/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2004-2021 The Stockfish developers (see AUTHORS file)
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-#include <algorithm>
#include <cassert>
-#include "bitcount.h"
+#include "bitboard.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 Stockfish {
namespace {
- // Table used to drive the defending king towards the edge of the board
+ // Used to drive the king towards the edge of the board
// in KX vs K and KQ vs KR endgames.
- const int MateTable[64] = {
- 100, 90, 80, 70, 70, 80, 90, 100,
- 90, 70, 60, 50, 50, 60, 70, 90,
- 80, 60, 40, 30, 30, 40, 60, 80,
- 70, 50, 30, 20, 20, 30, 50, 70,
- 70, 50, 30, 20, 20, 30, 50, 70,
- 80, 60, 40, 30, 30, 40, 60, 80,
- 90, 70, 60, 50, 50, 60, 70, 90,
- 100, 90, 80, 70, 70, 80, 90, 100,
- };
-
- // Table used to drive the defending king towards a corner square of the
- // right color in KBN vs K endgames.
- const int KBNKMateTable[64] = {
- 200, 190, 180, 170, 160, 150, 140, 130,
- 190, 180, 170, 160, 150, 140, 130, 140,
- 180, 170, 155, 140, 140, 125, 140, 150,
- 170, 160, 140, 120, 110, 140, 150, 160,
- 160, 150, 140, 110, 120, 140, 160, 170,
- 150, 140, 125, 140, 140, 155, 170, 180,
- 140, 130, 140, 150, 160, 170, 180, 190,
- 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 };
-
- // 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(code.length() > 0 && code.length() < 8);
- assert(code[0] == 'K');
-
- string sides[] = { code.substr(code.find('K', 1)), // Weaker
- code.substr(0, code.find('K', 1)) }; // Stronger
-
- transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
-
- string fen = sides[0] + char('0' + int(8 - code.length()))
- + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10";
-
- return Position(fen, false, 0).material_key();
+ // Values range from 27 (center squares) to 90 (in the corners)
+ inline int push_to_edge(Square s) {
+ int rd = edge_distance(rank_of(s)), fd = edge_distance(file_of(s));
+ return 90 - (7 * fd * fd / 2 + 7 * rd * rd / 2);
}
- template<typename M>
- void delete_endgame(const typename M::value_type& p) { delete p.second; }
+ // Used to drive the king towards A1H8 corners in KBN vs K endgames.
+ // Values range from 0 on A8H1 diagonal to 7 in A1H8 corners
+ inline int push_to_corner(Square s) {
+ return abs(7 - rank_of(s) - file_of(s));
+ }
-} // namespace
+ // Drive a piece close to or away from another piece
+ inline int push_close(Square s1, Square s2) { return 140 - 20 * distance(s1, s2); }
+ inline int push_away(Square s1, Square s2) { return 120 - push_close(s1, s2); }
+#ifndef NDEBUG
+ bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {
+ return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == pawnsCnt;
+ }
+#endif
-/// Endgames members definitions
+ // Map the square as if strongSide is white and strongSide's only pawn
+ // is on the left half of the board.
+ Square normalize(const Position& pos, Color strongSide, Square sq) {
-Endgames::Endgames() {
+ assert(pos.count<PAWN>(strongSide) == 1);
- add<KPK>("KPK");
- add<KNNK>("KNNK");
- add<KBNK>("KBNK");
- add<KRKP>("KRKP");
- add<KRKB>("KRKB");
- add<KRKN>("KRKN");
- add<KQKR>("KQKR");
- add<KBBKN>("KBBKN");
+ if (file_of(pos.square<PAWN>(strongSide)) >= FILE_E)
+ sq = flip_file(sq);
- add<KNPK>("KNPK");
- add<KRPKR>("KRPKR");
- add<KBPKB>("KBPKB");
- add<KBPKN>("KBPKN");
- add<KBPPKB>("KBPPKB");
- add<KRPPKRP>("KRPPKRP");
-}
+ return strongSide == WHITE ? sq : flip_rank(sq);
+ }
+
+} // namespace
-Endgames::~Endgames() {
- for_each(m1.begin(), m1.end(), delete_endgame<M1>);
- for_each(m2.begin(), m2.end(), delete_endgame<M2>);
-}
+namespace Endgames {
-template<EndgameType E>
-void Endgames::add(const string& code) {
+ std::pair<Map<Value>, Map<ScaleFactor>> maps;
- typedef typename eg_family<E>::type T;
+ void init() {
- map((T*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
- map((T*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
+ 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<KNNKP>("KNNKP");
+
+ add<KRPKR>("KRPKR");
+ add<KRPKB>("KRPKB");
+ add<KBPKB>("KBPKB");
+ add<KBPKN>("KBPKN");
+ add<KBPPKB>("KBPPKB");
+ add<KRPPKRP>("KRPPKRP");
+ }
}
/// Mate with KX vs K. This function is used to evaluate positions with
-/// King and plenty of material vs a lone king. It simply gives the
+/// king and plenty of material vs a lone king. It simply gives the
/// 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 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
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
+ // Stalemate detection with lone king
+ if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
+ return VALUE_DRAW;
+
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(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
+ + push_to_edge(weakKing)
+ + push_close(strongKing, weakKing);
- if ( pos.piece_count(strongerSide, QUEEN)
- || pos.piece_count(strongerSide, ROOK)
- || pos.piece_count(strongerSide, BISHOP) > 1)
- // TODO: check for two equal-colored bishops!
- result += VALUE_KNOWN_WIN;
+ if ( pos.count<QUEEN>(strongSide)
+ || pos.count<ROOK>(strongSide)
+ ||(pos.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
+ || ( (pos.pieces(strongSide, BISHOP) & ~DarkSquares)
+ && (pos.pieces(strongSide, BISHOP) & DarkSquares)))
+ result = std::min(result + VALUE_KNOWN_WIN, VALUE_TB_WIN_IN_MAX_PLY - 1);
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
/// 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.
+/// defending king towards a corner square that our bishop attacks.
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);
-
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
- Square bishopSquare = pos.piece_list(strongerSide, BISHOP)[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))
- {
- winnerKSq = mirror(winnerKSq);
- loserKSq = mirror(loserKSq);
- }
+ assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
+
+ Square strongKing = pos.square<KING>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
- Value result = VALUE_KNOWN_WIN
- + DistanceBonus[square_distance(winnerKSq, loserKSq)]
- + KBNKMateTable[loserKSq];
+ // If our bishop does not attack A1/H8, we flip the enemy king square
+ // to drive to opposite corners (A8/H1).
- return strongerSide == pos.side_to_move() ? result : -result;
+ Value result = (VALUE_KNOWN_WIN + 3520)
+ + push_close(strongKing, weakKing)
+ + 420 * push_to_corner(opposite_colors(strongBishop, SQ_A1) ? flip_file(weakKing) : weakKing);
+
+ assert(abs(result) < VALUE_TB_WIN_IN_MAX_PLY);
+ return strongSide == pos.side_to_move() ? result : -result;
}
-/// KP vs K. This endgame is evaluated with the help of a bitbase.
+/// KP vs K. This endgame is evaluated with the help of a bitbase
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);
-
- Square wksq, bksq, wpsq;
- Color stm;
+ assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- 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
- {
- wksq = ~pos.king_square(BLACK);
- bksq = ~pos.king_square(WHITE);
- wpsq = ~pos.piece_list(BLACK, PAWN)[0];
- stm = ~pos.side_to_move();
- }
+ // Assume strongSide is white and the pawn is on files A-D
+ Square strongKing = normalize(pos, strongSide, pos.square<KING>(strongSide));
+ Square strongPawn = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
+ Square weakKing = normalize(pos, strongSide, pos.square<KING>(weakSide));
- if (file_of(wpsq) >= FILE_E)
- {
- wksq = mirror(wksq);
- bksq = mirror(bksq);
- wpsq = mirror(wpsq);
- }
+ Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
- if (!probe_kpk_bitbase(wksq, wpsq, bksq, stm))
+ if (!Bitbases::probe(strongKing, strongPawn, weakKing, us))
return VALUE_DRAW;
- Value result = VALUE_KNOWN_WIN
- + PawnValueEndgame
- + Value(rank_of(wpsq));
+ Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(strongPawn));
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
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);
+ assert(verify_material(pos, strongSide, RookValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 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];
-
- if (strongerSide == BLACK)
- {
- wksq = ~wksq;
- wrsq = ~wrsq;
- bksq = ~bksq;
- bpsq = ~bpsq;
- }
-
- Square queeningSq = make_square(file_of(bpsq), RANK_1);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square strongRook = pos.square<ROOK>(strongSide);
+ Square weakPawn = pos.square<PAWN>(weakSide);
+ Square queeningSquare = make_square(file_of(weakPawn), relative_rank(weakSide, RANK_8));
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 (forward_file_bb(strongSide, strongKing) & weakPawn)
+ result = RookValueEg - distance(strongKing, weakPawn);
// 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 ( distance(weakKing, weakPawn) >= 3 + (pos.side_to_move() == weakSide)
+ && distance(weakKing, strongRook) >= 3)
+ result = RookValueEg - distance(strongKing, weakPawn);
// 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
- && rank_of(wksq) >= RANK_4
- && square_distance(wksq, bpsq) - tempo > 2)
- result = Value(80 - square_distance(wksq, bpsq) * 8);
+ else if ( relative_rank(strongSide, weakKing) <= RANK_3
+ && distance(weakKing, weakPawn) == 1
+ && relative_rank(strongSide, strongKing) >= RANK_4
+ && distance(strongKing, weakPawn) > 2 + (pos.side_to_move() == strongSide))
+ result = Value(80) - 8 * distance(strongKing, weakPawn);
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);
+ result = Value(200) - 8 * ( distance(strongKing, weakPawn + pawn_push(weakSide))
+ - distance(weakKing, weakPawn + pawn_push(weakSide))
+ - distance(weakPawn, queeningSquare));
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
-/// KR vs KB. This is very simple, and always returns drawish scores. The
+/// 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 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(push_to_edge(pos.square<KING>(weakSide)));
+ return strongSide == pos.side_to_move() ? result : -result;
}
-/// KR vs KN. The attacking side has slightly better winning chances than
+/// 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 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 weakKing = pos.square<KING>(weakSide);
+ Square weakKnight = pos.square<KNIGHT>(weakSide);
+ Value result = Value(push_to_edge(weakKing) + push_away(weakKing, weakKnight));
+ return strongSide == pos.side_to_move() ? result : -result;
+}
+
+
+/// KQ vs KP. In general, this is a win for the stronger side, but there are a
+/// few important exceptions. A pawn on 7th rank and on the A,C,F or H files
+/// with a king positioned next to it can be a draw, so in that case, we only
+/// use the distance between the kings.
+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 strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakPawn = pos.square<PAWN>(weakSide);
- const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 };
+ Value result = Value(push_close(strongKing, weakKing));
- 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, weakPawn) != RANK_7
+ || distance(weakKing, weakPawn) != 1
+ || ((FileBBB | FileDBB | FileEBB | FileGBB) & weakPawn))
+ result += QueenValueEg - PawnValueEg;
+
+ return strongSide == pos.side_to_move() ? result : -result;
}
-/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
+/// KQ vs KR. This is almost identical to KX vs K: we give the attacking
/// king a bonus for having the kings close together, and for forcing the
-/// defending king towards the edge. If we also take care to avoid null move
-/// for the defending side in the search, this is usually sufficient to be
-/// able to win KQ vs KR.
+/// defending king towards the edge. If we also take care to avoid null move for
+/// the defending side in the search, this is usually sufficient to win KQ vs KR.
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 strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
- Value result = QueenValueEndgame
- - RookValueEndgame
- + MateTable[loserKSq]
- + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+ Value result = QueenValueEg
+ - RookValueEg
+ + push_to_edge(weakKing)
+ + push_close(strongKing, weakKing);
- 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));
-
- Value result = BishopValueEndgame;
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square nsq = pos.piece_list(weakerSide, KNIGHT)[0];
+/// KNN vs KP. Very drawish, but there are some mate opportunities if we can
+/// press the weakSide King to a corner before the pawn advances too much.
+template<>
+Value Endgame<KNNKP>::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 * KnightValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- // Bonus for driving the defending king and knight apart
- result += Value(square_distance(bksq, nsq) * 32);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakPawn = pos.square<PAWN>(weakSide);
- // Bonus for restricting the knight's mobility
- result += Value((8 - popcount<Max15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
+ Value result = PawnValueEg
+ + 2 * push_to_edge(weakKing)
+ - 10 * relative_rank(weakSide, weakPawn);
- 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<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
+/// KB 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 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 strongPawns = pos.pieces(strongSide, PAWN);
+ Bitboard allPawns = pos.pieces(PAWN);
+
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square strongKing = pos.square<KING>(strongSide);
- // All pawns are on a single rook file ?
- if ( (pawnFile == FILE_A || pawnFile == FILE_H)
- && !(pawns & ~file_bb(pawnFile)))
+ // All strongSide pawns are on a single rook file?
+ if (!(strongPawns & ~FileABB) || !(strongPawns & ~FileHBB))
{
- 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 queeningSquare = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8));
+
+ if ( opposite_colors(queeningSquare, strongBishop)
+ && distance(queeningSquare, weakKing) <= 1)
+ return SCALE_FACTOR_DRAW;
+ }
- if ( opposite_colors(queeningSq, bishopSq)
- && abs(file_of(kingSq) - pawnFile) <= 1)
+ // If all the pawns are on the same B or G file, then it's potentially a draw
+ if ((!(allPawns & ~FileBBB) || !(allPawns & ~FileGBB))
+ && pos.non_pawn_material(weakSide) == 0
+ && pos.count<PAWN>(weakSide) >= 1)
+ {
+ // Get the least advanced weakSide pawn
+ Square weakPawn = frontmost_sq(strongSide, pos.pieces(weakSide, PAWN));
+
+ // There's 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, weakPawn) == RANK_7
+ && (strongPawns & (weakPawn + pawn_push(weakSide)))
+ && (opposite_colors(strongBishop, weakPawn) || !more_than_one(strongPawns)))
{
- // 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
- // 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);
- }
- // 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)
+ int strongKingDist = distance(weakPawn, strongKing);
+ int weakKingDist = distance(weakPawn, weakKing);
+
+ // It's a draw if the weak king is on its 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, weakKing) >= RANK_7
+ && weakKingDist <= 2
+ && weakKingDist <= strongKingDist)
return SCALE_FACTOR_DRAW;
}
}
+
return SCALE_FACTOR_NONE;
}
-/// 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.
+/// KQ vs KR and one or more pawns. It tests for fortress draws with a rook on
+/// the third rank defended by a pawn.
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 strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakRook = pos.square<ROOK>(weakSide);
+
+ if ( relative_rank(weakSide, weakKing) <= RANK_2
+ && relative_rank(weakSide, strongKing) >= RANK_4
+ && relative_rank(weakSide, weakRook) == RANK_3
+ && ( pos.pieces(weakSide, PAWN)
+ & attacks_bb<KING>(weakKing)
+ & pawn_attacks_bb(strongSide, weakRook)))
return SCALE_FACTOR_DRAW;
- }
+
return SCALE_FACTOR_NONE;
}
-/// 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.
+/// KRP vs KR. 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.
+/// which is mostly copied from Glaurung 1.x, and isn't very pretty.
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];
-
- // 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 = ~wksq;
- wrsq = ~wrsq;
- wpsq = ~wpsq;
- bksq = ~bksq;
- brsq = ~brsq;
- }
- if (file_of(wpsq) > FILE_D)
- {
- wksq = mirror(wksq);
- wrsq = mirror(wrsq);
- wpsq = mirror(wpsq);
- bksq = mirror(bksq);
- brsq = mirror(brsq);
- }
+ // Assume strongSide is white and the pawn is on files A-D
+ Square strongKing = normalize(pos, strongSide, pos.square<KING>(strongSide));
+ Square strongRook = normalize(pos, strongSide, pos.square<ROOK>(strongSide));
+ Square strongPawn = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
+ Square weakKing = normalize(pos, strongSide, pos.square<KING>(weakSide));
+ Square weakRook = normalize(pos, strongSide, pos.square<ROOK>(weakSide));
- File f = file_of(wpsq);
- Rank r = rank_of(wpsq);
- Square queeningSq = make_square(f, RANK_8);
- int tempo = (pos.side_to_move() == strongerSide);
+ File pawnFile = file_of(strongPawn);
+ Rank pawnRank = rank_of(strongPawn);
+ Square queeningSquare = make_square(pawnFile, 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.
- if ( r <= RANK_5
- && square_distance(bksq, queeningSq) <= 1
- && wksq <= SQ_H5
- && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
+ if ( pawnRank <= RANK_5
+ && distance(weakKing, queeningSquare) <= 1
+ && strongKing <= SQ_H5
+ && (rank_of(weakRook) == RANK_6 || (pawnRank <= RANK_3 && rank_of(strongRook) != 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
- && rank_of(wksq) + tempo <= RANK_6
- && (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3)))
+ if ( pawnRank == RANK_6
+ && distance(weakKing, queeningSquare) <= 1
+ && rank_of(strongKing) + tempo <= RANK_6
+ && (rank_of(weakRook) == RANK_1 || (!tempo && distance<File>(weakRook, strongPawn) >= 3)))
return SCALE_FACTOR_DRAW;
- if ( r >= RANK_6
- && bksq == queeningSq
- && rank_of(brsq) == RANK_1
- && (!tempo || square_distance(wksq, wpsq) >= 2))
+ if ( pawnRank >= RANK_6
+ && weakKing == queeningSquare
+ && rank_of(weakRook) == RANK_1
+ && (!tempo || distance(strongKing, strongPawn) >= 2))
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)
- && file_of(brsq) == FILE_A
- && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
+ if ( strongPawn == SQ_A7
+ && strongRook == SQ_A8
+ && (weakKing == SQ_H7 || weakKing == SQ_G7)
+ && file_of(weakRook) == FILE_A
+ && (rank_of(weakRook) <= RANK_3 || file_of(strongKing) >= FILE_D || rank_of(strongKing) <= 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.
- if ( r <= RANK_5
- && bksq == wpsq + DELTA_N
- && square_distance(wksq, wpsq) - tempo >= 2
- && square_distance(wksq, brsq) - tempo >= 2)
+ if ( pawnRank <= RANK_5
+ && weakKing == strongPawn + NORTH
+ && distance(strongKing, strongPawn) - tempo >= 2
+ && distance(strongKing, weakRook) - tempo >= 2)
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
- && 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))
- return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
+ if ( pawnRank == RANK_7
+ && pawnFile != FILE_A
+ && file_of(strongRook) == pawnFile
+ && strongRook != queeningSquare
+ && (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo)
+ && (distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo))
+ return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(strongKing, queeningSquare));
// Similar to the above, but with the pawn further back
- if ( f != FILE_A
- && 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)
- && ( square_distance(bksq, wrsq) + tempo >= 3
- || ( square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo
- && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wrsq) + tempo))))
+ if ( pawnFile != FILE_A
+ && file_of(strongRook) == pawnFile
+ && strongRook < strongPawn
+ && (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo)
+ && (distance(strongKing, strongPawn + NORTH) < distance(weakKing, strongPawn + NORTH) - 2 + tempo)
+ && ( distance(weakKing, strongRook) + tempo >= 3
+ || ( distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo
+ && (distance(strongKing, strongPawn + NORTH) < distance(weakKing, strongPawn) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- - 8 * square_distance(wpsq, queeningSq)
- - 2 * square_distance(wksq, queeningSq));
+ - 8 * distance(strongPawn, queeningSquare)
+ - 2 * distance(strongKing, queeningSquare));
- // If the pawn is not far advanced, and the defending king is somewhere in
+ // If the pawn is not far advanced and the defending king is somewhere in
// the pawn's path, it's probably a draw.
- if (r <= RANK_4 && bksq > wpsq)
+ if (pawnRank <= RANK_4 && weakKing > strongPawn)
{
- if (file_of(bksq) == file_of(wpsq))
+ if (file_of(weakKing) == file_of(strongPawn))
return ScaleFactor(10);
- if ( abs(file_of(bksq) - file_of(wpsq)) == 1
- && square_distance(wksq, bksq) > 2)
- return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
+ if ( distance<File>(weakKing, strongPawn) == 1
+ && distance(strongKing, weakKing) > 2)
+ return ScaleFactor(24 - 2 * distance(strongKing, weakKing));
}
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));
-/// 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.
+ // Test for a rook pawn
+ if (pos.pieces(PAWN) & (FileABB | FileHBB))
+ {
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakBishop = pos.square<BISHOP>(weakSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square strongPawn = pos.square<PAWN>(strongSide);
+ Rank pawnRank = relative_rank(strongSide, strongPawn);
+ Direction 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 (pawnRank == RANK_5 && !opposite_colors(weakBishop, strongPawn))
+ {
+ int d = distance(strongPawn + 3 * push, weakKing);
+
+ if (d <= 2 && !(d == 0 && weakKing == strongKing + 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 ( pawnRank == RANK_6
+ && distance(strongPawn + 2 * push, weakKing) <= 1
+ && (attacks_bb<BISHOP>(weakBishop) & (strongPawn + push))
+ && distance<File>(weakBishop, strongPawn) >= 2)
+ return ScaleFactor(8);
+ }
+
+ return SCALE_FACTOR_NONE;
+}
+
+/// KRPP vs KRP. There is just a single rule: if the stronger side has no passed
+/// pawns and the defending king is actively placed, the position is drawish.
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 strongPawn1 = lsb(pos.pieces(strongSide, PAWN));
+ Square strongPawn2 = msb(pos.pieces(strongSide, PAWN));
+ Square weakKing = pos.square<KING>(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, strongPawn1) || pos.pawn_passed(strongSide, strongPawn2))
return SCALE_FACTOR_NONE;
- Rank r = std::max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
+ Rank pawnRank = std::max(relative_rank(strongSide, strongPawn1), relative_rank(strongSide, strongPawn2));
- if ( file_distance(bksq, wpsq1) <= 1
- && file_distance(bksq, wpsq2) <= 1
- && relative_rank(strongerSide, bksq) > r)
+ if ( distance<File>(weakKing, strongPawn1) <= 1
+ && distance<File>(weakKing, strongPawn2) <= 1
+ && relative_rank(strongSide, weakKing) > pawnRank)
{
- switch (r) {
- case RANK_2: return ScaleFactor(10);
- case RANK_3: return ScaleFactor(10);
- case RANK_4: return ScaleFactor(15);
- case RANK_5: return ScaleFactor(20);
- case RANK_6: return ScaleFactor(40);
- default: assert(false);
- }
+ assert(pawnRank > RANK_1 && pawnRank < RANK_7);
+ return ScaleFactor(7 * pawnRank);
}
return SCALE_FACTOR_NONE;
}
-/// K and two or more pawns vs K. There is just a single rule here: If all pawns
+/// 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 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 weakKing = pos.square<KING>(weakSide);
+ Bitboard strongPawns = pos.pieces(strongSide, PAWN);
+
+ // If all pawns are ahead of the king on a single rook file, it's a draw.
+ if ( !(strongPawns & ~(FileABB | FileHBB))
+ && !(strongPawns & ~passed_pawn_span(weakSide, weakKing)))
+ return SCALE_FACTOR_DRAW;
- // 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))
- 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))
- return SCALE_FACTOR_DRAW;
- }
return SCALE_FACTOR_NONE;
}
-/// 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.
+/// KBP vs KB. 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 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 strongPawn = pos.square<PAWN>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakBishop = pos.square<BISHOP>(weakSide);
+ Square weakKing = pos.square<KING>(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 ( (forward_file_bb(strongSide, strongPawn) & weakKing)
+ && ( opposite_colors(weakKing, strongBishop)
+ || relative_rank(strongSide, weakKing) <= RANK_6))
return SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
- if (opposite_colors(strongerBishopSq, weakerBishopSq))
- {
- // We assume that the position is drawn in the following three situations:
- //
- // a. The pawn is on rank 5 or further back.
- // b. The defending king is somewhere in the pawn's path.
- // c. The defending bishop attacks some square along the pawn's path,
- // and is at least three squares away from the pawn.
- //
- // These rules are probably not perfect, but in practice they work
- // reasonably well.
-
- if (relative_rank(strongerSide, pawnSq) <= RANK_5)
- return SCALE_FACTOR_DRAW;
- else
- {
- Bitboard path = squares_in_front_of(strongerSide, pawnSq);
-
- if (path & pos.pieces(KING, weakerSide))
- return SCALE_FACTOR_DRAW;
+ if (opposite_colors(strongBishop, weakBishop))
+ return SCALE_FACTOR_DRAW;
- if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
- return SCALE_FACTOR_DRAW;
- }
- }
return SCALE_FACTOR_NONE;
}
-/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with
-/// opposite-colored bishops.
+/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
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 strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakBishop = pos.square<BISHOP>(weakSide);
- if (!opposite_colors(wbsq, bbsq))
+ if (!opposite_colors(strongBishop, weakBishop))
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 = rank_of(psq1);
- Rank r2 = rank_of(psq2);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square strongPawn1 = lsb(pos.pieces(strongSide, PAWN));
+ Square strongPawn2 = msb(pos.pieces(strongSide, PAWN));
Square blockSq1, blockSq2;
- if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
+ if (relative_rank(strongSide, strongPawn1) > relative_rank(strongSide, strongPawn2))
{
- blockSq1 = psq1 + pawn_push(strongerSide);
- blockSq2 = make_square(file_of(psq2), rank_of(psq1));
+ blockSq1 = strongPawn1 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(strongPawn2), rank_of(strongPawn1));
}
else
{
- blockSq1 = psq2 + pawn_push(strongerSide);
- blockSq2 = make_square(file_of(psq1), rank_of(psq2));
+ blockSq1 = strongPawn2 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(strongPawn1), rank_of(strongPawn2));
}
- switch (file_distance(psq1, psq2))
+ switch (distance<File>(strongPawn1, strongPawn2))
{
case 0:
- // 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)
- && opposite_colors(ksq, wbsq))
+ // Both pawns are on the same file. It's an easy draw if the defender firmly
+ // controls some square in the frontmost pawn's path.
+ if ( file_of(weakKing) == file_of(blockSq1)
+ && relative_rank(strongSide, weakKing) >= relative_rank(strongSide, blockSq1)
+ && opposite_colors(weakKing, strongBishop))
return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
case 1:
- // Pawns on neighboring 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))
- || abs(r1 - r2) >= 2))
+ // Pawns on adjacent files. It's a draw if the 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 ( weakKing == blockSq1
+ && opposite_colors(weakKing, strongBishop)
+ && ( weakBishop == blockSq2
+ || (attacks_bb<BISHOP>(blockSq2, pos.pieces()) & pos.pieces(weakSide, BISHOP))
+ || distance<Rank>(strongPawn1, strongPawn2) >= 2))
return SCALE_FACTOR_DRAW;
- else if ( ksq == blockSq2
- && opposite_colors(ksq, wbsq)
- && ( bbsq == blockSq1
- || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
+ else if ( weakKing == blockSq2
+ && opposite_colors(weakKing, strongBishop)
+ && ( weakBishop == blockSq1
+ || (attacks_bb<BISHOP>(blockSq1, pos.pieces()) & pos.pieces(weakSide, BISHOP))))
return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
}
-/// 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.
+/// KBP vs KN. 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 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))
- return SCALE_FACTOR_DRAW;
+ assert(verify_material(pos, strongSide, BishopValueMg, 1));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
- return SCALE_FACTOR_NONE;
-}
+ Square strongPawn = pos.square<PAWN>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
-
-/// 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 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);
-
- Square pawnSq = pos.piece_list(strongerSide, PAWN)[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_DRAW;
-
- if ( pawnSq == relative_square(strongerSide, SQ_H7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
+ if ( file_of(weakKing) == file_of(strongPawn)
+ && relative_rank(strongSide, strongPawn) < relative_rank(strongSide, weakKing)
+ && ( opposite_colors(weakKing, strongBishop)
+ || relative_rank(strongSide, weakKing) <= RANK_6))
return SCALE_FACTOR_DRAW;
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
-/// 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).
+/// KP vs KP. 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, it 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 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();
+ // Assume strongSide is white and the pawn is on files A-D
+ Square strongKing = normalize(pos, strongSide, pos.square<KING>(strongSide));
+ Square weakKing = normalize(pos, strongSide, pos.square<KING>(weakSide));
+ Square strongPawn = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
- if (strongerSide == BLACK)
- {
- wksq = ~wksq;
- bksq = ~bksq;
- wpsq = ~wpsq;
- stm = ~stm;
- }
-
- if (file_of(wpsq) >= FILE_E)
- {
- wksq = mirror(wksq);
- bksq = mirror(bksq);
- wpsq = mirror(wpsq);
- }
+ Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
// 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(strongPawn) >= RANK_5 && file_of(strongPawn) != 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(strongKing, strongPawn, weakKing, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}
+
+} // namespace Stockfish