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  1. /*
  2.     Texel - A UCI chess engine.
  3.     Copyright (C) 2012-2013  Peter Österlund, peterosterlund2@gmail.com
  4.  
  5.     This program is free software: you can redistribute it and/or modify
  6.     it under the terms of the GNU General Public License as published by
  7.     the Free Software Foundation, either version 3 of the License, or
  8.     (at your option) any later version.
  9.  
  10.     This program is distributed in the hope that it will be useful,
  11.     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12.     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13.     GNU General Public License for more details.
  14.  
  15.     You should have received a copy of the GNU General Public License
  16.     along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17. */
  18.  
  19. /*
  20.  * history.hpp
  21.  *
  22.  *  Created on: Feb 25, 2012
  23.  *      Author: petero
  24.  */
  25.  
  26. #ifndef HISTORY_HPP_
  27. #define HISTORY_HPP_
  28.  
  29. #include "piece.hpp"
  30. #include "position.hpp"
  31.  
  32. /**
  33.  * Implements the relative history heuristic.
  34.  */
  35. class History {
  36. public:
  37.     History();
  38.  
  39.     /** Clear all history information. */
  40.     void init();
  41.  
  42.     /** Rescale the history counters, so that future updates have more weight. */
  43.     void reScale();
  44.  
  45.     /** Record move as a success. */
  46.     void addSuccess(const Position& pos, const Move& m, int depth);
  47.  
  48.     /** Record move as a failure. */
  49.     void addFail(const Position& pos, const Move& m, int depth);
  50.  
  51.     /** Get a score between 0 and 49, depending of the success/fail ratio of the move. */
  52.     int getHistScore(const Position& pos, const Move& m) const;
  53.  
  54. private:
  55.     static int depthWeight(int depth);
  56.  
  57.     static int depthTable[6];
  58.  
  59.     struct Entry {
  60.         RelaxedShared<int> countSuccess;
  61.         RelaxedShared<int> countFail;
  62.         mutable RelaxedShared<int> score;
  63.     };
  64.     Entry ht[Piece::nPieceTypes][64];
  65. };
  66.  
  67.  
  68. inline
  69. History::History() {
  70.     init();
  71. }
  72.  
  73. inline int
  74. History::depthWeight(int depth) {
  75.     return depthTable[clamp(depth, 0, (int)COUNT_OF(depthTable)-1)];
  76. }
  77.  
  78. inline void
  79. History::addSuccess(const Position& pos, const Move& m, int depth) {
  80.     int p = pos.getPiece(m.from());
  81.     int cnt = depthWeight(depth);
  82.     Entry& e = ht[p][m.to()];
  83.     int val = e.countSuccess + cnt;
  84.     if (val + e.countFail > 1300) {
  85.         val /= 2;
  86.         e.countFail = e.countFail / 2;
  87.     }
  88.     e.countSuccess = val;
  89.     e.score = -1;
  90. }
  91.  
  92. inline void
  93. History::addFail(const Position& pos, const Move& m, int depth) {
  94.     int p = pos.getPiece(m.from());
  95.     int cnt = depthWeight(depth);
  96.     Entry& e = ht[p][m.to()];
  97.     int val = e.countFail + cnt;
  98.     if (val + e.countSuccess > 1300) {
  99.         val /= 2;
  100.         e.countSuccess = e.countSuccess / 2;
  101.     }
  102.     e.countFail = val;
  103.     e.score = -1;
  104. }
  105.  
  106. inline int
  107. History::getHistScore(const Position& pos, const Move& m) const {
  108.     int p = pos.getPiece(m.from());
  109.     const Entry& e = ht[p][m.to()];
  110.     int ret = e.score;
  111.     if (ret >= 0)
  112.         return ret;
  113.     int succ = e.countSuccess;
  114.     int fail = e.countFail;
  115.     if (succ + fail > 0) {
  116.         ret = succ * 49 / (succ + fail);
  117.     } else
  118.         ret = 0;
  119.     e.score = ret;
  120.     return ret;
  121. }
  122.  
  123. #endif /* HISTORY_HPP_ */
  124.