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/>.
21 #if !defined(HISTORY_H_INCLUDED)
22 #define HISTORY_H_INCLUDED
38 /// The History class stores statistics about how often different moves
39 /// have been successful or unsuccessful during the current search. These
40 /// statistics are used for reduction and move ordering decisions. History
41 /// entries are stored according only to moving piece and destination square,
42 /// in particular two moves with different origin but same destination and
43 /// same piece will be considered identical.
50 void success(Piece p, Square to, Depth d);
51 void failure(Piece p, Square to, Depth d);
52 int value(Piece p, Square to) const;
53 void set_gain(Piece p, Square to, Value delta);
54 Value gain(Piece p, Square to) const;
57 int history[16][64]; // [piece][square]
58 int maxStaticValueDelta[16][64]; // [piece][from_square][to_square]
63 //// Constants and variables
66 /// HistoryMax controls how often the history counters will be scaled down:
67 /// When the history score for a move gets bigger than HistoryMax, all
68 /// entries in the table are divided by 2. It is difficult to guess what
69 /// the ideal value of this constant is. Scaling down the scores often has
70 /// the effect that parts of the search tree which have been searched
71 /// recently have a bigger importance for move ordering than the moves which
72 /// have been searched a long time ago.
74 const int HistoryMax = 50000 * OnePly;
81 inline int History::value(Piece p, Square to) const {
82 return history[p][to];
85 inline Value History::gain(Piece p, Square to) const {
86 return Value(maxStaticValueDelta[p][to]);
89 #endif // !defined(HISTORY_H_INCLUDED)