Author: KarinsDad
Date: 18:38:52 03/22/99
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On March 22, 1999 at 20:44:59, Greg Lazarou wrote: >Do you really rotate them, or do you maintain the board in straight, 45 degree >(diagonals), 90 degree and 135 degree angles throughout? > >Greg I maintain the board in each orientation for each side and for an xor of the two sides and copy the boards into a position's child position, and then make the modification in each orientation for each move (which for me is currently 12 ANDs and 8 ORs, one OR for moving side, one AND for moving side, one AND for side attacked, and one OR and one AND for xor board for each of the 4 orientations, but I will check someday to see if it is faster to just handle the white and black bitboards and then just xor them into a third bitboard as needed). Since this requires 138 bytes (3 boards * 2 orientations * 8 bytes per board + 3 boards * 2 orientations * 15 bytes per board for diagonals), this scheme is a memory hog and wastes 7 bytes of data per board for the diagonals. I'm sure someone has come up with a fast way to rotate them, but I haven't had time to research it. I also use my bitboards to determine piece attacks, square control, king safety, open ranks, files, and diagonals (although I do not use the open diagonal info yet) etc. (in addition to generating moves as per James' message). KarinsDad > >On March 22, 1999 at 18:29:07, James Robertson wrote: > >>On March 22, 1999 at 17:06:44, Dann Corbit wrote: >> >>>I understand that you can represent a chess board as a rotated bit sets. But my >>>significantly stupid question is "Why rotate them -- what is the advantage?" >> >>To generate moves, you extract 8 adjacent bits from your 64-bit bitboard. This >>works great for rank moves since they are already perfectly lined up. But if you >>want to get file moves, you can't extract every 8th bit, and diagonal moves are >>even worse. If you rotate the bitboard, you can extract file and diagonal moves. >> >>James
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