/// <summary>
/// Makes a list of all the moves player of code 'code' can make'.
/// </summary>
// XXX: TODO - optimize this.
private static IEnumerable <Move> _findMoves(AIBoard board, int code)
{
int ocode = code == 1 ? 2 : 1;
// Go through all possible moves of each piece of code 'code' on the board
foreach (var gp in board.GetPieces(code))
{
for (int i = 0; i < 16; i++)
{
int xto = gp.Item1 + positioncheck[i][0], yto = gp.Item2 + positioncheck[i][1];
if (xto >= Board.SIZE_X || xto < 0 || yto >= Board.SIZE_Y || yto < 0)
{
continue;
}
if (board[xto, yto] != 0)
{
continue;
}
// Count conversions
int gain = board.Gain(xto, yto, ocode);
if (i < 8)
{
gain += 1;
}
yield return(new Move(gp.Item1, gp.Item2, xto, yto, i >= 8, gain));
//yield return new Move(gp.x, gp.y, xto, yto, i >= 8, 0); // Conversion count is never used, so 0 is used as a placeholder
}
}
}
/// <summary>
/// Heuristic evaluation of a board state for 'goodness'.
/// </summary>
private static int _score(AIBoard b, int code, int othercode)
{
// If b is in a game over state, return a score that represents a win or loss
if (b.GameOver)
{
if (b.Count(code) > b.Count(othercode))
{
return(int.MaxValue - 10);
}
else
{
return(-(int.MaxValue - 10));
}
}
// There are 3 major components to a good board state:
// - A small perimeter (not many spaces next to friendly pieces, which indicates a good structure)
// - The number of pieces within capturing range of an enemy
// - The friendly piece count
int perimeter = 0, pieces = b.Count(code), vulnpieces = 0;
// First find all friendly pieces
foreach (var gp in b.GetPieces(code))
{
// For each space next to this piece empty, add to the perimeter sum.
perimeter += b.EmptyAdjacent(gp.Item1, gp.Item2);
// If piece can be captured, add to vulnerable pieces.
if (b.IsVulnerable(gp.Item1, gp.Item2, othercode))
{
vulnpieces++;
}
}
// Bring together the scores and apply math to generate the best representative score of the board
return(25 * pieces - 8 * vulnpieces - 2 * perimeter); // Mess around with coefficients until ai works
}