/// <summary>
///
/// </summary>
/// <param name="board"></param>
/// <param name="protocol">Protocol will be used to write output of bestline</param>
public Engine(Board board, IProtocol protocol)
{
Exit = false;
Board = board;
Protocol = protocol;
elapsedTime = new Stopwatch();
historyMoves = new HistoryMoves();
killerMoves = new KillerMoves();
}
/// <summary>
/// Calculates best line in given depth
/// </summary>
/// <param name="maxDepth"></param>
/// <param name="timeLimit">Time limit in millisecond</param>
/// <returns></returns>
public Result Search(long timeLimit)
{
this.timeLimit = timeLimit;
int infinity = int.MaxValue;
int alpha = -infinity, beta = infinity, depth = 0, nodesCount = 0;
Result previousResult = null;
elapsedTime.Restart();
Result result;
var pv = new List<Move>();
Exit = false;
historyMoves = new HistoryMoves();
killerMoves = new KillerMoves();
for (iterationPly = 1; ; )
{
var score = AlphaBeta(alpha, beta, iterationPly, depth, pv, NullMove.Disabled, ref nodesCount);
if (score <= alpha || score >= beta)
{
//Aspiration window failed so make full window search again.
alpha = -infinity;
beta = infinity;
continue;
}
if ((!HaveTime() || Exit) && iterationPly > 1) //time control and stop mode
{
return previousResult;
}
alpha = score - Pawn.Piecevalue / 4; //Narrow Aspiration window
beta = score + Pawn.Piecevalue / 4;
//Save principal variation for next iteration
previousPV = new List<Move>();
previousPV.AddRange(pv);
result = new Result(iterationPly, score, elapsedTime.ElapsedMilliseconds, nodesCount, pv);
previousResult = new Result(iterationPly, score, elapsedTime.ElapsedMilliseconds, nodesCount, previousPV);
if (result.BestLine.Count > 0)
Protocol.WriteOutput(result);
if (Math.Abs(score) == Board.CheckMateValue || Exit || iterationPly>30) break;
iterationPly++;
nodesCount = 0;
}
return result;
}