X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=c8d222804008c5d78019439bf5a53da610642d5f;hp=8280131753b859ea1ea784230eb1abde1c23f7d8;hb=d9be00342cb1719b1ec510a4284f198607ce25df;hpb=14df99130f53a2a5f57260eb830b4c0029bd4e99

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 82801317..c8d22280 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
@@ -17,22 +17,21 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <cassert>
 #include <algorithm>
+#include <cassert>
 
+#include "bitboard.h"
 #include "bitcount.h"
 #include "endgame.h"
-#include "pawns.h"
+#include "movegen.h"
 
 using std::string;
 
-extern uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm);
-
 namespace {
 
-  // Table used to drive the defending king towards the edge of the board
+  // Table used to drive the king towards the edge of the board
   // in KX vs K and KQ vs KR endgames.
-  const int MateTable[64] = {
+  const int PushToEdges[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,
@@ -43,9 +42,9 @@ namespace {
     100, 90, 80, 70, 70, 80, 90, 100,
   };
 
-  // Table used to drive the defending king towards a corner square of the
+  // Table used to drive the king towards a corner square of the
   // right color in KBN vs K endgames.
-  const int KBNKMateTable[64] = {
+  const int PushToCorners[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,
@@ -56,47 +55,43 @@ namespace {
     130, 140, 150, 160, 170, 180, 190, 200
   };
 
-  // The attacking side is given a descending bonus based on distance between
-  // the two kings in basic endgames.
-  const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
+  // Tables used to drive a piece towards or away from another piece
+  const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
+  const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
 
-  // Build corresponding key code for the opposite color: "KBPKN" -> "KNKBP"
-  const string swap_colors(const string& keyCode) {
-
-    size_t idx = keyCode.find('K', 1);
-    return keyCode.substr(idx) + keyCode.substr(0, idx);
+#ifndef NDEBUG
+  bool verify_material(const Position& pos, Color c, Value npm, int num_pawns) {
+    return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == num_pawns;
   }
+#endif
 
-  // Get the material key of a position out of the given endgame key code
-  // like "KBPKN". The trick here is to first build up a 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 mat_key(const string& keyCode) {
+  // 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) {
 
-    assert(keyCode.length() > 0 && keyCode.length() < 8);
-    assert(keyCode[0] == 'K');
+    assert(code.length() > 0 && code.length() < 8);
+    assert(code[0] == 'K');
 
-    string fen;
-    size_t i = 0;
+    string sides[] = { code.substr(code.find('K', 1)),      // Weak
+                       code.substr(0, code.find('K', 1)) }; // Strong
 
-    // First add white and then black pieces
-    do fen += keyCode[i];                while (keyCode[++i] != 'K');
-    do fen += char(tolower(keyCode[i])); while (++i < keyCode.length());
+    std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
 
-    // Add file padding and remaining empty ranks
-    fen += string(1, '0' + int(8 - keyCode.length())) + "/8/8/8/8/8/8/8 w - - 0 10";
+    string fen =  sides[0] + char('0' + int(8 - code.length()))
+                + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10";
 
-    // Build a Position out of the fen string and get its material key
-    return Position(fen, false, 0).get_material_key();
+    return Position(fen, false, NULL).material_key();
   }
 
-} // namespace
+  template<typename M>
+  void delete_endgame(const typename M::value_type& p) { delete p.second; }
 
+} // namespace
 
-/// Endgames member definitions
 
-template<> const Endgames::M1& Endgames::map<Endgames::M1>() const { return m1; }
-template<> const Endgames::M2& Endgames::map<Endgames::M2>() const { return m2; }
+/// Endgames members definitions
 
 Endgames::Endgames() {
 
@@ -106,11 +101,14 @@ Endgames::Endgames() {
   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<KRPKB>("KRPKB");
   add<KBPKB>("KBPKB");
   add<KBPKN>("KBPKN");
   add<KBPPKB>("KBPPKB");
@@ -119,21 +117,15 @@ Endgames::Endgames() {
 
 Endgames::~Endgames() {
 
-  for (M1::const_iterator it = m1.begin(); it != m1.end(); ++it)
-      delete it->second;
-
-  for (M2::const_iterator it = m2.begin(); it != m2.end(); ++it)
-      delete it->second;
+  for_each(m1.begin(), m1.end(), delete_endgame<M1>);
+  for_each(m2.begin(), m2.end(), delete_endgame<M2>);
 }
 
 template<EndgameType E>
-void Endgames::add(const string& keyCode) {
+void Endgames::add(const string& code) {
 
-  typedef typename eg_family<E>::type T;
-  typedef typename Map<T>::type M;
-
-  const_cast<M&>(map<M>()).insert(std::make_pair(mat_key(keyCode), new Endgame<E>(WHITE)));
-  const_cast<M&>(map<M>()).insert(std::make_pair(mat_key(swap_colors(keyCode)), new Endgame<E>(BLACK)));
+  map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
+  map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
 }
 
 
@@ -144,24 +136,27 @@ void Endgames::add(const string& keyCode) {
 template<>
 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(verify_material(pos, weakSide, VALUE_ZERO, 0));
+  assert(!pos.checkers()); // Eval is never called when in check
+
+  // Stalemate detection with lone king
+  if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
+      return VALUE_DRAW;
 
-  Square winnerKSq = pos.king_square(strongerSide);
-  Square loserKSq = pos.king_square(weakerSide);
+  Square winnerKSq = pos.king_square(strongSide);
+  Square loserKSq = pos.king_square(weakSide);
 
-  Value result =   pos.non_pawn_material(strongerSide)
-                 + pos.piece_count(strongerSide, PAWN) * PawnValueEndgame
-                 + MateTable[loserKSq]
-                 + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+  Value result =  pos.non_pawn_material(strongSide)
+                + pos.count<PAWN>(strongSide) * PawnValueEg
+                + PushToEdges[loserKSq]
+                + PushClose[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!
+  if (   pos.count<QUEEN>(strongSide)
+      || pos.count<ROOK>(strongSide)
+      || pos.bishop_pair(strongSide))
       result += VALUE_KNOWN_WIN;
 
-  return strongerSide == pos.side_to_move() ? result : -result;
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
 
@@ -170,31 +165,27 @@ Value Endgame<KXK>::operator()(const Position& pos) const {
 template<>
 Value Endgame<KBNK>::operator()(const Position& pos) const {
 
-  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(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
 
-  Square winnerKSq = pos.king_square(strongerSide);
-  Square loserKSq = pos.king_square(weakerSide);
-  Square bishopSquare = pos.piece_list(strongerSide, BISHOP)[0];
+  Square winnerKSq = pos.king_square(strongSide);
+  Square loserKSq = pos.king_square(weakSide);
+  Square bishopSq = pos.list<BISHOP>(strongSide)[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 (opposite_colors(bishopSquare, SQ_A1))
+  if (opposite_colors(bishopSq, SQ_A1))
   {
       winnerKSq = mirror(winnerKSq);
       loserKSq = mirror(loserKSq);
   }
 
   Value result =  VALUE_KNOWN_WIN
-                + DistanceBonus[square_distance(winnerKSq, loserKSq)]
-                + KBNKMateTable[loserKSq];
+                + PushClose[square_distance(winnerKSq, loserKSq)]
+                + PushToCorners[loserKSq];
 
-  return strongerSide == pos.side_to_move() ? result : -result;
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
 
@@ -202,44 +193,35 @@ Value Endgame<KBNK>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, VALUE_ZERO, 1));
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
 
-  Square wksq, bksq, wpsq;
-  Color stm;
+  Square wksq = pos.king_square(strongSide);
+  Square bksq = pos.king_square(weakSide);
+  Square psq  = pos.list<PAWN>(strongSide)[0];
+  Color  us   = pos.side_to_move();
 
-  if (strongerSide == WHITE)
+  if (strongSide == BLACK)
   {
-      wksq = pos.king_square(WHITE);
-      bksq = pos.king_square(BLACK);
-      wpsq = pos.piece_list(WHITE, PAWN)[0];
-      stm = pos.side_to_move();
-  }
-  else
-  {
-      wksq = flip(pos.king_square(BLACK));
-      bksq = flip(pos.king_square(WHITE));
-      wpsq = flip(pos.piece_list(BLACK, PAWN)[0]);
-      stm = flip(pos.side_to_move());
+      wksq = ~wksq;
+      bksq = ~bksq;
+      psq  = ~psq;
+      us   = ~us;
   }
 
-  if (file_of(wpsq) >= FILE_E)
+  if (file_of(psq) >= FILE_E)
   {
       wksq = mirror(wksq);
       bksq = mirror(bksq);
-      wpsq = mirror(wpsq);
+      psq  = mirror(psq);
   }
 
-  if (!probe_kpk_bitbase(wksq, wpsq, bksq, stm))
+  if (!Bitbases::probe_kpk(wksq, psq, bksq, us))
       return VALUE_DRAW;
 
-  Value result =  VALUE_KNOWN_WIN
-                + PawnValueEndgame
-                + Value(rank_of(wpsq));
+  Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq));
 
-  return strongerSide == pos.side_to_move() ? result : -result;
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
 
@@ -250,55 +232,50 @@ Value Endgame<KPK>::operator()(const Position& pos) const {
 template<>
 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(weakerSide) == 0);
-  assert(pos.piece_count(weakerSide, PAWN) == 1);
-
-  Square wksq, wrsq, bksq, bpsq;
-  int tempo = (pos.side_to_move() == strongerSide);
+  assert(verify_material(pos, strongSide, RookValueMg, 0));
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
 
-  wksq = pos.king_square(strongerSide);
-  wrsq = pos.piece_list(strongerSide, ROOK)[0];
-  bksq = pos.king_square(weakerSide);
-  bpsq = pos.piece_list(weakerSide, PAWN)[0];
+  Square wksq = pos.king_square(strongSide);
+  Square bksq = pos.king_square(weakSide);
+  Square rsq  = pos.list<ROOK>(strongSide)[0];
+  Square psq  = pos.list<PAWN>(weakSide)[0];
 
-  if (strongerSide == BLACK)
+  if (strongSide == BLACK)
   {
-      wksq = flip(wksq);
-      wrsq = flip(wrsq);
-      bksq = flip(bksq);
-      bpsq = flip(bpsq);
+      wksq = ~wksq;
+      bksq = ~bksq;
+      rsq  = ~rsq;
+      psq  = ~psq;
   }
 
-  Square queeningSq = make_square(file_of(bpsq), RANK_1);
+  Square queeningSq = file_of(psq) | RANK_1;
   Value result;
 
   // If the stronger side's king is in front of the pawn, it's a win
-  if (wksq < bpsq && file_of(wksq) == file_of(bpsq))
-      result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+  if (wksq < psq && file_of(wksq) == file_of(psq))
+      result = RookValueEg - Value(square_distance(wksq, psq));
 
   // 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));
+  // it's a win.
+  else if (   square_distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
+           && square_distance(bksq, rsq) >= 3)
+      result = RookValueEg - Value(square_distance(wksq, psq));
 
   // If the pawn is far advanced and supported by the defending king,
   // the position is drawish
   else if (   rank_of(bksq) <= RANK_3
-           && square_distance(bksq, bpsq) == 1
+           && square_distance(bksq, psq) == 1
            && rank_of(wksq) >= RANK_4
-           && square_distance(wksq, bpsq) - tempo > 2)
-      result = Value(80 - square_distance(wksq, bpsq) * 8);
+           && square_distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
+      result = Value(80 - square_distance(wksq, psq) * 8);
 
   else
       result =  Value(200)
-              - Value(square_distance(wksq, bpsq + DELTA_S) * 8)
-              + Value(square_distance(bksq, bpsq + DELTA_S) * 8)
-              + Value(square_distance(bpsq, queeningSq) * 8);
+              - Value(square_distance(wksq, psq + DELTA_S) * 8)
+              + Value(square_distance(bksq, psq + DELTA_S) * 8)
+              + Value(square_distance(psq, queeningSq) * 8);
 
-  return strongerSide == pos.side_to_move() ? result : -result;
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
 
@@ -307,14 +284,11 @@ Value Endgame<KRKP>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, RookValueMg, 0));
+  assert(verify_material(pos, weakSide, BishopValueMg, 0));
 
-  Value result = Value(MateTable[pos.king_square(weakerSide)]);
-  return strongerSide == pos.side_to_move() ? result : -result;
+  Value result = Value(PushToEdges[pos.king_square(weakSide)]);
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
 
@@ -323,18 +297,37 @@ Value Endgame<KRKB>::operator()(const Position& pos) const {
 template<>
 Value Endgame<KRKN>::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(verify_material(pos, strongSide, RookValueMg, 0));
+  assert(verify_material(pos, weakSide, KnightValueMg, 0));
+
+  Square bksq = pos.king_square(weakSide);
+  Square bnsq = pos.list<KNIGHT>(weakSide)[0];
+  Value result = Value(PushToEdges[bksq] + PushAway[square_distance(bksq, bnsq)]);
+  return strongSide == 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(verify_material(pos, strongSide, QueenValueMg, 0));
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
+
+  Square winnerKSq = pos.king_square(strongSide);
+  Square loserKSq = pos.king_square(weakSide);
+  Square pawnSq = pos.list<PAWN>(weakSide)[0];
 
-  const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 };
+  Value result = Value(PushClose[square_distance(winnerKSq, loserKSq)]);
 
-  Square bksq = pos.king_square(weakerSide);
-  Square bnsq = pos.piece_list(weakerSide, KNIGHT)[0];
-  Value result = Value(MateTable[bksq] + penalty[square_distance(bksq, bnsq)]);
-  return strongerSide == pos.side_to_move() ? result : -result;
+  if (   relative_rank(weakSide, pawnSq) != RANK_7
+      || square_distance(loserKSq, pawnSq) != 1
+      || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq))
+      result += QueenValueEg - PawnValueEg;
+
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
 
@@ -346,60 +339,48 @@ Value Endgame<KRKN>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, QueenValueMg, 0));
+  assert(verify_material(pos, weakSide, RookValueMg, 0));
 
-  Square winnerKSq = pos.king_square(strongerSide);
-  Square loserKSq = pos.king_square(weakerSide);
+  Square winnerKSq = pos.king_square(strongSide);
+  Square loserKSq = pos.king_square(weakSide);
 
-  Value result =  QueenValueEndgame
-                - RookValueEndgame
-                + MateTable[loserKSq]
-                + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+  Value result =  QueenValueEg
+                - RookValueEg
+                + PushToEdges[loserKSq]
+                + PushClose[square_distance(winnerKSq, loserKSq)];
 
-  return strongerSide == pos.side_to_move() ? result : -result;
+  return strongSide == pos.side_to_move() ? result : -result;
 }
 
-template<>
-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));
+/// KBB vs KN. This is almost always a win. We try to push enemy king to a corner
+/// and away from his knight. For a reference of this difficult endgame see:
+/// en.wikipedia.org/wiki/Chess_endgame#Effect_of_tablebases_on_endgame_theory
 
-  Value result = BishopValueEndgame;
-  Square wksq = pos.king_square(strongerSide);
-  Square bksq = pos.king_square(weakerSide);
-  Square nsq = pos.piece_list(weakerSide, KNIGHT)[0];
+template<>
+Value Endgame<KBBKN>::operator()(const Position& pos) const {
 
-  // Bonus for attacking king close to defending king
-  result += Value(DistanceBonus[square_distance(wksq, bksq)]);
+  assert(verify_material(pos, strongSide, 2 * BishopValueMg, 0));
+  assert(verify_material(pos, weakSide, KnightValueMg, 0));
 
-  // Bonus for driving the defending king and knight apart
-  result += Value(square_distance(bksq, nsq) * 32);
+  Square winnerKSq = pos.king_square(strongSide);
+  Square loserKSq = pos.king_square(weakSide);
+  Square knightSq = pos.list<KNIGHT>(weakSide)[0];
 
-  // Bonus for restricting the knight's mobility
-  result += Value((8 - count_1s<CNT32_MAX15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
+  Value result =  VALUE_KNOWN_WIN
+                + PushToCorners[loserKSq]
+                + PushClose[square_distance(winnerKSq, loserKSq)]
+                + PushAway[square_distance(loserKSq, knightSq)];
 
-  return strongerSide == pos.side_to_move() ? result : -result;
+  return strongSide == 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 Endgame<KmmKm>::operator()(const Position&) const {
-  return VALUE_DRAW;
-}
+/// 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 Endgame<KNNK>::operator()(const Position&) const {
-  return VALUE_DRAW;
-}
 
 /// 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
@@ -408,49 +389,74 @@ Value Endgame<KNNK>::operator()(const Position&) const {
 template<>
 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(strongSide) == BishopValueMg);
+  assert(pos.count<PAWN>(strongSide) >= 1);
 
-  // No assertions about the material of weakerSide, because we want draws to
+  // No assertions about the material of weakSide, because we want draws to
   // be detected even when the weaker side has some pawns.
 
-  Bitboard pawns = pos.pieces(PAWN, strongerSide);
-  File pawnFile = file_of(pos.piece_list(strongerSide, PAWN)[0]);
+  Bitboard pawns = pos.pieces(strongSide, PAWN);
+  File pawnFile = file_of(pos.list<PAWN>(strongSide)[0]);
 
   // All pawns are on a single rook file ?
-  if (   (pawnFile == FILE_A || pawnFile == FILE_H)
+  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 kingSq = pos.king_square(weakerSide);
+      Square bishopSq = pos.list<BISHOP>(strongSide)[0];
+      Square queeningSq = relative_square(strongSide, pawnFile | RANK_8);
+      Square kingSq = pos.king_square(weakSide);
 
       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); rank--) {}
-              assert(rank >= RANK_2 && rank <= RANK_7);
-          }
-          else
-          {
-              for (rank = RANK_2; !(rank_bb(rank) & pawns); rank++) {}
-              rank = Rank(rank ^ 7);  // HACK to get the relative rank
-              assert(rank >= RANK_2 && rank <= RANK_7);
-          }
+          Square pawnSq = frontmost_sq(strongSide, 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)
+              || relative_rank(weakSide, kingSq) <= relative_rank(weakSide, pawnSq))
+              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(weakSide) == 0
+      && pos.count<PAWN>(weakSide) >= 1)
+  {
+      // Get weakSide pawn that is closest to home rank
+      Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN));
+
+      Square strongKingSq = pos.king_square(strongSide);
+      Square weakKingSq = pos.king_square(weakSide);
+      Square bishopSq = pos.list<BISHOP>(strongSide)[0];
+
+      // Potential for a draw if our pawn is blocked on the 7th rank
+      // the bishop cannot attack it or they only have one pawn left
+      if (   relative_rank(strongSide, weakPawnSq) == RANK_7
+          && (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
+          && (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 1))
+      {
+          int strongKingDist = square_distance(weakPawnSq, strongKingSq);
+          int weakKingDist = square_distance(weakPawnSq, weakKingSq);
+
+          // Draw if the weak king is on it's back two ranks, within 2
+          // squares of the blocking pawn and the strong king is not
+          // closer. (I think this rule only fails in practically
+          // unreachable positions such as 5k1K/6p1/6P1/8/8/3B4/8/8 w
+          // and positions where qsearch will immediately correct the
+          // problem such as 8/4k1p1/6P1/1K6/3B4/8/8/8 w)
+          if (   relative_rank(strongSide, weakKingSq) >= RANK_7
+              && weakKingDist <= 2
+              && weakKingDist <= strongKingDist)
               return SCALE_FACTOR_DRAW;
       }
   }
+
   return SCALE_FACTOR_NONE;
 }
 
@@ -460,23 +466,21 @@ ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
 template<>
 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);
-
-  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) & rank_bb(relative_rank(weakerSide, RANK_3)))
-      && (pos.pieces(PAWN, weakerSide) & rank_bb(relative_rank(weakerSide, RANK_2)))
-      && (pos.attacks_from<KING>(kingSq) & pos.pieces(PAWN, weakerSide)))
-  {
-      Square rsq = pos.piece_list(weakerSide, ROOK)[0];
-      if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(PAWN, weakerSide))
+  assert(verify_material(pos, strongSide, QueenValueMg, 0));
+  assert(pos.count<ROOK>(weakSide) == 1);
+  assert(pos.count<PAWN>(weakSide) >= 1);
+
+  Square kingSq = pos.king_square(weakSide);
+  Square rsq = pos.list<ROOK>(weakSide)[0];
+
+  if (    relative_rank(weakSide, kingSq) <= RANK_2
+      &&  relative_rank(weakSide, pos.king_square(strongSide)) >= RANK_4
+      && (pos.pieces(weakSide, ROOK) & rank_bb(relative_rank(weakSide, RANK_3)))
+      && (pos.pieces(weakSide, PAWN) & rank_bb(relative_rank(weakSide, RANK_2)))
+      && (pos.attacks_from<KING>(kingSq) & pos.pieces(weakSide, PAWN))
+      && (pos.attacks_from<PAWN>(rsq, strongSide) & pos.pieces(weakSide, PAWN)))
           return SCALE_FACTOR_DRAW;
-  }
+
   return SCALE_FACTOR_NONE;
 }
 
@@ -490,27 +494,26 @@ ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, RookValueMg, 1));
+  assert(verify_material(pos, weakSide,   RookValueMg, 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 wksq = pos.king_square(strongSide);
+  Square bksq = pos.king_square(weakSide);
+  Square wrsq = pos.list<ROOK>(strongSide)[0];
+  Square wpsq = pos.list<PAWN>(strongSide)[0];
+  Square brsq = pos.list<ROOK>(weakSide)[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)
+  if (strongSide == BLACK)
   {
-      wksq = flip(wksq);
-      wrsq = flip(wrsq);
-      wpsq = flip(wpsq);
-      bksq = flip(bksq);
-      brsq = flip(brsq);
+      wksq = ~wksq;
+      wrsq = ~wrsq;
+      wpsq = ~wpsq;
+      bksq = ~bksq;
+      brsq = ~brsq;
   }
+
   if (file_of(wpsq) > FILE_D)
   {
       wksq = mirror(wksq);
@@ -522,8 +525,8 @@ ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
 
   File f = file_of(wpsq);
   Rank r = rank_of(wpsq);
-  Square queeningSq = make_square(f, RANK_8);
-  int tempo = (pos.side_to_move() == strongerSide);
+  Square queeningSq = f | RANK_8;
+  int tempo = (pos.side_to_move() == strongSide);
 
   // If the pawn is not too far advanced and the defending king defends the
   // queening square, use the third-rank defence.
@@ -601,6 +604,49 @@ ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
   return SCALE_FACTOR_NONE;
 }
 
+template<>
+ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
+
+  assert(verify_material(pos, strongSide, RookValueMg, 1));
+  assert(verify_material(pos, weakSide, BishopValueMg, 0));
+
+  // Test for a rook pawn
+  if (pos.pieces(PAWN) & (FileABB | FileHBB))
+  {
+      Square ksq = pos.king_square(weakSide);
+      Square bsq = pos.list<BISHOP>(weakSide)[0];
+      Square psq = pos.list<PAWN>(strongSide)[0];
+      Rank rk = relative_rank(strongSide, psq);
+      Square push = pawn_push(strongSide);
+
+      // If the pawn is on the 5th rank and the pawn (currently) is on
+      // the same color square as the bishop then there is a chance of
+      // a fortress. Depending on the king position give a moderate
+      // reduction or a stronger one if the defending king is near the
+      // corner but not trapped there.
+      if (rk == RANK_5 && !opposite_colors(bsq, psq))
+      {
+          int d = square_distance(psq + 3 * push, ksq);
+
+          if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push))
+              return ScaleFactor(24);
+          else
+              return ScaleFactor(48);
+      }
+
+      // When the pawn has moved to the 6th rank we can be fairly sure
+      // it's drawn if the bishop attacks the square in front of the
+      // pawn from a reasonable distance and the defending king is near
+      // the corner
+      if (   rk == RANK_6
+          && square_distance(psq + 2 * push, ksq) <= 1
+          && (PseudoAttacks[BISHOP][bsq] & (psq + push))
+          && file_distance(bsq, psq) >= 2)
+          return ScaleFactor(8);
+  }
+
+  return SCALE_FACTOR_NONE;
+}
 
 /// 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
@@ -608,25 +654,22 @@ ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, RookValueMg, 2));
+  assert(verify_material(pos, weakSide,   RookValueMg, 1));
 
-  Square wpsq1 = pos.piece_list(strongerSide, PAWN)[0];
-  Square wpsq2 = pos.piece_list(strongerSide, PAWN)[1];
-  Square bksq = pos.king_square(weakerSide);
+  Square wpsq1 = pos.list<PAWN>(strongSide)[0];
+  Square wpsq2 = pos.list<PAWN>(strongSide)[1];
+  Square bksq = pos.king_square(weakSide);
 
   // Does the stronger side have a passed pawn?
-  if (   pos.pawn_is_passed(strongerSide, wpsq1)
-      || pos.pawn_is_passed(strongerSide, wpsq2))
+  if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
       return SCALE_FACTOR_NONE;
 
-  Rank r = std::max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
+  Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2));
 
   if (   file_distance(bksq, wpsq1) <= 1
       && file_distance(bksq, wpsq2) <= 1
-      && relative_rank(strongerSide, bksq) > r)
+      && relative_rank(strongSide, bksq) > r)
   {
       switch (r) {
       case RANK_2: return ScaleFactor(10);
@@ -646,30 +689,29 @@ ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
 template<>
 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(strongSide) == VALUE_ZERO);
+  assert(pos.count<PAWN>(strongSide) >= 2);
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
 
-  Square ksq = pos.king_square(weakerSide);
-  Bitboard pawns = pos.pieces(PAWN, strongerSide);
+  Square ksq = pos.king_square(weakSide);
+  Bitboard pawns = pos.pieces(strongSide, PAWN);
 
   // Are all pawns on the 'a' file?
   if (!(pawns & ~FileABB))
   {
       // Does the defending king block the pawns?
-      if (   square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
-          || (   file_of(ksq) == FILE_A
-              && !in_front_bb(strongerSide, ksq) & pawns))
+      if (   square_distance(ksq, relative_square(strongSide, SQ_A8)) <= 1
+          || (    file_of(ksq) == FILE_A
+              && !(in_front_bb(strongSide, rank_of(ksq)) & pawns)))
           return SCALE_FACTOR_DRAW;
   }
   // Are all pawns on the 'h' file?
   else if (!(pawns & ~FileHBB))
   {
     // Does the defending king block the pawns?
-    if (   square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
-        || (   file_of(ksq) == FILE_H
-            && !in_front_bb(strongerSide, ksq) & pawns))
+    if (   square_distance(ksq, relative_square(strongSide, SQ_H8)) <= 1
+        || (    file_of(ksq) == FILE_H
+            && !(in_front_bb(strongSide, rank_of(ksq)) & pawns)))
         return SCALE_FACTOR_DRAW;
   }
   return SCALE_FACTOR_NONE;
@@ -683,27 +725,23 @@ ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
 template<>
 ScaleFactor Endgame<KBPKB>::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) == BishopValueMidgame);
-  assert(pos.piece_count(weakerSide, BISHOP) == 1);
-  assert(pos.piece_count(weakerSide, PAWN) == 0);
+  assert(verify_material(pos, strongSide, BishopValueMg, 1));
+  assert(verify_material(pos, weakSide,   BishopValueMg, 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];
-  Square weakerKingSq = pos.king_square(weakerSide);
+  Square pawnSq = pos.list<PAWN>(strongSide)[0];
+  Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
+  Square weakBishopSq = pos.list<BISHOP>(weakSide)[0];
+  Square weakKingSq = pos.king_square(weakSide);
 
   // Case 1: Defending king blocks the pawn, and cannot be driven away
-  if (   file_of(weakerKingSq) == file_of(pawnSq)
-      && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
-      && (   opposite_colors(weakerKingSq, strongerBishopSq)
-          || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
+  if (   file_of(weakKingSq) == file_of(pawnSq)
+      && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
+      && (   opposite_colors(weakKingSq, strongBishopSq)
+          || relative_rank(strongSide, weakKingSq) <= RANK_6))
       return SCALE_FACTOR_DRAW;
 
   // Case 2: Opposite colored bishops
-  if (opposite_colors(strongerBishopSq, weakerBishopSq))
+  if (opposite_colors(strongBishopSq, weakBishopSq))
   {
       // We assume that the position is drawn in the following three situations:
       //
@@ -715,17 +753,17 @@ ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
       // These rules are probably not perfect, but in practice they work
       // reasonably well.
 
-      if (relative_rank(strongerSide, pawnSq) <= RANK_5)
+      if (relative_rank(strongSide, pawnSq) <= RANK_5)
           return SCALE_FACTOR_DRAW;
       else
       {
-          Bitboard path = squares_in_front_of(strongerSide, pawnSq);
+          Bitboard path = forward_bb(strongSide, pawnSq);
 
-          if (path & pos.pieces(KING, weakerSide))
+          if (path & pos.pieces(weakSide, KING))
               return SCALE_FACTOR_DRAW;
 
-          if (  (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
-              && square_distance(weakerBishopSq, pawnSq) >= 3)
+          if (  (pos.attacks_from<BISHOP>(weakBishopSq) & path)
+              && square_distance(weakBishopSq, pawnSq) >= 3)
               return SCALE_FACTOR_DRAW;
       }
   }
@@ -738,35 +776,31 @@ ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, BishopValueMg, 2));
+  assert(verify_material(pos, weakSide,   BishopValueMg, 0));
 
-  Square wbsq = pos.piece_list(strongerSide, BISHOP)[0];
-  Square bbsq = pos.piece_list(weakerSide, BISHOP)[0];
+  Square wbsq = pos.list<BISHOP>(strongSide)[0];
+  Square bbsq = pos.list<BISHOP>(weakSide)[0];
 
   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];
+  Square ksq = pos.king_square(weakSide);
+  Square psq1 = pos.list<PAWN>(strongSide)[0];
+  Square psq2 = pos.list<PAWN>(strongSide)[1];
   Rank r1 = rank_of(psq1);
   Rank r2 = rank_of(psq2);
   Square blockSq1, blockSq2;
 
-  if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
+  if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
   {
-      blockSq1 = psq1 + pawn_push(strongerSide);
-      blockSq2 = make_square(file_of(psq2), rank_of(psq1));
+      blockSq1 = psq1 + pawn_push(strongSide);
+      blockSq2 = file_of(psq2) | rank_of(psq1);
   }
   else
   {
-      blockSq1 = psq2 + pawn_push(strongerSide);
-      blockSq2 = make_square(file_of(psq1), rank_of(psq2));
+      blockSq1 = psq2 + pawn_push(strongSide);
+      blockSq2 = file_of(psq1) | rank_of(psq2);
   }
 
   switch (file_distance(psq1, psq2))
@@ -775,27 +809,27 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
     // Both pawns are on the same file. Easy draw if defender firmly controls
     // some square in the frontmost pawn's path.
     if (   file_of(ksq) == file_of(blockSq1)
-        && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
+        && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1)
         && 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
         && opposite_colors(ksq, wbsq)
         && (   bbsq == blockSq2
-            || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
+            || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
             || abs(r1 - r2) >= 2))
         return SCALE_FACTOR_DRAW;
 
     else if (   ksq == blockSq2
              && opposite_colors(ksq, wbsq)
              && (   bbsq == blockSq1
-                 || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
+                 || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakSide, BISHOP))))
         return SCALE_FACTOR_DRAW;
     else
         return SCALE_FACTOR_NONE;
@@ -813,21 +847,17 @@ ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
 template<>
 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);
-
-  Square pawnSq = pos.piece_list(strongerSide, PAWN)[0];
-  Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP)[0];
-  Square weakerKingSq = pos.king_square(weakerSide);
-
-  if (   file_of(weakerKingSq) == file_of(pawnSq)
-      && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
-      && (   opposite_colors(weakerKingSq, strongerBishopSq)
-          || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
+  assert(verify_material(pos, strongSide, BishopValueMg, 1));
+  assert(verify_material(pos, weakSide, KnightValueMg, 0));
+
+  Square pawnSq = pos.list<PAWN>(strongSide)[0];
+  Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
+  Square weakKingSq = pos.king_square(weakSide);
+
+  if (   file_of(weakKingSq) == file_of(pawnSq)
+      && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
+      && (   opposite_colors(weakKingSq, strongBishopSq)
+          || relative_rank(strongSide, weakKingSq) <= RANK_6))
       return SCALE_FACTOR_DRAW;
 
   return SCALE_FACTOR_NONE;
@@ -840,27 +870,42 @@ ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, KnightValueMg, 1));
+  assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
 
-  Square pawnSq = pos.piece_list(strongerSide, PAWN)[0];
-  Square weakerKingSq = pos.king_square(weakerSide);
+  Square pawnSq = pos.list<PAWN>(strongSide)[0];
+  Square weakKingSq = pos.king_square(weakSide);
 
-  if (   pawnSq == relative_square(strongerSide, SQ_A7)
-      && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
+  if (   pawnSq == relative_square(strongSide, SQ_A7)
+      && square_distance(weakKingSq, relative_square(strongSide, SQ_A8)) <= 1)
       return SCALE_FACTOR_DRAW;
 
-  if (   pawnSq == relative_square(strongerSide, SQ_H7)
-      && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
+  if (   pawnSq == relative_square(strongSide, SQ_H7)
+      && square_distance(weakKingSq, relative_square(strongSide, SQ_H8)) <= 1)
       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>(strongSide)[0];
+  Square bishopSq = pos.list<BISHOP>(weakSide)[0];
+  Square weakKingSq = pos.king_square(weakSide);
+
+  // 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(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
+      return ScaleFactor(square_distance(weakKingSq, pawnSq));
+
+  return SCALE_FACTOR_NONE;
+}
+
+
 /// 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
@@ -869,38 +914,35 @@ ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
 template<>
 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(verify_material(pos, strongSide, VALUE_ZERO, 1));
+  assert(verify_material(pos, weakSide,   VALUE_ZERO, 1));
 
-  Square wksq = pos.king_square(strongerSide);
-  Square bksq = pos.king_square(weakerSide);
-  Square wpsq = pos.piece_list(strongerSide, PAWN)[0];
-  Color stm = pos.side_to_move();
+  Square wksq = pos.king_square(strongSide);
+  Square bksq = pos.king_square(weakSide);
+  Square psq  = pos.list<PAWN>(strongSide)[0];
+  Color  us   = pos.side_to_move();
 
-  if (strongerSide == BLACK)
+  if (strongSide == BLACK)
   {
-      wksq = flip(wksq);
-      bksq = flip(bksq);
-      wpsq = flip(wpsq);
-      stm = flip(stm);
+      wksq = ~wksq;
+      bksq = ~bksq;
+      psq  = ~psq;
+      us   = ~us;
   }
 
-  if (file_of(wpsq) >= FILE_E)
+  if (file_of(psq) >= FILE_E)
   {
       wksq = mirror(wksq);
       bksq = mirror(bksq);
-      wpsq = mirror(wpsq);
+      psq  = mirror(psq);
   }
 
   // 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 (   rank_of(wpsq) >= RANK_5
-      && file_of(wpsq) != FILE_A)
+  if (rank_of(psq) >= RANK_5 && file_of(psq) != 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_bitbase(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
+  return Bitbases::probe_kpk(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
 }