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  1. /*
  2.   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
  3.   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
  4.   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
  5.   Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
  6.  
  7.   Stockfish is free software: you can redistribute it and/or modify
  8.   it under the terms of the GNU General Public License as published by
  9.   the Free Software Foundation, either version 3 of the License, or
  10.   (at your option) any later version.
  11.  
  12.   Stockfish is distributed in the hope that it will be useful,
  13.   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14.   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15.   GNU General Public License for more details.
  16.  
  17.   You should have received a copy of the GNU General Public License
  18.   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19. */
  20.  
  21. #ifndef SEARCH_H_INCLUDED
  22. #define SEARCH_H_INCLUDED
  23.  
  24. #include <vector>
  25.  
  26. #include "misc.h"
  27. #include "movepick.h"
  28. #include "types.h"
  29.  
  30. class Position;
  31.  
  32. namespace Search {
  33.  
  34. /// Threshold used for countermoves based pruning
  35. constexpr int CounterMovePruneThreshold = 0;
  36.  
  37.  
  38. /// Stack struct keeps track of the information we need to remember from nodes
  39. /// shallower and deeper in the tree during the search. Each search thread has
  40. /// its own array of Stack objects, indexed by the current ply.
  41.  
  42. struct Stack {
  43.   Move* pv;
  44.   PieceToHistory* continuationHistory;
  45.   int ply;
  46.   Move currentMove;
  47.   Move excludedMove;
  48.   Move killers[2];
  49.   Value staticEval;
  50.   int statScore;
  51.   int moveCount;
  52. };
  53.  
  54.  
  55. /// RootMove struct is used for moves at the root of the tree. For each root move
  56. /// we store a score and a PV (really a refutation in the case of moves which
  57. /// fail low). Score is normally set at -VALUE_INFINITE for all non-pv moves.
  58.  
  59. struct RootMove {
  60.  
  61.   explicit RootMove(Move m) : pv(1, m) {}
  62.   bool extract_ponder_from_tt(Position& pos);
  63.   bool operator==(const Move& m) const { return pv[0] == m; }
  64.   bool operator<(const RootMove& m) const { // Sort in descending order
  65.     return m.score != score ? m.score < score
  66.                             : m.previousScore < previousScore;
  67.   }
  68.  
  69.   Value score = -VALUE_INFINITE;
  70.   Value previousScore = -VALUE_INFINITE;
  71.   int selDepth = 0;
  72.   int tbRank;
  73.   Value tbScore;
  74.   std::vector<Move> pv;
  75. };
  76.  
  77. typedef std::vector<RootMove> RootMoves;
  78.  
  79.  
  80. /// LimitsType struct stores information sent by GUI about available time to
  81. /// search the current move, maximum depth/time, or if we are in analysis mode.
  82.  
  83. struct LimitsType {
  84.  
  85.   LimitsType() { // Init explicitly due to broken value-initialization of non POD in MSVC
  86.     time[WHITE] = time[BLACK] = inc[WHITE] = inc[BLACK] = npmsec = movetime = TimePoint(0);
  87.     movestogo = depth = mate = perft = infinite = 0;
  88.     nodes = 0;
  89.   }
  90.  
  91.   bool use_time_management() const {
  92.     return !(mate | movetime | depth | nodes | perft | infinite);
  93.   }
  94.  
  95.   std::vector<Move> searchmoves;
  96.   TimePoint time[COLOR_NB], inc[COLOR_NB], npmsec, movetime, startTime;
  97.   int movestogo, depth, mate, perft, infinite;
  98.   int64_t nodes;
  99. };
  100.  
  101. extern LimitsType Limits;
  102.  
  103. void init();
  104. void clear();
  105.  
  106. } // namespace Search
  107.  
  108. #endif // #ifndef SEARCH_H_INCLUDED
  109.