-/// MovePicker::score_captures(), MovePicker::score_noncaptures() and
-/// MovePicker::score_evasions() assign a numerical move ordering score
-/// to each move in a move list. The moves with highest scores will be
-/// picked first by next_move().
-
-void MovePicker::score_captures() {
- // Winning and equal captures in the main search are ordered by MVV/LVA.
- // Suprisingly, this appears to perform slightly better than SEE based
- // move ordering. The reason is probably that in a position with a winning
- // capture, capturing a more valuable (but sufficiently defended) piece
- // first usually doesn't hurt. The opponent will have to recapture, and
- // the hanging piece will still be hanging (except in the unusual cases
- // where it is possible to recapture with the hanging piece). Exchanging
- // big pieces before capturing a hanging piece probably helps to reduce
- // the subtree size.
- // In main search we want to push captures with negative SEE values to
- // badCaptures[] array, but instead of doing it now we delay till when
- // the move has been picked up in pick_move_from_list(), this way we save
- // some SEE calls in case we get a cutoff (idea from Pablo Vazquez).
- Move m;
-
- for (MoveStack* it = moves; it != end; ++it)
- {
- m = it->move;
- it->score = PieceValue[MG][pos.piece_on(to_sq(m))]
- - type_of(pos.piece_moved(m));
-
- if (type_of(m) == PROMOTION)
- it->score += PieceValue[MG][promotion_type(m)];
- }
-}
-
-void MovePicker::score_noncaptures() {
-
- Move m;
-
- for (MoveStack* it = moves; it != end; ++it)
- {
- m = it->move;
- it->score = Hist[pos.piece_moved(m)][to_sq(m)];
- }
-}
-
-void MovePicker::score_evasions() {
- // Try good captures ordered by MVV/LVA, then non-captures if destination square
- // is not under attack, ordered by history value, then bad-captures and quiet
- // moves with a negative SEE. This last group is ordered by the SEE score.
- Move m;
- int seeScore;
-
- if (end < moves + 2)
- return;
-
- for (MoveStack* it = moves; it != end; ++it)
- {
- m = it->move;
- if ((seeScore = pos.see_sign(m)) < 0)
- it->score = seeScore - History::Max; // Be sure we are at the bottom
- else if (pos.is_capture(m))
- it->score = PieceValue[MG][pos.piece_on(to_sq(m))]
- - type_of(pos.piece_moved(m)) + History::Max;
- else
- it->score = Hist[pos.piece_moved(m)][to_sq(m)];
- }