2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2009 Marco Costalba
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/>.
38 History::History() { clear(); }
41 /// History::clear() clears the history tables
43 void History::clear() {
44 memset(history, 0, 2 * 8 * 64 * sizeof(int));
45 memset(successCount, 0, 2 * 8 * 64 * sizeof(int));
46 memset(failureCount, 0, 2 * 8 * 64 * sizeof(int));
50 /// History::success() registers a move as being successful. This is done
51 /// whenever a non-capturing move causes a beta cutoff in the main search.
52 /// The three parameters are the moving piece, the destination square, and
55 void History::success(Piece p, Square to, Depth d) {
57 assert(piece_is_ok(p));
58 assert(square_is_ok(to));
60 history[p][to] += int(d) * int(d);
61 successCount[p][to]++;
63 // Prevent history overflow
64 if (history[p][to] >= HistoryMax)
65 for (int i = 0; i < 16; i++)
66 for (int j = 0; j < 64; j++)
71 /// History::failure() registers a move as being unsuccessful. The function is
72 /// called for each non-capturing move which failed to produce a beta cutoff
73 /// at a node where a beta cutoff was finally found.
75 void History::failure(Piece p, Square to) {
77 assert(piece_is_ok(p));
78 assert(square_is_ok(to));
80 failureCount[p][to]++;
84 /// History::move_ordering_score() returns an integer value used to order the
85 /// non-capturing moves in the MovePicker class.
87 int History::move_ordering_score(Piece p, Square to) const {
89 assert(piece_is_ok(p));
90 assert(square_is_ok(to));
92 return history[p][to];
96 /// History::ok_to_prune() decides whether a move has been sufficiently
97 /// unsuccessful that it makes sense to prune it entirely.
99 bool History::ok_to_prune(Piece p, Square to, Depth d) const {
101 assert(piece_is_ok(p));
102 assert(square_is_ok(to));
104 return (int(d) * successCount[p][to] < failureCount[p][to]);