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Re: [Bug-XBoard] Winboard bugs

From: Tim Mann
Subject: Re: [Bug-XBoard] Winboard bugs
Date: Sat, 21 Feb 2004 16:38:12 -0800

It's not WinBoard's job to catch violations of the rules by the engines.
They are assumed to know the rules.  WinBoard just makes a preliminary
(and as you've noticed, incomplete) test that you haven't made an
illegal move before sending it to the engine.  It also happens to catch
most illegal moves from the engine too, but not all.  The test is
especially loose for castling and en passant.

We could modify WinBoard to test exactingly for legal moves from
engines, and we may do that in the future.  However, there's nothing
that WinBoard could really do about that other than declare the game a
forfeit in your favor.  An engine can hardly be smart enough to deal
with some other program telling it "no, that move is illegal -- think
again."  :-)

Please be sure to report this bug to Usurper's author, and also the
authors of any other engines that you see making illegal moves.

On Sat, 21 Feb 2004 18:42:44 -0500, "John Widman" <address@hidden> wrote:
> Hello Tim,
> First, thank you greatly for your marvelous Winboard which has enriched the 
> lives of so many.
> I have noted a castling bug, which persists into the latest version 4.2.7.  I 
> noticed this when playing with Usurper, which is a very weak engine which 
> does not know the castling rules correctly, or perhaps not at all.
> It seems Usurper will violate every or almost every prohibition on castling 
> from time to time (like castling to get out of check, castling through 
> check), and it seems that Winboard catches some of these.  However, when 
> Usurper moves its king, then moves it back again to a position from which 
> castling is legal (not accounting that it has moved its king previously), 
> Winboard allows this.
> Another interesting example is a game with another of the weaker WinBoard 
> programs which, although behind, succeeded in advancing a pawn to the eighth 
> rank.  Seeing that promotion to a queen (or any other piece) still resulted 
> in its checkmate, it promoted to a second King!  Very creative, I thought.  
> What good are rules if you can't bend them once in awhile for a favorite 
> opponent?  So I played on.  When I tried to checkmate one king, the other one 
> would move.  Hmm. Maybe I had to checkmate both kings with the same move.  
> Not so easy.  Then I thought I should just capture one king first, then 
> checkmate the other. However, this attempt caused it to crash.
> Perhaps the responsibility for monitoring legal moves rests with the engines 
> and not Winboard.  If so, my comments are not of value to you and I apologize.
> Sincerely,
> John Widman

Tim Mann  address@hidden  http://tim-mann.org/

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