Author: Uri Blass
Date: 11:13:14 01/03/05
Go up one level in this thread
On January 03, 2005 at 11:39:29, Franz Hagra wrote: >[Event "?"] >[Site "?"] >[Date "2005.01.03"] >[Round "?"] >[White "?"] >[Black "?"] >[Result "*"] >[SetUp "1"] >[FEN "4k3/pppppppp/2b5/1b6/7B/6B1/PPPPPPPP/4K3 w - - 0 1"] >[PlyCount "0"] >[EventDate "2005.01.03"] >[SourceDate "2005.01.03"] > > * > >[Event "?"] >[Site "?"] >[Date "????.??.??"] >[Round "?"] >[White "?"] >[Black "?"] >[Result "*"] >[SetUp "1"] >[FEN "k7/8/8/6pp/6PP/BbBbBbBb/bBbBbBbB/7K w - - 0 1"] >[PlyCount "0"] >[EventDate "2005.01.03"] >[SourceDate "2005.01.03"] > > * > >CB9 is a really funny program They can only be store by winboard so I do not see something special in chessbase. There are many possible reasons that position can be illegal and I do not think that there is somebody who covered all the cases by a program. Proving that a position is illegal may be easy in some cases like the cases that you give but there are many cases when it is not easy to do it. The only way to prove without doubt that a position is legal is to compose a game that lead to the position and it is possible to compose many positions when it is not easy to compose the relevant game or illegal positions that it is not easy to prove that the position is illegal. Is the following position legal? [D]k7/8/8/6Pp/6b1/BbBbB1Bb/bBbBbBbB/6K1 b - - 0 1 both white and black promoted 7 bishops it is logical to assume that black pawns at files b d f promoted with no capture but what about pawns at files a c e g? They could make 4 captures of white rooks knights or queens or bishop and promote. It is probably legal but it is still no proof. What happens if you add 2 rooks to both sides? What happens if you also add 2 knights to both sides? At some point the position is going to be illegal but I think that it is illogical to expect a program to detect the exact point. There are a lot of illegal positions when the king is in check but I doubt if there is a single program in the world that detect the following positions as illegal(I hope that I did not mistake in detecting them as illegal) There are clearly harder cases and I only give examples that humans can detect in a short time. [D]3K4/8/8/8/8/8/4B3/2Rk4 b - - 0 1 [D]3K4/8/8/8/8/3R1B2/8/3k4 b - - 0 1 [D]3K4/8/8/3R4/8/5B2/8/3k4 b - - 0 1 [D]3K4/8/8/8/8/8/6k1/7B b - - 0 1 [D]3K4/8/8/8/8/6P1/5k2/7N b - - 0 1 [D]3K4/8/8/8/8/5k2/6P1/8 b - - 0 1 [D]Qn1K4/pk6/8/8/8/8/8/8 b - - 0 1 Uri
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