Fix a comment in HistoryMax description

[stockfish] / src / history.h

diff --git a/src/history.h b/src/history.h
index ced416a86178eb598d64b88b9e5897db3b09e53d..5c394cc8f17e2ed75f043ba01b0251e607127222 100644 (file)
--- a/src/history.h
+++ b/src/history.h
@@ -1,17 +1,18 @@
 /*
-  Glaurung, a UCI chess playing engine.
-  Copyright (C) 2004-2008 Tord Romstad
+  Stockfish, a UCI chess playing engine derived from Glaurung 2.1
+  Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
+  Copyright (C) 2008-2009 Marco Costalba
 
-  Glaurung is free software: you can redistribute it and/or modify
+  Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
-  
-  Glaurung is distributed in the hope that it will be useful,
+
+  Stockfish is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
-  
+
   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
@@ -33,24 +34,24 @@
 //// Types
 ////
 
-/// The History class stores statistics about how often different moves have
-/// been successful or unsuccessful during the current search.  These
-/// statistics are used for reduction and move ordering decisions.
+/// The History class stores statistics about how often different moves
+/// have been successful or unsuccessful during the current search. These
+/// statistics are used for reduction and move ordering decisions. History
+/// entries are stored according only to moving piece and destination square,
+/// in particular two moves with different origin but same destination and
+/// same piece will be considered identical.
 
 class History {
 
 public:
   History();
   void clear();
-  void success(Piece p, Move m, Depth d);
-  void failure(Piece p, Move m);
-  int move_ordering_score(Piece p, Move m) const;
-  bool ok_to_prune(Piece p, Move m, Depth d) const;
+  void success(Piece p, Square to, Depth d);
+  void failure(Piece p, Square to, Depth d);
+  int move_ordering_score(Piece p, Square to) const;
 
 private:
   int history[16][64];  // [piece][square]
-  int successCount[16][64];
-  int failureCount[16][64];
 };
 
 
@@ -60,17 +61,13 @@ private:
 
 /// HistoryMax controls how often the history counters will be scaled down:
 /// When the history score for a move gets bigger than HistoryMax, all
-/// entries in the table are divided by 2.  It is difficult to guess what
-/// the ideal value of this constant is.  Scaling down the scores often has
+/// entries in the table are divided by 4. It is difficult to guess what
+/// the ideal value of this constant is. Scaling down the scores often has
 /// the effect that parts of the search tree which have been searched
 /// recently have a bigger importance for move ordering than the moves which
 /// have been searched a long time ago.
-///
-/// Note that HistoryMax should probably be changed whenever the constant
-/// OnePly in depth.h is changed.  This is somewhat annoying.  Perhaps it
-/// would be better to scale down the history table at regular intervals?
 
-const int HistoryMax = 50000;
+const int HistoryMax = 25000 * OnePly;
 
 
 #endif // !defined(HISTORY_H_INCLUDED)