/*
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) 2008-2015 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
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-
-////
-//// Includes
-////
-
+#include <algorithm>
#include <cassert>
+#include "bitboard.h"
#include "bitcount.h"
#include "endgame.h"
+#include "movegen.h"
-
-////
-//// Local definitions
-////
+using std::string;
namespace {
- // Table used to drive the defending king towards the edge of the board
+ // Table used to drive the king towards the edge of the board
// in KX vs K and KQ vs KR endgames.
- const uint8_t 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,
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 uint8_t 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,
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 };
- // Penalty for big distance between king and knight for the defending king
- // and knight in KR vs KN endgames.
- const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 };
+#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
- // Bitbase for KP vs K
- uint8_t KPKBitbase[24576];
+ // 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) {
- // Various inline functions for accessing the above arrays
- inline Value mate_table(Square s) {
- return Value(MateTable[s]);
- }
+ assert(pos.count<PAWN>(strongSide) == 1);
- inline Value kbnk_mate_table(Square s) {
- return Value(KBNKMateTable[s]);
- }
+ if (file_of(pos.list<PAWN>(strongSide)[0]) >= FILE_E)
+ sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
+
+ if (strongSide == BLACK)
+ sq = ~sq;
- inline Value distance_bonus(int d) {
- return Value(DistanceBonus[d]);
+ return sq;
}
- inline Value krkn_king_knight_distance_penalty(int d) {
- return Value(KRKNKingKnightDistancePenalty[d]);
+ // Get the material key of 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 do the work for us.
+ 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)), // Weak
+ code.substr(0, code.find('K', 1)) }; // Strong
+
+ std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
+
+ string fen = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/"
+ + sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10";
+
+ return Position(fen, false, NULL).material_key();
}
- // Function for probing the KP vs K bitbase
- int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm);
+ template<typename M>
+ void delete_endgame(const typename M::value_type& p) { delete p.second; }
+
+} // namespace
+
+/// Endgames members definitions
+
+Endgames::Endgames() {
+
+ add<KPK>("KPK");
+ add<KNNK>("KNNK");
+ add<KBNK>("KBNK");
+ add<KRKP>("KRKP");
+ add<KRKB>("KRKB");
+ add<KRKN>("KRKN");
+ add<KQKP>("KQKP");
+ add<KQKR>("KQKR");
+
+ add<KNPK>("KNPK");
+ add<KNPKB>("KNPKB");
+ add<KRPKR>("KRPKR");
+ add<KRPKB>("KRPKB");
+ add<KBPKB>("KBPKB");
+ add<KBPKN>("KBPKN");
+ add<KBPPKB>("KBPPKB");
+ add<KRPPKRP>("KRPPKRP");
}
+Endgames::~Endgames() {
-////
-//// Functions
-////
+ for_each(m1.begin(), m1.end(), delete_endgame<M1>);
+ for_each(m2.begin(), m2.end(), delete_endgame<M2>);
+}
-/// init_bitbases() is called during program initialization, and simply loads
-/// bitbases from disk into memory. At the moment, there is only the bitbase
-/// for KP vs K, but we may decide to add other bitbases later.
-extern void generate_kpk_bitbase(uint8_t bitbase[]);
+template<EndgameType E>
+void Endgames::add(const string& code) {
-void init_bitbases() {
- generate_kpk_bitbase(KPKBitbase);
+ map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
+ map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
}
/// 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 EvaluationFunction<KXK>::apply(const Position& pos) const {
+Value Endgame<KXK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
+ assert(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 winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
- Value result = pos.non_pawn_material(strongerSide)
- + pos.piece_count(strongerSide, PAWN) * PawnValueEndgame
- + mate_table(loserKSq)
- + distance_bonus(square_distance(winnerKSq, loserKSq));
+ Value result = pos.non_pawn_material(strongSide)
+ + pos.count<PAWN>(strongSide) * PawnValueEg
+ + PushToEdges[loserKSq]
+ + PushClose[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.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
+ ||(pos.count<BISHOP>(strongSide) > 1 && opposite_colors(pos.list<BISHOP>(strongSide)[0],
+ pos.list<BISHOP>(strongSide)[1])))
result += VALUE_KNOWN_WIN;
- 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.
template<>
-Value EvaluationFunction<KBNK>::apply(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 (!same_color_squares(bishopSquare, SQ_A1))
+Value Endgame<KBNK>::operator()(const Position& pos) const {
+
+ assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 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 flip the kings in order
+ // to drive the enemy toward corners A8 or H1.
+ if (opposite_colors(bishopSq, SQ_A1))
{
- winnerKSq = flop_square(winnerKSq);
- loserKSq = flop_square(loserKSq);
+ winnerKSq = ~winnerKSq;
+ loserKSq = ~loserKSq;
}
Value result = VALUE_KNOWN_WIN
- + distance_bonus(square_distance(winnerKSq, loserKSq))
- + kbnk_mate_table(loserKSq);
+ + PushClose[distance(winnerKSq, loserKSq)]
+ + PushToCorners[loserKSq];
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
/// KP vs K. This endgame is evaluated with the help of a bitbase.
template<>
-Value EvaluationFunction<KPK>::apply(const Position& pos) const {
+Value Endgame<KPK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square wksq, bksq, wpsq;
- Color stm;
+ // Assume strongSide is white and the pawn is on files A-D
+ Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+ Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+ Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[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 = flip_square(pos.king_square(BLACK));
- bksq = flip_square(pos.king_square(WHITE));
- wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
- stm = opposite_color(pos.side_to_move());
- }
-
- if (square_file(wpsq) >= FILE_E)
- {
- wksq = flop_square(wksq);
- bksq = flop_square(bksq);
- wpsq = flop_square(wpsq);
- }
+ Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
- if (!probe_kpk(wksq, wpsq, bksq, stm))
+ if (!Bitbases::probe(wksq, psq, bksq, us))
return VALUE_DRAW;
- Value result = VALUE_KNOWN_WIN
- + PawnValueEndgame
- + Value(square_rank(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;
}
/// far advanced with support of the king, while the attacking king is far
/// away.
template<>
-Value EvaluationFunction<KRKP>::apply(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);
+Value Endgame<KRKP>::operator()(const Position& pos) const {
- 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 = relative_square(strongSide, pos.king_square(strongSide));
+ Square bksq = relative_square(strongSide, pos.king_square(weakSide));
+ Square rsq = relative_square(strongSide, pos.list<ROOK>(strongSide)[0]);
+ Square psq = relative_square(strongSide, pos.list<PAWN>(weakSide)[0]);
- if (strongerSide == BLACK)
- {
- wksq = flip_square(wksq);
- wrsq = flip_square(wrsq);
- bksq = flip_square(bksq);
- bpsq = flip_square(bpsq);
- }
-
- Square queeningSq = make_square(square_file(bpsq), RANK_1);
+ Square queeningSq = make_square(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 && square_file(wksq) == square_file(bpsq))
- result = RookValueEndgame - Value(square_distance(wksq, bpsq));
+ if (wksq < psq && file_of(wksq) == file_of(psq))
+ result = RookValueEg - 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 ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
+ && distance(bksq, rsq) >= 3)
+ result = RookValueEg - distance(wksq, psq);
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
- else if ( square_rank(bksq) <= RANK_3
- && square_distance(bksq, bpsq) == 1
- && square_rank(wksq) >= RANK_4
- && square_distance(wksq, bpsq) - tempo > 2)
- result = Value(80 - square_distance(wksq, bpsq) * 8);
+ else if ( rank_of(bksq) <= RANK_3
+ && distance(bksq, psq) == 1
+ && rank_of(wksq) >= RANK_4
+ && distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
+ result = Value(80) - 8 * distance(wksq, psq);
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(wksq, psq + DELTA_S)
+ - distance(bksq, psq + DELTA_S)
+ - distance(psq, queeningSq));
- 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
/// score is slightly bigger when the defending king is close to the edge.
template<>
-Value EvaluationFunction<KRKB>::apply(const Position& pos) const {
+Value Endgame<KRKB>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
+ assert(verify_material(pos, strongSide, RookValueMg, 0));
+ assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Value result = mate_table(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;
}
-/// 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 EvaluationFunction<KRKN>::apply(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);
+Value Endgame<KRKN>::operator()(const Position& pos) const {
- Square defendingKSq = pos.king_square(weakerSide);
- Square nSq = pos.piece_list(weakerSide, KNIGHT, 0);
+ assert(verify_material(pos, strongSide, RookValueMg, 0));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
- int d = square_distance(defendingKSq, nSq);
- Value result = Value(10)
- + mate_table(defendingKSq)
- + krkn_king_knight_distance_penalty(d);
-
- return strongerSide == pos.side_to_move() ? result : -result;
+ Square bksq = pos.king_square(weakSide);
+ Square bnsq = pos.list<KNIGHT>(weakSide)[0];
+ Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]);
+ return strongSide == pos.side_to_move() ? result : -result;
}
-/// 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.
+/// 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 EvaluationFunction<KQKR>::apply(const Position& pos) const {
+Value Endgame<KQKP>::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, VALUE_ZERO, 1));
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
+ Square winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
+ Square pawnSq = pos.list<PAWN>(weakSide)[0];
- Value result = QueenValueEndgame
- - RookValueEndgame
- + mate_table(loserKSq)
- + distance_bonus(square_distance(winnerKSq, loserKSq));
+ Value result = Value(PushClose[distance(winnerKSq, loserKSq)]);
- return strongerSide == pos.side_to_move() ? result : -result;
-}
+ if ( relative_rank(weakSide, pawnSq) != RANK_7
+ || distance(loserKSq, pawnSq) != 1
+ || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq))
+ result += QueenValueEg - PawnValueEg;
-template<>
-Value EvaluationFunction<KBBKN>::apply(const Position& pos) const {
+ return strongSide == pos.side_to_move() ? result : -result;
+}
- assert(pos.piece_count(strongerSide, BISHOP) == 2);
- assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
- assert(pos.pieces(PAWN) == EmptyBoardBB);
- Value result = BishopValueEndgame;
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square nsq = pos.piece_list(weakerSide, KNIGHT, 0);
+/// 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 win KQ vs KR.
+template<>
+Value Endgame<KQKR>::operator()(const Position& pos) const {
- // Bonus for attacking king close to defending king
- result += distance_bonus(square_distance(wksq, bksq));
+ assert(verify_material(pos, strongSide, QueenValueMg, 0));
+ assert(verify_material(pos, weakSide, RookValueMg, 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);
- // Bonus for restricting the knight's mobility
- result += Value((8 - count_1s<CNT32_MAX15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
+ Value result = QueenValueEg
+ - RookValueEg
+ + PushToEdges[loserKSq]
+ + PushClose[distance(winnerKSq, loserKSq)];
- 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 EvaluationFunction<KmmKm>::apply(const Position&) const {
- return VALUE_DRAW;
-}
+/// Some cases of trivial draws
+template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
-template<>
-Value EvaluationFunction<KNNK>::apply(const Position&) const {
- return VALUE_DRAW;
-}
-/// KBPKScalingFunction scales endgames where the stronger side has king,
-/// bishop and one or more pawns. It checks for draws with rook pawns and a
-/// bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_ZERO is
-/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
+/// 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 ScalingFunction<KBPsK>::apply(const Position& pos) const {
+ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) >= 1);
+ assert(pos.non_pawn_material(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 = square_file(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)
- && (pawns & ~file_bb(pawnFile)) == EmptyBoardBB)
+ if ( (pawnFile == FILE_A || pawnFile == FILE_H)
+ && !(pawns & ~file_bb(pawnFile)))
{
- Square bishopSq = pos.piece_list(strongerSide, BISHOP, 0);
- Square queeningSq = relative_square(strongerSide, make_square(pawnFile, RANK_8));
- Square kingSq = pos.king_square(weakerSide);
+ Square bishopSq = pos.list<BISHOP>(strongSide)[0];
+ Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8));
+ Square kingSq = pos.king_square(weakSide);
- if ( !same_color_squares(queeningSq, bishopSq)
- && file_distance(square_file(kingSq), pawnFile) <= 1)
+ if ( opposite_colors(queeningSq, bishopSq)
+ && distance(queeningSq, kingSq) <= 1)
+ return SCALE_FACTOR_DRAW;
+ }
+
+ // If all the pawns are on the same B or G file, then it's potentially a 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 the 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];
+
+ // 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, weakPawnSq) == RANK_7
+ && (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
+ && (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 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
- // frontmost pawn.
- Rank rank;
- if (strongerSide == WHITE)
- {
- for (rank = RANK_7; (rank_bb(rank) & pawns) == EmptyBoardBB; rank--) {}
- assert(rank >= RANK_2 && rank <= RANK_7);
- }
- else
- {
- for (rank = RANK_2; (rank_bb(rank) & pawns) == EmptyBoardBB; rank++) {}
- rank = Rank(rank ^ 7); // HACK to get the relative rank
- assert(rank >= RANK_2 && rank <= RANK_7);
- }
- // If the defending king has distance 1 to the promotion square or
- // is placed somewhere in front of the pawn, it's a draw.
- if ( square_distance(kingSq, queeningSq) <= 1
- || relative_rank(strongerSide, kingSq) >= rank)
- return SCALE_FACTOR_ZERO;
+ int strongKingDist = distance(weakPawnSq, strongKingSq);
+ int weakKingDist = distance(weakPawnSq, weakKingSq);
+
+ // 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, weakKingSq) >= RANK_7
+ && weakKingDist <= 2
+ && weakKingDist <= strongKingDist)
+ return SCALE_FACTOR_DRAW;
}
}
+
return SCALE_FACTOR_NONE;
}
-/// KQKRPScalingFunction scales endgames where the stronger side has only
-/// king and queen, while the weaker side has at least a rook and a pawn.
-/// It tests for fortress draws with a rook on the third rank defended by
-/// a pawn.
+/// 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 ScalingFunction<KQKRPs>::apply(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))
- return SCALE_FACTOR_ZERO;
- }
+ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
+
+ 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
+ && relative_rank(weakSide, rsq) == RANK_3
+ && ( pos.pieces(weakSide, PAWN)
+ & pos.attacks_from<KING>(kingSq)
+ & pos.attacks_from<PAWN>(rsq, strongSide)))
+ return SCALE_FACTOR_DRAW;
+
return SCALE_FACTOR_NONE;
}
-/// KRPKRScalingFunction scales KRP vs KR endgames. This function knows a
-/// handful of the most important classes of drawn positions, but is far
-/// from perfect. It would probably be a good idea to add more knowledge
-/// in the future.
+/// 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 ScalingFunction<KRPKR>::apply(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);
-
- 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 = flip_square(wksq);
- wrsq = flip_square(wrsq);
- wpsq = flip_square(wpsq);
- bksq = flip_square(bksq);
- brsq = flip_square(brsq);
- }
- if (square_file(wpsq) > FILE_D)
- {
- wksq = flop_square(wksq);
- wrsq = flop_square(wrsq);
- wpsq = flop_square(wpsq);
- bksq = flop_square(bksq);
- brsq = flop_square(brsq);
- }
+ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
+
+ assert(verify_material(pos, strongSide, RookValueMg, 1));
+ assert(verify_material(pos, weakSide, RookValueMg, 0));
+
+ // Assume strongSide is white and the pawn is on files A-D
+ Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+ Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+ Square wrsq = normalize(pos, strongSide, pos.list<ROOK>(strongSide)[0]);
+ Square wpsq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+ Square brsq = normalize(pos, strongSide, pos.list<ROOK>(weakSide)[0]);
- File f = square_file(wpsq);
- Rank r = square_rank(wpsq);
+ File f = file_of(wpsq);
+ Rank r = rank_of(wpsq);
Square queeningSq = make_square(f, RANK_8);
- int tempo = (pos.side_to_move() == strongerSide);
+ 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
+ && distance(bksq, queeningSq) <= 1
&& wksq <= SQ_H5
- && (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
- return SCALE_FACTOR_ZERO;
+ && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
+ return SCALE_FACTOR_DRAW;
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
if ( r == RANK_6
- && square_distance(bksq, queeningSq) <= 1
- && square_rank(wksq) + tempo <= RANK_6
- && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
- return SCALE_FACTOR_ZERO;
+ && distance(bksq, queeningSq) <= 1
+ && rank_of(wksq) + tempo <= RANK_6
+ && (rank_of(brsq) == RANK_1 || (!tempo && distance(file_of(brsq), f) >= 3)))
+ return SCALE_FACTOR_DRAW;
if ( r >= RANK_6
&& bksq == queeningSq
- && square_rank(brsq) == RANK_1
- && (!tempo || square_distance(wksq, wpsq) >= 2))
- return SCALE_FACTOR_ZERO;
+ && rank_of(brsq) == RANK_1
+ && (!tempo || distance(wksq, wpsq) >= 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)
- && square_file(brsq) == FILE_A
- && (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
- return SCALE_FACTOR_ZERO;
+ && file_of(brsq) == FILE_A
+ && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
+ return SCALE_FACTOR_DRAW;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
if ( r <= RANK_5
&& bksq == wpsq + DELTA_N
- && square_distance(wksq, wpsq) - tempo >= 2
- && square_distance(wksq, brsq) - tempo >= 2)
- return SCALE_FACTOR_ZERO;
+ && distance(wksq, wpsq) - tempo >= 2
+ && distance(wksq, brsq) - 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
- && square_file(wrsq) == f
+ && file_of(wrsq) == f
&& wrsq != queeningSq
- && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
- && (square_distance(wksq, queeningSq) < square_distance(bksq, wrsq) + tempo))
- return ScaleFactor(SCALE_FACTOR_MAX - 2 * square_distance(wksq, queeningSq));
+ && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
+ && (distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo))
+ return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(wksq, queeningSq));
// Similar to the above, but with the pawn further back
if ( f != FILE_A
- && square_file(wrsq) == f
+ && file_of(wrsq) == f
&& wrsq < wpsq
- && (square_distance(wksq, queeningSq) < square_distance(bksq, queeningSq) - 2 + tempo)
- && (square_distance(wksq, wpsq + DELTA_N) < square_distance(bksq, wpsq + DELTA_N) - 2 + tempo)
- && ( 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))))
+ && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
+ && (distance(wksq, wpsq + DELTA_N) < distance(bksq, wpsq + DELTA_N) - 2 + tempo)
+ && ( distance(bksq, wrsq) + tempo >= 3
+ || ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo
+ && (distance(wksq, wpsq + DELTA_N) < distance(bksq, wrsq) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- - 8 * square_distance(wpsq, queeningSq)
- - 2 * square_distance(wksq, queeningSq));
+ - 8 * distance(wpsq, queeningSq)
+ - 2 * distance(wksq, queeningSq));
- // 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 (square_file(bksq) == square_file(wpsq))
+ if (file_of(bksq) == file_of(wpsq))
return ScaleFactor(10);
- if ( abs(square_file(bksq) - square_file(wpsq)) == 1
- && square_distance(wksq, bksq) > 2)
- return ScaleFactor(24 - 2 * square_distance(wksq, bksq));
+ if ( distance<File>(bksq, wpsq) == 1
+ && distance(wksq, bksq) > 2)
+ return ScaleFactor(24 - 2 * distance(wksq, bksq));
}
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 = 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
+ && distance(psq + 2 * push, ksq) <= 1
+ && (PseudoAttacks[BISHOP][bsq] & (psq + push))
+ && distance<File>(bsq, psq) >= 2)
+ return ScaleFactor(8);
+ }
+
+ return SCALE_FACTOR_NONE;
+}
-/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
-/// single pattern: If the stronger side has no pawns and the defending king
-/// is actively placed, the position is drawish.
+/// 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 ScalingFunction<KRPPKRP>::apply(const Position& pos) const {
+ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
- assert(pos.piece_count(strongerSide, PAWN) == 2);
- assert(pos.non_pawn_material(weakerSide) == RookValueMidgame);
- assert(pos.piece_count(weakerSide, PAWN) == 1);
+ assert(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 = 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)
+ if ( distance<File>(bksq, wpsq1) <= 1
+ && distance<File>(bksq, wpsq2) <= 1
+ && relative_rank(strongSide, bksq) > r)
{
switch (r) {
case RANK_2: return ScaleFactor(10);
}
-/// KPsKScalingFunction scales endgames with king and two or more pawns
-/// against king. There is just a single rule here: If all pawns are on
-/// the same rook file and are blocked by the defending king, it's a draw.
+/// K and two or more pawns vs K. There is just a single rule here: If all pawns
+/// are on the same rook file and are blocked by the defending king, it's a draw.
template<>
-ScaleFactor ScalingFunction<KPsK>::apply(const Position& pos) const {
+ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.piece_count(strongerSide, PAWN) >= 2);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(pos.non_pawn_material(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);
+ Square psq = pos.list<PAWN>(strongSide)[0];
+
+ // If all pawns are ahead of the king, on a single rook file and
+ // the king is within one file of the pawns, it's a draw.
+ if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq)))
+ && !((pawns & ~FileABB) && (pawns & ~FileHBB))
+ && distance<File>(ksq, psq) <= 1)
+ return SCALE_FACTOR_DRAW;
- // Are all pawns on the 'a' file?
- if ((pawns & ~FileABB) == EmptyBoardBB)
- {
- // Does the defending king block the pawns?
- if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
- || ( square_file(ksq) == FILE_A
- && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
- return SCALE_FACTOR_ZERO;
- }
- // Are all pawns on the 'h' file?
- else if ((pawns & ~FileHBB) == EmptyBoardBB)
- {
- // Does the defending king block the pawns?
- if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
- || ( square_file(ksq) == FILE_H
- && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB))
- return SCALE_FACTOR_ZERO;
- }
return SCALE_FACTOR_NONE;
}
-/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
-/// If the defending king is somewhere along the path of the pawn, and the
-/// square of the king is not of the same color as the stronger side's bishop,
-/// it's a draw. If the two bishops have opposite color, it's almost always
-/// a draw.
+/// 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 ScalingFunction<KBPKB>::apply(const Position& pos) const {
+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 ( square_file(weakerKingSq) == square_file(pawnSq)
- && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( !same_color_squares(weakerKingSq, strongerBishopSq)
- || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return SCALE_FACTOR_ZERO;
+ 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 (!same_color_squares(strongerBishopSq, weakerBishopSq))
+ if (opposite_colors(strongBishopSq, weakBishopSq))
{
// We assume that the position is drawn in the following three situations:
//
// These rules are probably not perfect, but in practice they work
// reasonably well.
- if (relative_rank(strongerSide, pawnSq) <= RANK_5)
- return SCALE_FACTOR_ZERO;
+ 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))
- return SCALE_FACTOR_ZERO;
+ if (path & pos.pieces(weakSide, KING))
+ return SCALE_FACTOR_DRAW;
- if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
- return SCALE_FACTOR_ZERO;
+ if ( (pos.attacks_from<BISHOP>(weakBishopSq) & path)
+ && distance(weakBishopSq, pawnSq) >= 3)
+ return SCALE_FACTOR_DRAW;
}
}
return SCALE_FACTOR_NONE;
}
-/// KBPPKBScalingFunction scales KBPP vs KB endgames. 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 ScalingFunction<KBPPKB>::apply(const Position& pos) const {
+ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 2);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(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 (same_color_squares(wbsq, bbsq))
- // Not opposite-colored bishops, no scaling
+ if (!opposite_colors(wbsq, bbsq))
return SCALE_FACTOR_NONE;
- Square ksq = pos.king_square(weakerSide);
- Square psq1 = pos.piece_list(strongerSide, PAWN, 0);
- Square psq2 = pos.piece_list(strongerSide, PAWN, 1);
- Rank r1 = square_rank(psq1);
- Rank r2 = square_rank(psq2);
+ Square 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(square_file(psq2), square_rank(psq1));
+ blockSq1 = psq1 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(psq2), rank_of(psq1));
}
else
{
- blockSq1 = psq2 + pawn_push(strongerSide);
- blockSq2 = make_square(square_file(psq1), square_rank(psq2));
+ blockSq1 = psq2 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(psq1), rank_of(psq2));
}
- switch (file_distance(psq1, psq2))
+ switch (distance<File>(psq1, psq2))
{
case 0:
- // Both pawns are on the same file. Easy draw if defender firmly controls
- // some square in the frontmost pawn's path.
- if ( square_file(ksq) == square_file(blockSq1)
- && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
- && !same_color_squares(ksq, wbsq))
- return SCALE_FACTOR_ZERO;
+ // 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(ksq) == file_of(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
- // in front of the frontmost pawn's path, and the square diagonally behind
- // this square on the file of the other pawn.
+ // 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 ( ksq == blockSq1
- && !same_color_squares(ksq, wbsq)
+ && opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq2
- || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
- || rank_distance(r1, r2) >= 2))
- return SCALE_FACTOR_ZERO;
+ || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
+ || distance(r1, r2) >= 2))
+ return SCALE_FACTOR_DRAW;
else if ( ksq == blockSq2
- && !same_color_squares(ksq, wbsq)
+ && opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq1
- || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
- return SCALE_FACTOR_ZERO;
+ || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakSide, BISHOP))))
+ return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
}
-/// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule:
-/// If the defending king is somewhere along the path of the pawn, and the
-/// square of the king is not of the same color as the stronger side's bishop,
-/// it's a draw.
+/// 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 ScalingFunction<KBPKN>::apply(const Position& pos) const {
+ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMidgame);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(verify_material(pos, strongSide, BishopValueMg, 1));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
- Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
- Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
- Square weakerKingSq = pos.king_square(weakerSide);
+ Square pawnSq = pos.list<PAWN>(strongSide)[0];
+ Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
+ Square weakKingSq = pos.king_square(weakSide);
- if ( square_file(weakerKingSq) == square_file(pawnSq)
- && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( !same_color_squares(weakerKingSq, strongerBishopSq)
- || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return SCALE_FACTOR_ZERO;
+ 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;
}
-/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule:
-/// If the pawn is a rook pawn on the 7th rank and the defending king prevents
-/// the pawn from advancing, the position is drawn.
+/// KNP vs K. There is a single rule: if the pawn is a rook pawn on the 7th rank
+/// and the defending king prevents the pawn from advancing, the position is drawn.
template<>
-ScaleFactor ScalingFunction<KNPK>::apply(const Position& pos) const {
-
- 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);
+ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
- Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
- Square weakerKingSq = pos.king_square(weakerSide);
+ assert(verify_material(pos, strongSide, KnightValueMg, 1));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- if ( pawnSq == relative_square(strongerSide, SQ_A7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
- return SCALE_FACTOR_ZERO;
+ // Assume strongSide is white and the pawn is on files A-D
+ Square pawnSq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+ Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide));
- if ( pawnSq == relative_square(strongerSide, SQ_H7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
- return SCALE_FACTOR_ZERO;
+ if (pawnSq == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1)
+ return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
-/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing
-/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest
-/// side has a draw without the pawn, she probably has at least a draw with
-/// the pawn as well. The exception is when the stronger side's pawn is far
-/// advanced and not on a rook file; in this case it is often possible to win
-/// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
+/// KNP vs KB. If knight can block bishop from taking pawn, it's a win.
+/// Otherwise the position is drawn.
template<>
-ScaleFactor ScalingFunction<KPKP>::apply(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);
-
- Square wksq, bksq, wpsq;
- Color stm;
-
- 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 = flip_square(pos.king_square(BLACK));
- bksq = flip_square(pos.king_square(WHITE));
- wpsq = flip_square(pos.piece_list(BLACK, PAWN, 0));
- stm = opposite_color(pos.side_to_move());
- }
+ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
- if (square_file(wpsq) >= FILE_E)
- {
- wksq = flop_square(wksq);
- bksq = flop_square(bksq);
- wpsq = flop_square(wpsq);
- }
+ Square pawnSq = pos.list<PAWN>(strongSide)[0];
+ Square bishopSq = pos.list<BISHOP>(weakSide)[0];
+ Square weakKingSq = pos.king_square(weakSide);
- // If the pawn has advanced to the fifth rank or further, and is not a
- // rook pawn, it's too dangerous to assume that it's at least a draw.
- if ( square_rank(wpsq) >= RANK_5
- && square_file(wpsq) != FILE_A)
- return SCALE_FACTOR_NONE;
+ // 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(distance(weakKingSq, pawnSq));
- // Probe the KPK bitbase with the weakest side's pawn removed. If it's a
- // draw, it's probably at least a draw even with the pawn.
- return probe_kpk(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_NONE;
}
-namespace {
+/// 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 {
- // Probe the KP vs K bitbase
+ assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm) {
+ // Assume strongSide is white and the pawn is on files A-D
+ Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
+ Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
+ Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
- int wp = square_file(wpsq) + 4 * (square_rank(wpsq) - 1);
- int index = int(stm) + 2 * bksq + 128 * wksq + 8192 * wp;
+ Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
- assert(index >= 0 && index < 24576 * 8);
+ // 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(psq) >= RANK_5 && file_of(psq) != FILE_A)
+ return SCALE_FACTOR_NONE;
- return KPKBitbase[index / 8] & (1 << (index & 7));
- }
+ // Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw,
+ // it's probably at least a draw even with the pawn.
+ return Bitbases::probe(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}
projects / stockfish / blobdiff