:

> Philipp attached pgn for the game to the bug report in savannah.  It's
> here: https://savannah.gnu.org/bugs/download.php?file_id=37590
>
> On Sun, Jun 26, 2016 at 11:10 PM,  wrote:
>
>> If you don't show the position where this happened, there is no way
>> telling what the problem was. Normally XBoard corrects all ins for a side
>> with a bare King to a draw, and then appends this "but bare king" phrase
>> to the result message. This is mainly meant for wins by forfeit (e.g.
>> flagging), as in normal chess it should not be possible to checkmate when
>> you have only a king. (There was a problem in variant atomic, where it
>> actually quite usual that a king is the only piece left after you explode
>> the opponent king with your last pieces, but this was fixed in 4.9.0.)
>>
>> So was there a bare king? Was it a checkmate? Who was checkmated?
>>
>> Op Ma, 27 juni, 2016 1:48 am schreef Philipp Claßen:
>> > Follow-up Comment #1, bug #48321 (project xboard):
>> >
>> >
>> > XBoard version was 4.9.0 on Arch Linux
>> >
>> >
>> > ___
>> >
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>> > Reply to this item at:
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>> >
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Re: [Bug-XBoard] [bug #48321] Strange 'adjudication: Checkmate but bare king'

[Tim Mann]

Philipp attached pgn for the game to the bug report in savannah.  It's
here: https://savannah.gnu.org/bugs/download.php?file_id=37590

On Sun, Jun 26, 2016 at 11:10 PM,  wrote:

> If you don't show the position where this happened, there is no way
> telling what the problem was. Normally XBoard corrects all ins for a side
> with a bare King to a draw, and then appends this "but bare king" phrase
> to the result message. This is mainly meant for wins by forfeit (e.g.
> flagging), as in normal chess it should not be possible to checkmate when
> you have only a king. (There was a problem in variant atomic, where it
> actually quite usual that a king is the only piece left after you explode
> the opponent king with your last pieces, but this was fixed in 4.9.0.)
>
> So was there a bare king? Was it a checkmate? Who was checkmated?
>
> Op Ma, 27 juni, 2016 1:48 am schreef Philipp Claßen:
> > Follow-up Comment #1, bug #48321 (project xboard):
> >
> >
> > XBoard version was 4.9.0 on Arch Linux
> >
> >
> > ___
> >
> >
> > Reply to this item at:
> >
> >
> > 
> >
> >
> > ___
> > Message sent via/by Savannah
> > http://savannah.gnu.org/
> >
> >
> >
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> > Bug-XBoard@gnu.org
> > https://lists.gnu.org/mailman/listinfo/bug-xboard
> >
> >
>
>
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