Author: Michael Henderson
Date: 07:19:14 09/21/04
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On September 21, 2004 at 09:40:50, Stuart Cracraft wrote: >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 Only hash it in when he can. Also, remember to hash it "out" when ep doesn't apply anymore. Michael
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