Author: David Rasmussen
Date: 12:30:46 01/25/03
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On January 25, 2003 at 13:43:53, Russell Reagan wrote: >On January 25, 2003 at 13:20:10, David Rasmussen wrote: > >>Talking bitboards, what is the most natural board orientation for IA32 >>assembler? I would think that a1=0, a2=1 etc. would be unnatural, for example. > >The easiest for me to visualize is a1=0, b1=1...a2=8...h8=63. This seems the >most natural to me since we are taught about the (x,y) coordinate system in >school, and it works nicely since x increases as the file increases (a,b,c...) >and the rank numbers obviously increase. > I agree with that. >As for a 32-bit model, I think most natural would be having half the board in >one 32-bit value, and since we always view a chess board from either white or >black's point of view (and not from the side), it would make sense to either >start at a1=0, b1=1, etc. or to start with h1=0, g1=1, etc., but h1=0 seems >unnatural, to me at least. You could also start with a8=0, b8=1, etc. since that >is how a FEN string is read in (starting at a8), but I think a1=0, b1=1... is >the most natural. Sure. But let me make things clearer: Wanting to implement common bitboard operations (FirstBit(), PopCount() etc.) on IA32, what is the most natural orientation to choose? I think a1=0, b1=1, ... is more natural than a8=0, a7=1, ..., in the sense that the code for, say, FirstBit(), in IA32 assembler will be more effecient in the first than in the latter. /David
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