// get the type of piece at a given board address
private static PieceMoveType PieceTypeAtAddress(PiecePositions.Player player, BoardAddress address)
{
if ((address.Position & player.Pawns) != 0)
{
return(PieceMoveType.Pawn);
}
else if ((address.Position & player.Knights) != 0)
{
return(PieceMoveType.Knight);
}
else if ((address.Position & player.Bishops) != 0)
{
return(PieceMoveType.Bishop);
}
else if ((address.Position & player.Rooks) != 0)
{
return(PieceMoveType.Rook);
}
else if ((address.Position & player.Queens) != 0)
{
return(PieceMoveType.Queen);
}
else if ((address.Position & player.King) != 0)
{
return(PieceMoveType.King);
}
else
{
Debug.WriteLine("no piece found at specified position"); return(PieceMoveType.Undefined);
}
}
// the material value for a given player
private int MaterialValue(PiecePositions.Player player)
{
int Result = 0;
foreach (ulong pawn in Utilities.BitSplit(player.Pawns))
{
Result += PawnValue;
}
foreach (ulong knight in Utilities.BitSplit(player.Knights))
{
Result += KnightValue;
}
foreach (ulong bishop in Utilities.BitSplit(player.Knights))
{
Result += BishopValue;
}
foreach (ulong rook in Utilities.BitSplit(player.Knights))
{
Result += RookValue;
}
foreach (ulong queen in Utilities.BitSplit(player.Knights))
{
Result += QueenValue;
}
return(Result);
}
// apply a move to a given board
internal static Board ApplyMove(Board board, Move move)
{
var Result = new Board();
Result.ActiveColorWhite = board.ActiveColorWhite;
/// update piece positions ///
Result.Pieces = new PiecePositions(board.Pieces);
Result.Pieces.All &= ~(move.From.Position | move.To.Position);
PiecePositions.Player ActiveP = Result.ActivePlayer;
switch (move.MoveType)
{
case PieceMoveType.Pawn:
ActiveP.Pawns |= move.To.Position;
break;
case PieceMoveType.Knight:
case PieceMoveType.PawnKnight:
ActiveP.Knights |= move.To.Position;
break;
case PieceMoveType.Bishop:
case PieceMoveType.PawnBishop:
ActiveP.Bishops |= move.To.Position;
break;
case PieceMoveType.Rook:
case PieceMoveType.PawnRook:
ActiveP.Rooks |= move.To.Position;
break;
case PieceMoveType.Queen:
case PieceMoveType.PawnQueen:
ActiveP.Queens |= move.To.Position;
break;
case PieceMoveType.King:
ActiveP.King |= move.To.Position;
break;
case PieceMoveType.KingQueenside:
ActiveP.King |= move.To.Position;
if (board.ActiveColorWhite)
{
ActiveP.Rooks &= ~Masks.WhiteQueenSideRookInitPos;
ActiveP.Rooks |= Masks.WhiteQueenSideRookPostCastlePos;
}
else
{
ActiveP.Rooks &= ~Masks.BlackQueenSideRookInitPos;
ActiveP.Rooks |= Masks.BlackQueenSideRookPostCastlePos;
}
break;
case PieceMoveType.KingKingside:
ActiveP.King |= move.To.Position;
if (board.ActiveColorWhite)
{
ActiveP.Rooks &= ~Masks.WhiteKingSideRookInitPos;
ActiveP.Rooks |= Masks.WhiteQueenSideRookPostCastlePos;
}
else
{
ActiveP.Rooks &= ~Masks.BlackKingSideRookInitPos;
ActiveP.Rooks |= Masks.BlackKingSideRookPostCastlePos;
}
break;
default:
throw new ArgumentException("invalid move type");
}
/// update the draw counter ///
bool PawnMoved = move.MoveType < PieceMoveType.Knight;
bool CaptureOccured = (move.To.Position & (board.InactivePlayer.All | board.EnPassantTarget)) != 0;
if (PawnMoved || CaptureOccured)
{
Result.HalfMoveClock = 0; // reset
}
else
{
Result.HalfMoveClock = (byte)(board.HalfMoveClock + 1); // increment
}
/// check for en passant target ///
if (PawnMoved && (move.From.Position & Masks.Ranks27) != 0)
{
if (board.ActiveColorWhite && ((move.From.Position << 16) & move.To.Position) != 0)
{
Result.EnPassantTarget = move.From.Position << 8;
}
else if (!board.ActiveColorWhite && ((move.From.Position >> 16) & move.To.Position) != 0)
{
Result.EnPassantTarget = move.From.Position >> 8;
}
}
/// update castling availability ///
// copy the availablity of the inactive player and store the past availablity for the active player
Result.CastlingAvailability = new Board.Castling();
Board.Castling.Move PastActiveCastlingStatus, NewActiveCastlingStatus;
if (board.ActiveColorWhite)
{
Result.CastlingAvailability.Black = board.CastlingAvailability.Black;
PastActiveCastlingStatus = board.CastlingAvailability.White;
}
else
{
Result.CastlingAvailability.White = board.CastlingAvailability.White;
PastActiveCastlingStatus = board.CastlingAvailability.Black;
}
// was castling already disallowed or did the king just move?
if (PastActiveCastlingStatus == Board.Castling.Move.Disallowed || (move.MoveType >= PieceMoveType.King)) // yes
{
NewActiveCastlingStatus = Board.Castling.Move.Disallowed;
}
else // no
{
switch (PastActiveCastlingStatus)
{
case Board.Castling.Move.KingSide:
if (KingSideRookMoved(board))
{
NewActiveCastlingStatus = Board.Castling.Move.Disallowed;
}
else
{
NewActiveCastlingStatus = Board.Castling.Move.KingSide;
}
break;
case Board.Castling.Move.QueenSide:
if (QueenSideRookMoved(board))
{
NewActiveCastlingStatus = Board.Castling.Move.Disallowed;
}
else
{
NewActiveCastlingStatus = Board.Castling.Move.QueenSide;
}
break;
case Board.Castling.Move.BothSides:
if (QueenSideRookMoved(board))
{
NewActiveCastlingStatus = Board.Castling.Move.KingSide;
}
else if (KingSideRookMoved(board))
{
NewActiveCastlingStatus = Board.Castling.Move.KingSide;
}
else
{
NewActiveCastlingStatus = Board.Castling.Move.BothSides;
}
break;
default:
throw new Exception(string.Format("invalid castling status \"{0}\"", PastActiveCastlingStatus));
}
if (board.ActiveColorWhite)
{
Result.CastlingAvailability.White = NewActiveCastlingStatus;
}
else
{
Result.CastlingAvailability.Black = NewActiveCastlingStatus;
}
}
/// update full move counter ///
if (!board.ActiveColorWhite)
{
Result.FullMoveNumber++; // on black player's move
}
/// switch the active player ///
Result.ActiveColorWhite = !board.ActiveColorWhite;
/// update past move tracker ///
Result.PastMoves = new Queue <Move>(board.PastMoves); // copy references to the past moves
if (Result.PastMoves.Count == 8)
{
Result.PastMoves.Dequeue(); // limit at 8 moves
}
Result.PastMoves.Enqueue(move); // add the current move
return(Result);
}
// create a move from a diff of two boards
private static Move BoardDiff(Board before, Board after)
{
// cache player handles
PiecePositions.Player ActivePlayerBefore = before.ActivePlayer;
PiecePositions.Player InactivePlayerAfter = after.InactivePlayer;
var Result = new Move();
/// get the starting positions of the moving pieces ///
ulong MultiPositions = ActivePlayerBefore.All & ~InactivePlayerAfter.All;
if (MultiPositions == 0)
{
Debug.WriteLine("none of the active player's pieces moved"); return(null);
}
bool TwoPieceFlag = false;
ulong RookStartPosition = 0;
ulong RookEndPosition = 0;
ulong[] Positions = new List <ulong>(Utilities.BitSplit(MultiPositions)).ToArray();
PieceMoveType FromPiece, ToPiece;
if (Positions.Length > 2) // more than two moved pieces
{
Debug.WriteLine("more than two pieces moved");
return(null);
}
else if (Positions.Length == 2) // double piece move (castle)
{
TwoPieceFlag = true;
FromPiece = PieceTypeAtAddress(ActivePlayerBefore, new BoardAddress(Positions[0]));
if (FromPiece != PieceMoveType.King)
{
if (FromPiece != PieceMoveType.Rook)
{
Debug.WriteLine("two pieces moved, but a rook was not one of them");
return(null);
}
FromPiece = PieceTypeAtAddress(ActivePlayerBefore, new BoardAddress(Positions[1]));
if (FromPiece != PieceMoveType.King)
{
Debug.WriteLine("two pieces moved, but the king was not one of them"); return(null);
}
Result.From = new BoardAddress(Positions[1]);
RookStartPosition = Positions[0];
}
else
{
if (PieceTypeAtAddress(ActivePlayerBefore, new BoardAddress(Positions[1])) != PieceMoveType.Rook)
{
Debug.WriteLine("two pieces moved, but a rook was not one of them");
return(null);
}
Result.From = new BoardAddress(Positions[0]);
RookStartPosition = Positions[1];
}
}
else // single piece moved
{
Result.From = new BoardAddress(Positions[0]);
FromPiece = PieceTypeAtAddress(ActivePlayerBefore, new BoardAddress(Positions[0]));
}
/// get the ending position of the moving piece ///
MultiPositions = InactivePlayerAfter.All & ~ActivePlayerBefore.All;
Positions = new List <ulong>(Utilities.BitSplit(MultiPositions)).ToArray();
if (MultiPositions == 0)
{
Debug.WriteLine("the active player lost a piece on thier turn"); return(null);
}
if (Positions.Length > 2) // more than two pieces moved
{
Debug.WriteLine("a piece was added to the board");
return(null);
}
else if (Positions.Length == 2) // double piece move (castle)
{
if (!TwoPieceFlag)
{
Debug.WriteLine("a piece was added to the board"); return(null);
}
ToPiece = PieceTypeAtAddress(InactivePlayerAfter, new BoardAddress(Positions[0]));
if (ToPiece != PieceMoveType.King)
{
if (ToPiece != PieceMoveType.Rook)
{
Debug.WriteLine("two pieces moved, but a rook was not one of them"); return(null);
}
ToPiece = PieceTypeAtAddress(InactivePlayerAfter, new BoardAddress(Positions[1]));
if (ToPiece != PieceMoveType.King)
{
Debug.WriteLine("two pieces moved, but the king was not one of them"); return(null);
}
Result.To = new BoardAddress(Positions[1]);
RookEndPosition = Positions[0];
}
else
{
if (PieceTypeAtAddress(InactivePlayerAfter, new BoardAddress(Positions[1])) != PieceMoveType.Rook)
{
Debug.WriteLine("two pieces moved, but a rook was not one of them");
return(null);
}
Result.To = new BoardAddress(Positions[0]);
RookEndPosition = Positions[1];
}
}
else // single piece moved
{
if (TwoPieceFlag)
{
Debug.WriteLine("the active player lost a piece on thier turn"); return(null);
}
Result.To = new BoardAddress(Positions[0]);
ToPiece = PieceTypeAtAddress(InactivePlayerAfter, new BoardAddress(Positions[0]));
}
Result.MoveType = MoveTypeFromPieceTypes(FromPiece, ToPiece);
if (TwoPieceFlag) // update king move to a castling move
{
if (Result.MoveType != PieceMoveType.King) // sanity check
{
Debug.WriteLine("the move indicates a castle, but the king didn't move");
return(null);
}
if (before.ActiveColorWhite) // white player's move
{
if ((RookStartPosition ^ Masks.WhiteKingSideRookInitPos) == 0) // king side castle
{
if ((RookEndPosition ^ Masks.WhiteKingSideRookPostCastlePos) != 0) // does the rook's end position agree?
{
Debug.WriteLine("the move indicates a kingside castle, but the rook didn't move to its proper position");
return(null);
}
Result.MoveType = PieceMoveType.KingKingside;
}
else if ((RookStartPosition ^ Masks.WhiteQueenSideRookInitPos) == 0) // queenside castle
{
if ((RookEndPosition ^ Masks.WhiteQueenSideRookPostCastlePos) != 0) // does the rook's end position agree?
{
Debug.WriteLine("the move indicates a queenside castle, but the rook didn't move to its proper position");
return(null);
}
Result.MoveType = PieceMoveType.KingQueenside;
}
else // invalid
{
Debug.WriteLine("the move indicates a castle, but the rook was not in its proper position");
return(null);
}
}
else // black player's move
{
if ((RookStartPosition ^ Masks.BlackKingSideRookInitPos) == 0) // king side castle
{
if ((RookEndPosition ^ Masks.BlackKingSideRookPostCastlePos) != 0) // does the rook's end position agree?
{
Debug.WriteLine("the move indicates a kingside castle, but the rook didn't move to its proper position");
return(null);
}
Result.MoveType = PieceMoveType.KingKingside;
}
else if ((RookStartPosition ^ Masks.BlackQueenSideRookInitPos) == 0) // queenside castle
{
if ((RookEndPosition ^ Masks.BlackQueenSideRookPostCastlePos) != 0) // does the rook's end position agree?
{
Debug.WriteLine("the move indicates a queenside castle, but the rook didn't move to its proper position");
return(null);
}
Result.MoveType = PieceMoveType.KingQueenside;
}
else // invalid
{
Debug.WriteLine("the move indicates a castle, but the rook was not in its proper position");
return(null);
}
}
}
return(Result);
}