/// <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> getLegalMove(BoardHelper board, Position pos, bool verify_check = true)
{
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == PieceType.None)
{
return(new List <Position>());
}
switch (p.piece)
{
case PieceType.Pawn:
return(LegalMoveSet.Pawn(board, pos, verify_check));
case PieceType.Rook:
return(LegalMoveSet.Rook(board, pos, verify_check));
case PieceType.Knight:
return(LegalMoveSet.Knight(board, pos, verify_check));
case PieceType.Bishop:
return(LegalMoveSet.Bishop(board, pos, verify_check));
case PieceType.Queen:
return(LegalMoveSet.Queen(board, pos, verify_check));
case PieceType.King:
return(LegalMoveSet.King(board, pos, verify_check));
default:
return(new List <Position>());
}
}
private static List <Position> Rook(BoardHelper board, Position pos, bool verify_check = true)
{
List <Position> moves = new List <Position>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == PieceType.None)
{
return(moves);
}
// slide along vert/hor for possible moves
moves.AddRange(Slide(board, p.player, pos, new Position(1, 0)));
moves.AddRange(Slide(board, p.player, pos, new Position(-1, 0)));
moves.AddRange(Slide(board, p.player, pos, new Position(0, 1)));
moves.AddRange(Slide(board, p.player, pos, new Position(0, -1)));
if (verify_check)// make sure each move doesn't put us in check
{
for (int i = moves.Count - 1; i >= 0; i--)
{
BoardHelper b2 = LegalMoveSet.move(board, new Move(pos, moves[i]));
if (isCheck(b2, p.player))
{
moves.RemoveAt(i);
}
}
}
return(moves);
}
private static List <Position> Knight(BoardHelper board, Position pos, bool verify_check = true)
{
List <Position> moves = new List <Position>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == PieceType.None)
{
return(moves);
}
// collect all relative moves possible
List <Position> relative = new List <Position>();
relative.Add(new Position(2, 1));
relative.Add(new Position(2, -1));
relative.Add(new Position(-2, 1));
relative.Add(new Position(-2, -1));
relative.Add(new Position(1, 2));
relative.Add(new Position(-1, 2));
relative.Add(new Position(1, -2));
relative.Add(new Position(-1, -2));
// iterate moves
foreach (Position move in relative)
{
Position moved = new Position(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 == PieceType.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--)
{
BoardHelper b2 = LegalMoveSet.move(board, new Move(pos, moves[i]));
if (isCheck(b2, p.player))
{
moves.RemoveAt(i);
}
}
}
return(moves);
}
private static bool allowCastle(BoardHelper board, PieceSide player, Position 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 == PieceType.Rook &&
board.Grid[pos.number][rookPos].player == player && board.Grid[pos.number][rookPos].lastPosition.Equals(new Position(-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 != PieceType.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
BoardHelper b2 = LegalMoveSet.move(board, new Move(pos, new Position(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);
}
public int fitness(PieceSide 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 pos in Pieces[PieceSide.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 pos in Pieces[PieceSide.White])
{
whiteMoves += LegalMoveSet.getLegalMove(this, pos).Count;
whitePieces[(int)Grid[pos.number][pos.letter].piece]++;
}
// if viewing from black side
if (max == PieceSide.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, List <Position> > getPlayerMoves(BoardHelper b, PieceSide player)
{
Dictionary <Position, List <Position> > moves = new Dictionary <Position, List <Position> >();
foreach (Position pos in b.Pieces[player])
{
if (b.Grid[pos.number][pos.letter].piece != PieceType.None)
{
if (!moves.ContainsKey(pos))
{
moves[pos] = new List <Position>();
}
moves[pos].AddRange(LegalMoveSet.getLegalMove(b, pos));
}
}
return(moves);
}
private static List <Position> Pawn(BoardHelper board, Position pos, bool verify_check = true)
{
List <Position> moves = new List <Position>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == PieceType.None)
{
return(moves);
}
// gather relative moves
List <Position> relative = new List <Position>();
relative.Add(new Position(-1, 1 * ((p.player == PieceSide.Black) ? -1 : 1)));
relative.Add(new Position(0, 1 * ((p.player == PieceSide.Black) ? -1 : 1)));
relative.Add(new Position(0, 2 * ((p.player == PieceSide.Black) ? -1 : 1)));
relative.Add(new Position(1, 1 * ((p.player == PieceSide.Black) ? -1 : 1)));
// iterate moves
foreach (Position move in relative)
{
Position moved = new Position(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 == PieceType.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 == PieceSide.Black) ? 6 : 1);
if (board.Grid[moved.number + step][moved.letter].piece == PieceType.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 == PieceType.None)
{
moves.Add(moved);
}
// angled attack
else if (moved.letter != pos.letter && board.Grid[moved.number][moved.letter].piece != PieceType.None && board.Grid[moved.number][moved.letter].player != p.player)
{
moves.Add(moved);
}
// en passant
else if (isEnPassant(board, new Move(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--)
{
BoardHelper b2 = LegalMoveSet.move(board, new Move(pos, moves[i]));
if (isCheck(b2, p.player))
{
moves.RemoveAt(i);
}
}
}
return(moves);
}
private static List <Position> King(BoardHelper board, Position pos, bool verify_check = true)
{
List <Position> moves = new List <Position>();
piece_t p = board.Grid[pos.number][pos.letter];
if (p.piece == PieceType.None)
{
return(moves);
}
// collect all relative moves possible
List <Position> relative = new List <Position>();
relative.Add(new Position(-1, 1));
relative.Add(new Position(0, 1));
relative.Add(new Position(1, 1));
relative.Add(new Position(-1, 0));
relative.Add(new Position(1, 0));
relative.Add(new Position(-1, -1));
relative.Add(new Position(0, -1));
relative.Add(new Position(1, -1));
// Iterate moves
foreach (Position move in relative)
{
Position moved = new Position(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 == PieceType.None || board.Grid[moved.number][moved.letter].player != p.player)
{
if (verify_check) // make sure we don't put ourselves in check
{
BoardHelper b2 = LegalMoveSet.move(board, new Move(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(-1, -1)))
{
bool castleRight = allowCastle(board, p.player, pos, true);
bool castleLeft = allowCastle(board, p.player, pos, false);
if (castleRight)
{
moves.Add(new Position(6, pos.number));
}
if (castleLeft)
{
moves.Add(new Position(2, pos.number));
}
}
}
return(moves);
}
private Move MiniMaxAB(BoardHelper board, PieceSide turn)
{
RUNNING = true; // we've started running
STOP = false; // no interupt command sent
MAX = turn; // who is maximizing
// gather all possible moves
Dictionary <Position, List <Position> > moves = LegalMoveSet.getPlayerMoves(board, turn);
// because we're threading safely store best result from each thread
int[] bestresults = new int[moves.Count];
Move[] bestmoves = new Move[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(new Position(-1, -1), new Position(-1, -1));
// for each move for the current piece(thread)
foreach (Position move in movelist.Value)
{
if (STOP) // interupt
{
state.Stop();
return;
}
// make initial move and start recursion
BoardHelper b2 = LegalMoveSet.move(board, new Move(movelist.Key, move));
int result = mimaab(b2, (turn == PieceSide.White) ? PieceSide.Black : PieceSide.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(-1, -1)) && bestresults[index] == int.MinValue))
{
bestresults[index] = result;
bestmoves[index].from = movelist.Key;
bestmoves[index].to = move;
}
}
});
// interupted
if (STOP)
{
return(new Move(new Position(-1, -1), new Position(-1, -1)));
}
// find the best of the thread results
int best = int.MinValue;
Move m = new Move(new Position(-1, -1), new Position(-1, -1));
for (int i = 0; i < bestmoves.Length; i++)
{
if (best < bestresults[i] || (m.to.Equals(new Position(-1, -1)) && !bestmoves[i].to.Equals(new Position(-1, -1))))
{
best = bestresults[i];
m = bestmoves[i];
}
}
return(m);
}
private int mimaab(BoardHelper board, PieceSide turn, int depth, int alpha, int beta)
{
// base case, at maximum depth return board fitness
if (depth >= DEPTH)
{
return(board.fitness(MAX));
}
else
{
List <BoardHelper> boards = new List <BoardHelper>();
// get available moves / board states from moves for the current player
foreach (Position pos in board.Pieces[turn])
{
if (STOP)
{
return(-1); // interupts
}
List <Position> moves = LegalMoveSet.getLegalMove(board, pos);
foreach (Position move in moves)
{
if (STOP)
{
return(-1); // interupts
}
BoardHelper b2 = LegalMoveSet.move(board, new Move(pos, move));
boards.Add(b2);
}
}
int a = alpha, b = beta;
if (turn != MAX) // minimize
{
foreach (BoardHelper b2 in boards)
{
if (STOP)
{
return(-1); // interupt
}
b = Math.Min(b, mimaab(b2, (turn == PieceSide.White) ? PieceSide.Black : PieceSide.White, depth + 1, a, b));
if (a >= b)
{
return(a);
}
}
return(b);
}
else // maximize
{
foreach (BoardHelper b2 in boards)
{
if (STOP)
{
return(-1); // interupt
}
a = Math.Max(a, mimaab(b2, (turn == PieceSide.White) ? PieceSide.Black : PieceSide.White, depth + 1, a, b));
if (a >= b)
{
return(b);
}
}
return(a);
}
}
}
