Magic::index()

[stockfish] / src / bitboard.h

diff --git a/src/bitboard.h b/src/bitboard.h
index 38870a2be69fbd8a33ca8a50e610db4a29dd7c86..ed7e318ca3198ed970aa9508752bf10e1e7d4ded 100644 (file)
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -82,6 +82,20 @@ struct Magic {
   Bitboard  magic;
   Bitboard* attacks;
   unsigned  shift;
+
+  /// looks up the index using the 'magic bitboards' approach.
+  unsigned index(Bitboard occupied) const {
+
+      if (HasPext)
+          return unsigned(pext(occupied, mask));
+
+      if (Is64Bit)
+          return unsigned(((occupied & mask) * magic) >> shift);
+
+      unsigned lo = unsigned(occupied) & unsigned(mask);
+      unsigned hi = unsigned(occupied >> 32) & unsigned(mask >> 32);
+      return (lo * unsigned(magic) ^ hi * unsigned(magic >> 32)) >> shift;
+  }
 };
 
 extern Magic RookMagics[SQUARE_NB];
@@ -186,7 +200,7 @@ inline Bitboard forward_bb(Color c, Square s) {
 /// pawn_attack_span() returns a bitboard representing all the squares that can be
 /// attacked by a pawn of the given color when it moves along its file, starting
 /// from the given square:
-///       PawnAttackSpan[c][s] = in_front_bb(c, rank_of(s)) & adjacent_files_bb(s);
+///       PawnAttackSpan[c][s] = in_front_bb(c, rank_of(s)) & adjacent_files_bb(file_of(s));
 
 inline Bitboard pawn_attack_span(Color c, Square s) {
   return PawnAttackSpan[c][s];
@@ -222,26 +236,13 @@ template<> inline int distance<Rank>(Square x, Square y) { return distance(rank_
 
 
 /// attacks_bb() returns a bitboard representing all the squares attacked by a
-/// piece of type Pt (bishop or rook) placed on 's'. The helper magic_index()
-/// looks up the index using the 'magic bitboards' approach.
-inline unsigned magic_index(const Magic& m, Bitboard occupied) {
-
-  if (HasPext)
-      return unsigned(pext(occupied, m.mask));
-
-  if (Is64Bit)
-      return unsigned(((occupied & m.mask) * m.magic) >> m.shift);
-
-  unsigned lo = unsigned(occupied) & unsigned(m.mask);
-  unsigned hi = unsigned(occupied >> 32) & unsigned(m.mask >> 32);
-  return (lo * unsigned(m.magic) ^ hi * unsigned(m.magic >> 32)) >> m.shift;
-}
+/// piece of type Pt (bishop or rook) placed on 's'.
 
 template<PieceType Pt>
 inline Bitboard attacks_bb(Square s, Bitboard occupied) {
 
   const Magic& M = Pt == ROOK ? RookMagics[s] : BishopMagics[s];
-  return M.attacks[magic_index(M, occupied)];
+  return M.attacks[M.index(occupied)];
 }
 
 inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
@@ -251,7 +252,7 @@ inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {
   switch (pt)
   {
   case BISHOP: return attacks_bb<BISHOP>(s, occupied);
-  case ROOK  : return attacks_bb<ROOK>(s, occupied);
+  case ROOK  : return attacks_bb<  ROOK>(s, occupied);
   case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
   default    : return PseudoAttacks[pt][s];
   }