X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=65b858613dd8f74ae6ad73674187473e059afe25;hp=913be63f1702c21eb4d76277c2cc4a6daaeb3954;hb=aecdbfc4a000c72fcc2642f54ce83967913a16ba;hpb=94b9c65e09b5d396bebb29b62d9979139b5fbdfa

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 913be63f..65b85861 100644
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2013 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
@@ -17,27 +17,21 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-
-////
-//// Includes
-////
-
+#include <algorithm>
 #include <cassert>
 
-#include "bitbase.h"
+#include "bitboard.h"
 #include "bitcount.h"
 #include "endgame.h"
+#include "movegen.h"
 
-
-////
-//// Local definitions
-////
+using std::string;
 
 namespace {
 
   // Table used to drive the defending king towards the edge of the board
   // in KX vs K and KQ vs KR endgames.
-  const uint8_t MateTable[64] = {
+  const int MateTable[SQUARE_NB] = {
     100, 90, 80, 70, 70, 80, 90, 100,
      90, 70, 60, 50, 50, 60, 70,  90,
      80, 60, 40, 30, 30, 40, 60,  80,
@@ -50,7 +44,7 @@ namespace {
 
   // Table used to drive the defending king towards a corner square of the
   // right color in KBN vs K endgames.
-  const uint8_t KBNKMateTable[64] = {
+  const int KBNKMateTable[SQUARE_NB] = {
     200, 190, 180, 170, 160, 150, 140, 130,
     190, 180, 170, 160, 150, 140, 130, 140,
     180, 170, 155, 140, 140, 125, 140, 150,
@@ -65,46 +59,66 @@ namespace {
   // the two kings in basic endgames.
   const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
 
-  // Penalty for big distance between king and knight for the defending king
-  // and knight in KR vs KN endgames.
-  const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 };
+  // Get the material key of a Position out of the given endgame key code
+  // like "KBPKN". The trick here is to first forge an ad-hoc fen string
+  // and then let a Position object to do the work for us. Note that the
+  // fen string could correspond to an illegal position.
+  Key key(const string& code, Color c) {
 
-  // Bitbase for KP vs K
-  uint8_t KPKBitbase[24576];
+    assert(code.length() > 0 && code.length() < 8);
+    assert(code[0] == 'K');
 
-  // Various inline functions for accessing the above arrays
-  inline Value mate_table(Square s) {
-    return Value(MateTable[s]);
-  }
+    string sides[] = { code.substr(code.find('K', 1)),      // Weaker
+                       code.substr(0, code.find('K', 1)) }; // Stronger
 
-  inline Value kbnk_mate_table(Square s) {
-    return Value(KBNKMateTable[s]);
-  }
+    std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
 
-  inline Value distance_bonus(int d) {
-    return Value(DistanceBonus[d]);
-  }
+    string fen =  sides[0] + char('0' + int(8 - code.length()))
+                + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10";
 
-  inline Value krkn_king_knight_distance_penalty(int d) {
-    return Value(KRKNKingKnightDistancePenalty[d]);
+    return Position(fen, false, NULL).material_key();
   }
 
-  // Function for probing the KP vs K bitbase
-  int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm);
+  template<typename M>
+  void delete_endgame(const typename M::value_type& p) { delete p.second; }
+
+} // namespace
+
+
+/// Endgames members definitions
 
+Endgames::Endgames() {
+
+  add<KPK>("KPK");
+  add<KNNK>("KNNK");
+  add<KBNK>("KBNK");
+  add<KRKP>("KRKP");
+  add<KRKB>("KRKB");
+  add<KRKN>("KRKN");
+  add<KQKP>("KQKP");
+  add<KQKR>("KQKR");
+  add<KBBKN>("KBBKN");
+
+  add<KNPK>("KNPK");
+  add<KNPKB>("KNPKB");
+  add<KRPKR>("KRPKR");
+  add<KBPKB>("KBPKB");
+  add<KBPKN>("KBPKN");
+  add<KBPPKB>("KBPPKB");
+  add<KRPPKRP>("KRPPKRP");
 }
 
+Endgames::~Endgames() {
 
-////
-//// Functions
-////
+  for_each(m1.begin(), m1.end(), delete_endgame<M1>);
+  for_each(m2.begin(), m2.end(), delete_endgame<M2>);
+}
 
-/// init_bitbases() is called during program initialization, and simply loads
-/// bitbases from disk into memory.  At the moment, there is only the bitbase
-/// for KP vs K, but we may decide to add other bitbases later.
+template<EndgameType E>
+void Endgames::add(const string& code) {
 
-void init_bitbases() {
-  generate_kpk_bitbase(KPKBitbase);
+  map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
+  map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
 }
 
 
@@ -113,23 +127,27 @@ void init_bitbases() {
 /// attacking side a bonus for driving the defending king towards the edge
 /// of the board, and for keeping the distance between the two kings small.
 template<>
-Value EvaluationFunction<KXK>::apply(const Position& pos) const {
+Value Endgame<KXK>::operator()(const Position& pos) const {
 
   assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
-  assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
+  assert(!pos.count<PAWN>(weakerSide));
+  assert(!pos.checkers()); // Eval is never called when in check
+
+  // Stalemate detection with lone king
+  if (pos.side_to_move() == weakerSide && !MoveList<LEGAL>(pos).size())
+      return VALUE_DRAW;
 
   Square winnerKSq = pos.king_square(strongerSide);
   Square loserKSq = pos.king_square(weakerSide);
 
   Value result =   pos.non_pawn_material(strongerSide)
-                 + pos.piece_count(strongerSide, PAWN) * PawnValueEndgame
-                 + mate_table(loserKSq)
-                 + distance_bonus(square_distance(winnerKSq, loserKSq));
-
-  if (   pos.piece_count(strongerSide, QUEEN)
-      || pos.piece_count(strongerSide, ROOK)
-      || pos.piece_count(strongerSide, BISHOP) > 1)
-      // TODO: check for two equal-colored bishops!
+                 + pos.count<PAWN>(strongerSide) * PawnValueEg
+                 + MateTable[loserKSq]
+                 + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+
+  if (   pos.count<QUEEN>(strongerSide)
+      || pos.count<ROOK>(strongerSide)
+      || pos.bishop_pair(strongerSide))
       result += VALUE_KNOWN_WIN;
 
   return strongerSide == pos.side_to_move() ? result : -result;
@@ -139,31 +157,31 @@ Value EvaluationFunction<KXK>::apply(const Position& pos) const {
 /// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the
 /// defending king towards a corner square of the right color.
 template<>
-Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
+Value Endgame<KBNK>::operator()(const Position& pos) const {
 
+  assert(pos.non_pawn_material(strongerSide) == KnightValueMg + BishopValueMg);
   assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
-  assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
-  assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame + BishopValueMidgame);
-  assert(pos.piece_count(strongerSide, BISHOP) == 1);
-  assert(pos.piece_count(strongerSide, KNIGHT) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) == 0);
+  assert(pos.count<BISHOP>(strongerSide) == 1);
+  assert(pos.count<KNIGHT>(strongerSide) == 1);
+  assert(pos.count<  PAWN>(strongerSide) == 0);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
 
   Square winnerKSq = pos.king_square(strongerSide);
   Square loserKSq = pos.king_square(weakerSide);
-  Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
+  Square bishopSq = pos.list<BISHOP>(strongerSide)[0];
 
   // kbnk_mate_table() tries to drive toward corners A1 or H8,
   // if we have a bishop that cannot reach the above squares we
   // mirror the kings so to drive enemy toward corners A8 or H1.
-  if (!same_color_squares(bishopSquare, SQ_A1))
+  if (opposite_colors(bishopSq, SQ_A1))
   {
-      winnerKSq = flop_square(winnerKSq);
-      loserKSq = flop_square(loserKSq);
+      winnerKSq = mirror(winnerKSq);
+      loserKSq = mirror(loserKSq);
   }
 
   Value result =  VALUE_KNOWN_WIN
-                + distance_bonus(square_distance(winnerKSq, loserKSq))
-                + kbnk_mate_table(loserKSq);
+                + DistanceBonus[square_distance(winnerKSq, loserKSq)]
+                + KBNKMateTable[loserKSq];
 
   return strongerSide == pos.side_to_move() ? result : -result;
 }
@@ -171,44 +189,42 @@ Value EvaluationFunction<KBNK>::apply(const Position& pos) const {
 
 /// KP vs K. This endgame is evaluated with the help of a bitbase.
 template<>
-Value EvaluationFunction<KPK>::apply(const Position& pos) const {
+Value Endgame<KPK>::operator()(const Position& pos) const {
 
   assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
   assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
-  assert(pos.piece_count(strongerSide, PAWN) == 1);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.count<PAWN>(strongerSide) == 1);
+  assert(pos.count<PAWN>(weakerSide  ) == 0);
 
   Square wksq, bksq, wpsq;
-  Color stm;
+  Color us;
 
   if (strongerSide == WHITE)
   {
       wksq = pos.king_square(WHITE);
       bksq = pos.king_square(BLACK);
-      wpsq = pos.piece_list(WHITE, PAWN, 0);
-      stm = pos.side_to_move();
+      wpsq = pos.list<PAWN>(WHITE)[0];
+      us   = pos.side_to_move();
   }
   else
   {
-      wksq = flip_square(pos.king_square(BLACK));
-      bksq = flip_square(pos.king_square(WHITE));
-      wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
-      stm = opposite_color(pos.side_to_move());
+      wksq = ~pos.king_square(BLACK);
+      bksq = ~pos.king_square(WHITE);
+      wpsq = ~pos.list<PAWN>(BLACK)[0];
+      us   = ~pos.side_to_move();
   }
 
-  if (square_file(wpsq) >= FILE_E)
+  if (file_of(wpsq) >= FILE_E)
   {
-      wksq = flop_square(wksq);
-      bksq = flop_square(bksq);
-      wpsq = flop_square(wpsq);
+      wksq = mirror(wksq);
+      bksq = mirror(bksq);
+      wpsq = mirror(wpsq);
   }
 
-  if (!probe_kpk(wksq, wpsq, bksq, stm))
+  if (!Bitbases::probe_kpk(wksq, wpsq, bksq, us))
       return VALUE_DRAW;
 
-  Value result =  VALUE_KNOWN_WIN
-                + PawnValueEndgame
-                + Value(square_rank(wpsq));
+  Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(wpsq));
 
   return strongerSide == pos.side_to_move() ? result : -result;
 }
@@ -219,47 +235,47 @@ Value EvaluationFunction<KPK>::apply(const Position& pos) const {
 /// far advanced with support of the king, while the attacking king is far
 /// away.
 template<>
-Value EvaluationFunction<KRKP>::apply(const Position& pos) const {
+Value Endgame<KRKP>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
-  assert(pos.piece_count(strongerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(strongerSide) == RookValueMg);
   assert(pos.non_pawn_material(weakerSide) == 0);
-  assert(pos.piece_count(weakerSide, PAWN) == 1);
+  assert(pos.count<PAWN>(strongerSide) == 0);
+  assert(pos.count<PAWN>(weakerSide  ) == 1);
 
   Square wksq, wrsq, bksq, bpsq;
   int tempo = (pos.side_to_move() == strongerSide);
 
   wksq = pos.king_square(strongerSide);
-  wrsq = pos.piece_list(strongerSide, ROOK, 0);
   bksq = pos.king_square(weakerSide);
-  bpsq = pos.piece_list(weakerSide, PAWN, 0);
+  wrsq = pos.list<ROOK>(strongerSide)[0];
+  bpsq = pos.list<PAWN>(weakerSide)[0];
 
   if (strongerSide == BLACK)
   {
-      wksq = flip_square(wksq);
-      wrsq = flip_square(wrsq);
-      bksq = flip_square(bksq);
-      bpsq = flip_square(bpsq);
+      wksq = ~wksq;
+      wrsq = ~wrsq;
+      bksq = ~bksq;
+      bpsq = ~bpsq;
   }
 
-  Square queeningSq = make_square(square_file(bpsq), RANK_1);
+  Square queeningSq = file_of(bpsq) | RANK_1;
   Value result;
 
   // If the stronger side's king is in front of the pawn, it's a win
-  if (wksq < bpsq && square_file(wksq) == square_file(bpsq))
-      result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+  if (wksq < bpsq && file_of(wksq) == file_of(bpsq))
+      result = RookValueEg - Value(square_distance(wksq, bpsq));
 
   // If the weaker side's king is too far from the pawn and the rook,
   // it's a win
   else if (   square_distance(bksq, bpsq) - (tempo ^ 1) >= 3
            && square_distance(bksq, wrsq) >= 3)
-      result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+      result = RookValueEg - Value(square_distance(wksq, bpsq));
 
   // If the pawn is far advanced and supported by the defending king,
   // the position is drawish
-  else if (   square_rank(bksq) <= RANK_3
+  else if (   rank_of(bksq) <= RANK_3
            && square_distance(bksq, bpsq) == 1
-           && square_rank(wksq) >= RANK_4
+           && rank_of(wksq) >= RANK_4
            && square_distance(wksq, bpsq) - tempo > 2)
       result = Value(80 - square_distance(wksq, bpsq) * 8);
 
@@ -276,15 +292,15 @@ Value EvaluationFunction<KRKP>::apply(const Position& pos) const {
 /// KR vs KB. This is very simple, and always returns drawish scores.  The
 /// score is slightly bigger when the defending king is close to the edge.
 template<>
-Value EvaluationFunction<KRKB>::apply(const Position& pos) const {
+Value Endgame<KRKB>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
-  assert(pos.piece_count(strongerSide, PAWN) == 0);
-  assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
-  assert(pos.piece_count(weakerSide, BISHOP) == 1);
+  assert(pos.non_pawn_material(strongerSide) == RookValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == BishopValueMg);
+  assert(pos.count<BISHOP>(weakerSide  ) == 1);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
+  assert(pos.count<  PAWN>(strongerSide) == 0);
 
-  Value result = mate_table(pos.king_square(weakerSide));
+  Value result = Value(MateTable[pos.king_square(weakerSide)]);
   return strongerSide == pos.side_to_move() ? result : -result;
 }
 
@@ -292,22 +308,50 @@ Value EvaluationFunction<KRKB>::apply(const Position& pos) const {
 /// KR vs KN.  The attacking side has slightly better winning chances than
 /// in KR vs KB, particularly if the king and the knight are far apart.
 template<>
-Value EvaluationFunction<KRKN>::apply(const Position& pos) const {
+Value Endgame<KRKN>::operator()(const Position& pos) const {
+
+  assert(pos.non_pawn_material(strongerSide) == RookValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == KnightValueMg);
+  assert(pos.count<KNIGHT>(weakerSide  ) == 1);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
+  assert(pos.count<  PAWN>(strongerSide) == 0);
+
+  const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 };
+
+  Square bksq = pos.king_square(weakerSide);
+  Square bnsq = pos.list<KNIGHT>(weakerSide)[0];
+  Value result = Value(MateTable[bksq] + penalty[square_distance(bksq, bnsq)]);
+  return strongerSide == pos.side_to_move() ? result : -result;
+}
+
+
+/// KQ vs KP.  In general, a win for the stronger side, however, there are a few
+/// important exceptions.  Pawn on 7th rank, A,C,F or H file, with king next can
+/// be a draw, so we scale down to distance between kings only.
+template<>
+Value Endgame<KQKP>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
-  assert(pos.piece_count(strongerSide, PAWN) == 0);
-  assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
-  assert(pos.piece_count(weakerSide, KNIGHT) == 1);
+  assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == VALUE_ZERO);
+  assert(pos.count<PAWN>(strongerSide) == 0);
+  assert(pos.count<PAWN>(weakerSide  ) == 1);
+
+  Square winnerKSq = pos.king_square(strongerSide);
+  Square loserKSq = pos.king_square(weakerSide);
+  Square pawnSq = pos.list<PAWN>(weakerSide)[0];
 
-  Square defendingKSq = pos.king_square(weakerSide);
-  Square nSq = pos.piece_list(weakerSide, KNIGHT, 0);
+  Value result =  QueenValueEg
+                - PawnValueEg
+                + DistanceBonus[square_distance(winnerKSq, loserKSq)];
 
-  int d = square_distance(defendingKSq, nSq);
-  Value result =   Value(10)
-                 + mate_table(defendingKSq)
-                 + krkn_king_knight_distance_penalty(d);
+  if (   square_distance(loserKSq, pawnSq) == 1
+      && relative_rank(weakerSide, pawnSq) == RANK_7)
+  {
+      File f = file_of(pawnSq);
 
+      if (f == FILE_A || f == FILE_C || f == FILE_F || f == FILE_H)
+          result = Value(DistanceBonus[square_distance(winnerKSq, loserKSq)]);
+  }
   return strongerSide == pos.side_to_move() ? result : -result;
 }
 
@@ -318,189 +362,189 @@ Value EvaluationFunction<KRKN>::apply(const Position& pos) const {
 /// for the defending side in the search, this is usually sufficient to be
 /// able to win KQ vs KR.
 template<>
-Value EvaluationFunction<KQKR>::apply(const Position& pos) const {
+Value Endgame<KQKR>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
-  assert(pos.piece_count(strongerSide, PAWN) == 0);
-  assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == RookValueMg);
+  assert(pos.count<PAWN>(strongerSide) == 0);
+  assert(pos.count<PAWN>(weakerSide  ) == 0);
 
   Square winnerKSq = pos.king_square(strongerSide);
   Square loserKSq = pos.king_square(weakerSide);
 
-  Value result =  QueenValueEndgame
-                - RookValueEndgame
-                + mate_table(loserKSq)
-                + distance_bonus(square_distance(winnerKSq, loserKSq));
+  Value result =  QueenValueEg
+                - RookValueEg
+                + MateTable[loserKSq]
+                + DistanceBonus[square_distance(winnerKSq, loserKSq)];
 
   return strongerSide == pos.side_to_move() ? result : -result;
 }
 
 template<>
-Value EvaluationFunction<KBBKN>::apply(const Position& pos) const {
+Value Endgame<KBBKN>::operator()(const Position& pos) const {
 
-  assert(pos.piece_count(strongerSide, BISHOP) == 2);
-  assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
-  assert(pos.piece_count(weakerSide, KNIGHT) == 1);
-  assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
-  assert(pos.pieces(PAWN) == EmptyBoardBB);
+  assert(pos.non_pawn_material(strongerSide) == 2 * BishopValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == KnightValueMg);
+  assert(pos.count<BISHOP>(strongerSide) == 2);
+  assert(pos.count<KNIGHT>(weakerSide  ) == 1);
+  assert(!pos.pieces(PAWN));
 
-  Value result = BishopValueEndgame;
+  Value result = BishopValueEg;
   Square wksq = pos.king_square(strongerSide);
   Square bksq = pos.king_square(weakerSide);
-  Square nsq = pos.piece_list(weakerSide, KNIGHT, 0);
+  Square nsq = pos.list<KNIGHT>(weakerSide)[0];
 
   // Bonus for attacking king close to defending king
-  result += distance_bonus(square_distance(wksq, bksq));
+  result += Value(DistanceBonus[square_distance(wksq, bksq)]);
 
   // Bonus for driving the defending king and knight apart
   result += Value(square_distance(bksq, nsq) * 32);
 
   // Bonus for restricting the knight's mobility
-  result += Value((8 - count_1s_max_15(pos.attacks_from<KNIGHT>(nsq))) * 8);
+  result += Value((8 - popcount<Max15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
 
   return strongerSide == pos.side_to_move() ? result : -result;
 }
 
 
-/// K and two minors vs K and one or two minors or K and two knights against
-/// king alone are always draw.
-template<>
-Value EvaluationFunction<KmmKm>::apply(const Position&) const {
-  return VALUE_ZERO;
-}
+/// Some cases of trivial draws
+template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
+template<> Value Endgame<KmmKm>::operator()(const Position&) const { return VALUE_DRAW; }
 
-template<>
-Value EvaluationFunction<KNNK>::apply(const Position&) const {
-  return VALUE_ZERO;
-}
 
-/// KBPKScalingFunction scales endgames where the stronger side has king,
-/// bishop and one or more pawns. It checks for draws with rook pawns and a
-/// bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_ZERO is
-/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
+/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and
+/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
+/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
 /// will be used.
 template<>
-ScaleFactor ScalingFunction<KBPsK>::apply(const Position& pos) const {
+ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
-  assert(pos.piece_count(strongerSide, BISHOP) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) >= 1);
+  assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
+  assert(pos.count<BISHOP>(strongerSide) == 1);
+  assert(pos.count<  PAWN>(strongerSide) >= 1);
 
   // No assertions about the material of weakerSide, because we want draws to
   // be detected even when the weaker side has some pawns.
 
-  Bitboard pawns = pos.pieces(PAWN, strongerSide);
-  File pawnFile = square_file(pos.piece_list(strongerSide, PAWN, 0));
+  Bitboard pawns = pos.pieces(strongerSide, PAWN);
+  File pawnFile = file_of(pos.list<PAWN>(strongerSide)[0]);
 
   // All pawns are on a single rook file ?
-  if (   (pawnFile == FILE_A || pawnFile == FILE_H)
-      && (pawns & ~file_bb(pawnFile)) == EmptyBoardBB)
+  if (    (pawnFile == FILE_A || pawnFile == FILE_H)
+      && !(pawns & ~file_bb(pawnFile)))
   {
-      Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0);
-      Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
+      Square bishopSq = pos.list<BISHOP>(strongerSide)[0];
+      Square queeningSq = relative_square(strongerSide, pawnFile | RANK_8);
       Square kingSq = pos.king_square(weakerSide);
 
-      if (  !same_color_squares(queeningSq, bishopSq)
-          && file_distance(square_file(kingSq), pawnFile) <= 1)
+      if (   opposite_colors(queeningSq, bishopSq)
+          && abs(file_of(kingSq) - pawnFile) <= 1)
       {
           // The bishop has the wrong color, and the defending king is on the
-          // file of the pawn(s) or the neighboring file. Find the rank of the
+          // file of the pawn(s) or the adjacent file. Find the rank of the
           // frontmost pawn.
-          Rank rank;
-          if (strongerSide == WHITE)
-          {
-              for (rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--) {}
-              assert(rank >= RANK_2 && rank <= RANK_7);
-          }
-          else
-          {
-              for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
-              rank = Rank(rank ^ 7);  // HACK to get the relative rank
-              assert(rank >= RANK_2 && rank <= RANK_7);
-          }
+          Rank rank = relative_rank(strongerSide, lsb(weakerSide, pawns));
           // If the defending king has distance 1 to the promotion square or
           // is placed somewhere in front of the pawn, it's a draw.
           if (   square_distance(kingSq, queeningSq) <= 1
               || relative_rank(strongerSide, kingSq) >= rank)
-              return SCALE_FACTOR_ZERO;
+              return SCALE_FACTOR_DRAW;
       }
   }
+
+  // All pawns on same B or G file? Then potential draw
+  if (    (pawnFile == FILE_B || pawnFile == FILE_G)
+      && !(pos.pieces(PAWN) & ~file_bb(pawnFile))
+      && pos.non_pawn_material(weakerSide) == 0
+      && pos.count<PAWN>(weakerSide) >= 1)
+  {
+      // Get weakerSide pawn that is closest to home rank
+      Square weakerPawnSq = lsb(weakerSide, pos.pieces(weakerSide, PAWN));
+
+      Square strongerKingSq = pos.king_square(strongerSide);
+      Square weakerKingSq = pos.king_square(weakerSide);
+      Square bishopSq = pos.list<BISHOP>(strongerSide)[0];
+
+      // Draw if weaker pawn is on rank 7, bishop can't attack the pawn, and
+      // weaker king can stop opposing opponent's king from penetrating.
+      if (   relative_rank(strongerSide, weakerPawnSq) == RANK_7
+          && opposite_colors(bishopSq, weakerPawnSq)
+          && square_distance(weakerPawnSq, weakerKingSq) <= square_distance(weakerPawnSq, strongerKingSq))
+          return SCALE_FACTOR_DRAW;
+  }
+
   return SCALE_FACTOR_NONE;
 }
 
 
-/// KQKRPScalingFunction scales endgames where the stronger side has only
-/// king and queen, while the weaker side has at least a rook and a pawn.
-/// It tests for fortress draws with a rook on the third rank defended by
-/// a pawn.
+/// K and queen vs K, rook and one or more pawns. It tests for fortress draws with
+/// a rook on the third rank defended by a pawn.
 template<>
-ScaleFactor ScalingFunction<KQKRPs>::apply(const Position& pos) const {
+ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
-  assert(pos.piece_count(strongerSide, QUEEN) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) == 0);
-  assert(pos.piece_count(weakerSide, ROOK) == 1);
-  assert(pos.piece_count(weakerSide, PAWN) >= 1);
+  assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
+  assert(pos.count<QUEEN>(strongerSide) == 1);
+  assert(pos.count< PAWN>(strongerSide) == 0);
+  assert(pos.count< ROOK>(weakerSide  ) == 1);
+  assert(pos.count< PAWN>(weakerSide  ) >= 1);
 
   Square kingSq = pos.king_square(weakerSide);
-  if (   relative_rank(weakerSide, kingSq) <= RANK_2
-      && relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4
-      && (pos.pieces(ROOK, weakerSide) & relative_rank_bb(weakerSide, RANK_3))
-      && (pos.pieces(PAWN, weakerSide) & relative_rank_bb(weakerSide, RANK_2))
-      && (pos.attacks_from<KING>(kingSq) & pos.pieces(PAWN, weakerSide)))
+  if (    relative_rank(weakerSide, kingSq) <= RANK_2
+      &&  relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4
+      && (pos.pieces(weakerSide, ROOK) & rank_bb(relative_rank(weakerSide, RANK_3)))
+      && (pos.pieces(weakerSide, PAWN) & rank_bb(relative_rank(weakerSide, RANK_2)))
+      && (pos.attacks_from<KING>(kingSq) & pos.pieces(weakerSide, PAWN)))
   {
-      Square rsq = pos.piece_list(weakerSide, ROOK, 0);
-      if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(PAWN, weakerSide))
-          return SCALE_FACTOR_ZERO;
+      Square rsq = pos.list<ROOK>(weakerSide)[0];
+      if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(weakerSide, PAWN))
+          return SCALE_FACTOR_DRAW;
   }
   return SCALE_FACTOR_NONE;
 }
 
 
-/// KRPKRScalingFunction scales KRP vs KR endgames. This function knows a
-/// handful of the most important classes of drawn positions, but is far
-/// from perfect. It would probably be a good idea to add more knowledge
-/// in the future.
+/// K, rook and one pawn vs K and a rook. This function knows a handful of the
+/// most important classes of drawn positions, but is far from perfect. It would
+/// probably be a good idea to add more knowledge in the future.
 ///
 /// It would also be nice to rewrite the actual code for this function,
 /// which is mostly copied from Glaurung 1.x, and not very pretty.
 template<>
-ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
+ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
-  assert(pos.piece_count(strongerSide, PAWN) == 1);
-  assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(strongerSide) == RookValueMg);
+  assert(pos.non_pawn_material(weakerSide)   == RookValueMg);
+  assert(pos.count<PAWN>(strongerSide) == 1);
+  assert(pos.count<PAWN>(weakerSide  ) == 0);
 
   Square wksq = pos.king_square(strongerSide);
-  Square wrsq = pos.piece_list(strongerSide, ROOK, 0);
-  Square wpsq = pos.piece_list(strongerSide, PAWN, 0);
   Square bksq = pos.king_square(weakerSide);
-  Square brsq = pos.piece_list(weakerSide, ROOK, 0);
+  Square wrsq = pos.list<ROOK>(strongerSide)[0];
+  Square wpsq = pos.list<PAWN>(strongerSide)[0];
+  Square brsq = pos.list<ROOK>(weakerSide)[0];
 
   // Orient the board in such a way that the stronger side is white, and the
   // pawn is on the left half of the board.
   if (strongerSide == BLACK)
   {
-      wksq = flip_square(wksq);
-      wrsq = flip_square(wrsq);
-      wpsq = flip_square(wpsq);
-      bksq = flip_square(bksq);
-      brsq = flip_square(brsq);
+      wksq = ~wksq;
+      wrsq = ~wrsq;
+      wpsq = ~wpsq;
+      bksq = ~bksq;
+      brsq = ~brsq;
   }
-  if (square_file(wpsq) > FILE_D)
+  if (file_of(wpsq) > FILE_D)
   {
-      wksq = flop_square(wksq);
-      wrsq = flop_square(wrsq);
-      wpsq = flop_square(wpsq);
-      bksq = flop_square(bksq);
-      brsq = flop_square(brsq);
+      wksq = mirror(wksq);
+      wrsq = mirror(wrsq);
+      wpsq = mirror(wpsq);
+      bksq = mirror(bksq);
+      brsq = mirror(brsq);
   }
 
-  File f = square_file(wpsq);
-  Rank r = square_rank(wpsq);
-  Square queeningSq = make_square(f, RANK_8);
+  File f = file_of(wpsq);
+  Rank r = rank_of(wpsq);
+  Square queeningSq = f | RANK_8;
   int tempo = (pos.side_to_move() == strongerSide);
 
   // If the pawn is not too far advanced and the defending king defends the
@@ -508,31 +552,31 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
   if (   r <= RANK_5
       && square_distance(bksq, queeningSq) <= 1
       && wksq <= SQ_H5
-      && (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
-      return SCALE_FACTOR_ZERO;
+      && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
+      return SCALE_FACTOR_DRAW;
 
   // The defending side saves a draw by checking from behind in case the pawn
   // has advanced to the 6th rank with the king behind.
   if (   r == RANK_6
       && square_distance(bksq, queeningSq) <= 1
-      && square_rank(wksq) + tempo <= RANK_6
-      && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
-      return SCALE_FACTOR_ZERO;
+      && rank_of(wksq) + tempo <= RANK_6
+      && (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3)))
+      return SCALE_FACTOR_DRAW;
 
   if (   r >= RANK_6
       && bksq == queeningSq
-      && square_rank(brsq) == RANK_1
+      && rank_of(brsq) == RANK_1
       && (!tempo || square_distance(wksq, wpsq) >= 2))
-      return SCALE_FACTOR_ZERO;
+      return SCALE_FACTOR_DRAW;
 
   // White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
   // and the black rook is behind the pawn.
   if (   wpsq == SQ_A7
       && wrsq == SQ_A8
       && (bksq == SQ_H7 || bksq == SQ_G7)
-      && square_file(brsq) == FILE_A
-      && (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
-      return SCALE_FACTOR_ZERO;
+      && file_of(brsq) == FILE_A
+      && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
+      return SCALE_FACTOR_DRAW;
 
   // If the defending king blocks the pawn and the attacking king is too far
   // away, it's a draw.
@@ -540,14 +584,14 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
       && bksq == wpsq + DELTA_N
       && square_distance(wksq, wpsq) - tempo >= 2
       && square_distance(wksq, brsq) - tempo >= 2)
-      return SCALE_FACTOR_ZERO;
+      return SCALE_FACTOR_DRAW;
 
   // Pawn on the 7th rank supported by the rook from behind usually wins if the
   // attacking king is closer to the queening square than the defending king,
   // and the defending king cannot gain tempi by threatening the attacking rook.
   if (   r == RANK_7
       && f != FILE_A
-      && square_file(wrsq) == f
+      && file_of(wrsq) == f
       && wrsq != queeningSq
       && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
       && (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
@@ -555,7 +599,7 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
 
   // Similar to the above, but with the pawn further back
   if (   f != FILE_A
-      && square_file(wrsq) == f
+      && file_of(wrsq) == f
       && wrsq < wpsq
       && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
       && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
@@ -570,9 +614,9 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
   // the pawn's path, it's probably a draw.
   if (r <= RANK_4 && bksq > wpsq)
   {
-      if (square_file(bksq) == square_file(wpsq))
+      if (file_of(bksq) == file_of(wpsq))
           return ScaleFactor(10);
-      if (   abs(square_file(bksq) - square_file(wpsq)) == 1
+      if (   abs(file_of(bksq) - file_of(wpsq)) == 1
           && square_distance(wksq, bksq) > 2)
           return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
   }
@@ -580,19 +624,19 @@ ScaleFactor ScalingFunction<KRPKR>::apply(const Position& pos) const {
 }
 
 
-/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
-/// single pattern: If the stronger side has no pawns and the defending king
+/// K, rook and two pawns vs K, rook and one pawn. There is only a single
+/// pattern: If the stronger side has no passed pawns and the defending king
 /// is actively placed, the position is drawish.
 template<>
-ScaleFactor ScalingFunction<KRPPKRP>::apply(const Position& pos) const {
+ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
-  assert(pos.piece_count(strongerSide, PAWN) == 2);
-  assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
-  assert(pos.piece_count(weakerSide, PAWN) == 1);
+  assert(pos.non_pawn_material(strongerSide) == RookValueMg);
+  assert(pos.non_pawn_material(weakerSide)   == RookValueMg);
+  assert(pos.count<PAWN>(strongerSide) == 2);
+  assert(pos.count<PAWN>(weakerSide  ) == 1);
 
-  Square wpsq1 = pos.piece_list(strongerSide, PAWN, 0);
-  Square wpsq2 = pos.piece_list(strongerSide, PAWN, 1);
+  Square wpsq1 = pos.list<PAWN>(strongerSide)[0];
+  Square wpsq2 = pos.list<PAWN>(strongerSide)[1];
   Square bksq = pos.king_square(weakerSide);
 
   // Does the stronger side have a passed pawn?
@@ -600,7 +644,7 @@ ScaleFactor ScalingFunction<KRPPKRP>::apply(const Position& pos) const {
       || pos.pawn_is_passed(strongerSide, wpsq2))
       return SCALE_FACTOR_NONE;
 
-  Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
+  Rank r = std::max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
 
   if (   file_distance(bksq, wpsq1) <= 1
       && file_distance(bksq, wpsq2) <= 1
@@ -619,71 +663,69 @@ ScaleFactor ScalingFunction<KRPPKRP>::apply(const Position& pos) const {
 }
 
 
-/// KPsKScalingFunction scales endgames with king and two or more pawns
-/// against king. There is just a single rule here: If all pawns are on
-/// the same rook file and are blocked by the defending king, it's a draw.
+/// K and two or more pawns vs K. There is just a single rule here: If all pawns
+/// are on the same rook file and are blocked by the defending king, it's a draw.
 template<>
-ScaleFactor ScalingFunction<KPsK>::apply(const Position& pos) const {
+ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
 
   assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
-  assert(pos.piece_count(strongerSide, PAWN) >= 2);
-  assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(weakerSide)   == VALUE_ZERO);
+  assert(pos.count<PAWN>(strongerSide) >= 2);
+  assert(pos.count<PAWN>(weakerSide  ) == 0);
 
   Square ksq = pos.king_square(weakerSide);
-  Bitboard pawns = pos.pieces(PAWN, strongerSide);
+  Bitboard pawns = pos.pieces(strongerSide, PAWN);
 
   // Are all pawns on the 'a' file?
-  if ((pawns & ~FileABB) == EmptyBoardBB)
+  if (!(pawns & ~FileABB))
   {
       // Does the defending king block the pawns?
       if (   square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
-          || (   square_file(ksq) == FILE_A
-              && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
-          return SCALE_FACTOR_ZERO;
+          || (    file_of(ksq) == FILE_A
+              && !(in_front_bb(strongerSide, rank_of(ksq)) & pawns)))
+          return SCALE_FACTOR_DRAW;
   }
   // Are all pawns on the 'h' file?
-  else if ((pawns & ~FileHBB) == EmptyBoardBB)
+  else if (!(pawns & ~FileHBB))
   {
     // Does the defending king block the pawns?
     if (   square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
-        || (   square_file(ksq) == FILE_H
-            && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
-        return SCALE_FACTOR_ZERO;
+        || (    file_of(ksq) == FILE_H
+            && !(in_front_bb(strongerSide, rank_of(ksq)) & pawns)))
+        return SCALE_FACTOR_DRAW;
   }
   return SCALE_FACTOR_NONE;
 }
 
 
-/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
-/// If the defending king is somewhere along the path of the pawn, and the
-/// square of the king is not of the same color as the stronger side's bishop,
-/// it's a draw. If the two bishops have opposite color, it's almost always
-/// a draw.
+/// K, bishop and a pawn vs K and a bishop. There are two rules: If the defending
+/// king is somewhere along the path of the pawn, and the square of the king is
+/// not of the same color as the stronger side's bishop, it's a draw. If the two
+/// bishops have opposite color, it's almost always a draw.
 template<>
-ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
-
-  assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
-  assert(pos.piece_count(strongerSide, BISHOP) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) == 1);
-  assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
-  assert(pos.piece_count(weakerSide, BISHOP) == 1);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
-
-  Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
-  Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
-  Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0);
+ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
+
+  assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == BishopValueMg);
+  assert(pos.count<BISHOP>(strongerSide) == 1);
+  assert(pos.count<BISHOP>(weakerSide  ) == 1);
+  assert(pos.count<  PAWN>(strongerSide) == 1);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
+
+  Square pawnSq = pos.list<PAWN>(strongerSide)[0];
+  Square strongerBishopSq = pos.list<BISHOP>(strongerSide)[0];
+  Square weakerBishopSq = pos.list<BISHOP>(weakerSide)[0];
   Square weakerKingSq = pos.king_square(weakerSide);
 
   // Case 1: Defending king blocks the pawn, and cannot be driven away
-  if (   square_file(weakerKingSq) == square_file(pawnSq)
+  if (   file_of(weakerKingSq) == file_of(pawnSq)
       && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
-      && (  !same_color_squares(weakerKingSq, strongerBishopSq)
+      && (   opposite_colors(weakerKingSq, strongerBishopSq)
           || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
-      return SCALE_FACTOR_ZERO;
+      return SCALE_FACTOR_DRAW;
 
   // Case 2: Opposite colored bishops
-  if (!same_color_squares(strongerBishopSq, weakerBishopSq))
+  if (opposite_colors(strongerBishopSq, weakerBishopSq))
   {
       // We assume that the position is drawn in the following three situations:
       //
@@ -696,57 +738,57 @@ ScaleFactor ScalingFunction<KBPKB>::apply(const Position& pos) const {
       // reasonably well.
 
       if (relative_rank(strongerSide, pawnSq) <= RANK_5)
-          return SCALE_FACTOR_ZERO;
+          return SCALE_FACTOR_DRAW;
       else
       {
-          Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
-          if (ray & pos.pieces(KING, weakerSide))
-              return SCALE_FACTOR_ZERO;
+          Bitboard path = forward_bb(strongerSide, pawnSq);
 
-          if (  (pos.attacks_from<BISHOP>(weakerBishopSq) & ray)
+          if (path & pos.pieces(weakerSide, KING))
+              return SCALE_FACTOR_DRAW;
+
+          if (  (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
               && square_distance(weakerBishopSq, pawnSq) >= 3)
-              return SCALE_FACTOR_ZERO;
+              return SCALE_FACTOR_DRAW;
       }
   }
   return SCALE_FACTOR_NONE;
 }
 
 
-/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic
-/// draws with opposite-colored bishops.
+/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with
+/// opposite-colored bishops.
 template<>
-ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
+ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
-  assert(pos.piece_count(strongerSide, BISHOP) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) == 2);
-  assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
-  assert(pos.piece_count(weakerSide, BISHOP) == 1);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == BishopValueMg);
+  assert(pos.count<BISHOP>(strongerSide) == 1);
+  assert(pos.count<BISHOP>(weakerSide  ) == 1);
+  assert(pos.count<  PAWN>(strongerSide) == 2);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
 
-  Square wbsq = pos.piece_list(strongerSide, BISHOP, 0);
-  Square bbsq = pos.piece_list(weakerSide, BISHOP, 0);
+  Square wbsq = pos.list<BISHOP>(strongerSide)[0];
+  Square bbsq = pos.list<BISHOP>(weakerSide)[0];
 
-  if (same_color_squares(wbsq, bbsq))
-      // Not opposite-colored bishops, no scaling
+  if (!opposite_colors(wbsq, bbsq))
       return SCALE_FACTOR_NONE;
 
   Square ksq = pos.king_square(weakerSide);
-  Square psq1 = pos.piece_list(strongerSide, PAWN, 0);
-  Square psq2 = pos.piece_list(strongerSide, PAWN, 1);
-  Rank r1 = square_rank(psq1);
-  Rank r2 = square_rank(psq2);
+  Square psq1 = pos.list<PAWN>(strongerSide)[0];
+  Square psq2 = pos.list<PAWN>(strongerSide)[1];
+  Rank r1 = rank_of(psq1);
+  Rank r2 = rank_of(psq2);
   Square blockSq1, blockSq2;
 
   if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
   {
       blockSq1 = psq1 + pawn_push(strongerSide);
-      blockSq2 = make_square(square_file(psq2), square_rank(psq1));
+      blockSq2 = file_of(psq2) | rank_of(psq1);
   }
   else
   {
       blockSq1 = psq2 + pawn_push(strongerSide);
-      blockSq2 = make_square(square_file(psq1), square_rank(psq2));
+      blockSq2 = file_of(psq1) | rank_of(psq2);
   }
 
   switch (file_distance(psq1, psq2))
@@ -754,29 +796,29 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
   case 0:
     // Both pawns are on the same file. Easy draw if defender firmly controls
     // some square in the frontmost pawn's path.
-    if (   square_file(ksq) == square_file(blockSq1)
+    if (   file_of(ksq) == file_of(blockSq1)
         && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
-        && !same_color_squares(ksq, wbsq))
-        return SCALE_FACTOR_ZERO;
+        && opposite_colors(ksq, wbsq))
+        return SCALE_FACTOR_DRAW;
     else
         return SCALE_FACTOR_NONE;
 
   case 1:
-    // Pawns on neighboring files. Draw if defender firmly controls the square
+    // Pawns on adjacent files. Draw if defender firmly controls the square
     // in front of the frontmost pawn's path, and the square diagonally behind
     // this square on the file of the other pawn.
     if (   ksq == blockSq1
-        && !same_color_squares(ksq, wbsq)
+        && opposite_colors(ksq, wbsq)
         && (   bbsq == blockSq2
-            || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
-            || rank_distance(r1, r2) >= 2))
-        return SCALE_FACTOR_ZERO;
+            || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakerSide, BISHOP))
+            || abs(r1 - r2) >= 2))
+        return SCALE_FACTOR_DRAW;
 
     else if (   ksq == blockSq2
-             && !same_color_squares(ksq, wbsq)
+             && opposite_colors(ksq, wbsq)
              && (   bbsq == blockSq1
-                 || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
-        return SCALE_FACTOR_ZERO;
+                 || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakerSide, BISHOP))))
+        return SCALE_FACTOR_DRAW;
     else
         return SCALE_FACTOR_NONE;
 
@@ -787,123 +829,118 @@ ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) const {
 }
 
 
-/// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule:
-/// If the defending king is somewhere along the path of the pawn, and the
-/// square of the king is not of the same color as the stronger side's bishop,
-/// it's a draw.
+/// K, bisop and a pawn vs K and knight. There is a single rule: If the defending
+/// king is somewhere along the path of the pawn, and the square of the king is
+/// not of the same color as the stronger side's bishop, it's a draw.
 template<>
-ScaleFactor ScalingFunction<KBPKN>::apply(const Position& pos) const {
+ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
-  assert(pos.piece_count(strongerSide, BISHOP) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) == 1);
-  assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
-  assert(pos.piece_count(weakerSide, KNIGHT) == 1);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == KnightValueMg);
+  assert(pos.count<BISHOP>(strongerSide) == 1);
+  assert(pos.count<KNIGHT>(weakerSide  ) == 1);
+  assert(pos.count<  PAWN>(strongerSide) == 1);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
 
-  Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
-  Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
+  Square pawnSq = pos.list<PAWN>(strongerSide)[0];
+  Square strongerBishopSq = pos.list<BISHOP>(strongerSide)[0];
   Square weakerKingSq = pos.king_square(weakerSide);
 
-  if (   square_file(weakerKingSq) == square_file(pawnSq)
+  if (   file_of(weakerKingSq) == file_of(pawnSq)
       && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
-      && (  !same_color_squares(weakerKingSq, strongerBishopSq)
+      && (   opposite_colors(weakerKingSq, strongerBishopSq)
           || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
-      return SCALE_FACTOR_ZERO;
+      return SCALE_FACTOR_DRAW;
 
   return SCALE_FACTOR_NONE;
 }
 
 
-/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule:
-/// If the pawn is a rook pawn on the 7th rank and the defending king prevents
-/// the pawn from advancing, the position is drawn.
+/// K, knight and a pawn vs K. There is a single rule: If the pawn is a rook pawn
+/// on the 7th rank and the defending king prevents the pawn from advancing, the
+/// position is drawn.
 template<>
-ScaleFactor ScalingFunction<KNPK>::apply(const Position& pos) const {
+ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
 
-  assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
-  assert(pos.piece_count(strongerSide, KNIGHT) == 1);
-  assert(pos.piece_count(strongerSide, PAWN) == 1);
-  assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(pos.non_pawn_material(strongerSide) == KnightValueMg);
+  assert(pos.non_pawn_material(weakerSide  ) == VALUE_ZERO);
+  assert(pos.count<KNIGHT>(strongerSide) == 1);
+  assert(pos.count<  PAWN>(strongerSide) == 1);
+  assert(pos.count<  PAWN>(weakerSide  ) == 0);
 
-  Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
+  Square pawnSq = pos.list<PAWN>(strongerSide)[0];
   Square weakerKingSq = pos.king_square(weakerSide);
 
   if (   pawnSq == relative_square(strongerSide, SQ_A7)
       && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
-      return SCALE_FACTOR_ZERO;
+      return SCALE_FACTOR_DRAW;
 
   if (   pawnSq == relative_square(strongerSide, SQ_H7)
       && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
-      return SCALE_FACTOR_ZERO;
+      return SCALE_FACTOR_DRAW;
+
+  return SCALE_FACTOR_NONE;
+}
+
+
+/// K, knight and a pawn vs K and bishop. If knight can block bishop from taking
+/// pawn, it's a win. Otherwise, drawn.
+template<>
+ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
+
+  Square pawnSq = pos.list<PAWN>(strongerSide)[0];
+  Square bishopSq = pos.list<BISHOP>(weakerSide)[0];
+  Square weakerKingSq = pos.king_square(weakerSide);
+
+  // King needs to get close to promoting pawn to prevent knight from blocking.
+  // Rules for this are very tricky, so just approximate.
+  if (forward_bb(strongerSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
+      return ScaleFactor(square_distance(weakerKingSq, pawnSq));
 
   return SCALE_FACTOR_NONE;
 }
 
 
-/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing
-/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest
-/// side has a draw without the pawn, she probably has at least a draw with
-/// the pawn as well. The exception is when the stronger side's pawn is far
-/// advanced and not on a rook file; in this case it is often possible to win
-/// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
+/// K and a pawn vs K and a pawn. This is done by removing the weakest side's
+/// pawn and probing the KP vs K bitbase: If the weakest side has a draw without
+/// the pawn, she probably has at least a draw with the pawn as well. The exception
+/// is when the stronger side's pawn is far advanced and not on a rook file; in
+/// this case it is often possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
 template<>
-ScaleFactor ScalingFunction<KPKP>::apply(const Position& pos) const {
+ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
 
   assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
-  assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
-  assert(pos.piece_count(WHITE, PAWN) == 1);
-  assert(pos.piece_count(BLACK, PAWN) == 1);
+  assert(pos.non_pawn_material(weakerSide  ) == VALUE_ZERO);
+  assert(pos.count<PAWN>(WHITE) == 1);
+  assert(pos.count<PAWN>(BLACK) == 1);
 
-  Square wksq, bksq, wpsq;
-  Color stm;
+  Square wksq = pos.king_square(strongerSide);
+  Square bksq = pos.king_square(weakerSide);
+  Square wpsq = pos.list<PAWN>(strongerSide)[0];
+  Color us = pos.side_to_move();
 
-  if (strongerSide == WHITE)
-  {
-      wksq = pos.king_square(WHITE);
-      bksq = pos.king_square(BLACK);
-      wpsq = pos.piece_list(WHITE, PAWN, 0);
-      stm = pos.side_to_move();
-  }
-  else
+  if (strongerSide == BLACK)
   {
-      wksq = flip_square(pos.king_square(BLACK));
-      bksq = flip_square(pos.king_square(WHITE));
-      wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
-      stm = opposite_color(pos.side_to_move());
+      wksq = ~wksq;
+      bksq = ~bksq;
+      wpsq = ~wpsq;
+      us   = ~us;
   }
 
-  if (square_file(wpsq) >= FILE_E)
+  if (file_of(wpsq) >= FILE_E)
   {
-      wksq = flop_square(wksq);
-      bksq = flop_square(bksq);
-      wpsq = flop_square(wpsq);
+      wksq = mirror(wksq);
+      bksq = mirror(bksq);
+      wpsq = mirror(wpsq);
   }
 
   // If the pawn has advanced to the fifth rank or further, and is not a
   // rook pawn, it's too dangerous to assume that it's at least a draw.
-  if (   square_rank(wpsq) >= RANK_5
-      && square_file(wpsq) != FILE_A)
+  if (   rank_of(wpsq) >= RANK_5
+      && file_of(wpsq) != FILE_A)
       return SCALE_FACTOR_NONE;
 
-  // Probe the KPK bitbase with the weakest side's pawn removed. If it's a
-  // draw, it's probably at least a draw even with the pawn.
-  return probe_kpk(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO;
-}
-
-
-namespace {
-
-  // Probe the KP vs K bitbase
-
-  int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) {
-
-    int wp = square_file(wpsq) + 4 * (square_rank(wpsq) - 1);
-    int index = int(stm) + 2 * bksq + 128 * wksq + 8192 * wp;
-
-    assert(index >= 0 && index < 24576 * 8);
-
-    return KPKBitbase[index / 8] & (1 << (index & 7));
-  }
+  // Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw,
+  // it's probably at least a draw even with the pawn.
+  return Bitbases::probe_kpk(wksq, wpsq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
 }