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
27 /// The History class stores statistics about how often different moves
28 /// have been successful or unsuccessful during the current search. These
29 /// statistics are used for reduction and move ordering decisions. History
30 /// entries are stored according only to moving piece and destination square,
31 /// in particular two moves with different origin but same destination and
32 /// same piece will be considered identical.
38 Value value(Piece p, Square to) const;
39 void add(Piece p, Square to, Value bonus);
40 Value gain(Piece p, Square to) const;
41 void update_gain(Piece p, Square to, Value g);
43 static const Value MaxValue = Value(2000);
46 Value history[16][64]; // [piece][to_square]
47 Value maxGains[16][64]; // [piece][to_square]
50 inline void History::clear() {
51 memset(history, 0, 16 * 64 * sizeof(Value));
52 memset(maxGains, 0, 16 * 64 * sizeof(Value));
55 inline Value History::value(Piece p, Square to) const {
56 return history[p][to];
59 inline void History::add(Piece p, Square to, Value bonus) {
60 if (abs(history[p][to] + bonus) < MaxValue) history[p][to] += bonus;
63 inline Value History::gain(Piece p, Square to) const {
64 return maxGains[p][to];
67 inline void History::update_gain(Piece p, Square to, Value g) {
68 maxGains[p][to] = std::max(g, maxGains[p][to] - 1);
71 #endif // !defined(HISTORY_H_INCLUDED)