Changes

While using eight lookups to intersect sounds expensive on the first glance, SISSY Bitboards yields up to eight [[Direction#RayDirections|ray-directions]] of a queen in one run with cheap instructions and high [https://en.wikipedia.org/wiki/Instructions_per_cycle IPC] potential, and thus may be an alternative for [[Magic Bitboards|magic bitboards]] on architectures with slow 64-bit multiplication, in particular for the queen.

One may half =Rook Attacks=If combined with the table size by combining occupancy indices of two consecutive ranks, since their relevant bits on [[DiagonalsFirst Rank Attacks#AttacksOnAllRanks|diagonalrank lookup]] and for SISSY fileAttacks only, one can dense the occupy index range to 2, considering only blockers on the same file.<pre>U64 rss[6][Anti-Diagonals|anti-diagonal64][2] are always disjoint.; // 6K

U64 fileAttacks(U64 occ, enumSquare sq) { occ >>=Rook Attacks=(sq & 7); // shift occupancy to A file returnIf combined with the rss[0][First Rank Attacks#AttacksOnAllRanks|sq][(occ >> 8) & 1] & // 2nd rank lookup rss[1][sq] to dense the occupy index range to [(occ >> 16) & 1] & rss[2, considering only blockers on the same file, ][sq][(occ >> 24) & 1] & rss[3][sq][(occ >> 32) & 1] & SISSY file attack generation looks not that competitive compared to other techniques as well, see for instance rss[4][Kindergarten Bitboards#File-Attacks|Kindergarten file attackssq][(occ >> 40) & 1] or & rss[5][Hyperbola Quintessencesq][(occ >> 48) & 1].; // 7th rank} </pre>One may try some more index trickery for instance considering 3 ranks each, for an upper and lower half:

U64 rss[62][264][648]; // 6K8K

rss[0][sq][((occ >> 822) & 1][sq] & // 2nd rank rss[1][4) | ((occ >> 1615) & 1][sq] & rss[2][) | ((occ >> 248) & 1][sq)] & // rank 4,3,2 rss[31][sq][((occ >> 3246) & 1][sq] & rss[4][) | ((occ >> 4039) & 1][sq] & rss[5][2) | ((occ >> 4832) & 1][sq)] ; // 7th rank7,6,5}