private double AlphaBeta(Board b, int depth, double alpha, double beta, int colour, ref Move bestMoveYet)
{
if (depth == 0)
return b.ScoreBoard();
else
{
if (colour == 1)
{
for (int i = 0; i < b.AllMovesCount; i++)
{
Move move = b.AllMoves[i];
double result = AlphaBeta(b.GetBoardAfterMove(move.From, move.To), depth - 1, alpha, beta, -colour, ref bestMoveYet);
nodesVisited++;
if (result > alpha)
{
alpha = result;
if (depth == MaxAlphaBetaDepth) bestMoveYet = move;
}
if (beta <= alpha)
{
betaSkips++;
goto skip1;
}
}
skip1:
return alpha;
}
else if (colour == -1)
{
for (int i = 0; i < b.AllMovesCount; i++)
{
Move move = b.AllMoves[i];
double result = AlphaBeta(b.GetBoardAfterMove(move.From, move.To), depth - 1, alpha, beta, -colour, ref bestMoveYet);
nodesVisited++;
if (result < beta)
{
beta = result;
if (depth == MaxAlphaBetaDepth) bestMoveYet = move;
//bestMoveYet = move;
}
if (beta <= alpha)
{
betaSkips++;
goto skip2;
}
}
skip2:
return beta;
}
else throw new ApplicationException();
}
throw new ApplicationException();
}
private double Negamax(Board b, int depth, double alpha, double beta, int colour)
{
Tuple<int, double> tuple = m_Zasher.GetDepthScoreTuple(b);
// If the same or better calculation of this state has already been made, use it.
if (tuple != null && tuple.Item1 >= depth && depth < MaxNegamaxDepth)
{
if (depth > 0) hashUsed++;
if (depth >= 0) hashUsed++;
return colour * tuple.Item2;
}
if (depth == 0)
{
double score = b.ScoreBoard();
m_Zasher.SetDepthScoreTuple(b, new Tuple<int, double>(0, score));
hashNotUsed++;
return colour * score;
}
else
{
for (int i = 0; i < b.AllMovesCount; i++)
{
Move move = b.AllMoves[i];
Board boardAfterMove = new Board(b);
bool moveOk = boardAfterMove.MakeMove(move.From, move.To);
if (moveOk)
{
double score = -Negamax(boardAfterMove, depth - 1, -beta, -alpha, -colour);
// Cache this score
m_Zasher.AddIfBetter(boardAfterMove, new Tuple<int, double>(depth - 1, colour * score));
nodesVisited++;
if (score >= beta)
return score;
if (score > alpha)
{
alpha = score;
}
if (depth == MaxNegamaxDepth)
{
m_RankedMoves.Add(new Tuple<Move, double>(move, colour * score));
m_Zasher.AddIfBetter(b, new Tuple<int, double>(depth, colour * score));
}
}
}
return alpha;
}
}