/// The Stats struct stores moves statistics. According to the template parameter
-/// the class can store both History and Gains type statistics. History records
+/// the class can store History, Gains and Refutations statistics. History records
/// how often different moves have been successful or unsuccessful during the
/// current search and is used for reduction and move ordering decisions. Gains
/// records the move's best evaluation gain from one ply to the next and is used
-/// for pruning decisions. Entries are stored according only to moving piece and
-/// destination square, in particular two moves with different origin but same
-/// destination and same piece will be considered identical.
-template<bool Gain>
+/// for pruning decisions. Refutations store the move that refute a previous one.
+/// Entries are stored according only to moving piece and destination square, in
+/// particular two moves with different origin but same destination and same piece
+/// will be considered identical.
+template<bool Gain, typename T>
struct Stats {
static const Value Max = Value(2000);
- const Value* operator[](Piece p) const { return &table[p][0]; }
+ const T* operator[](Piece p) const { return &table[p][0]; }
void clear() { memset(table, 0, sizeof(table)); }
+ void update(Piece p, Square to, Move m) { table[p][to] = m; }
void update(Piece p, Square to, Value v) {
if (Gain)
}
private:
- Value table[PIECE_NB][SQUARE_NB];
+ T table[PIECE_NB][SQUARE_NB];
};
-typedef Stats<false> History;
-typedef Stats<true> Gains;
+typedef Stats<true, Value> Gains;
+typedef Stats<false, Value> History;
+typedef Stats<false, Move> Refutations;
/// MovePicker class is used to pick one pseudo legal move at a time from the
MovePicker& operator=(const MovePicker&); // Silence a warning under MSVC
public:
- MovePicker(const Position&, Move, Depth, const History&, Search::Stack*, Value);
+ MovePicker(const Position&, Move, Depth, const History&, const Refutations&, Search::Stack*, Value);
MovePicker(const Position&, Move, Depth, const History&, Square);
MovePicker(const Position&, Move, const History&, PieceType);
template<bool SpNode> Move next_move();
Search::Stack* ss;
Depth depth;
Move ttMove;
- MoveStack killers[2];
+ MoveStack killers[3];
Square recaptureSquare;
int captureThreshold, phase;
MoveStack *cur, *end, *endQuiets, *endBadCaptures;