Author: Dann Corbit
Date: 10:42:39 11/30/04
Go up one level in this thread
On November 30, 2004 at 13:25:08, James Swafford wrote: >On November 30, 2004 at 12:51:38, Andrew N. Hunt wrote: > >>Hi! >> >>I've recently implemented bitboards (standard and rotated) and have a question >>about pre-computing moves which contain blocked squares. Let's say I have the >>occupied rank: >> >>bQ, wN, _, wR, _, bP, bN, _ >> >>and I want to find the valid moves for the white Rook. How do I handle modifying >>its bitboard rank: 11010110 to remove the blocked squares and only store the >>available squares: 01101100? (which I can then And with the white/black pieces >>to find valid Rook moves) >> >>Maybe I'm missing something obvious... :-? > >You need to precompute a two dimension array >Bitboard rank_moves[64][256]. The first index is the square >the rook is on. The second index is the state of the rank >(in this case 11010110 base 2). > >You'll need a similar array for files and diagonals >(one for the a1->h8 direction and one more for the h1->a8 >direction). > >Just build these arrays in your program initialization >by doing some looping. You can get by with 128 entries instead of 256 in most cases, because a piece never attacks or defends the square it is standing on.
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