/// Constructors of the MovePicker class. As arguments we pass information
/// to help it to return the (presumably) good moves first, to decide which
/// moves to return (in the quiescence search, for instance, we only want to
/// search captures, promotions and some checks) and how important good move
/// ordering is at the current node.
public MovePicker(Position p, Move ttm, Depth d, HistoryStats h, Move[] cm, Move[] fm, Stack s)
{
pos = p;
history = h;
depth = d;
Debug.Assert(d > DepthS.DEPTH_ZERO);
cur = end = 0;
endBadCaptures = Types.MAX_MOVES - 1;
countermoves = cm;
followupmoves = fm;
ss = s;
if (p.checkers() != 0)
{
stage = StagesS.EVASION;
}
else
{
stage = StagesS.MAIN_SEARCH;
}
ttMove = (ttm != 0 && pos.pseudo_legal(ttm) ? ttm : MoveS.MOVE_NONE);
end += ((ttMove != MoveS.MOVE_NONE) ? 1 : 0);
}
public MovePicker(Position p, Move ttm, Depth d, HistoryStats h, Square sq)
{
pos = p;
history = h;
cur = 0;
end = 0;
Debug.Assert(d <= DepthS.DEPTH_ZERO);
if (p.checkers() != 0)
{
stage = StagesS.EVASION;
}
else if (d > DepthS.DEPTH_QS_NO_CHECKS)
{
stage = StagesS.QSEARCH_0;
}
else if (d > DepthS.DEPTH_QS_RECAPTURES)
{
stage = StagesS.QSEARCH_1;
// Skip TT move if is not a capture or a promotion. This avoids qsearch
// tree explosion due to a possible perpetual check or similar rare cases
// when TT table is full.
if (ttm != 0 && !pos.capture_or_promotion(ttm))
{
ttm = MoveS.MOVE_NONE;
}
}
else
{
stage = StagesS.RECAPTURE;
recaptureSquare = sq;
ttm = MoveS.MOVE_NONE;
}
ttMove = (ttm != 0 && pos.pseudo_legal(ttm) ? ttm : MoveS.MOVE_NONE);
end += ((ttMove != MoveS.MOVE_NONE) ? 1 : 0);
}
public MovePicker(Position p, Move ttm, HistoryStats h, PieceType pt)
{
pos = p;
history = h;
cur = 0;
end = 0;
Debug.Assert(pos.checkers() == 0);
stage = StagesS.PROBCUT;
// In ProbCut we generate only captures that are better than the parent's
// captured piece.
captureThreshold = Position.PieceValue[PhaseS.MG][pt];
ttMove = (ttm != 0 && pos.pseudo_legal(ttm) ? ttm : MoveS.MOVE_NONE);
if (ttMove != 0 && (!pos.capture(ttMove) || pos.see(ttMove) <= captureThreshold))
{
ttMove = MoveS.MOVE_NONE;
}
end += ((ttMove != MoveS.MOVE_NONE) ? 1 : 0);
}