Author: frank phillips
Date: 04:42:16 10/07/99
Go up one level in this thread
On October 06, 1999 at 20:27:02, Dan Newman wrote: >On October 06, 1999 at 07:32:00, Bas Hamstra wrote: > >>On October 06, 1999 at 05:42:45, Dan Newman wrote: >> >>>On October 05, 1999 at 12:00:19, Robert Hyatt wrote: >>> >>>>I have finished writing a paper for the JICCA on the rotated bitmap approach >>>>to chess... although it includes traditional (non-rotated) bitmaps as well >>>>since an understanding of them is necessary to appreciate rotated bitmaps. >>>> >>>>There is very little literature to reference, excepting the paper in the >>>>old Chess Skill in Man and Machine book, so I thought that I would at least >>>>mention the names of current (and past, such as Kaissa) programs that are or >>>>did use bitboards. >>>> >>>>If you are using them, either post the particulars here (name of program, >>>>author, affiliation [if any], and so forth) and I'll include it. >>>> >>>>Thanks... >>>> >>>>Bob >>> >>>I'm working on one now that I am provisionally calling Shrike (after >>>the bird that impales its prey on cactus needles), but I've only been >>>working on this one for about 2 1/2 weeks... >>> >>>It uses non-rotated bitboards and so must frequently scan the board >>>for slider move generation and attack detection. >>> >>>So far I like it. It's given me the simplest move generator and >>>make/undo code that I've gotten so far. It is slightly slower >>>generating moves than my 0x88 program, but I suspect/hope that will >>>be offset by gains elsewhere--specifically in the SEE and eval. >>> >>>Name: Shrike >>>Author: Dan Newman >>> >>>-Dan. >> >> >>About that scanning the board: >> >>I have a simple testversion that too uses non rotated bitboards. If I want to >>know if a pseudo attack is blocked by any piece I use: >> >> BlackPieces & WhitePieces & BlockMask[FromSquare][ToSquare] > >I think you meant: > (BlackPieces | WhitePieces) & BlockMask[FromSquare][ToSquare] > >> >>The array BlockMask is a bitboard array which for each square to each other >>square (if possible, only "slider type") contains the bitmap. It works well, is >>easy and still fast. >> >> >>Regards, >>Bas Hamstra. > >That's neat. I'll have to try it. The only worry I'd have is the >space that BlockMask takes up (32k if I've calculated correctly) and >how that might affect the cache. But it can be used in a lot of places >(move gen, SEE, in check test, eval, any place that needs to calculate >attacks) and seems like it'd be a lot quicker than scanning. > >-Dan. I found this to be slower (not much) than a mixed approach using the integer-offsets-array approach for sliders when the bitboard test indicated a pseudo attack. With offsets you can often catch the queen attacks early, when testing for rook attacks and bishop attacks. Should bitboards or rotated bitboard be faster? Frank
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