Author: José de Jesús García Ruvalcaba
Date: 08:55:50 05/19/99
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On May 19, 1999 at 11:32:51, Heiner Marxen wrote: >On May 18, 1999 at 08:02:09, Peter Klausler wrote: > >>On May 17, 1999 at 21:15:59, Dann Corbit wrote: >> >>>You would also need to store e.p. square, if any, I think. Ten bits more >>>[5ep+4castle+1stm]gives 174 bits. >> >>Two bits are all you need for the en passant file, actually. >>There can be at most four pawns of the opponent on his >>fourth rank next to a pawn of the player (on his fifth). > >Wrong. There can be 5 such pawns. E.g. 8/8/8/8/PpPPpPPp/8/8/8 b - >Even when we know already that there is an e.p. possible, we still >have to distinguish up to at least 5 cases. Your position has five pawns on the fifth rank next to three of the opponent in the fourth rank. You and Peter are counting different things: he is counting the pawns in the fourth rank next to opponent pawns on their fifth rank (so for your position that count is three, less than four). It is not neccesary to distinguish which pawns can make an en-passant capture, it is enough to know pawn can be taken en-passant. That is the reason Peter counts the pawns on the fourth rank (which can be captured en-passant) and not those which can make the capture. José.
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