Author: Tom Kerrigan
Date: 10:25:03 04/22/00
Go up one level in this thread
On April 21, 2000 at 13:21:56, J. Wesley Cleveland wrote: >On April 21, 2000 at 02:03:53, Dann Corbit wrote: > >>On April 21, 2000 at 01:44:07, Tom Kerrigan wrote: >>>On April 20, 2000 at 11:58:55, KarinsDad wrote: >>>>On April 20, 2000 at 04:21:58, James Robertson wrote: >>>> >>>>>What is the current minumum number of bits required to store a chess position? >>>>>If somebody could send me instructions on how to encode a chess position in as >>>>>few bits as possible, I would be very happy. >>>>> >>>>>Thanks, >>>>>James >>>>>jrobertson@newmail.net >>>> >>>> >>>>I think the answer is around 155 or so bits with a enumeration algorithm, but >>>>I'm not sure if anyone has actually written one and proved it. The reason is >>>>that it would be a bit of a bear to write (but doable). >>>> >>>>My best is 162 bits with the algorithm I put together. It also has not been >>>>written. However, it would be quicker to calculate than an enumeration >>>>algorithm. >>>> >>>>A good algorithm is the one used in EDP. It requires 192 bits, but is extremely >>>>simple to code up. Something like: >>>> >>>> 64 64 bits bitboard >>>>128 4 bits per piece times 32 pieces >>> >>>Hmm. I wonder if some sort of Huffman encoding would be useful for the bitboard. >>>Of course, then you get positions that are variable bit lengths, but if that's >>>not a requirement... >> >>that is an excellent idea for average length reduction, but I think it will >>actually expand the worst case length by a few bits. > >I don't think so. Say you use the simplest Huffman of 3 bits for pawns, and 4 >bits for other pieces. For every two promotions (adds 2 bits), one man must be >removed (subtracts 3-4 bits), so the total length is smaller. Notice my idea was to use Huffman encoding for the bitboard, and not the pieces. -Tom
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