/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2014 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
/// The Stats struct stores moves statistics. According to the template parameter
-/// the class can store History and Countermoves. History records how often
+/// the class can store History, Gains and Countermoves. History records how often
/// different moves have been successful or unsuccessful during the current search
-/// and is used for reduction and move ordering decisions.
+/// 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.
/// Countermoves store the move that refute a previous one. Entries are stored
-/// according only to moving piece and destination square, hence two moves with
+/// using only the moving piece and destination square, hence two moves with
/// different origin but same destination and piece will be considered identical.
-template<typename T>
+template<bool Gain, typename T>
struct Stats {
static const Value Max = Value(2000);
void update(Piece p, Square to, Value v) {
- if (abs(table[p][to] + v) < Max)
+ if (Gain)
+ table[p][to] = std::max(v, table[p][to] - 1);
+
+ else if (abs(table[p][to] + v) < Max)
table[p][to] += v;
}
T table[PIECE_NB][SQUARE_NB];
};
-typedef Stats<Value> HistoryStats;
-typedef Stats<std::pair<Move, Move> > CountermovesStats;
+typedef Stats< true, Value> GainsStats;
+typedef Stats<false, Value> HistoryStats;
+typedef Stats<false, std::pair<Move, Move> > MovesStats;
/// MovePicker class is used to pick one pseudo legal move at a time from the
public:
MovePicker(const Position&, Move, Depth, const HistoryStats&, Square);
MovePicker(const Position&, Move, const HistoryStats&, PieceType);
- MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Search::Stack*);
+ MovePicker(const Position&, Move, Depth, const HistoryStats&, Move*, Move*, Search::Stack*);
template<bool SpNode> Move next_move();
const HistoryStats& history;
Search::Stack* ss;
Move* countermoves;
+ Move* followupmoves;
Depth depth;
Move ttMove;
- ExtMove killers[4];
+ ExtMove killers[6];
Square recaptureSquare;
int captureThreshold, stage;
ExtMove *cur, *end, *endQuiets, *endBadCaptures;