/// <summary>
/// Detects Checkmate, Stalemate or Draw conditions.
/// </summary>
/// <returns>True if no legal moves, or only kings left.</returns>
public bool detectCheckmate()
{
bool wkingonly = this.Board.Pieces[Player.WHITE].Count == 1 && this.Board.Grid[this.Board.Pieces[Player.WHITE][0].number][this.Board.Pieces[Player.WHITE][0].letter].piece == Piece.KING;
bool bkingonly = this.Board.Pieces[Player.BLACK].Count == 1 && this.Board.Grid[this.Board.Pieces[Player.BLACK][0].number][this.Board.Pieces[Player.BLACK][0].letter].piece == Piece.KING;
if (!LegalMoveSet.hasMoves(this.Board, this.Turn))
{
if (LegalMoveSet.isCheck(this.Board, this.Turn))
{
this.m_UI.LogMove("Checkmate!\n");
this.m_UI.SetStatus(false, ((this.Turn == Player.WHITE) ? "Black" : "White") + " wins!");
}
else
{
this.m_UI.LogMove("Stalemate!\n");
}
return(true);
}
else if (wkingonly && bkingonly)
{
this.m_UI.LogMove("Draw.\n");
return(true);
}
return(false);
}
/// <summary>
/// Get any legal move from the current position on the provided board.
/// </summary>
/// <param name="board">The state of the game.</param>
/// <param name="pos">The piece/position to check for valid moves.</param>
/// <param name="verify_check">Whether or not to recurse and check if the current move puts you in check.</param>
/// <returns>A list of positions the piece can move to.</returns>
public static List <position_t> getLegalMove(ChessBoard board, position_t pos, bool verify_check = true)
{
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == Piece.NONE)
{
return(new List <position_t>());
}
switch (p.piece)
{
case Piece.PAWN:
return(LegalMoveSet.Pawn(board, pos, verify_check));
case Piece.ROOK:
return(LegalMoveSet.Rook(board, pos, verify_check));
case Piece.KNIGHT:
return(LegalMoveSet.Knight(board, pos, verify_check));
case Piece.BISHOP:
return(LegalMoveSet.Bishop(board, pos, verify_check));
case Piece.QUEEN:
return(LegalMoveSet.Queen(board, pos, verify_check));
case Piece.KING:
return(LegalMoveSet.King(board, pos, verify_check));
default:
return(new List <position_t>());
}
}
private static List <position_t> Rook(ChessBoard board, position_t pos, bool verify_check = true)
{
List <position_t> moves = new List <position_t>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == Piece.NONE)
{
return(moves);
}
// slide along vert/hor for possible moves
moves.AddRange(Slide(board, p.player, pos, new position_t(1, 0)));
moves.AddRange(Slide(board, p.player, pos, new position_t(-1, 0)));
moves.AddRange(Slide(board, p.player, pos, new position_t(0, 1)));
moves.AddRange(Slide(board, p.player, pos, new position_t(0, -1)));
if (verify_check)// make sure each move doesn't put us in check
{
for (int i = moves.Count - 1; i >= 0; i--)
{
ChessBoard b2 = LegalMoveSet.move(board, new move_t(pos, moves[i]));
if (isCheck(b2, p.player))
{
moves.RemoveAt(i);
}
}
}
return(moves);
}
private static List <position_t> Knight(ChessBoard board, position_t pos, bool verify_check = true)
{
List <position_t> moves = new List <position_t>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == Piece.NONE)
{
return(moves);
}
// collect all relative moves possible
List <position_t> relative = new List <position_t>();
relative.Add(new position_t(2, 1));
relative.Add(new position_t(2, -1));
relative.Add(new position_t(-2, 1));
relative.Add(new position_t(-2, -1));
relative.Add(new position_t(1, 2));
relative.Add(new position_t(-1, 2));
relative.Add(new position_t(1, -2));
relative.Add(new position_t(-1, -2));
// iterate moves
foreach (position_t move in relative)
{
position_t moved = new position_t(move.letter + pos.letter, move.number + pos.number);
// bounds check
if (moved.letter < 0 || moved.letter > 7 || moved.number < 0 || moved.number > 7)
{
continue;
}
// if empty space or attacking
if (board.Grid[moved.number][moved.letter].piece == Piece.NONE ||
board.Grid[moved.number][moved.letter].player != p.player)
{
moves.Add(moved);
}
}
if (verify_check)// make sure each move doesn't put us in check
{
for (int i = moves.Count - 1; i >= 0; i--)
{
ChessBoard b2 = LegalMoveSet.move(board, new move_t(pos, moves[i]));
if (isCheck(b2, p.player))
{
moves.RemoveAt(i);
}
}
}
return(moves);
}
private static bool allowCastle(ChessBoard board, Player player, position_t pos, bool isRight)
{
bool isValid = true;
int rookPos;
int kingDirection;
if (isRight)
{
rookPos = 7;
kingDirection = 1;
}
else
{
rookPos = 0;
kingDirection = -1;
}
//Check for valid right castling
// Is the peice at H,7 a rook owned by the player and has it moved
if (board.Grid[pos.number][rookPos].piece == Piece.ROOK &&
board.Grid[pos.number][rookPos].player == player && board.Grid[pos.number][rookPos].lastPosition.Equals(new position_t(-1, -1)))
{
// Check that the adjacent two squares are empty
for (int i = 0; i < 2; i++)
{
if (board.Grid[pos.number][pos.letter + (i + 1) * kingDirection].piece != Piece.NONE)
{
isValid = false;
break;
}
}
// Don't bother running secondary checks if the way isn't even clear
if (isValid)
{
for (int i = 0; i < 2; i++)
{
// Move kings postion over i squares to check if king is passing over an attackable
// square
ChessBoard b2 = LegalMoveSet.move(board, new move_t(pos, new position_t(pos.letter + (i + 1) * kingDirection, pos.number)));
// Attackable square is in between king and rook so
// its not possible to castle to the right rook
if (isCheck(b2, player))
{
isValid = false;
break;
}
}
}
}
else
{
isValid = false;
}
return(isValid);
}
/// <summary>
/// Calculate and return the boards fitness value.
/// </summary>
/// <param name="max">Who's side are we viewing from.</param>
/// <returns>The board fitness value, what else?</returns>
public int fitness(Player max)
{
int fitness = 0;
int[] blackPieces = { 0, 0, 0, 0, 0, 0 };
int[] whitePieces = { 0, 0, 0, 0, 0, 0 };
int blackMoves = 0;
int whiteMoves = 0;
// sum up the number of moves and pieces
foreach (position_t pos in Pieces[Player.BLACK])
{
blackMoves += LegalMoveSet.getLegalMove(this, pos).Count;
blackPieces[(int)Grid[pos.number][pos.letter].piece]++;
}
// sum up the number of moves and pieces
foreach (position_t pos in Pieces[Player.WHITE])
{
whiteMoves += LegalMoveSet.getLegalMove(this, pos).Count;
whitePieces[(int)Grid[pos.number][pos.letter].piece]++;
}
// if viewing from black side
if (max == Player.BLACK)
{
// apply weighting to piece counts
for (int i = 0; i < 6; i++)
{
fitness += pieceWeights[i] * (blackPieces[i] - whitePieces[i]);
}
// apply move value
fitness += (int)(0.5 * (blackMoves - whiteMoves));
}
else
{
// apply weighting to piece counts
for (int i = 0; i < 6; i++)
{
fitness += pieceWeights[i] * (whitePieces[i] - blackPieces[i]);
}
// apply move value
fitness += (int)(0.5 * (whiteMoves - blackMoves));
}
return(fitness);
}
/// <summary>
/// Get all legal moves for the player on the current board.
/// </summary>
/// <param name="b">The state of the game.</param>
/// <param name="player">The player whose moves you want.</param>
/// <returns>A 1-to-many dictionary of moves from one position to many</returns>
public static Dictionary <position_t, List <position_t> > getPlayerMoves(ChessBoard b, Player player)
{
Dictionary <position_t, List <position_t> > moves = new Dictionary <position_t, List <position_t> >();
foreach (position_t pos in b.Pieces[player])
{
if (b.Grid[pos.number][pos.letter].piece != Piece.NONE)
{
if (!moves.ContainsKey(pos))
{
moves[pos] = new List <position_t>();
}
moves[pos].AddRange(LegalMoveSet.getLegalMove(b, pos));
}
}
return(moves);
}
private void MakeMove(move_t m)
{
// start move log output
string move = (this.Turn == Player.WHITE) ? "W" : "B";
move += ":\t";
// piece
switch (this.Board.Grid[m.from.number][m.from.letter].piece)
{
case Piece.PAWN:
move += "P";
break;
case Piece.ROOK:
move += "R";
break;
case Piece.KNIGHT:
move += "k";
break;
case Piece.BISHOP:
move += "B";
break;
case Piece.QUEEN:
move += "Q";
break;
case Piece.KING:
move += "K";
break;
}
// kill
if (this.Board.Grid[m.to.number][m.to.letter].piece != Piece.NONE || LegalMoveSet.isEnPassant(this.Board, m))
{
move += "x";
}
// letter
switch (m.to.letter)
{
case 0: move += "a"; break;
case 1: move += "b"; break;
case 2: move += "c"; break;
case 3: move += "d"; break;
case 4: move += "e"; break;
case 5: move += "f"; break;
case 6: move += "g"; break;
case 7: move += "h"; break;
}
// number
move += (m.to.number + 1).ToString();
// update board / make actual move
this.Board = LegalMoveSet.move(this.Board, m);
// if that move put someone in check
if (LegalMoveSet.isCheck(this.Board, (Turn == Player.WHITE) ? Player.BLACK : Player.WHITE))
{
move += "+";
}
// show log
this.m_UI.LogMove(move + "\n");
}
public List <position_t> Select(position_t pos)
{
// has previously selected something
if (this.Board.Grid[this.Selection.number][this.Selection.letter].piece != Piece.NONE &&
this.Turn == this.Board.Grid[this.Selection.number][this.Selection.letter].player &&
(this.m_nPlayers == 2 ||
this.Turn == Player.WHITE))
{
// get previous selections moves and determine if we chose a legal one by clicking
List <position_t> moves = LegalMoveSet.getLegalMove(this.Board, this.Selection);
foreach (position_t move in moves)
{
if (move.Equals(pos))
{
// we selected a legal move so update the board
MakeMove(new move_t(this.Selection, pos));
// If piece that was just moved is a king and it moved anyhthing other than 1 square, it was
// a castling move, so we need to move the rook
if (this.Board.Grid[pos.number][pos.letter].piece == Piece.KING && Math.Abs(pos.letter - this.Selection.letter) == 2)
{
int row = (this.Turn == Player.WHITE) ? 0 : 7;
// Left rook
if (pos.letter < 4)
{
LegalMoveSet.move(this.Board, new move_t(new position_t(0, row), new position_t(3, row)));
}
// right rook
else
{
LegalMoveSet.move(this.Board, new move_t(new position_t(7, row), new position_t(5, row)));
}
}
// finish move
switchPlayer();
if (detectCheckmate())
{
return(new List <position_t>());
}
if (this.m_nPlayers == 1) // start ai
{
new Thread(AISelect).Start(); // thread turn
}
return(new List <position_t>());
}
}
}
// first click, let's show possible moves
if (this.Board.Grid[pos.number][pos.letter].player == this.Turn && (this.m_nPlayers == 2 || this.Turn == Player.WHITE))
{
List <position_t> moves = LegalMoveSet.getLegalMove(this.Board, pos);
this.Selection = pos;
return(moves);
}
// reset
this.Selection = new position_t();
return(new List <position_t>());
}
private static int mimaab(ChessBoard board, Player turn, int depth, int alpha, int beta)
{
// base case, at maximum depth return board fitness
if (depth >= DEPTH)
{
return(board.fitness(MAX));
}
else
{
List <ChessBoard> boards = new List <ChessBoard>();
// get available moves / board states from moves for the current player
foreach (position_t pos in board.Pieces[turn])
{
if (STOP)
{
return(-1); // interupts
}
List <position_t> moves = LegalMoveSet.getLegalMove(board, pos);
foreach (position_t move in moves)
{
if (STOP)
{
return(-1); // interupts
}
ChessBoard b2 = LegalMoveSet.move(board, new move_t(pos, move));
boards.Add(b2);
}
}
int a = alpha, b = beta;
if (turn != MAX) // minimize
{
foreach (ChessBoard b2 in boards)
{
if (STOP)
{
return(-1); // interupt
}
b = Math.Min(b, mimaab(b2, (turn == Player.WHITE) ? Player.BLACK : Player.WHITE, depth + 1, a, b));
if (a >= b)
{
return(a);
}
}
return(b);
}
else // maximize
{
foreach (ChessBoard b2 in boards)
{
if (STOP)
{
return(-1); // interupt
}
a = Math.Max(a, mimaab(b2, (turn == Player.WHITE) ? Player.BLACK : Player.WHITE, depth + 1, a, b));
if (a >= b)
{
return(b);
}
}
return(a);
}
}
}
public static move_t MiniMaxAB(ChessBoard board, Player turn)
{
RUNNING = true; // we've started running
STOP = false; // no interupt command sent
MAX = turn; // who is maximizing
// gather all possible moves
Dictionary <position_t, List <position_t> > moves = LegalMoveSet.getPlayerMoves(board, turn);
// because we're threading safely store best result from each thread
int[] bestresults = new int[moves.Count];
move_t[] bestmoves = new move_t[moves.Count];
// thread the generation of each move
Parallel.ForEach(moves, (movelist, state, index) =>
{
if (STOP) // interupt
{
state.Stop();
return;
}
// initialize thread best
bestresults[index] = int.MinValue;
bestmoves[index] = new move_t(new position_t(-1, -1), new position_t(-1, -1));
// for each move for the current piece(thread)
foreach (position_t move in movelist.Value)
{
if (STOP) // interupt
{
state.Stop();
return;
}
// make initial move and start recursion
ChessBoard b2 = LegalMoveSet.move(board, new move_t(movelist.Key, move));
int result = mimaab(b2, (turn == Player.WHITE) ? Player.BLACK : Player.WHITE, 1, Int32.MinValue, Int32.MaxValue);
// if result is better or best hasn't been set yet
if (bestresults[index] < result || (bestmoves[index].to.Equals(new position_t(-1, -1)) && bestresults[index] == int.MinValue))
{
bestresults[index] = result;
bestmoves[index].from = movelist.Key;
bestmoves[index].to = move;
}
}
});
// interupted
if (STOP)
{
return(new move_t(new position_t(-1, -1), new position_t(-1, -1)));
}
// find the best of the thread results
int best = int.MinValue;
move_t m = new move_t(new position_t(-1, -1), new position_t(-1, -1));
for (int i = 0; i < bestmoves.Length; i++)
{
if (best < bestresults[i] || (m.to.Equals(new position_t(-1, -1)) && !bestmoves[i].to.Equals(new position_t(-1, -1))))
{
best = bestresults[i];
m = bestmoves[i];
}
}
return(m);
}
private static List <position_t> Pawn(ChessBoard board, position_t pos, bool verify_check = true)
{
List <position_t> moves = new List <position_t>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == Piece.NONE)
{
return(moves);
}
// gather relative moves
List <position_t> relative = new List <position_t>();
relative.Add(new position_t(-1, 1 * ((p.player == Player.BLACK) ? -1 : 1)));
relative.Add(new position_t(0, 1 * ((p.player == Player.BLACK) ? -1 : 1)));
relative.Add(new position_t(0, 2 * ((p.player == Player.BLACK) ? -1 : 1)));
relative.Add(new position_t(1, 1 * ((p.player == Player.BLACK) ? -1 : 1)));
// iterate moves
foreach (position_t move in relative)
{
position_t moved = new position_t(move.letter + pos.letter, move.number + pos.number);
// bounds check
if (moved.letter < 0 || moved.letter > 7 || moved.number < 0 || moved.number > 7)
{
continue;
}
// double forward move
if (moved.letter == pos.letter && board.Grid[moved.number][moved.letter].piece == Piece.NONE && Math.Abs(moved.number - pos.number) == 2)
{
// check the first step
int step = -((moved.number - pos.number) / (Math.Abs(moved.number - pos.number)));
bool hasnt_moved = pos.number == ((p.player == Player.BLACK) ? 6 : 1);
if (board.Grid[moved.number + step][moved.letter].piece == Piece.NONE && hasnt_moved)
{
moves.Add(moved);
}
}
// if it's not blocked we can move forward
else if (moved.letter == pos.letter && board.Grid[moved.number][moved.letter].piece == Piece.NONE)
{
moves.Add(moved);
}
// angled attack
else if (moved.letter != pos.letter && board.Grid[moved.number][moved.letter].piece != Piece.NONE && board.Grid[moved.number][moved.letter].player != p.player)
{
moves.Add(moved);
}
// en passant
else if (isEnPassant(board, new move_t(pos, moved)))
{
moves.Add(moved);
}
}
if (verify_check)// make sure each move doesn't put us in check
{
for (int i = moves.Count - 1; i >= 0; i--)
{
ChessBoard b2 = LegalMoveSet.move(board, new move_t(pos, moves[i]));
if (isCheck(b2, p.player))
{
moves.RemoveAt(i);
}
}
}
return(moves);
}
private static List <position_t> King(ChessBoard board, position_t pos, bool verify_check = true)
{
List <position_t> moves = new List <position_t>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == Piece.NONE)
{
return(moves);
}
// collect all relative moves possible
List <position_t> relative = new List <position_t>();
relative.Add(new position_t(-1, 1));
relative.Add(new position_t(0, 1));
relative.Add(new position_t(1, 1));
relative.Add(new position_t(-1, 0));
relative.Add(new position_t(1, 0));
relative.Add(new position_t(-1, -1));
relative.Add(new position_t(0, -1));
relative.Add(new position_t(1, -1));
// Iterate moves
foreach (position_t move in relative)
{
position_t moved = new position_t(move.letter + pos.letter, move.number + pos.number);
// bound check
if (moved.letter < 0 || moved.letter > 7 || moved.number < 0 || moved.number > 7)
{
continue;
}
// if it's not blocked we can move
if (board.Grid[moved.number][moved.letter].piece == Piece.NONE || board.Grid[moved.number][moved.letter].player != p.player)
{
if (verify_check) // make sure we don't put ourselves in check
{
ChessBoard b2 = LegalMoveSet.move(board, new move_t(pos, moved));
if (!isCheck(b2, p.player))
{
moves.Add(moved);
}
}
else
{
moves.Add(moved);
}
}
}
// Castling
/* A king can only castle if:
* king has not moved
* rook has not moved
* king is not in check
* king does not end up in check
* king does not pass through any other peieces
* king does not pass through any squares under attack
* king knows secret handshake
*/
if (verify_check)
{
if (!isCheck(board, p.player) &&
p.lastPosition.Equals(new position_t(-1, -1)))
{
bool castleRight = allowCastle(board, p.player, pos, true);
bool castleLeft = allowCastle(board, p.player, pos, false);
if (castleRight)
{
moves.Add(new position_t(6, pos.number));
}
if (castleLeft)
{
moves.Add(new position_t(2, pos.number));
}
}
}
return(moves);
}
private void BoardClick(object sender, EventArgs e)
{
if (chess != null && !m_checkmate)
{
// clear board
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
{
Board[i][j].BackColor = ((i + j) % 2 == 0) ? Color.Black : Color.White;
}
}
for (int i = 0; i < 8; i++)
{
int k = Array.IndexOf(Board[i], sender);
if (k > -1)
{
// draw highlighting
if ((!m_manualBoard || m_finalizedBoard) && !m_aigame)
{
List <position_t> moves = chess.Select(new position_t(k, i));
foreach (position_t move in moves)
{
if ((chess.Board.Grid[move.number][move.letter].player != chess.Turn &&
chess.Board.Grid[move.number][move.letter].piece != Piece.NONE) ||
LegalMoveSet.isEnPassant(chess.Board, new move_t(chess.Selection, move)))
{
// attack
Board[move.number][move.letter].BackColor = Color.Red;
}
else
{
// move
Board[move.number][move.letter].BackColor = Color.Yellow;
}
}
}
// place piece
else
{
chess.Board.SetPiece(m_manualPiece, m_manualPlayer, k, i);
SetPiece(m_manualPiece, m_manualPlayer, k, i);
if (m_manualPiece == Piece.KING)
{
if (m_manualPlayer == Player.WHITE)
{
White_King.Enabled = false;
}
else
{
Black_King.Enabled = false;
}
// both players have kings, we could technically start
if (!White_King.Enabled && !Black_King.Enabled)
{
doneToolStripMenuItem.Enabled = true;
}
}
}
}
}
}
}