Author: Uri Blass
Date: 08:29:49 12/29/02
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On December 29, 2002 at 10:16:33, Dan Andersson wrote: >There are a number of way to check if a pawn position is pseudo-legal. >Backtracking is fairly cheap. And if you want to bound it by the number of >captures made it is easy. Add a cost array and you are done. A quicker test is >using this property: > The 'backwards capture triangle' area of any pawn must not have more pawns in >it than the number of squares at its base. This can also be bounded by the >available number of captures. > P > xxx > xxxxx > bbbbbbb > >MvH Dan Andersson I did not think a lot about the problem but you need first a clear definition to decide if a pawn structure is legal It is easy to detect part of the illegal structures but proving that all the other structures are possible is not a trivial task. Here is an example that is not trivial Is the following pawn structure legal? [D]4k3/8/P7/PPPPPPP1/1ppppppp/7p/8/4K3 w - - 0 1 After one minute of looking at the position I coould not convince myself that it has to be legal but also could not find a proof that it is illegal. It is clear that if you add a piece it is illegal. Uri
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