public SearchResult(int node, Move move, TimeSpan time)
{
VisitedNode = node;
BestMove = move;
Elapse = time;
}
private int Negamax(int depth, int alpha, int beta, int color, bool debug, bool allowNull)
{
Stopwatch sw = null;
if (depth == MaxDepth)
{
sw = new Stopwatch();
sw.Start();
}
if (depth <= 0)
{
int score = Evaluate(color, debug, depth = 0);
return(score);
}
//Null move
if (allowNull)
{
int nullTurn = -color;
int nullValue = -Negamax(depth - 1 - 2, -beta, -beta + 1, nullTurn, debug, false);
if (nullValue >= beta)
{
return(nullValue); //Cut off
}
}
List <Move> possibleMoves = null;
possibleMoves = (debug) ? DebugLegalMoves() : examinedBoard.LegalMovesForPlayer(color);
if (possibleMoves.Count == 0)
{
int score = Evaluate(color, debug, depth);
return(score);
}
int bestValue = Int32.MinValue;
Move bestMove = null;
OrderMove(possibleMoves, depth);
foreach (Move eleMove in possibleMoves)
{
visitedNode++;
examinedBoard.MakeMove(eleMove);
//Print information
//Console.Write("\n" + new string('\t', MaxDepth - depth) + eleMove.ToString());
int value = -Negamax(depth - 1, -beta, -alpha, -color, debug, nullPruning);
examinedBoard.UndoMove(eleMove);
//save hisEval
if (depth == MaxDepth)
{
hisEval[eleMove.ToString()] = value;
}
// We found a new max, also keep track of move
if (value > bestValue)
{
bestValue = value;
bestMove = eleMove;
}
// If our max is greater than our lower bound, update our lower bound
if (value > alpha)
{
alpha = value;
}
// Alpha-beta pruning
if (alpha >= beta)
{
//Console.Write(new string('\t', MaxDepth - depth) + "Cut off");
//Save killer move
if (eleMove.Capture == '.')
{
searchKiller[MaxDepth - depth, 1] = searchKiller[MaxDepth - depth, 0];
searchKiller[MaxDepth - depth, 0] = eleMove;
}
//save history
SaveHistoryHeuristic(eleMove, depth);
break;
}
}
if (depth == MaxDepth)
{
sw.Stop();
Result = new SearchResult(visitedNode, bestMove, sw.Elapsed);
}
return(bestValue);
}
private MNResult AlphaBeta(int depth, int beta, int alpha, Move move, bool player, bool debug = false)
{
//BLACK is max player
bool isMaxPlayer = (player == BLACK) ? true : false;
if (depth == 0)
{
return(EvaluateNode(move, player, debug));
}
List <Move> possibleMoves = null;
if (!debug)
{
possibleMoves = examinedBoard.PossibleMoves(player);
}
else
{
Console.Write("How many moves are there:");
int count = Convert.ToInt32(Console.ReadLine());
possibleMoves = new List <Move>();
for (int i = 0; i < count; i++)
{
Move debugMove = new Move(1, 4, 3, 4, this.examinedBoard);
possibleMoves.Add(debugMove);
}
}
if (possibleMoves.Count == 0)
{
return(EvaluateNode(move, player, debug));
}
//sort later
foreach (Move eleMove in possibleMoves)
{
examinedBoard.MakeMove(eleMove);
bool nextPlayer = !player;
MNResult result = AlphaBeta(depth - 1, beta, alpha, eleMove, nextPlayer, debug);
int value = result.Value;
examinedBoard.UndoMove(eleMove);
//BLACK is Max Player
if (isMaxPlayer)
{
if (value > alpha) //Max Nodes can only make restriction on the lower bound
{
alpha = value;
if (depth == MaxDepth)
{
move = result.Move;
}
}
}
else
{
if (value < beta)
{
beta = value;
if (depth == MaxDepth)
{
move = result.Move;
}
}
}
if (alpha >= beta) //pruning
{
if (isMaxPlayer)
{
return(new MNResult(move, alpha));
}
else
{
return(new MNResult(move, beta));
}
}
}
// Travel all child node, no prunning
if (isMaxPlayer)
{
//value of node is alpha value
return(new MNResult(move, alpha));
}
else
{
//value of min node is beta value
return(new MNResult(move, beta));
}
}
