  This paper describes an approach for obtaining direct access to the attacked
squares of sliding pieces without resorting to rotated bitboards. The technique
involves creating four hash tables using the built in hash arrays from an
interpreted, high level language. The rank, file, and diagonal occupancy are
first isolated by masking the desired portion of the board. The attacked
squares are then directly retrieved from the hash tables. Maintaining
incrementally updated rotated bitboards becomes unnecessary as does all the
updating, mapping and shifting required to access the attacked squares.
Finally, rotated bitboard move generation speed is compared with that of the
direct hash table lookup method.

Data Structures and Algorithms