/// search captures, promotions, and some checks) and how important good move
/// ordering is at the current node.
+/// MovePicker constructor for the main search
MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
const PieceToHistory** ch, Move cm, Move* killers_p)
: pos(p), mainHistory(mh), contHistory(ch), countermove(cm),
stage += (ttMove == MOVE_NONE);
}
-MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh,
- const PieceToHistory** ch, Square s)
- : pos(p), mainHistory(mh), contHistory(ch) {
+/// MovePicker constructor for quiescence search
+MovePicker::MovePicker(const Position& p, Move ttm, Depth d, const ButterflyHistory* mh, Square s)
+ : pos(p), mainHistory(mh) {
assert(d <= DEPTH_ZERO);
stage += (ttMove == MOVE_NONE);
}
+/// MovePicker constructor for ProbCut: we generate captures with SEE higher
+/// than or equal to the given threshold.
MovePicker::MovePicker(const Position& p, Move ttm, Value th)
: pos(p), threshold(th) {
assert(!pos.checkers());
stage = PROBCUT;
-
- // In ProbCut we generate captures with SEE higher than or equal to the given threshold
ttMove = ttm
&& pos.pseudo_legal(ttm)
&& pos.capture(ttm)
stage += (ttMove == MOVE_NONE);
}
+/// score() assigns a numerical value to each move in a list, used for sorting.
+/// Captures are ordered by Most Valuable Victim (MVV), preferring captures
+/// near our home rank. Quiets are ordered using the histories.
+template<GenType Type>
+void MovePicker::score() {
-/// score() assigns a numerical value to each move in a move list. The moves with
-/// highest values will be picked first.
-template<>
-void MovePicker::score<CAPTURES>() {
- // Winning and equal captures in the main search are ordered by MVV, preferring
- // captures near our home rank. Surprisingly, this appears to perform slightly
- // better than SEE-based move ordering: exchanging big pieces before capturing
- // a hanging piece probably helps to reduce the subtree size.
- // In the 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, saving some SEE calls in case we get a cutoff.
- for (auto& m : *this)
- m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(200 * relative_rank(pos.side_to_move(), to_sq(m)));
-}
-
-template<>
-void MovePicker::score<QUIETS>() {
+ static_assert(Type == CAPTURES || Type == QUIETS || Type == EVASIONS, "Wrong type");
for (auto& m : *this)
- m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
- + (*contHistory[0])[pos.moved_piece(m)][to_sq(m)]
- + (*contHistory[1])[pos.moved_piece(m)][to_sq(m)]
- + (*contHistory[3])[pos.moved_piece(m)][to_sq(m)];
-}
-
-template<>
-void MovePicker::score<EVASIONS>() {
- // Try captures ordered by MVV/LVA, then non-captures ordered by stats heuristics
- for (auto& m : *this)
- if (pos.capture(m))
+ if (Type == CAPTURES)
m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
- - Value(type_of(pos.moved_piece(m))) + (1 << 28);
- else
- m.value = (*mainHistory)[pos.side_to_move()][from_to(m)];
-}
+ - Value(200 * relative_rank(pos.side_to_move(), to_sq(m)));
+
+ else if (Type == QUIETS)
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)]
+ + (*contHistory[0])[pos.moved_piece(m)][to_sq(m)]
+ + (*contHistory[1])[pos.moved_piece(m)][to_sq(m)]
+ + (*contHistory[3])[pos.moved_piece(m)][to_sq(m)];
+ else // Type == EVASIONS
+ {
+ if (pos.capture(m))
+ m.value = PieceValue[MG][pos.piece_on(to_sq(m))]
+ - Value(type_of(pos.moved_piece(m)));
+ else
+ m.value = (*mainHistory)[pos.side_to_move()][from_to(m)] - (1 << 28);
+ }
+}
/// next_move() is the most important method of the MovePicker class. It returns
/// a new pseudo legal move every time it is called, until there are no more moves