Author: Heiner Marxen
Date: 15:42:19 07/11/01
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On July 11, 2001 at 16:37:38, Dann Corbit wrote: >On July 11, 2001 at 16:16:29, Artem Pyatakov wrote: > >>I was just in the process of making my own program hash, and I was looking at >>the Gerbil 01 source code for some guidance, but I noticed something strange. >> >>Does Gerbil at this point NOT hash En Passant squares? >>Am I correctly thinking that this information should be hashed? > >Gerbil has the smartest e.p. hashing of any program I have ever seen. I intend >to brashly copy it, as soon as I find the time. > >Gerbil hashes ONLY those e.p. information points where the pawn can *actually* >be taken which is just plain brilliant. It will result in a lot more hash hits >for no apparent penalty. > >An example of the genius of Bruce Moreland. I have not yet looked into the sources of Gerbil, please excuse my ignorance. If the above means "can actually be taken by a *legal* move", then it appears to be really new. If thew above means "can actually be taken by a *pseudo legal* move", then this is not really new. It has been discussed some time ago (on this board IIRC). E.g. Chest does so, by setting the flag "e.p. is possible" within move execution only for those pawn double steps with an enemy pawn in the correct position (left or right of the moving pawn's target). This is not perfect, but much better than flagging each double step. As a consequence the FEN generated from such positions is not strictly correct according to the standard from SJE, but IMO the standard should be changed, here. Regards, Heiner
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