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 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/>.
42 /// History::clear() clears the history tables.
44 void History::clear() {
45 memset(history, 0, 2 * 8 * 64 * sizeof(int));
46 memset(successCount, 0, 2 * 8 * 64 * sizeof(int));
47 memset(failureCount, 0, 2 * 8 * 64 * sizeof(int));
51 /// History::success() registers a move as being successful. This is done
52 /// whenever a non-capturing move causes a beta cutoff in the main search.
53 /// The three parameters are the moving piece, the move itself, and the
56 void History::success(Piece p, Move m, Depth d) {
57 assert(piece_is_ok(p));
58 assert(move_is_ok(m));
60 history[p][move_to(m)] += int(d) * int(d);
61 successCount[p][move_to(m)]++;
63 // Prevent history overflow:
64 if(history[p][move_to(m)] >= 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, Move m) {
76 assert(piece_is_ok(p));
77 assert(move_is_ok(m));
79 failureCount[p][move_to(m)]++;
83 /// History::move_ordering_score() returns an integer value used to order the
84 /// non-capturing moves in the MovePicker class.
86 int History::move_ordering_score(Piece p, Move m) const {
87 assert(piece_is_ok(p));
88 assert(move_is_ok(m));
90 return history[p][move_to(m)];
94 /// History::ok_to_prune() decides whether a move has been sufficiently
95 /// unsuccessful that it makes sense to prune it entirely.
97 bool History::ok_to_prune(Piece p, Move m, Depth d) const {
98 assert(piece_is_ok(p));
99 assert(move_is_ok(m));
101 return (int(d) * successCount[p][move_to(m)] < failureCount[p][move_to(m)]);