Author: Uri Blass
Date: 03:18:44 10/01/03
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On September 30, 2003 at 21:10:32, Johan de Koning wrote: >On September 29, 2003 at 05:10:00, Uri Blass wrote: > >>On September 29, 2003 at 03:13:13, Johan de Koning wrote: > >>>Anyway, I think I'll skip the experiment with fully normalized TT entries. >>>(That's with inactive files removed, and the remaining files flipped/sorted >>>into canonical form). That would be good for a complete retrograde analysis, >>>but it won't beat alpha-beta on a fixed starting position. >> >>I do not see a reason that it won't beat alpha beta because it does not mean not >>using alpha beta. > >Sorry, that was a bit unclear. >The it in "it won't beat" was intended to mean full retrograde analysis. > >>If you do normalized TT entries then you need to change your TT to include >>numbers instead of moves and when you try hash move first you may calculate the >>move based on the number. > >I'm not sure if you have some kind of magic unique number in mind. >As long as normalization is merely shuffling files, there will be an 8<->8 map >that transforms the board and the move(s) equally in both directions. Though >the move from the search might be mapped to an irrelevant file. My idea was to give every move number when you order the pawns based on the file and if the file is equal based on the rank. For example in the opening position a3->0 a4->1 b3->2 b4->3 ... h3->14 h4->15 without b2 c2 a3->0 a4->1 d3->2 d4->3 ... h3->10 h4->11 You save in the hash tables only number of 4 bits instead of move and when you have hash hit you translate the number to a move by generating the list of legal moves. The only problem here is that I did not include symmetry of abcdefh and acdefgh but it can be corrected by starting the numbers from the a file in case 1 and starting from the h file in case 2. > >>killer moves and history tables if you use them for order of moves do not need >>to be changed. > >IMHO it is more elegant to normalize each position immediately after Make(). >In that case killers or whatever global move stats need to be discarded. :-) You need to normalize the position in order to compare the hash key but normalizing the position does not contradict also remembering the position of the board to use it for killers and history tables. You should have the position twice(normalized and not normalized). Uri
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