⚡ Check sliding pieces attacks last in IsSquaredAttacked (#369)

* Check sliding pieces attacks last in `IsSquaredAttacked` * Make 'oppositeColorIndex' faster
lynx-chess · Aug 21, 2023 · df15872 · df15872
1 parent f97e38c
commit df15872
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Showing 2 changed files with 15 additions and 14 deletions.
diff --git a/src/Lynx/Attacks.cs b/src/Lynx/Attacks.cs
@@ -105,38 +105,40 @@ public static bool IsSquaredAttacked(int squareIndex, Side sideToMove, BitBoard[
     {
         Utils.Assert(sideToMove != Side.Both);
 
-        var offset = Utils.PieceOffset(sideToMove);
+        var sideToMoveInt = (int)sideToMove;
+        var offset = Utils.PieceOffset(sideToMoveInt);
 
         // I tried to order them from most to least likely
         return
-            IsSquareAttackedByPawns(squareIndex, sideToMove, offset, piecePosition)
+            IsSquareAttackedByPawns(squareIndex, sideToMoveInt, offset, piecePosition)
+            || IsSquareAttackedByKing(squareIndex, offset, piecePosition)
             || IsSquareAttackedByKnights(squareIndex, offset, piecePosition)
             || IsSquareAttackedByBishops(squareIndex, offset, piecePosition, occupancy, out var bishopAttacks)
             || IsSquareAttackedByRooks(squareIndex, offset, piecePosition, occupancy, out var rookAttacks)
-            || IsSquareAttackedByQueens(offset, bishopAttacks, rookAttacks, piecePosition)
-            || IsSquareAttackedByKing(squareIndex, offset, piecePosition);
+            || IsSquareAttackedByQueens(offset, bishopAttacks, rookAttacks, piecePosition);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static bool IsSquareInCheck(int squareIndex, Side sideToMove, BitBoard[] piecePosition, BitBoard[] occupancy)
     {
         Utils.Assert(sideToMove != Side.Both);
 
-        var offset = Utils.PieceOffset(sideToMove);
+        var sideToMoveInt = (int)sideToMove;
+        var offset = Utils.PieceOffset(sideToMoveInt);
 
         // I tried to order them from most to least likely
         return
             IsSquareAttackedByRooks(squareIndex, offset, piecePosition, occupancy, out var rookAttacks)
             || IsSquareAttackedByBishops(squareIndex, offset, piecePosition, occupancy, out var bishopAttacks)
             || IsSquareAttackedByQueens(offset, bishopAttacks, rookAttacks, piecePosition)
             || IsSquareAttackedByKnights(squareIndex, offset, piecePosition)
-            || IsSquareAttackedByPawns(squareIndex, sideToMove, offset, piecePosition);
+            || IsSquareAttackedByPawns(squareIndex, sideToMoveInt, offset, piecePosition);
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    private static bool IsSquareAttackedByPawns(int squareIndex, Side sideToMove, int offset, BitBoard[] pieces)
+    private static bool IsSquareAttackedByPawns(int squareIndex, int sideToMove, int offset, BitBoard[] pieces)
     {
-        var oppositeColorIndex = ((int)sideToMove + 1) % 2;
+        var oppositeColorIndex = sideToMove ^ 1;
 
         return (PawnAttacks[oppositeColorIndex, squareIndex] & pieces[offset]) != default;
     }

diff --git a/src/Lynx/MoveGenerator.cs b/src/Lynx/MoveGenerator.cs
@@ -391,14 +391,13 @@ private static bool IsAnyPawnMoveValid(Position position, int offset)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     private static bool IsAnyCastlingMoveValid(Position position, int offset)
     {
-        var piece = (int)Piece.K + offset;
-        var oppositeSide = (Side)Utils.OppositeSide(position.Side);
-
-        int sourceSquare = position.PieceBitBoards[piece].GetLS1BIndex(); // There's for sure only one
-
-        // Castles
         if (position.Castle != default)
         {
+            var piece = (int)Piece.K + offset;
+            var oppositeSide = (Side)Utils.OppositeSide(position.Side);
+
+            int sourceSquare = position.PieceBitBoards[piece].GetLS1BIndex(); // There's for sure only one
+
             if (position.Side == Side.White)
             {
                 bool ise1Attacked = Attacks.IsSquaredAttackedBySide((int)BoardSquare.e1, position, oppositeSide);