Author: Heiner Marxen
Date: 14:16:30 02/09/01
Go up one level in this thread
On February 09, 2001 at 16:17:56, John Merlino wrote:
>On February 09, 2001 at 08:40:05, Uri Blass wrote:
>
>>On February 09, 2001 at 08:25:02, Hans Havermann wrote:
>>
>>>On February 09, 2001 at 06:51:15, leonid wrote:
>>>
>>>>>[D]1bqQBnRn/3N2Qb/Q1QN2np/1Q1Q1qpk/4Qqbn/2B1Qrnn/2Q5/K1R5 w - -
>>>
>>>Black has too many promotions. :)
>>
>>Right.
>>
>>Most chess programs cannot analyze positions when black has 7 promotions and 2
>>pawns.
>>
>>Chessbase programs do not accept the position and the engine is not
>>important(after Board, Setup position,paste Fen I cannot tell the program ok.
>>
>>I think that it is a bug in the chessbase interface because the interface is
>>made for many engines and it is possible that some of the engines have no
>>problem to analyze the illegal position.
>>
>>I think that the interface should allow putting illegal position in the board
>>and I do not understand the decision not to allow putting illegal positions.
>>
>>Uri
>
>Chessmaster will not let you set up illegal positions either. How should an
>engine respond with a pawn on the eighth rank? Or two kings of the same color?
>Or the Black King in check with White to move? At what point do you say that "we
>can accept this illegal position, but not this one"?
>
>jm
(1) Clearly illegal are positions where the rules of the game are not
applicable. Examples are:
- missing king
- multiple kings
- king can be captured
- pawns on first or 8th rank
(2) Often illegal are positions which would violate an implementation
restriction. Example:
- more than 16 pieces of one side
(3) Some positions are not reachable by a legal game, but also do not have
the problems (1) or (2). Examples:
- unreachable pawn structures (a2,a3,b2)
- unreachable material balance (10 queens of one side)
(1) should always be rejected.
(2) is different for each program and must be rejected by that program.
The rest may well be accepted.
A maximally strict rejection would be forced to find a proof game, showing
that the position in question can be reached in a legal chess game.
That is very non-trivial to implement.
Heiner
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