const int BishopCheck = 2;
const int KnightCheck = 3;
+ const int UnsupportedPinnedPiece = 2;
+
// KingDanger[Color][attackUnits] contains the actual king danger weighted
// scores, indexed by color and by a calculated integer number.
Score KingDanger[COLOR_NB][128];
if (b)
attackUnits += KnightCheck * popcount<Max15>(b);
+ // Penalty for pinned pieces not defended by a pawn
+ if (ei.pinnedPieces[Us] & ~ei.attackedBy[Us][PAWN])
+ attackUnits += UnsupportedPinnedPiece;
+
// To index KingDanger[] attackUnits must be in [0, 99] range
attackUnits = std::min(99, std::max(0, attackUnits));