public IterativeSearch(Board board, long maxNodes = long.MaxValue)
{
_root = new Board(board);
_killers = new KillerMoves(4);
_history = new History();
_maxNodes = maxNodes;
}
internal static IEnumerable <(Move Move, Board Board)> Play(Board position, int depth, KillerMoves killers, History history)
{
//1. Is there a known best move for this position? (PV Node)
if (Transpositions.GetBestMove(position, out Move bestMove))
{
var nextPosition = new Board(position, bestMove);
yield return(bestMove, nextPosition);
}
//2. Try all captures ordered by Mvv-Lva
foreach (var capture in MoveList.SortedCaptures(position))
{
var nextPosition = new Board(position, capture);
if (!nextPosition.IsChecked(position.SideToMove))
{
yield return(capture, nextPosition);
}
}
//3. Play quiet moves that have caused a beta cutoff elsewhere if available
foreach (Move killer in killers.Get(depth))
{
if (position[killer.ToSquare] != Piece.None || !position.IsPlayable(killer))
{
continue;
}
var nextPosition = new Board(position, killer);
if (!nextPosition.IsChecked(position.SideToMove))
{
yield return(killer, nextPosition);
}
}
//4. Play the remaining quiet moves ordered by history
foreach (var move in MoveList.SortedQuiets(position, history))
{
if (killers.Contains(depth, move))
{
continue;
}
var nextPosition = new Board(position, move);
if (!nextPosition.IsChecked(position.SideToMove))
{
yield return(move, nextPosition);
}
}
}