public static int Heuristic(ulong board, List <ulong> possible_moves = null)
{
if (Board.CurrentPlayerHasLessThanThree(board))
{
return(-1000); // this is a losing position
}
if (possible_moves == null)
{
possible_moves = Board.GetMoves(board);
}
if (possible_moves.Count == 0)
{
return(-1000); // this is a losing position
}
/* We score +1 for a move, +2 if it forms a mill */
int score = 0;
var old_runs = Board.GetRunPieces(board);
foreach (var move in possible_moves)
{
var new_runs = Board.GetRunPieces(move);
if (new_runs != old_runs && Board.CountBits(new_runs) >= Board.CountBits(old_runs))
{
score += 5;
}
else
{
score++;
}
}
return(score);
}
int minimax(ulong board, int depth, bool maximizingPlayer, out ulong move)
{
if (cache_v[depth].TryGetValue(board, out var cached))
{
move = cache_move[depth][board]; return(cached);
}
var children = Board.GetMoves(board);
if (depth == 0 || Board.CurrentPlayerHasLessThanThree(board) || children.Count == 0)
{
move = 0UL;
return(Heuristic(board, IsWhite, children));
}
if (maximizingPlayer)
{
var bestValue = int.MinValue;
ulong best_move = 0UL;
foreach (var child in children)
{
var v = minimax(child, depth - 1, false, out var unused);
if (v > bestValue)
{
bestValue = v;
best_move = child;
}
}
move = best_move;
cache_v[depth][board] = bestValue;
cache_move[depth][board] = move;
return(bestValue);
}
else
{
// minimizing player
var bestValue = int.MaxValue;
ulong best_move = 0UL;
foreach (var child in children)
{
var v = minimax(child, depth - 1, true, out var unused);
if (v < bestValue)
{
bestValue = v;
best_move = child;
}
}
move = best_move;
cache_v[depth][board] = bestValue;
cache_move[depth][board] = move;
return(bestValue);
}
}
public bool MakeTurn()
{
if (next_player)
{
Console.WriteLine("Turn: " + (turn++).ToString());
}
Board.PrintBoard(board);
List <ulong> AllowedMoves = null;
if (Board.CurrentPlayerHasLessThanThree(board) || (AllowedMoves = Board.GetMoves(board)).Count == 0)
{
// Current player has lost
if (next_player)
{
Console.Write("Black");
}
else
{
Console.Write("White");
}
Console.WriteLine(" Wins!");
return(false);
}
while (true)
{
ulong move;
if (next_player)
{
move = White.GetMove(board);
}
else
{
move = Black.GetMove(board);
}
// ensure move is valid
foreach (var allowed_move in AllowedMoves)
{
if (allowed_move == move)
{
next_player = !next_player;
DumpMove(board, move);
board = move;
return(true);
}
}
// move is invalid
if (next_player)
{
White.IllegalMove(move);
}
else
{
Black.IllegalMove(move);
}
// request again
}
}