/*
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) 2008-2012 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/>.
*/
-#include <cassert>
#include <algorithm>
+#include <cassert>
#include "bitcount.h"
#include "endgame.h"
-#include "pawns.h"
+#include "movegen.h"
using std::string;
// the two kings in basic endgames.
const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
- // Penalty for big distance between king and knight for the defending king
- // and knight in KR vs KN endgames.
- const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 };
-
- // Build corresponding key code for the opposite color: "KBPKN" -> "KNKBP"
- const string swap_colors(const string& keyCode) {
-
- size_t idx = keyCode.find('K', 1);
- return keyCode.substr(idx) + keyCode.substr(0, idx);
- }
-
- // Get the material key of a position out of the given endgame key code
- // like "KBPKN". The trick here is to first build up a FEN string and then
- // let a Position object to do the work for us. Note that the FEN string
- // could correspond to an illegal position.
- Key mat_key(const string& keyCode) {
+ // Get the material key of a Position out of the given endgame key code
+ // like "KBPKN". The trick here is to first forge an ad-hoc fen string
+ // and then let a Position object to do the work for us. Note that the
+ // fen string could correspond to an illegal position.
+ Key key(const string& code, Color c) {
- assert(keyCode.length() > 0 && keyCode.length() < 8);
- assert(keyCode[0] == 'K');
+ assert(code.length() > 0 && code.length() < 8);
+ assert(code[0] == 'K');
- string fen;
- size_t i = 0;
+ string sides[] = { code.substr(code.find('K', 1)), // Weaker
+ code.substr(0, code.find('K', 1)) }; // Stronger
- // First add white and then black pieces
- do fen += keyCode[i]; while (keyCode[++i] != 'K');
- do fen += char(tolower(keyCode[i])); while (++i < keyCode.length());
+ transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
- // Add file padding and remaining empty ranks
- fen += string(1, '0' + int(8 - keyCode.length())) + "/8/8/8/8/8/8/8 w - - 0 10";
+ string fen = sides[0] + char('0' + int(8 - code.length()))
+ + sides[1] + "/8/8/8/8/8/8/8 w - - 0 10";
- // Build a Position out of the fen string and get its material key
- return Position(fen, false, 0).get_material_key();
+ return Position(fen, false, NULL).material_key();
}
-} // namespace
+ template<typename M>
+ void delete_endgame(const typename M::value_type& p) { delete p.second; }
+} // namespace
-/// Endgames member definitions
-template<> const Endgames::M1& Endgames::map<Endgames::M1>() const { return m1; }
-template<> const Endgames::M2& Endgames::map<Endgames::M2>() const { return m2; }
+/// Endgames members definitions
Endgames::Endgames() {
Endgames::~Endgames() {
- for (M1::const_iterator it = m1.begin(); it != m1.end(); ++it)
- delete it->second;
-
- for (M2::const_iterator it = m2.begin(); it != m2.end(); ++it)
- delete it->second;
+ for_each(m1.begin(), m1.end(), delete_endgame<M1>);
+ for_each(m2.begin(), m2.end(), delete_endgame<M2>);
}
template<EndgameType E>
-void Endgames::add(const string& keyCode) {
-
- typedef typename eg_family<E>::type T;
- typedef typename Map<T>::type M;
+void Endgames::add(const string& code) {
- const_cast<M&>(map<M>()).insert(std::make_pair(mat_key(keyCode), new Endgame<E>(WHITE)));
- const_cast<M&>(map<M>()).insert(std::make_pair(mat_key(swap_colors(keyCode)), new Endgame<E>(BLACK)));
+ map((Endgame<E>*)0)[key(code, WHITE)] = new Endgame<E>(WHITE);
+ map((Endgame<E>*)0)[key(code, BLACK)] = new Endgame<E>(BLACK);
}
/// 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>::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);
+ // Stalemate detection with lone king
+ if ( pos.side_to_move() == weakerSide
+ && !pos.in_check()
+ && !MoveList<MV_LEGAL>(pos).size()) {
+ return VALUE_DRAW;
+ }
+
Square winnerKSq = pos.king_square(strongerSide);
Square loserKSq = pos.king_square(weakerSide);
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;
+ || pos.bishop_pair(strongerSide)) {
+ result += VALUE_KNOWN_WIN;
+ }
return strongerSide == 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 Endgame<KBNK>::apply(const Position& pos) const {
+Value Endgame<KBNK>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
/// KP vs K. This endgame is evaluated with the help of a bitbase.
template<>
-Value Endgame<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);
}
else
{
- wksq = flip(pos.king_square(BLACK));
- bksq = flip(pos.king_square(WHITE));
- wpsq = flip(pos.piece_list(BLACK, PAWN)[0]);
- stm = flip(pos.side_to_move());
+ wksq = ~pos.king_square(BLACK);
+ bksq = ~pos.king_square(WHITE);
+ wpsq = ~pos.piece_list(BLACK, PAWN)[0];
+ stm = ~pos.side_to_move();
}
if (file_of(wpsq) >= FILE_E)
/// far advanced with support of the king, while the attacking king is far
/// away.
template<>
-Value Endgame<KRKP>::apply(const Position& pos) const {
+Value Endgame<KRKP>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
if (strongerSide == BLACK)
{
- wksq = flip(wksq);
- wrsq = flip(wrsq);
- bksq = flip(bksq);
- bpsq = flip(bpsq);
+ wksq = ~wksq;
+ wrsq = ~wrsq;
+ bksq = ~bksq;
+ bpsq = ~bpsq;
}
Square queeningSq = make_square(file_of(bpsq), RANK_1);
/// 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>::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);
/// 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>::apply(const Position& pos) const {
+Value Endgame<KRKN>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
assert(pos.piece_count(weakerSide, PAWN) == 0);
assert(pos.piece_count(weakerSide, KNIGHT) == 1);
- Square defendingKSq = pos.king_square(weakerSide);
- Square nSq = pos.piece_list(weakerSide, KNIGHT)[0];
-
- int d = square_distance(defendingKSq, nSq);
- Value result = Value(10)
- + MateTable[defendingKSq]
- + KRKNKingKnightDistancePenalty[d];
+ const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 };
+ 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;
}
/// for the defending side in the search, this is usually sufficient to be
/// able to win KQ vs KR.
template<>
-Value Endgame<KQKR>::apply(const Position& pos) const {
+Value Endgame<KQKR>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 0);
}
template<>
-Value Endgame<KBBKN>::apply(const Position& pos) const {
+Value Endgame<KBBKN>::operator()(const Position& pos) const {
assert(pos.piece_count(strongerSide, BISHOP) == 2);
assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMidgame);
result += Value(square_distance(bksq, nsq) * 32);
// Bonus for restricting the knight's mobility
- result += Value((8 - count_1s<CNT32_MAX15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
+ result += Value((8 - popcount<Max15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
return strongerSide == pos.side_to_move() ? result : -result;
}
/// K and two minors vs K and one or two minors or K and two knights against
/// king alone are always draw.
template<>
-Value Endgame<KmmKm>::apply(const Position&) const {
+Value Endgame<KmmKm>::operator()(const Position&) const {
return VALUE_DRAW;
}
template<>
-Value Endgame<KNNK>::apply(const Position&) const {
+Value Endgame<KNNK>::operator()(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
+/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and
+/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
+/// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling
/// will be used.
template<>
-ScaleFactor Endgame<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);
&& abs(file_of(kingSq) - pawnFile) <= 1)
{
// The bishop has the wrong color, and the defending king is on the
- // file of the pawn(s) or the neighboring file. Find the rank of the
+ // file of the pawn(s) or the adjacent file. Find the rank of the
// frontmost pawn.
Rank rank;
if (strongerSide == WHITE)
// is placed somewhere in front of the pawn, it's a draw.
if ( square_distance(kingSq, queeningSq) <= 1
|| relative_rank(strongerSide, kingSq) >= rank)
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
}
}
return SCALE_FACTOR_NONE;
}
-/// KQKRPScalingFunction scales endgames where the stronger side has only
-/// king and queen, while the weaker side has at least a rook and a pawn.
-/// It tests for fortress draws with a rook on the third rank defended by
-/// a pawn.
+/// K and queen vs K, rook and one or more pawns. It tests for fortress draws with
+/// a rook on the third rank defended by a pawn.
template<>
-ScaleFactor Endgame<KQKRPs>::apply(const Position& pos) const {
+ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == QueenValueMidgame);
assert(pos.piece_count(strongerSide, QUEEN) == 1);
{
Square rsq = pos.piece_list(weakerSide, ROOK)[0];
if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(PAWN, weakerSide))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
}
return SCALE_FACTOR_NONE;
}
-/// KRPKRScalingFunction scales KRP vs KR endgames. This function knows a
-/// handful of the most important classes of drawn positions, but is far
-/// from perfect. It would probably be a good idea to add more knowledge
-/// in the future.
+/// K, rook and one pawn vs K and a rook. This function knows a handful of the
+/// most important classes of drawn positions, but is far from perfect. It would
+/// probably be a good idea to add more knowledge in the future.
///
/// It would also be nice to rewrite the actual code for this function,
/// which is mostly copied from Glaurung 1.x, and not very pretty.
template<>
-ScaleFactor Endgame<KRPKR>::apply(const Position& pos) const {
+ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == RookValueMidgame);
assert(pos.piece_count(strongerSide, PAWN) == 1);
// pawn is on the left half of the board.
if (strongerSide == BLACK)
{
- wksq = flip(wksq);
- wrsq = flip(wrsq);
- wpsq = flip(wpsq);
- bksq = flip(bksq);
- brsq = flip(brsq);
+ wksq = ~wksq;
+ wrsq = ~wrsq;
+ wpsq = ~wpsq;
+ bksq = ~bksq;
+ brsq = ~brsq;
}
if (file_of(wpsq) > FILE_D)
{
&& square_distance(bksq, queeningSq) <= 1
&& wksq <= SQ_H5
&& (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
- return SCALE_FACTOR_ZERO;
+ 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.
&& square_distance(bksq, queeningSq) <= 1
&& rank_of(wksq) + tempo <= RANK_6
&& (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3)))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
if ( r >= RANK_6
&& bksq == queeningSq
&& rank_of(brsq) == RANK_1
&& (!tempo || square_distance(wksq, wpsq) >= 2))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
&& (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))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
&& bksq == wpsq + DELTA_N
&& square_distance(wksq, wpsq) - tempo >= 2
&& square_distance(wksq, brsq) - tempo >= 2)
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
}
-/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a
-/// single pattern: If the stronger side has no pawns and the defending king
+/// K, rook and two pawns vs K, rook and one pawn. There is only a single
+/// pattern: If the stronger side has no passed pawns and the defending king
/// is actively placed, the position is drawish.
template<>
-ScaleFactor Endgame<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);
}
-/// 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 Endgame<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);
if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
|| ( file_of(ksq) == FILE_A
&& !in_front_bb(strongerSide, ksq) & pawns))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
}
// Are all pawns on the 'h' file?
else if (!(pawns & ~FileHBB))
if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
|| ( file_of(ksq) == FILE_H
&& !in_front_bb(strongerSide, ksq) & pawns))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
}
return SCALE_FACTOR_NONE;
}
-/// KBPKBScalingFunction scales KBP vs KB endgames. There are two rules:
-/// If the defending king is somewhere along the path of the pawn, and the
-/// square of the king is not of the same color as the stronger side's bishop,
-/// it's a draw. If the two bishops have opposite color, it's almost always
-/// a draw.
+/// K, bishop and a pawn vs K and a bishop. There are two rules: If the defending
+/// king is somewhere along the path of the pawn, and the square of the king is
+/// not of the same color as the stronger side's bishop, it's a draw. If the two
+/// bishops have opposite color, it's almost always a draw.
template<>
-ScaleFactor Endgame<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);
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& ( opposite_colors(weakerKingSq, strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
if (opposite_colors(strongerBishopSq, weakerBishopSq))
// reasonably well.
if (relative_rank(strongerSide, pawnSq) <= RANK_5)
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
else
{
Bitboard path = squares_in_front_of(strongerSide, pawnSq);
if (path & pos.pieces(KING, weakerSide))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
&& square_distance(weakerBishopSq, pawnSq) >= 3)
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
}
}
return SCALE_FACTOR_NONE;
}
-/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic
-/// draws with opposite-colored bishops.
+/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with
+/// opposite-colored bishops.
template<>
-ScaleFactor Endgame<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);
if ( file_of(ksq) == file_of(blockSq1)
&& relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
&& opposite_colors(ksq, wbsq))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
case 1:
- // Pawns on neighboring files. Draw if defender firmly controls the square
+ // Pawns on adjacent files. Draw if defender firmly controls the square
// in front of the frontmost pawn's path, and the square diagonally behind
// this square on the file of the other pawn.
if ( ksq == blockSq1
&& ( bbsq == blockSq2
|| (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(BISHOP, weakerSide))
|| abs(r1 - r2) >= 2))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
else if ( ksq == blockSq2
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq1
|| (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(BISHOP, weakerSide))))
- return SCALE_FACTOR_ZERO;
+ 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.
+/// K, bisop and a pawn vs K and knight. There is a single rule: If the defending
+/// king is somewhere along the path of the pawn, and the square of the king is
+/// not of the same color as the stronger side's bishop, it's a draw.
template<>
-ScaleFactor Endgame<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);
&& relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
&& ( opposite_colors(weakerKingSq, strongerBishopSq)
|| relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
-/// KNPKScalingFunction scales KNP vs K endgames. There is a single rule:
-/// If the pawn is a rook pawn on the 7th rank and the defending king prevents
-/// the pawn from advancing, the position is drawn.
+/// K, knight and a pawn vs K. There is a single rule: If the pawn is a rook pawn
+/// on the 7th rank and the defending king prevents the pawn from advancing, the
+/// position is drawn.
template<>
-ScaleFactor Endgame<KNPK>::apply(const Position& pos) const {
+ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == KnightValueMidgame);
assert(pos.piece_count(strongerSide, KNIGHT) == 1);
if ( pawnSq == relative_square(strongerSide, SQ_A7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
if ( pawnSq == relative_square(strongerSide, SQ_H7)
&& square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
- return SCALE_FACTOR_ZERO;
+ return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
-/// KPKPScalingFunction scales KP vs KP endgames. This is done by removing
-/// the weakest side's pawn and probing the KP vs K bitbase: If the weakest
-/// side has a draw without the pawn, she probably has at least a draw with
-/// the pawn as well. The exception is when the stronger side's pawn is far
-/// advanced and not on a rook file; in this case it is often possible to win
-/// (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
+/// K and a pawn vs K and a pawn. This is done by removing the weakest side's
+/// pawn and probing the KP vs K bitbase: If the weakest side has a draw without
+/// the pawn, she probably has at least a draw with the pawn as well. The exception
+/// is when the stronger side's pawn is far advanced and not on a rook file; in
+/// this case it is often possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1).
template<>
-ScaleFactor Endgame<KPKP>::apply(const Position& pos) const {
+ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
assert(pos.piece_count(WHITE, PAWN) == 1);
assert(pos.piece_count(BLACK, PAWN) == 1);
- Square wksq, bksq, wpsq;
- Color stm;
+ 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();
- if (strongerSide == WHITE)
- {
- wksq = pos.king_square(WHITE);
- bksq = pos.king_square(BLACK);
- wpsq = pos.piece_list(WHITE, PAWN)[0];
- stm = pos.side_to_move();
- }
- else
+ if (strongerSide == BLACK)
{
- wksq = flip(pos.king_square(BLACK));
- bksq = flip(pos.king_square(WHITE));
- wpsq = flip(pos.piece_list(BLACK, PAWN)[0]);
- stm = flip(pos.side_to_move());
+ wksq = ~wksq;
+ bksq = ~bksq;
+ wpsq = ~wpsq;
+ stm = ~stm;
}
if (file_of(wpsq) >= FILE_E)
&& file_of(wpsq) != FILE_A)
return SCALE_FACTOR_NONE;
- // Probe the KPK bitbase with the weakest side's pawn removed. If it's a
- // draw, it's probably at least a draw even with the pawn.
- return probe_kpk_bitbase(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO;
+ // 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;
}
projects / stockfish / blobdiff