Partially restore HistoryMax

[stockfish] / src / history.h

diff --git a/src/history.h b/src/history.h
index f2559499279dc22b0c652ab3198de6736ffcf643..47543d54db7ad2995791246a763e843c5bf79464 100644 (file)
--- a/src/history.h
+++ b/src/history.h
@@ -1,77 +1,76 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008 Marco Costalba
+  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
 
   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.
-  
+
   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/>.
 */
 
-
 #if !defined(HISTORY_H_INCLUDED)
 #define HISTORY_H_INCLUDED
 
-////
-//// Includes
-////
+#include <cstring>
 
 #include "depth.h"
 #include "move.h"
 #include "piece.h"
+#include "value.h"
 
 
-////
-//// 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();
+  History() { clear(); }
   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;
+  int value(Piece p, Square to) const;
+  void update(Piece p, Square to, Value delta);
+  Value gain(Piece p, Square to) const;
+  void update_gain(Piece p, Square to, Value delta);
+
+  static const int MaxValue = (1 << 29); // To avoid an overflow
 
 private:
-  int history[16][64];  // [piece][square]
-  int successCount[16][64];
-  int failureCount[16][64];
+  Value history[16][64];  // [piece][to_square]
+  Value maxGains[16][64]; // [piece][to_square]
 };
 
+inline void History::clear() {
+  memset(history,  0, 16 * 64 * sizeof(int));
+  memset(maxGains, 0, 16 * 64 * sizeof(int));
+}
 
-////
-//// Constants and variables
-////
+inline int History::value(Piece p, Square to) const {
+  return history[p][to];
+}
 
-/// 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
-/// 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?
+inline void History::update(Piece p, Square to, Value bonus) {
+  if (abs(history[p][to]) < MaxValue) history[p][to] += bonus;
+}
 
-const int HistoryMax = 50000;
+inline Value History::gain(Piece p, Square to) const {
+  return maxGains[p][to];
+}
 
+inline void History::update_gain(Piece p, Square to, Value gain) {
+  maxGains[p][to] = (gain >= maxGains[p][to] ? gain : maxGains[p][to] - 1);
+}
 
 #endif // !defined(HISTORY_H_INCLUDED)