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  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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  Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
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  Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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  Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
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  Stockfish is free software: you can redistribute it and/or modify
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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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  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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  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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  (at your option) any later version.
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namespace {
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namespace {
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  // Table used to drive the king towards the edge of the board
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  // Table used to drive the king towards the edge of the board
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  // in KX vs K and KQ vs KR endgames.
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  // in KX vs K and KQ vs KR endgames.
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  const int PushToEdges[SQUARE_NB] = {
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  constexpr int PushToEdges[SQUARE_NB] = {
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    100, 90, 80, 70, 70, 80, 90, 100,
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    100, 90, 80, 70, 70, 80, 90, 100,
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     90, 70, 60, 50, 50, 60, 70,  90,
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     90, 70, 60, 50, 50, 60, 70,  90,
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     80, 60, 40, 30, 30, 40, 60,  80,
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     80, 60, 40, 30, 30, 40, 60,  80,
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     70, 50, 30, 20, 20, 30, 50,  70,
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     70, 50, 30, 20, 20, 30, 50,  70,
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     70, 50, 30, 20, 20, 30, 50,  70,
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     70, 50, 30, 20, 20, 30, 50,  70,
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    100, 90, 80, 70, 70, 80, 90, 100
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    100, 90, 80, 70, 70, 80, 90, 100
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  };
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  };
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  // Table used to drive the king towards a corner square of the
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  // Table used to drive the king towards a corner square of the
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  // right color in KBN vs K endgames.
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  // right color in KBN vs K endgames.
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  const int PushToCorners[SQUARE_NB] = {
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  constexpr int PushToCorners[SQUARE_NB] = {
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    200, 190, 180, 170, 160, 150, 140, 130,
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    200, 190, 180, 170, 160, 150, 140, 130,
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    190, 180, 170, 160, 150, 140, 130, 140,
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    190, 180, 170, 160, 150, 140, 130, 140,
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    180, 170, 155, 140, 140, 125, 140, 150,
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    180, 170, 155, 140, 140, 125, 140, 150,
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    170, 160, 140, 120, 110, 140, 150, 160,
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    170, 160, 140, 120, 110, 140, 150, 160,
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    160, 150, 140, 110, 120, 140, 160, 170,
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    160, 150, 140, 110, 120, 140, 160, 170,
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    140, 130, 140, 150, 160, 170, 180, 190,
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    140, 130, 140, 150, 160, 170, 180, 190,
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    130, 140, 150, 160, 170, 180, 190, 200
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    130, 140, 150, 160, 170, 180, 190, 200
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  };
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  };
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  // Tables used to drive a piece towards or away from another piece
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  // Tables used to drive a piece towards or away from another piece
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  const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
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  constexpr int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
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  const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
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  constexpr int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
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  // Pawn Rank based scaling factors used in KRPPKRP endgame
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  // Pawn Rank based scaling factors used in KRPPKRP endgame
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  const int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 };
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  constexpr int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 };
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#ifndef NDEBUG
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#ifndef NDEBUG
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  bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {
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  bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {
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    return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == pawnsCnt;
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    return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == pawnsCnt;
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  }
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  }
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    return sq;
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    return sq;
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  }
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  }
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} // namespace
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} // namespace
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 - 
 
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 - 
 
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/// Endgames members definitions
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 - 
 
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Endgames::Endgames() {
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 - 
 
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  add<KPK>("KPK");
 - 
 
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  add<KNNK>("KNNK");
 - 
 
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  add<KBNK>("KBNK");
 - 
 
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  add<KRKP>("KRKP");
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  add<KRKB>("KRKB");
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  add<KRKN>("KRKN");
 - 
 
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  add<KQKP>("KQKP");
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  add<KQKR>("KQKR");
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  add<KNPK>("KNPK");
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  add<KNPKB>("KNPKB");
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  add<KRPKR>("KRPKR");
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  add<KRPKB>("KRPKB");
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  add<KBPKB>("KBPKB");
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  add<KBPKN>("KBPKN");
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  add<KBPPKB>("KBPPKB");
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  add<KRPPKRP>("KRPPKRP");
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}
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/// Mate with KX vs K. This function is used to evaluate positions with
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/// Mate with KX vs K. This function is used to evaluate positions with
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/// king and plenty of material vs a lone king. It simply gives the
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/// king and plenty of material vs a lone king. It simply gives the
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/// attacking side a bonus for driving the defending king towards the edge
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/// attacking side a bonus for driving the defending king towards the edge
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  Square queeningSq = make_square(file_of(psq), RANK_1);
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  Square queeningSq = make_square(file_of(psq), RANK_1);
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  Value result;
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  Value result;
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  // If the stronger side's king is in front of the pawn, it's a win
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  // If the stronger side's king is in front of the pawn, it's a win
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  if (wksq < psq && file_of(wksq) == file_of(psq))
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  if (forward_file_bb(WHITE, wksq) & psq)
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      result = RookValueEg - distance(wksq, psq);
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      result = RookValueEg - distance(wksq, psq);
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  // If the weaker side's king is too far from the pawn and the rook,
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  // If the weaker side's king is too far from the pawn and the rook,
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  // it's a win.
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  // it's a win.
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  else if (   distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
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  else if (   distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
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  return strongSide == pos.side_to_move() ? result : -result;
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  return strongSide == pos.side_to_move() ? result : -result;
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}
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}
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/// KR vs KB. This is very simple, and always returns drawish scores.  The
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/// KR vs KB. This is very simple, and always returns drawish scores. The
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/// score is slightly bigger when the defending king is close to the edge.
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/// score is slightly bigger when the defending king is close to the edge.
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template<>
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template<>
246 
Value Endgame<KRKB>::operator()(const Position& pos) const {
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Value Endgame<KRKB>::operator()(const Position& pos) const {
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  assert(verify_material(pos, strongSide, RookValueMg, 0));
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  assert(verify_material(pos, strongSide, RookValueMg, 0));
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          || relative_rank(strongSide, weakKingSq) <= RANK_6))
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          || relative_rank(strongSide, weakKingSq) <= RANK_6))
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      return SCALE_FACTOR_DRAW;
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      return SCALE_FACTOR_DRAW;
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632 
  // Case 2: Opposite colored bishops
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  // Case 2: Opposite colored bishops
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  if (opposite_colors(strongBishopSq, weakBishopSq))
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  if (opposite_colors(strongBishopSq, weakBishopSq))
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  {
 - 
 
635 
      // We assume that the position is drawn in the following three situations:
 - 
 
636 
      //
 - 
 
637 
      //   a. The pawn is on rank 5 or further back.
 - 
 
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      //   b. The defending king is somewhere in the pawn's path.
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      //   c. The defending bishop attacks some square along the pawn's path,
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      //      and is at least three squares away from the pawn.
 - 
 
641 
      //
 - 
 
642 
      // These rules are probably not perfect, but in practice they work
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      // reasonably well.
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      return SCALE_FACTOR_DRAW;
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645 
      if (relative_rank(strongSide, pawnSq) <= RANK_5)
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646 
          return SCALE_FACTOR_DRAW;
 - 
 
647 
 
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648 
      Bitboard path = forward_file_bb(strongSide, pawnSq);
 - 
 
649 
 
 - 
 
650 
      if (path & pos.pieces(weakSide, KING))
 - 
 
651 
          return SCALE_FACTOR_DRAW;
 - 
 
652 
 
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653 
      if (  (pos.attacks_from<BISHOP>(weakBishopSq) & path)
 - 
 
654 
          && distance(weakBishopSq, pawnSq) >= 3)
 - 
 
655 
          return SCALE_FACTOR_DRAW;
 - 
 
656 
  }
 - 
 
657 
  return SCALE_FACTOR_NONE;
 612 
  return SCALE_FACTOR_NONE;
658 
}
 613 
}
659 
 
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661 
/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
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/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops