Author: Robert Hyatt
Date: 07:13:25 11/13/01
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On November 13, 2001 at 09:16:09, Uri Blass wrote: >On November 13, 2001 at 08:31:09, William Penn wrote: > >>I suspect this has been discussed before but I didn't pay attention, so please >>pardon my redundancy. If you could just point me in the right direction, much >>appreciated... >> >>Can't we make some assumptions without compromising very much practical playing >>strength and significantly reduce the size of the endgame tablebases? For >>example it seems a waste to generate separate positions for "white to move" and >>"black to move". > >It is also a waste of space to remember the exact number of moves to mate and >knowing the number of moves divided by 2 is enough and if you know it you can >calculate the exact number of moves to mate. I don't see how that will work. If I probe deeply in the search and get two mate scores of "mate in X" how will I be sure I take the path toward a mate that is one move closer than I am at now? Because it is possible that the next search I do will (at best) be able to find a mate in X-1 if we have real mate scores, but with this /2 stuff we only find mate in X again and never move closer. To save 1 bit, that seems like a tough problem to handle, not to mention that it will also cost more in the indexing code since the scores won't be on one- byte boundaries any longer. > > > Surely there is a reasonable simplification in that regard >>based on symmetry. > >Symmetry is used in building the tablebases > > > Promotion of a pawn to less than a Queen is rare and could be >>disregarded. > >This is going to save time in generating the tablebases with pawns but it is not >going to chnage much the space that is needed for the 3-4-5 piece tablebases. It will also produce wrong answers... > > Perhaps castling can be disregarded because it seldom happens in >>the endgame. > >It is already disregarded. > > I suppose we must keep en passant(?). I'm guessing that the size >>could be reduced to perhaps only 1GB for all of the 3-4-5 piece positions vs the >>current 7GB. > >Part of the 7GB is for generating unimportant tablebases of a king and three >pieces against a king when there is no position with king and 3 pieces against >king when programs cannot win. > >Uri
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