/// <summary>
/// Calculate the heuristic for the state of the board, based on this player.
/// </summary>
/// <param name="board">The current state of the board in the search.</param>
/// <returns>The heuristic for this node in the search.</returns>
private int CalculateMiniMaxHeuristic(Board board)
{
// safety-check the board parameter
if (board == null)
{
throw new ArgumentNullException("board");
}
int myPieces = board.GetColorCount(BoardColor);
int otherPieces = board.GetOppositeColorCount(BoardColor);
int heuristic = myPieces - otherPieces;
// in order to stop the algorithm from going straight to the nearest edge,
// introduce some randomness
if (myPieces + otherPieces <= randomHeuristicCutoff)
{
heuristic += (int)(2.0 * random.NextDouble());
}
return(heuristic);
}
/// <summary>
/// Update the AI player.
/// </summary>
/// <param name="board">The current game board.</param>
public override void Update(Board board)
{
// safety-check the board parameter
if (board == null)
{
throw new ArgumentNullException("board");
}
// if it's not our turn, then we're done
if (board.CurrentColor != BoardColor)
{
return;
}
// generate a new move.
Move move;
bool moveFound = false;
// in order to begin the game with some variety, the AI will make random
// acceptable moves until 25 moves have been made, then switch to minimax
int totalPieces = board.GetColorCount(BoardColor) +
board.GetOppositeColorCount(BoardColor);
if (totalPieces <= randomMoveCutoff)
{
moveFound = GenerateMoveRandom(board, out move);
}
else
{
moveFound = GenerateMoveMiniMax(board, maximumDepth, out move);
}
// apply the move
if (moveFound)
{
board.ApplyMove(BoardColor, move);
}
else
{
board.Pass(BoardColor);
}
}
