// Checks first level and makes final call
public static Vector2 MakeDecision(BoardState board, int depth)
{
depth--;
double maxScore = double.MinValue;
Vector2 bestMove = new Vector2(0, 0);
ArrayList moves = board.AvailableMoves(false);
foreach (Vector2 move in moves)
{
BoardState newBoard = board.CreateCopy();
newBoard.AIEnabled = true;
newBoard.PlacePiece((int)move.x, (int)move.y, false);
double score = Evaluation.EvaluateBoard(newBoard, BoardState.Pieces.white, BoardState.Pieces.black);
if (depth > 0)
{
score += SearchDepth(newBoard, true, -1, depth);
}
if (score > maxScore)
{
maxScore = score;
bestMove = move;
}
GameObject.Destroy(newBoard.gameObject);
}
return(bestMove);
}
private static double SearchDepth(BoardState board, bool isBlack, int miniMaxVal, int depth)
{
depth--;
if (depth < 25)
{
Debug.Log(depth);
}
double maxScore = int.MinValue;
BoardState.Pieces myPiece;
BoardState.Pieces opponentPiece;
ArrayList moves = board.AvailableMoves(isBlack);
if (isBlack)
{
myPiece = BoardState.Pieces.black;
opponentPiece = BoardState.Pieces.white;
}
else
{
myPiece = BoardState.Pieces.white;
opponentPiece = BoardState.Pieces.black;
}
foreach (Vector2 move in moves)
{
BoardState newBoard = board.CreateCopy();
newBoard.AIEnabled = true;
newBoard.PlacePiece((int)move.x, (int)move.y, isBlack);
double score = Evaluation.EvaluateBoard(newBoard, myPiece, opponentPiece);
if (depth > 0)
{
score += SearchDepth(newBoard, !isBlack, -1 * miniMaxVal, depth);
}
if (score > maxScore)
{
maxScore = score;
}
GameObject.Destroy(newBoard.gameObject);
}
return(miniMaxVal * maxScore);
}
// Evaluation criteria adpated from: https://kartikkukreja.wordpress.com/2013/03/30/heuristic-function-for-reversiothello/
public static double EvaluateBoard(BoardState board, BoardState.Pieces myPiece, BoardState.Pieces opponentPiece)
{
int my_tiles = 0, opp_tiles = 0, i, j, k, my_front_tiles = 0, opp_front_tiles = 0, x, y;
double p = 0, c = 0, l = 0, m = 0, f = 0, d = 0;
int[] X1 = { -1, -1, 0, 1, 1, 1, 0, -1 };
int[] Y1 = { 0, 1, 1, 1, 0, -1, -1, -1 };
int[,] V = new int[8, 8]
{
{ 20, -3, 11, 8, 8, 11, -3, 20 },
{ -3, -7, -4, 1, 1, -4, -7, -3 },
{ 11, -4, 2, 2, 2, 2, -4, 11 },
{ 8, 1, 2, -3, -3, 2, 1, 8 },
{ 8, 1, 2, -3, -3, 2, 1, 8 },
{ 11, -4, 2, 2, 2, 2, -4, 11 },
{ -3, -7, -4, 1, 1, -4, -7, -3 },
{ 20, -3, 11, 8, 8, 11, -3, 20 },
};
// Piece difference, frontier disks and disk squares
for (i = 0; i < 8; i++)
{
for (j = 0; j < 8; j++)
{
if (board.board[i, j] == myPiece)
{
d += V[i, j];
my_tiles++;
}
else if (board.board[i, j] == opponentPiece)
{
d -= V[i, j];
opp_tiles++;
}
if (board.board[i, j] != BoardState.Pieces.empty)
{
for (k = 0; k < 8; k++)
{
x = i + X1[k]; y = j + Y1[k];
if (x >= 0 && x < 8 && y >= 0 && y < 8 && board.board[i, j] == BoardState.Pieces.empty)
{
if (board.board[i, j] == myPiece)
{
my_front_tiles++;
}
else
{
opp_front_tiles++;
}
break;
}
}
}
}
}
if (my_tiles > opp_tiles)
{
p = (100.0 * my_tiles) / (my_tiles + opp_tiles);
}
else if (my_tiles < opp_tiles)
{
p = -(100.0 * opp_tiles) / (my_tiles + opp_tiles);
}
else
{
p = 0;
}
if (my_front_tiles > opp_front_tiles)
{
f = -(100.0 * my_front_tiles) / (my_front_tiles + opp_front_tiles);
}
else if (my_front_tiles < opp_front_tiles)
{
f = (100.0 * opp_front_tiles) / (my_front_tiles + opp_front_tiles);
}
else
{
f = 0;
}
// Corner occupancy
my_tiles = opp_tiles = 0;
if (board.board[0, 0] == myPiece)
{
my_tiles++;
}
else if (board.board[0, 0] == opponentPiece)
{
opp_tiles++;
}
if (board.board[0, 7] == myPiece)
{
my_tiles++;
}
else if (board.board[0, 7] == opponentPiece)
{
opp_tiles++;
}
if (board.board[7, 0] == myPiece)
{
my_tiles++;
}
else if (board.board[7, 0] == opponentPiece)
{
opp_tiles++;
}
if (board.board[7, 7] == myPiece)
{
my_tiles++;
}
else if (board.board[7, 7] == opponentPiece)
{
opp_tiles++;
}
c = 25 * (my_tiles - opp_tiles);
// Corner closeness
my_tiles = opp_tiles = 0;
if (board.board[0, 0] == BoardState.Pieces.empty)
{
if (board.board[0, 1] == myPiece)
{
my_tiles++;
}
else if (board.board[0, 1] == opponentPiece)
{
opp_tiles++;
}
if (board.board[1, 1] == myPiece)
{
my_tiles++;
}
else if (board.board[1, 1] == opponentPiece)
{
opp_tiles++;
}
if (board.board[1, 0] == myPiece)
{
my_tiles++;
}
else if (board.board[1, 0] == opponentPiece)
{
opp_tiles++;
}
}
if (board.board[0, 7] == BoardState.Pieces.empty)
{
if (board.board[0, 6] == myPiece)
{
my_tiles++;
}
else if (board.board[0, 6] == opponentPiece)
{
opp_tiles++;
}
if (board.board[1, 6] == myPiece)
{
my_tiles++;
}
else if (board.board[1, 6] == opponentPiece)
{
opp_tiles++;
}
if (board.board[1, 7] == myPiece)
{
my_tiles++;
}
else if (board.board[1, 7] == opponentPiece)
{
opp_tiles++;
}
}
if (board.board[7, 0] == BoardState.Pieces.empty)
{
if (board.board[7, 1] == myPiece)
{
my_tiles++;
}
else if (board.board[7, 1] == opponentPiece)
{
opp_tiles++;
}
if (board.board[6, 1] == myPiece)
{
my_tiles++;
}
else if (board.board[6, 1] == opponentPiece)
{
opp_tiles++;
}
if (board.board[6, 0] == myPiece)
{
my_tiles++;
}
else if (board.board[6, 0] == opponentPiece)
{
opp_tiles++;
}
}
if (board.board[7, 7] == BoardState.Pieces.empty)
{
if (board.board[6, 7] == myPiece)
{
my_tiles++;
}
else if (board.board[6, 7] == opponentPiece)
{
opp_tiles++;
}
if (board.board[6, 6] == myPiece)
{
my_tiles++;
}
else if (board.board[6, 6] == opponentPiece)
{
opp_tiles++;
}
if (board.board[7, 6] == myPiece)
{
my_tiles++;
}
else if (board.board[7, 6] == opponentPiece)
{
opp_tiles++;
}
}
l = -12.5 * (my_tiles - opp_tiles);
// Mobility
my_tiles = board.AvailableMoves((myPiece == BoardState.Pieces.black)).Count;
opp_tiles = board.AvailableMoves((myPiece != BoardState.Pieces.black)).Count;
if (my_tiles > opp_tiles)
{
m = (100.0 * my_tiles) / (my_tiles + opp_tiles);
}
else if (my_tiles < opp_tiles)
{
m = -(100.0 * opp_tiles) / (my_tiles + opp_tiles);
}
else
{
m = 0;
}
// final weighted score
double score = (10 * p) + (801.724 * c) + (382.026 * l) + (78.922 * m) + (74.396 * f) + (10 * d);
return(score);
}
