Author: Stuart Cracraft
Date: 06:40:50 09/21/04
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On September 21, 2004 at 00:37:19, Michael Henderson wrote: >On September 21, 2004 at 00:15:42, Stuart Cracraft wrote: > >>On September 20, 2004 at 00:56:26, Michael Henderson wrote: >> >>>>>1. When you make a two-square pawn move, and the opponent cannot make an ep >>>>>capture, do you hash-xor the "target" ep square in the hash table? >>>> >>>>Currently no special handling is done for the hash table in regards to >>>>enpassant. That information is not recorded in any way. >>> >>>What I meant to say was do you hash in any ep target stuff into the hash key >>>when you make a two-square pawn move, whether opponent can capture ep or not? >>> >>>Michael >> >>I don't do this and hadn't considered it. >> >>What side effects would you expect from the absence of this? > >consider two positions: A, and B. Positions A and B are identical in every >respect but en-passant availability. Position A has a white pawn at e4 and a >black pawn at d4. In position B white has just played e2e4 and black has a pawn >at d4 -- so en passant capture. > >Now Search(): >Then black comes to position A --does a search, whatever-- and finally hash >stores. > >At some other node in the tree, black comes to position B and uses position A >from the hash table to cutoff that node. That does not take into account any ep >captures you have at position B, so your search can screw up. > >Michael Okay you've convinced me. "When you make a two-square pawn move, and the opponent cannot make an ep >>>>>capture, do you hash-xor the "target" ep square in the hash table?" But I would have thought I would hash-xor in the target ep square only if my opponent *could* make the ep capture. But the above implies that I should do it when he can't? Stuart
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