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/>.
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 move itself, and the
55 void History::success(Piece p, Move m, Depth d) {
56 assert(piece_is_ok(p));
57 assert(move_is_ok(m));
59 history[p][move_to(m)] += int(d) * int(d);
60 successCount[p][move_to(m)]++;
62 // Prevent history overflow:
63 if(history[p][move_to(m)] >= HistoryMax)
64 for(int i = 0; i < 16; i++)
65 for(int j = 0; j < 64; j++)
70 /// History::failure() registers a move as being unsuccessful. The function is
71 /// called for each non-capturing move which failed to produce a beta cutoff
72 /// at a node where a beta cutoff was finally found.
74 void History::failure(Piece p, Move m) {
75 assert(piece_is_ok(p));
76 assert(move_is_ok(m));
78 failureCount[p][move_to(m)]++;
82 /// History::move_ordering_score() returns an integer value used to order the
83 /// non-capturing moves in the MovePicker class.
85 int History::move_ordering_score(Piece p, Move m) const {
86 assert(piece_is_ok(p));
87 assert(move_is_ok(m));
89 return history[p][move_to(m)];
93 /// History::ok_to_prune() decides whether a move has been sufficiently
94 /// unsuccessful that it makes sense to prune it entirely.
96 bool History::ok_to_prune(Piece p, Move m, Depth d) const {
97 assert(piece_is_ok(p));
98 assert(move_is_ok(m));
100 return (int(d) * successCount[p][move_to(m)] < failureCount[p][move_to(m)]);