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436fa5c8fa
Both with added comment and changing the API to reflect that only destination square and moved piece is important for history. No functional change. Signed-off-by: Marco Costalba <mcostalba@gmail.com>
81 lines
2.5 KiB
C++
81 lines
2.5 KiB
C++
/*
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Stockfish, a UCI chess playing engine derived from Glaurung 2.1
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Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
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Copyright (C) 2008-2009 Marco Costalba
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Stockfish is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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Stockfish is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#if !defined(HISTORY_H_INCLUDED)
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#define HISTORY_H_INCLUDED
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////
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//// Includes
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////
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#include "depth.h"
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#include "move.h"
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#include "piece.h"
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////
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//// Types
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////
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/// The History class stores statistics about how often different moves
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/// have been successful or unsuccessful during the current search. These
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/// statistics are used for reduction and move ordering decisions. History
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/// entries are stored according only to moving piece and destination square,
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/// in particular two moves with different origin but same destination and
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/// same piece will be considered identical.
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class History {
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public:
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History();
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void clear();
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void success(Piece p, Square to, Depth d);
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void failure(Piece p, Square to);
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int move_ordering_score(Piece p, Square to) const;
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bool ok_to_prune(Piece p, Square to, Depth d) const;
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private:
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int history[16][64]; // [piece][square]
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int successCount[16][64];
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int failureCount[16][64];
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};
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////
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//// Constants and variables
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////
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/// HistoryMax controls how often the history counters will be scaled down:
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/// When the history score for a move gets bigger than HistoryMax, all
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/// entries in the table are divided by 2. It is difficult to guess what
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/// the ideal value of this constant is. Scaling down the scores often has
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/// the effect that parts of the search tree which have been searched
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/// recently have a bigger importance for move ordering than the moves which
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/// have been searched a long time ago.
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///
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/// Note that HistoryMax should probably be changed whenever the constant
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/// OnePly in depth.h is changed. This is somewhat annoying. Perhaps it
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/// would be better to scale down the history table at regular intervals?
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const int HistoryMax = 50000;
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#endif // !defined(HISTORY_H_INCLUDED)
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