Author: Robert Hyatt
Date: 07:00:09 10/04/98
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On October 04, 1998 at 05:24:42, blass uri wrote: > >On October 03, 1998 at 22:07:23, Robert Hyatt wrote: > > >It really wouldn't help, because this would reduce the size of the current >>tablebases by 1/4, because they use 8 bit values. > >How can you use 8 bit values >only to store the move you may need 6 bits because you may have more than 32 >legal moves even only with king and queen. > >do you mean 8 bits only to store the result and that the tablebases use more >than 8 bits for position(8 bits for result and 5 or 6 bits for the move)? > >you can save space in the harddisk by not storing the result and computing it by >playing the right moves against yourself but in this case you are slower. > >Uri there are no "moves" in the database. It is a huge stream of bytes indexed by a "Godel" number that is simply a concatenation of the squares each piece sit on. IE let's number the squares a1=0... h8=63. put the white knight on a1, white king on b1, white bishop on c1 and black king on d1. All we do is take the 4 squares and compute b1<<18 + a1<<12 + c1<<6 + d1... which gives us a number that indexes into the database, and the value we find there is +Mate in N, -Mate in N, or Draw (0). No moves, no pieces, etc. The pieces (the squares they stand on) form the key, the result at that position is how many moves to mate, or else "draw"
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