3 files changed, 56 insertions, 35 deletions

diff --git a/src/board/board.cpp b/src/board/board.cpp
index e68bf80..16efbd3 100644
--- a/src/board/board.cpp
+++ b/src/board/board.cpp
@@ -10,7 +10,6 @@
 int PositionToIndex(Position i) { return i.rank * 8 + i.file; }
 
 Position FindKing(Game *b, bool color) {
-
   return IndexToPosition(__builtin_ctzll(b->PieceBitboards[color][KING]));
 }
 UndoMove MakeMove(Move move, Game *g) {
diff --git a/src/moves.cpp b/src/moves.cpp
index 8f21140..4cd7076 100644
--- a/src/moves.cpp
+++ b/src/moves.cpp
@@ -9,38 +9,63 @@
 #include "board/board.hpp"
 #include "moves.hpp"
 
-void GenerateKnightMoves(Game *b, int from, std::vector<Move> &moves,
-                         bool GenerateQuietMoves) {
-  Piece knight = b->pieces[from];
-  if (knight.type != KNIGHT) {
-    assert(false && "Calling generate knight moves on non knight");
-    return;
-  }
-  // Knight moves: https://www.chessprogramming.org/Knight_Pattern
-  constexpr std::array<int, 8> knight_moves{-10, 6, 15, 17, 10, -6, -15, -17};
-
-  for (int offset : knight_moves) {
-    int next = from + offset;
-    if (next >= 64 || next < 0) {
-      continue;
-    }
-    const int fileDelta = std::abs((next % 8) - (from % 8));
-    if (fileDelta != 1 && fileDelta != 2) {
-      continue;
-    };
-    bool hasFriendlyPiece = b->turn
-                                ? (b->WhitePieceBitboard & (1ULL << (next)))
-                                : (b->BlackPieceBitboard & (1ULL << (next)));
-    bool isCaptuare = b->PieceBitboard & (1ULL << next);
-    if (hasFriendlyPiece) {
-      continue;
-    }
-    if (!GenerateQuietMoves && isCaptuare) {
-      continue;
+constexpr uint64_t KNIGHT_ATTACKS[64] = {
+    0x0000000000020400ULL, 0x0000000000050800ULL, 0x00000000000A1100ULL,
+    0x0000000000142200ULL, 0x0000000000284400ULL, 0x0000000000508800ULL,
+    0x0000000000A01000ULL, 0x0000000000402000ULL, 0x0000000002040004ULL,
+    0x0000000005080008ULL, 0x000000000A110011ULL, 0x0000000014220022ULL,
+    0x0000000028440044ULL, 0x0000000050880088ULL, 0x00000000A0100010ULL,
+    0x0000000040200020ULL, 0x0000000204000402ULL, 0x0000000508000805ULL,
+    0x0000000A1100110AULL, 0x0000001422002214ULL, 0x0000002844004428ULL,
+    0x0000005088008850ULL, 0x000000A0100010A0ULL, 0x0000004020002040ULL,
+    0x0000020400040200ULL, 0x0000050800080500ULL, 0x00000A1100110A00ULL,
+    0x0000142200221400ULL, 0x0000284400442800ULL, 0x0000508800885000ULL,
+    0x0000A0100010A000ULL, 0x0000402000204000ULL, 0x0002040004020000ULL,
+    0x0005080008050000ULL, 0x000A1100110A0000ULL, 0x0014220022140000ULL,
+    0x0028440044280000ULL, 0x0050880088500000ULL, 0x00A0100010A00000ULL,
+    0x0040200020400000ULL, 0x0204000402000000ULL, 0x0508000805000000ULL,
+    0x0A1100110A000000ULL, 0x1422002214000000ULL, 0x2844004428000000ULL,
+    0x5088008850000000ULL, 0xA0100010A0000000ULL, 0x4020002040000000ULL,
+    0x0400040200000000ULL, 0x0800080500000000ULL, 0x1100110A00000000ULL,
+    0x2200221400000000ULL, 0x4400442800000000ULL, 0x8800885000000000ULL,
+    0x100010A000000000ULL, 0x2000204000000000ULL, 0x0004020000000000ULL,
+    0x0008050000000000ULL, 0x00110A0000000000ULL, 0x0022140000000000ULL,
+    0x0044280000000000ULL, 0x0088500000000000ULL, 0x0010A00000000000ULL,
+    0x0020400000000000ULL};
+
+static void GenerateKnightMoves(Game *b, std::vector<Move> &moves,
+                                bool GenerateQuietMoves) {
+  uint64_t knights = b->PieceBitboards[b->turn][KNIGHT];
+  while (knights != 0) {
+    int from = __builtin_ctzll(knights);
+    knights &= knights - 1;
+    uint64_t knight_attacks = KNIGHT_ATTACKS[from];
+    while (knight_attacks != 0) {
+      int next = __builtin_ctzll(knight_attacks);
+      knight_attacks &= knight_attacks - 1;
+
+      if (next >= 64 || next < 0) {
+        continue;
+      }
+      const int fileDelta = std::abs((next % 8) - (from % 8));
+      if (fileDelta != 1 && fileDelta != 2) {
+        continue;
+      };
+      bool hasFriendlyPiece = b->turn
+                                  ? (b->WhitePieceBitboard & (1ULL << (next)))
+                                  : (b->BlackPieceBitboard & (1ULL << (next)));
+      bool isCaptuared = b->PieceBitboard & (1ULL << next);
+      if (hasFriendlyPiece) {
+        continue;
+      }
+      if (!GenerateQuietMoves && !isCaptuared) {
+        continue;
+      }
+      moves.push_back({IndexToPosition(from), IndexToPosition(next)});
     }
-    moves.push_back({IndexToPosition(from), IndexToPosition(next)});
   }
 };
+
 void GeneratePawnMoves(Game *b, int from, std::vector<Move> &moves,
                        bool quietMoves) {
   Piece pawn = b->pieces[from];
@@ -146,6 +171,8 @@ std::vector<Move> GetPseudoLegalMoves(Game *b, bool GenerateQuietMoves) {
   std::vector<Move> moves;
   moves.reserve(40);
 
+  GenerateKnightMoves(b, moves, GenerateQuietMoves);
+
   constexpr std::array<int, 4> rook_Moves{-1, 1, 8, -8};
   constexpr std::array<int, 4> bishop_Moves{-9, 9, -7, 7};
 
@@ -164,9 +191,6 @@ std::vector<Move> GetPseudoLegalMoves(Game *b, bool GenerateQuietMoves) {
     if (piece.type == PAWN) {
       GeneratePawnMoves(b, i, moves, GenerateQuietMoves);
     }
-    if (piece.type == KNIGHT) {
-      GenerateKnightMoves(b, i, moves, GenerateQuietMoves);
-    };
     if (piece.type == BISHOP) {
       GenerateSlidingMoves(b, i, bishop_Moves, moves, GenerateQuietMoves);
     }
diff --git a/src/moves.hpp b/src/moves.hpp
index e48d7f8..3764be4 100644
--- a/src/moves.hpp
+++ b/src/moves.hpp
@@ -12,8 +12,6 @@ void GenerateSlidingMoves(Game *g, int from,
                           std::vector<Move> &moves, bool GenerateQuietMoves);
 void GenerateKingMoves(Game *g, int from, std::vector<Move> &moves,
                        bool GenerateQuietMoves);
-void GenerateKnightMoves(Game *b, int from, std::vector<Move> &moves,
-                         bool GenerateQuietMoves);
 void GeneratePawnMoves(Game *b, int from, std::vector<Move> &moves,
                        bool GenerateQuietMoves);
 void GenerateCastlingMoves(int from, Game *g, std::vector<Move> &moves);