Author: Dann Corbit
Date: 22:31:10 10/18/01
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On October 19, 2001 at 01:20:38, Dann Corbit wrote: >For pawnless and rookless tablebase files: > >The name of the file tells the pieces (e.g. KBBKQ) >Side-to-move King, Bishop, Bishop >Side-not-to-move King, Queen >No bits needed to encode this data. > >Then, 5 bits for the positions of the pieces (0-63) times the 5 pieces = 25 bits > >This is the key (the above 25 bits). >So for any tablebase of this format, there are 2^25 entries. > >The answer is encoded as follows: >Then the move to make (which we can encode in 8 bits -- the move number from 0 >to 255 considering the moves as sorted lexically or as output by a specific move >generator.) Another "SQUISH-ER-ATOR" idea. When we have some sets of pieces (consider with side to move = KNN) there are only a few moves possible. You can never have more than 24 choices (for instance) when you have KNN and it is your turn to move. Hence, for this tablebase, we would only need 5 bits to store the move choice. For any tablebase, we will have some maximum for the number of possible move choices. That's how many bits we need to encode any given move choice. Since the number of bits is a multiplier, it can make a very large difference in size. My 50 megs for a 5 man file shrinks to 50 * 5/8 = 31 megs. for all tablebase files starting with KNNK* [D]8/1K6/5N2/8/8/3N4/8/7k w - - There may be similar savings for other files. > >Then we need status: >Won/Loss/Drawn/Broken -- > 4 states means 2 bits. > >That is 12 bits. So any pawnless/rookless tablebase file will need a total of: >12*(2^25) = 402653184 bits = 50,331,648 bytes before compression. > >How does this compare with a decompressed 5 piece Nalimov tablebase file? > >For positions with rooks or pawns, we could just use a format like the current >one. > >Seems like it might be a real big win for 6,7,8 man tablebase files. Each file >will be exactly 5 times larger than the file one generation before it before >compression. > >So a 6 man tablebase file would take 250 megs before compression. >And a 7 man tablebase file would take 1250 megs before compression. >etc. > >Is my brain the cause of pain because the notion is insane?
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