Author: Dan Newman
Date: 15:06:48 02/24/99
Go up one level in this thread
On February 24, 1999 at 17:01:45, Robert Hyatt wrote: >On February 24, 1999 at 15:09:52, Larry Griffiths wrote: > >>On February 23, 1999 at 16:40:50, Robert Hyatt wrote: >> >>>On February 23, 1999 at 14:33:03, Larry Griffiths wrote: >>> >>>>Dan, >>>> >>>>I read your post on hash collisions. I have tried some hamming distance >>>>code and I see little difference when compared to generating random >>>>numbers. I have been thinking of writing code that does what you said >>>>where 64 bits must have 32 bits (or 50%) turned on in each number. I also see >>>>where there are many references to the 12 pieces times 64 squares = 768 >>>>hash codes. Since the a Bishop can only control 32 possible squares and >>>>there are 4 bishops, then 128 of the 768 are unused. Also, Pawns only >>>>use 48 squares for each side, so 32 squares are unused by pawns. >>>>768-128-48 leaves 592 hashcodes for the piece square table. >>>>Food for thought? Errors in my thinking? >>>> >>>>Larry. >>> >>> >>>A couple. First there are 12 _types_ of pieces. And since each side has >>>two bishops on opposite colors, all 64 random numbers are needed for the >>>bishops. >>> >>>you can get away with leaving 16 out of the pawn random numbers since none >>>exist on the 1st/8th rank. There are not 4 sets of 64 numbers for the 4 >>>bishops. There are two sets of 64, one for black bishops, one for white >>>bishops. Because the bishops are not 'unique' and are interchangable. In >>>fact, after promoting to a B, that B is identical to the B that existed early >>>in the game on the same color square. >>> >>>So you _could_ reduce this to 752 numbers... but then you need a few more >>>for things like castling status, enpassant status, so you take those back >>>again. >> >> >>Bob, >> >>I can get away with leaving 16 out of the pawn random numbers and I have >>two pawn tables so 16 * 2 = 32. So I could reduce this to 768-32 or 736? >> >>I also saw a post that your table is 1024 entries. What are the other >>4 tables (256 entries) used for? >> >>Thanks for your reply. >> >>Larry :-) > >I think that was Don's post about 1024. I have exactly 12 * 64 entries in >mine... and yes you can safely leave those table entries 0 since they will >never be used anyway... I think I may have been the source of that bit of disinformation. I use your piece numbering scheme in my 0x88 program (p=1,n=2,k=3,b=5,r=6,q=7) and use piece number to index my table of random numbers... -Dan. > >but don't forget you need to handle enpassant and castling privileges as well >for both sides...
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