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<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 the
// badCaptures[] array, but instead of doing it now we delay until the move
// has been picked up in pick_move_from_list(). This way we save some SEE
// calls in case we get a cutoff.
Move m;
for (ExtMove* it = moves; it != end; ++it)
{
m = it->move;
/*
評価値は取る駒の駒評価値から駒種をValueにキャストした数を引いている
引いている意味は不明
*/
it->value = PieceValue[MG][pos.piece_on(to_sq(m))]
- Value(type_of(pos.moved_piece(m)));
/*
もし指し手パターンがアンパッサンだったら
PAWNの評価値を追加する
（アンパッサンの時のPAWNの動きではto座標に敵の駒がいないので）
*/
if (type_of(m) == ENPASSANT)
it->value += PieceValue[MG][PAWN];
/*
指し手パターンが成りだったら、なった駒種の駒評価値からPAWNの駒評価値を引いたもの（昇格評価値）を追加している
*/
else if (type_of(m) == PROMOTION)
it->value += PieceValue[MG][promotion_type(m)] - PieceValue[MG][PAWN];
}
}