2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
11 Stockfish is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program. If not, see <http://www.gnu.org/licenses/>.
20 #if !defined(HISTORY_H_INCLUDED)
21 #define HISTORY_H_INCLUDED
31 /// The History class stores statistics about how often different moves
32 /// have been successful or unsuccessful during the current search. These
33 /// statistics are used for reduction and move ordering decisions. History
34 /// entries are stored according only to moving piece and destination square,
35 /// in particular two moves with different origin but same destination and
36 /// same piece will be considered identical.
41 History() { clear(); }
43 int value(Piece p, Square to) const;
44 void update(Piece p, Square to, Value delta);
45 Value gain(Piece p, Square to) const;
46 void update_gain(Piece p, Square to, Value delta);
48 static const int MaxValue = (1 << 29); // To avoid an overflow
51 Value history[16][64]; // [piece][to_square]
52 Value maxGains[16][64]; // [piece][to_square]
55 inline void History::clear() {
56 memset(history, 0, 16 * 64 * sizeof(int));
57 memset(maxGains, 0, 16 * 64 * sizeof(int));
60 inline int History::value(Piece p, Square to) const {
61 return history[p][to];
64 inline void History::update(Piece p, Square to, Value bonus) {
65 if (abs(history[p][to]) < MaxValue) history[p][to] += bonus;
68 inline Value History::gain(Piece p, Square to) const {
69 return maxGains[p][to];
72 inline void History::update_gain(Piece p, Square to, Value gain) {
73 maxGains[p][to] = (gain >= maxGains[p][to] ? gain : maxGains[p][to] - 1);
76 #endif // !defined(HISTORY_H_INCLUDED)