private static void GetBishopMoves(Board board, int square, int[] moves, ref int count)
{
int x = Board.X(square);
int y = Board.Y(square);
Color color = board.GetColor(square);
int target = 0;
// Move up right
target = square + 9;
while (target < 64 && Board.X(target) > x && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target += 9;
}
// Move up left
target = square + 7;
while (target < 64 && Board.X(target) < x && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target += 7;
}
// Move down right
target = square - 7;
while (target >= 0 && Board.X(target) > x && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target -= 7;
}
// Move down left
target = square - 9;
while (target >= 0 && Board.X(target) < x && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target -= 9;
}
}
private static void GetRookMoves(Board board, int square, int[] moves, ref int count)
{
Color color = board.GetColor(square);
int target = 0;
// Move up
target = square + 8;
while (target < 64 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target += 8;
}
// Move down
target = square - 8;
while (target >= 0 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target -= 8;
}
// Move right
target = square + 1;
while (Board.X(target) > Board.X(square) && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target++;
}
// Move left
target = square - 1;
while (Board.X(target) < Board.X(square) && board.GetColor(target) != color)
{
moves[count] = target;
count++;
if (board.State[target] != 0) // enemy piece
{
break;
}
target--;
}
}
public static ulong Calculate(Board board)
{
ulong hash = 0;
for (int i = 0; i < 64; i++)
{
var color = board.GetColor(i);
if (color == Color.None)
{
continue;
}
var piece = board.GetPiece(i);
hash = hash ^ Keys[Index[Colors.Val(color, piece)], i];
}
int castling = board.CastlingRights.Select(x => (int)x).Aggregate((total, x) => total | x);
hash = hash ^ Keys[IndexPlayerTurn, (int)board.PlayerTurn];
hash = hash ^ Keys[IndexCastling, castling];
hash = hash ^ Keys[IndexEnPassant, board.EnPassantTile];
return(hash);
}
/// <summary>
/// Evaluates how many pieces can attack each tile.
/// Returns an array of 64 ints, each number represents the number of attackers
/// for that square
/// </summary>
/// <param name="board"></param>
/// <param name="attackerColor"></param>
/// <returns></returns>
public int[] GetAttackBoard(Color attackerColor)
{
Board board = this;
Color color = attackerColor;
var attackBoard = new int[64];
// Search for all pieces of the attacker's color
for (int i = 0; i < 64; i++)
{
if (board.GetColor(i) != color)
{
continue;
}
// find all the moves this piece can make
var moves = Attacks.GetAttacks(board, i);
// mark them on the attack board
foreach (int move in moves)
{
attackBoard[move]++;
}
}
return(attackBoard);
}
/// <summary>
/// Figures out if the specified move puts or keeps your own king in check, which is illegal
/// </summary>
/// <param name="board"></param>
/// <param name="from"></param>
/// <param name="to"></param>
/// <returns></returns>
public bool MoveSelfChecks(int from, int to)
{
Board board = this;
Color colorToMove = board.GetColor(from);
board = board.Copy();
board.Move(from, to, false);
bool ok = board.IsChecked(colorToMove);
return(ok);
}
/// <summary>
/// Returns the tile of the pawn that is killed in an en passant capture
/// </summary>
/// <param name="board"></param>
/// <param name="from"></param>
/// <param name="to"></param>
/// <returns></returns>
public static int EnPassantVictim(Board board, int from, int to)
{
var color = board.GetColor(from);
if (color == Color.White)
{
return(to - 8);
}
if (color == Color.Black)
{
return(to + 8);
}
throw new Exception("Unrecognized color");
}
/// <summary>
/// Returns all moves, valid or not, for the current player
/// </summary>
/// <param name="board"></param>
/// <returns></returns>
public static Move[] GetMoves(Board board)
{
var moves = new List <Move>();
var player = board.PlayerTurn;
for (int i = 0; i < 64; i++)
{
if (board.GetColor(i) != player)
{
continue;
}
Piece piece = board.GetPiece(i);
var dest = GetMoves(board, i);
for (int j = 0; j < dest.Length; j++)
{
var move = new Move();
move.From = i;
move.To = dest[j];
moves.Add(move);
if (CanPromote(move.To, player, piece))
{
var move2 = move.Copy();
var move3 = move.Copy();
var move4 = move.Copy();
move.Promotion = Piece.Knight;
move2.Promotion = Piece.Bishop;
move3.Promotion = Piece.Rook;
move4.Promotion = Piece.Queen;
moves.Add(move2);
moves.Add(move3);
moves.Add(move4);
}
}
}
return(moves.ToArray());
}
/// <summary>
/// Checks if the move is pawn moving 2 tiles, and returns the tile at which it can be captured
/// (between from and to). Returns 0 if the piece can not be captured in an en passant move
/// </summary>
/// <param name="board"></param>
/// <param name="from"></param>
/// <param name="to"></param>
/// <returns></returns>
public static int EnPassantTile(Board board, int from, int to)
{
var color = board.GetColor(from);
var piece = board.GetPiece(from);
var y = Board.Y(from);
if (piece != Piece.Pawn)
{
return(0);
}
if (color == Color.White && y == 1 && to == (from + 16))
{
return(from + 8);
}
if (color == Color.Black && y == 6 && to == (from - 16))
{
return(from - 8);
}
return(0);
}
/// <summary>
/// Checks if a piece on the board can be promoted
/// </summary>
/// <param name="square"></param>
/// <param name="pieceType"></param>
/// <returns></returns>
public bool CanPromote(int square)
{
Board board = this;
// Can only promote pawns
if (board.GetPiece(square) != Piece.Pawn)
{
return(false);
}
Color color = board.GetColor(square);
if (Board.Y(square) == 7 && color == Color.White)
{
return(true);
}
if (Board.Y(square) == 0 && color == Color.Black)
{
return(true);
}
return(false);
}
private static void GetKingMoves(Board board, int square, int[] moves, ref int count)
{
int x = Board.X(square);
int y = Board.Y(square);
Color color = board.GetColor(square);
int target = 0;
if (y < 7)
{
target = square + 7;
if (x > 0 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
target = square + 8;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
target = square + 9;
if (x < 7 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
target = square - 1;
if (x > 0 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
target = square + 1;
if (x < 7 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
if (y > 0)
{
target = square - 9;
if (x > 0 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
target = square - 8;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
target = square - 7;
if (x < 7 && board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// castling
// no quares between rook and king can be occupied, the king cannot pass through any checked attacked squares
if (color == Color.White && square == 4)
{
if (board.CanCastleKWhite && board.State[5] == 0 && board.State[6] == 0)
{
var attacks = board.GetAttackBoard(Color.Black);
if (attacks[4] == 0 && attacks[5] == 0 && attacks[6] == 0)
{
moves[count] = 6;
count++;
}
}
if (board.CanCastleQWhite && board.State[3] == 0 && board.State[2] == 0 && board.State[1] == 0)
{
var attacks = board.GetAttackBoard(Color.Black);
if (attacks[2] == 0 && attacks[3] == 0 && attacks[4] == 0)
{
moves[count] = 2;
count++;
}
}
}
else if (color == Color.Black && square == 60)
{
if (board.CanCastleKBlack && board.State[61] == 0 && board.State[62] == 0)
{
var attacks = board.GetAttackBoard(Color.White);
if (attacks[60] == 0 && attacks[61] == 0 && attacks[62] == 0)
{
moves[count] = 62;
count++;
}
}
if (board.CanCastleQBlack && board.State[59] == 0 && board.State[58] == 0 && board.State[57] == 0)
{
var attacks = board.GetAttackBoard(Color.White);
if (attacks[58] == 0 && attacks[59] == 0 && attacks[60] == 0)
{
moves[count] = 58;
count++;
}
}
}
}
private static void GetKnightMoves(Board board, int square, int[] moves, ref int count)
{
// -x-x- -0-1-
// x---x 2---3
// --O-- --O--
// x---x 4---5
// -x-x- -6-7-
int target = 0;
int x = Board.X(square);
int y = Board.Y(square);
Color color = board.GetColor(square);
// 0
if (x > 0 && y < 6)
{
target = square + 15;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// 1
if (x < 7 && y < 6)
{
target = square + 17;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// 2
if (x > 1 && y < 7)
{
target = square + 6;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// 3
if (x < 6 && y < 7)
{
target = square + 10;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// -x-x- -0-1-
// x---x 2---3
// --O-- --O--
// x---x 4---5
// -x-x- -6-7-
// 4
if (x > 1 && y > 0)
{
target = square - 10;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// 5
if (x < 6 && y > 0)
{
target = square - 6;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// 6
if (x > 0 && y > 1)
{
target = square - 17;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
// 7
if (x < 7 && y > 1)
{
target = square - 15;
if (board.GetColor(target) != color)
{
moves[count] = target;
count++;
}
}
}
private static void GetPawnMoves(Board board, int square, int[] moves, ref int count)
{
int x = Board.X(square);
int y = Board.Y(square);
Color color = board.GetColor(square);
if (y == 0 || y == 7) // cannot ever happen
{
return;
}
if (color == Color.White)
{
// move forward
int target = square + 8;
if (target < 64 && board.State[target] == 0)
{
moves[count] = target;
count++;
target = square + 16;
if (y == 1 && board.State[target] == 0)
{
moves[count] = target;
count++;
}
}
// capture left
target = square + 7;
if (x > 0 && y < 7 && board.GetColor(target) == Color.Black)
{
moves[count] = target;
count++;
}
// capture right
target = square + 9;
if (x < 7 && y < 7 && board.GetColor(target) == Color.Black)
{
moves[count] = target;
count++;
}
// en passant left
target = square + 7;
if (y == 4 && x > 0 && board.EnPassantTile == target && board.State[target - 8] == ((int)Piece.Pawn | (int)Color.Black))
{
moves[count] = target;
count++;
}
// en passant right
target = square + 9;
if (y == 4 && x < 7 && board.EnPassantTile == target && board.State[target - 8] == ((int)Piece.Pawn | (int)Color.Black))
{
moves[count] = target;
count++;
}
}
else
{
int target = square - 8;
if (target >= 0 && board.State[target] == 0)
{
moves[count] = target;
count++;
target = square - 16;
if (y == 6 && board.State[target] == 0)
{
moves[count] = target;
count++;
}
}
// capture left
target = square - 9;
if (x > 0 && y > 0 && board.GetColor(target) == Color.White)
{
moves[count] = target;
count++;
}
// capture right
target = square - 7;
if (x < 7 && y > 0 && board.GetColor(target) == Color.White)
{
moves[count] = target;
count++;
}
// en passant left
target = square - 9;
if (y == 3 && x > 0 && board.EnPassantTile == target && board.State[target + 8] == Colors.Val(Piece.Pawn, Color.White))
{
moves[count] = target;
count++;
}
// en passant right
target = square - 7;
if (y == 3 && x < 7 && board.EnPassantTile == target && board.State[target + 8] == Colors.Val(Piece.Pawn, Color.White))
{
moves[count] = target;
count++;
}
}
}
private static void GetPawnAttacks(Board board, int square, int[] moves, ref int count)
{
int x = Board.X(square);
int y = Board.Y(square);
Color color = board.GetColor(square);
if (color == Color.White)
{
// capture left
int target = square + 7;
if (x > 0 && y < 7)
{
moves[count] = target;
count++;
}
// capture right
target = square + 9;
if (x < 7 && y < 7)
{
moves[count] = target;
count++;
}
// en passant left
target = square + 7;
if (y == 4 && x > 0 && board.EnPassantTile == target && board.State[target - 8] == Colors.Val(Piece.Pawn, Color.Black))
{
moves[count] = target - 8; // I'm ATTACKING the pawn at target-8 even though I move to target
count++;
}
// en passant right
target = square + 9;
if (y == 4 && x < 7 && board.EnPassantTile == target && board.State[target - 8] == Colors.Val(Piece.Pawn, Color.Black))
{
moves[count] = target - 8; // I'm ATTACKING the pawn at target-8 even though I move to target
count++;
}
}
else
{
// capture left
int target = square - 9;
if (x > 0 && y > 0)
{
moves[count] = target;
count++;
}
// capture right
target = square - 7;
if (x < 7 && y > 0)
{
moves[count] = target;
count++;
}
// en passant left
target = square - 9;
if (y == 3 && x > 0 && board.EnPassantTile == target && board.State[target + 8] == Colors.Val(Piece.Pawn, Color.White))
{
moves[count] = target + 8; // I'm ATTACKING the pawn at target+8 even though I move to target
count++;
}
// en passant right
target = square - 7;
if (y == 3 && x < 7 && board.EnPassantTile == target && board.State[target + 8] == Colors.Val(Piece.Pawn, Color.White))
{
moves[count] = target + 8; // I'm ATTACKING the pawn at target+8 even though I move to target
count++;
}
}
}
private static void GetKingAttacks(Board board, int square, int[] moves, ref int count)
{
int x = Board.X(square);
int y = Board.Y(square);
Color color = board.GetColor(square);
int target = 0;
if (y < 7)
{
target = square + 7;
if (x > 0)
{
moves[count] = target;
count++;
}
target = square + 8;
moves[count] = target;
count++;
target = square + 9;
if (x < 7)
{
moves[count] = target;
count++;
}
}
target = square - 1;
if (x > 0)
{
moves[count] = target;
count++;
}
target = square + 1;
if (x < 7)
{
moves[count] = target;
count++;
}
if (y > 0)
{
target = square - 9;
if (x > 0)
{
moves[count] = target;
count++;
}
target = square - 8;
moves[count] = target;
count++;
target = square - 7;
if (x < 7)
{
moves[count] = target;
count++;
}
}
}