c# - C# 中国际象棋的 MiniMax 算法无法正常工作
问题描述
一个星期以来,我一直在尝试在我的 C# 国际象棋引擎中实现 minimax 算法,它做出了合法的移动,但没有有意义的移动。我找不到错误,希望有人能发现它。我试图通过测试每种方法来隔离问题,除了极小值之外,它们似乎都可以正常工作。
public enum Piece
{
Empty, Pawn_W, Pawn_B, Knight_W, Knight_B,
Bishop_W, Bishop_B, Rook_W, Rook_B,
Queen_W, Queen_B, King_W, King_B
}
public bool IsPieceWhite(Piece piece)
{
if (piece == Piece.Pawn_W || piece == Piece.Knight_W ||
piece == Piece.Bishop_W || piece == Piece.Rook_W ||
piece == Piece.Queen_W || piece == Piece.King_W)
return true;
else return false;
}
public bool IsPieceBlack(Piece piece)
{
if (piece == Piece.Pawn_B || piece == Piece.Knight_B ||
piece == Piece.Bishop_B || piece == Piece.Rook_B ||
piece == Piece.Queen_B || piece == Piece.King_B)
return true;
else return false;
}
public int GetPieceWorth(Piece piece)
{
if (piece == Piece.Pawn_W || piece == Piece.Pawn_B)
return 1;
if (piece == Piece.Knight_W || piece == Piece.Knight_B)
return 3;
if (piece == Piece.Bishop_W || piece == Piece.Bishop_B)
return 3;
if (piece == Piece.Rook_W || piece == Piece.Rook_B)
return 5;
if (piece == Piece.Queen_W || piece == Piece.Queen_B)
return 9;
if (piece == Piece.King_W || piece == Piece.King_B)
return 9999999;
return 0;
}
Piece[,] CurrentBoard = GetStartingBoard();
Piece[,] bestMove;
public int depthB = 3;
public double minimax(Piece[,] board, int depth, bool maximizingPlayer)
{
if (depth == 0)
{
double result = EvaluatePosition(board, maximizingPlayer);
return result;
}
if (maximizingPlayer)
{
double best = Double.MinValue;
double value = Double.MinValue;
foreach (var move in GenerateMoves(board, maximizingPlayer))
{
Piece[,] clonedMove = CloneBoard(move);
value = Math.Max(value, minimax(clonedMove, depth - 1, false));
if (depth == depthB && value >= best)
{
best = value;
bestMove = clonedMove;
}
}
return value;
}
else
{
double best = Double.MaxValue;
double value = Double.MaxValue;
foreach (var move in GenerateMoves(board, maximizingPlayer))
{
Piece[,] clonedMove = CloneBoard(move);
value = Math.Min(value, minimax(clonedMove, depth - 1, true));
if (depth == depthB && value <= best)
{
best = value;
bestMove = clonedMove;
}
}
return value;
}
}
public Piece[,] CloneBoard(Piece[,] boardPos)
{
Piece[,] copy = boardPos.Clone() as Piece[,];
return copy;
}
public double EvaluatePosition(Piece[,] boardPos, bool ForWhite)
{
double eval = 0;
for (int i = 0; i < 8; i++)
{
for (int j = 0; j < 8; j++)
{
if (boardPos[i, j] != Piece.Empty)
{
if (IsPieceWhite(boardPos[i, j]))
{
eval += GetPieceWorth(boardPos[i, j]);
}
else if (IsPieceBlack(boardPos[i, j]))
{
eval -= GetPieceWorth(boardPos[i, j]);
}
}
}
}
if (ForWhite)
return eval;
else
return eval * -1;
}
//a-h,0-7
//Piece[,] board = new Piece[8, 8];
public static Piece[,] GetStartingBoard()
{
Piece[,] board = new Piece[8, 8];
for (int i = 0; i < 8; i++)
{
//initiate pawns
board[1, i] = Piece.Pawn_W;
board[6, i] = Piece.Pawn_B;
}
//white pieces
board[0, 0] = Piece.Rook_W;
board[0, 1] = Piece.Knight_W;
board[0, 2] = Piece.Bishop_W;
board[0, 3] = Piece.Queen_W;
board[0, 4] = Piece.King_W;
board[0, 5] = Piece.Bishop_W;
board[0, 6] = Piece.Knight_W;
board[0, 7] = Piece.Rook_W;
//black pieces
board[7, 0] = Piece.Rook_B;
board[7, 1] = Piece.Knight_B;
board[7, 2] = Piece.Bishop_B;
board[7, 3] = Piece.Queen_B;
board[7, 4] = Piece.King_B;
board[7, 5] = Piece.Bishop_B;
board[7, 6] = Piece.Knight_B;
board[7, 7] = Piece.Rook_B;
//test
//board[1, 4] = Piece.Pawn_B;
//board[6, 2] = Piece.Pawn_W;
return board;
}
我上传了一段引擎与自己对战的短片,以展示奇怪的动作:https ://www.youtube.com/watch?v=A0HVgXYSciY
解决方案
终于能够使极小极大函数工作。感谢所有的帮助!
工作方法:
public int minimax(Piece[,] board, int depth, bool maximizingPlayer, bool WhiteToPlay)
{
if (depth == 0)
{
int result = EvaluatePosition(board, WhiteToPlay);
return result;
}
var moves = GenerateMoves(board, WhiteToPlay);
if (maximizingPlayer)
{
int value = int.MinValue;
foreach (var move in moves)
{
int minmaxResult = minimax(move, depth - 1, false, !WhiteToPlay);
value = Math.Max(value, minmaxResult);
if (depth == depthB)
{
moveScores.Add(move, minmaxResult);
}
}
return value;
}
else
{
int value = int.MaxValue;
foreach (var move in moves)
{
int minmaxResult = minimax(move, depth - 1, true, !WhiteToPlay);
value = Math.Min(value, minmaxResult);
if (depth == depthB)
{
moveScores.Add(move, minmaxResult);
}
}
return value;
}
}
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