Author: Dieter Buerssner
Date: 16:47:44 03/19/02
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On March 19, 2002 at 14:46:59, Robert Hyatt wrote: >On March 19, 2002 at 13:40:54, bob o wrote: > >>4. Is it possible for a program to need just one of the tablebase files instead >>of the pair? For instance, let's say that you had an endgame of: white- ke1 pawn >>e2, black- ke8. And suppose you only had kpk.nbw.emd. Is it possible for the >>program with white to say, "Ok I know that I have a mate in N moves." Then it >>makes a move. Then black says "I can't find the correct TB file. But I found >>kpk.nbw.emd. Now let me search every possible black move for me and white's best >>reply, and leave him in the worst possible position." It seems that if this is >>possible, then you could cut the storage space in half by doing a quick 2-ply >>search. > >That is possible in some cases. The problem is that there are identical >positions with black and white on move. If you don't have one, then you can >go to the computational task of inverting the board, which inverts the side >on move, but that takes a bit of time... You say in some cases. Inverting would help in KQKQ, KRKR, KBKB, KNKN and KPKP and some 6-men tables. The first 4 and the 6-men tables are already handled in Eugene Nalimov's code (actually KQKQ.nbw and KQKQ.nbb are identical). So, engines that use a recent version of the probing code, do not need kqkq.nbb, etc. For unsymmetrical cases (all 5-men) inverting board/side to move does not help. I think, here really a 1 ply search, like described by (the other) Bob or the method I described in the other followup is needed. Regards, Dieter
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