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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
Copyright (C) 2008-2012 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 Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
Stockfish is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <>.
#if !defined(HISTORY_H_INCLUDED)
#include <algorithm>
#include <cstring>
#include "types.h"
/// The History class stores statistics about how often different moves
/// have been successful or unsuccessful during the current search. These
/// statistics are used for reduction and move ordering decisions. History
/// 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.
class History {
void clear();
Value value(Piece p, Square to) const;
void add(Piece p, Square to, Value bonus);
Value gain(Piece p, Square to) const;
void update_gain(Piece p, Square to, Value g);
static const Value MaxValue = Value(2000);
Value history[16][64]; // [piece][to_square]
Value maxGains[16][64]; // [piece][to_square]
inline void History::clear() {
memset(history, 0, 16 * 64 * sizeof(Value));
memset(maxGains, 0, 16 * 64 * sizeof(Value));
inline Value History::value(Piece p, Square to) const {
return history[p][to];
inline void History::add(Piece p, Square to, Value bonus) {
if (abs(history[p][to] + bonus) < MaxValue) history[p][to] += bonus;
inline Value History::gain(Piece p, Square to) const {
return maxGains[p][to];
inline void History::update_gain(Piece p, Square to, Value g) {
maxGains[p][to] = std::max(g, maxGains[p][to] - 1);
#endif // !defined(HISTORY_H_INCLUDED)
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