/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 Marco Costalba
+ Copyright (C) 2004-2020 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/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
-#include "bitbase.h"
+#include "bitboard.h"
#include "endgame.h"
-
-
-////
-//// Constants and variables
-////
-
-/// Evaluation functions
-
-// Generic "mate lone king" eval
-KXKEvaluationFunction EvaluateKXK = KXKEvaluationFunction(WHITE);
-KXKEvaluationFunction EvaluateKKX = KXKEvaluationFunction(BLACK);
-
-// KBN vs K
-KBNKEvaluationFunction EvaluateKBNK = KBNKEvaluationFunction(WHITE);
-KBNKEvaluationFunction EvaluateKKBN = KBNKEvaluationFunction(BLACK);
-
-// KP vs K
-KPKEvaluationFunction EvaluateKPK = KPKEvaluationFunction(WHITE);
-KPKEvaluationFunction EvaluateKKP = KPKEvaluationFunction(BLACK);
-
-// KR vs KP
-KRKPEvaluationFunction EvaluateKRKP = KRKPEvaluationFunction(WHITE);
-KRKPEvaluationFunction EvaluateKPKR = KRKPEvaluationFunction(BLACK);
-
-// KR vs KB
-KRKBEvaluationFunction EvaluateKRKB = KRKBEvaluationFunction(WHITE);
-KRKBEvaluationFunction EvaluateKBKR = KRKBEvaluationFunction(BLACK);
-
-// KR vs KN
-KRKNEvaluationFunction EvaluateKRKN = KRKNEvaluationFunction(WHITE);
-KRKNEvaluationFunction EvaluateKNKR = KRKNEvaluationFunction(BLACK);
-
-// KQ vs KR
-KQKREvaluationFunction EvaluateKQKR = KQKREvaluationFunction(WHITE);
-KQKREvaluationFunction EvaluateKRKQ = KQKREvaluationFunction(BLACK);
-
-// KBB vs KN
-KBBKNEvaluationFunction EvaluateKBBKN = KBBKNEvaluationFunction(WHITE);
-KBBKNEvaluationFunction EvaluateKNKBB = KBBKNEvaluationFunction(BLACK);
-
-// K and two minors vs K and one or two minors
-KmmKmEvaluationFunction EvaluateKmmKm = KmmKmEvaluationFunction(WHITE);
-
-
-/// Scaling functions
-
-// KBP vs K
-KBPKScalingFunction ScaleKBPK = KBPKScalingFunction(WHITE);
-KBPKScalingFunction ScaleKKBP = KBPKScalingFunction(BLACK);
-
-// KQ vs KRP
-KQKRPScalingFunction ScaleKQKRP = KQKRPScalingFunction(WHITE);
-KQKRPScalingFunction ScaleKRPKQ = KQKRPScalingFunction(BLACK);
-
-// KRP vs KR
-KRPKRScalingFunction ScaleKRPKR = KRPKRScalingFunction(WHITE);
-KRPKRScalingFunction ScaleKRKRP = KRPKRScalingFunction(BLACK);
-
-// KRPP vs KRP
-KRPPKRPScalingFunction ScaleKRPPKRP = KRPPKRPScalingFunction(WHITE);
-KRPPKRPScalingFunction ScaleKRPKRPP = KRPPKRPScalingFunction(BLACK);
-
-// King and pawns vs king
-KPsKScalingFunction ScaleKPsK = KPsKScalingFunction(WHITE);
-KPsKScalingFunction ScaleKKPs = KPsKScalingFunction(BLACK);
-
-// KBP vs KB
-KBPKBScalingFunction ScaleKBPKB = KBPKBScalingFunction(WHITE);
-KBPKBScalingFunction ScaleKBKBP = KBPKBScalingFunction(BLACK);
-
-// KBP vs KN
-KBPKNScalingFunction ScaleKBPKN = KBPKNScalingFunction(WHITE);
-KBPKNScalingFunction ScaleKNKBP = KBPKNScalingFunction(BLACK);
-
-// KNP vs K
-KNPKScalingFunction ScaleKNPK = KNPKScalingFunction(WHITE);
-KNPKScalingFunction ScaleKKNP = KNPKScalingFunction(BLACK);
-
-// KPKP
-KPKPScalingFunction ScaleKPKPw = KPKPScalingFunction(WHITE);
-KPKPScalingFunction ScaleKPKPb = KPKPScalingFunction(BLACK);
-
-
-////
-//// Local definitions
-////
+#include "movegen.h"
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 uint8_t 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 uint8_t 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 };
-
- // Bitbase for KP vs K
- uint8_t KPKBitbase[24576];
-
- // 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 };
-
- // Various inline functions for accessing the above arrays
- inline Value mate_table(Square s) {
- return Value(MateTable[s]);
+ // 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);
}
- inline Value kbnk_mate_table(Square s) {
- return Value(KBNKMateTable[s]);
+ // 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));
}
- inline Value distance_bonus(int d) {
- return Value(DistanceBonus[d]);
- }
+ // 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); }
- inline Value krkn_king_knight_distance_penalty(int d) {
- return Value(KRKNKingKnightDistancePenalty[d]);
+#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
- // Function for probing the KP vs K bitbase
- int probe_kpk(Square wksq, Square wpsq, Square bksq, Color stm);
+ // 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) {
-}
+ assert(pos.count<PAWN>(strongSide) == 1);
+ if (file_of(pos.square<PAWN>(strongSide)) >= FILE_E)
+ sq = flip_file(sq);
-////
-//// Functions
-////
+ return strongSide == WHITE ? sq : flip_rank(sq);
+ }
-/// Constructors
+} // namespace
-EndgameEvaluationFunction::EndgameEvaluationFunction(Color c) : strongerSide(c) {
- weakerSide = opposite_color(strongerSide);
-}
-KXKEvaluationFunction::KXKEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KBNKEvaluationFunction::KBNKEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KPKEvaluationFunction::KPKEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KRKPEvaluationFunction::KRKPEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KRKBEvaluationFunction::KRKBEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KRKNEvaluationFunction::KRKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KQKREvaluationFunction::KQKREvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KBBKNEvaluationFunction::KBBKNEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
-KmmKmEvaluationFunction::KmmKmEvaluationFunction(Color c) : EndgameEvaluationFunction(c) {}
+namespace Endgames {
+ std::pair<Map<Value>, Map<ScaleFactor>> maps;
-ScalingFunction::ScalingFunction(Color c) : strongerSide(c) {
- weakerSide = opposite_color(c);
-}
+ void init() {
+
+ 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");
-KBPKScalingFunction::KBPKScalingFunction(Color c) : ScalingFunction(c) {}
-KQKRPScalingFunction::KQKRPScalingFunction(Color c) : ScalingFunction(c) {}
-KRPKRScalingFunction::KRPKRScalingFunction(Color c) : ScalingFunction(c) {}
-KRPPKRPScalingFunction::KRPPKRPScalingFunction(Color c) : ScalingFunction(c) {}
-KPsKScalingFunction::KPsKScalingFunction(Color c) : ScalingFunction(c) {}
-KBPKBScalingFunction::KBPKBScalingFunction(Color c) : ScalingFunction(c) {}
-KBPKNScalingFunction::KBPKNScalingFunction(Color c) : ScalingFunction(c) {}
-KNPKScalingFunction::KNPKScalingFunction(Color c) : ScalingFunction(c) {}
-KPKPScalingFunction::KPKPScalingFunction(Color c) : ScalingFunction(c) {}
+ 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 {
-Value KXKEvaluationFunction::apply(const Position& pos) {
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
+ assert(!pos.checkers()); // Eval is never called when in check
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- assert(pos.piece_count(weakerSide, PAWN) == Value(0));
+ // Stalemate detection with lone king
+ if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
+ return VALUE_DRAW;
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(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
+ + push_to_edge(weakKing)
+ + push_close(strongKing, weakKing);
- if ( pos.piece_count(strongerSide, QUEEN) > 0
- || pos.piece_count(strongerSide, ROOK) > 0
- || 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 {
-Value KBNKEvaluationFunction::apply(const Position& pos) {
+ assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- assert(pos.piece_count(weakerSide, PAWN) == Value(0));
- 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 strongKing = pos.square<KING>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
- Square bishopSquare = pos.piece_list(strongerSide, BISHOP, 0);
+ // If our bishop does not attack A1/H8, we flip the enemy king square
+ // to drive to opposite corners (A8/H1).
- if (square_color(bishopSquare) == BLACK)
- {
- winnerKSq = flop_square(winnerKSq);
- loserKSq = flop_square(loserKSq);
- }
+ Value result = (VALUE_KNOWN_WIN + 3520)
+ + push_close(strongKing, weakKing)
+ + 420 * push_to_corner(opposite_colors(strongBishop, SQ_A1) ? flip_file(weakKing) : weakKing);
- Value result = VALUE_KNOWN_WIN
- + distance_bonus(square_distance(winnerKSq, loserKSq))
- + kbnk_mate_table(loserKSq);
-
- return (strongerSide == pos.side_to_move() ? result : -result);
+ 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.
-
-Value KPKEvaluationFunction::apply(const Position& pos) {
+/// 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(0));
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- 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;
-
- 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());
- }
+ // 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 (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(strongKing, strongPawn, weakKing, us))
return VALUE_DRAW;
- Value result = VALUE_KNOWN_WIN
- + PawnValueEndgame
- + Value(square_rank(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;
}
/// a bitbase. The function below returns drawish scores when the pawn is
/// far advanced with support of the king, while the attacking king is far
/// away.
+template<>
+Value Endgame<KRKP>::operator()(const Position& pos) const {
-Value KRKPEvaluationFunction::apply(const Position& pos) {
-
- 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 = 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 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 && square_file(wksq) == square_file(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 ( 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 ( 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 {
-Value KRKBEvaluationFunction::apply(const Position& pos) {
-
- 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 (pos.side_to_move() == strongerSide ? 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 {
-Value KRKNEvaluationFunction::apply(const Position& pos) {
+ assert(verify_material(pos, strongSide, RookValueMg, 0));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
- 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);
+ 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;
+}
- Square defendingKSq = pos.king_square(weakerSide);
- Square nSq = pos.piece_list(weakerSide, KNIGHT, 0);
- Value result = Value(10) + mate_table(defendingKSq) +
- krkn_king_knight_distance_penalty(square_distance(defendingKSq, nSq));
+/// 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 {
- return (strongerSide == pos.side_to_move())? result : -result;
-}
+ 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);
-/// 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.
+ Value result = Value(push_close(strongKing, weakKing));
-Value KQKREvaluationFunction::apply(const Position& pos) {
+ if ( relative_rank(weakSide, weakPawn) != RANK_7
+ || distance(weakKing, weakPawn) != 1
+ || ((FileBBB | FileDBB | FileEBB | FileGBB) & weakPawn))
+ result += QueenValueEg - PawnValueEg;
- 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);
+ return strongSide == pos.side_to_move() ? result : -result;
+}
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
- Value result = QueenValueEndgame
- - RookValueEndgame
- + mate_table(loserKSq)
- + distance_bonus(square_distance(winnerKSq, loserKSq));
+/// 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 {
- return (strongerSide == pos.side_to_move())? result : -result;
-}
+ assert(verify_material(pos, strongSide, QueenValueMg, 0));
+ assert(verify_material(pos, weakSide, RookValueMg, 0));
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
-Value KBBKNEvaluationFunction::apply(const Position& pos) {
+ Value result = QueenValueEg
+ - RookValueEg
+ + push_to_edge(weakKing)
+ + push_close(strongKing, weakKing);
- 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.pawns() == EmptyBoardBB);
+ return strongSide == pos.side_to_move() ? result : -result;
+}
- Value result = BishopValueEndgame;
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square nsq = pos.piece_list(weakerSide, KNIGHT, 0);
- // Bonus for attacking king close to defending king
- result += distance_bonus(square_distance(wksq, bksq));
+/// 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 driving the defending king and knight apart
- result += Value(square_distance(bksq, nsq) * 32);
+ assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- // Bonus for restricting the knight's mobility
- result += Value((8 - count_1s_max_15(pos.piece_attacks<KNIGHT>(nsq))) * 8);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakPawn = pos.square<PAWN>(weakSide);
- return (strongerSide == pos.side_to_move() ? result : -result);
+ Value result = PawnValueEg
+ + 2 * push_to_edge(weakKing)
+ - 10 * relative_rank(weakSide, weakPawn);
+
+ return strongSide == pos.side_to_move() ? result : -result;
}
-Value KmmKmEvaluationFunction::apply(const Position &pos) {
- return Value(0);
-}
+/// Some cases of trivial draws
+template<> 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, ScaleFactor(0) 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 Endgame<KBPsK>::operator()(const Position& pos) const {
-ScaleFactor KBPKScalingFunction::apply(const Position& pos) {
+ assert(pos.non_pawn_material(strongSide) == BishopValueMg);
+ assert(pos.count<PAWN>(strongSide) >= 1);
- assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) >= 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.pawns(strongerSide);
- File pawnFile = square_file(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)) == EmptyBoardBB)
+ // 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 ( square_color(queeningSq) != square_color(bishopSq)
- && file_distance(square_file(kingSq), pawnFile) <= 1)
+ if ( opposite_colors(queeningSquare, strongBishop)
+ && distance(queeningSquare, weakKing) <= 1)
+ return SCALE_FACTOR_DRAW;
+ }
+
+ // 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) == 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 ScaleFactor(0);
+ 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;
}
-/// 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 Endgame<KQKRPs>::operator()(const Position& pos) const {
-ScaleFactor KQKRPScalingFunction::apply(const Position& pos) {
+ assert(verify_material(pos, strongSide, QueenValueMg, 0));
+ assert(pos.count<ROOK>(weakSide) == 1);
+ assert(pos.count<PAWN>(weakSide) >= 1);
- 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 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;
- Square kingSq = pos.king_square(weakerSide);
- if ( relative_rank(weakerSide, kingSq) <= RANK_2
- && relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4
- && (pos.rooks(weakerSide) & relative_rank_bb(weakerSide, RANK_3))
- && (pos.pawns(weakerSide) & relative_rank_bb(weakerSide, RANK_2))
- && (pos.piece_attacks<KING>(kingSq) & pos.pawns(weakerSide)))
- {
- Square rsq = pos.piece_list(weakerSide, ROOK, 0);
- if (pos.pawn_attacks(strongerSide, rsq) & pos.pawns(weakerSide))
- return ScaleFactor(0);
- }
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.
-
-ScaleFactor KRPKRScalingFunction::apply(const Position &pos) {
+/// 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 = 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);
- }
+ // 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 = square_file(wpsq);
- Rank r = square_rank(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
- && (square_rank(brsq) == RANK_6 || (r <= RANK_3 && square_rank(wrsq) != RANK_6)))
- return ScaleFactor(0);
+ 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
- && square_rank(wksq) + tempo <= RANK_6
- && (square_rank(brsq) == RANK_1 || (!tempo && abs(square_file(brsq) - f) >= 3)))
- return ScaleFactor(0);
-
- if ( r >= RANK_6
- && bksq == queeningSq
- && square_rank(brsq) == RANK_1
- && (!tempo || square_distance(wksq, wpsq) >= 2))
- return ScaleFactor(0);
+ 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 ( 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)
- && square_file(brsq) == FILE_A
- && (square_rank(brsq) <= RANK_3 || square_file(wksq) >= FILE_D || square_rank(wksq) <= RANK_5))
- return ScaleFactor(0);
+ 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)
- return ScaleFactor(0);
+ 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
- && square_file(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
- && square_file(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 (square_file(bksq) == square_file(wpsq))
+ if (file_of(weakKing) == file_of(strongPawn))
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>(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 {
-/// 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.
-
-ScaleFactor KRPPKRPScalingFunction::apply(const Position &pos) {
-
- 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, 1));
+ assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Square wpsq1 = pos.piece_list(strongerSide, PAWN, 0);
- Square wpsq2 = pos.piece_list(strongerSide, PAWN, 1);
- Square bksq = pos.king_square(weakerSide);
-
- // Does the stronger side have a passed pawn?
- if ( pos.pawn_is_passed(strongerSide, wpsq1)
- || pos.pawn_is_passed(strongerSide, wpsq2))
- return SCALE_FACTOR_NONE;
-
- Rank r = Max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
-
- if ( file_distance(bksq, wpsq1) <= 1
- && file_distance(bksq, wpsq2) <= 1
- && relative_rank(strongerSide, bksq) > r)
+ // Test for a rook pawn
+ if (pos.pieces(PAWN) & (FileABB | FileHBB))
{
- 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);
+ 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 {
-/// 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.
-
-ScaleFactor KPsKScalingFunction::apply(const Position &pos) {
+ assert(verify_material(pos, strongSide, RookValueMg, 2));
+ assert(verify_material(pos, weakSide, RookValueMg, 1));
- assert(pos.non_pawn_material(strongerSide) == Value(0));
- assert(pos.piece_count(strongerSide, PAWN) >= 2);
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ Square strongPawn1 = pos.squares<PAWN>(strongSide)[0];
+ Square strongPawn2 = pos.squares<PAWN>(strongSide)[1];
+ Square weakKing = pos.square<KING>(weakSide);
- Bitboard pawns = pos.pawns(strongerSide);
-
- // Are all pawns on the 'a' file?
- if ((pawns & ~FileABB) == EmptyBoardBB)
- {
- // Does the defending king block the pawns?
- Square ksq = pos.king_square(weakerSide);
- if (square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1)
- return ScaleFactor(0);
- else if( square_file(ksq) == FILE_A
- && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
- return ScaleFactor(0);
- else
- return SCALE_FACTOR_NONE;
- }
- // Are all pawns on the 'h' file?
- else if ((pawns & ~FileHBB) == EmptyBoardBB)
- {
- // Does the defending king block the pawns?
- Square ksq = pos.king_square(weakerSide);
- if (square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1)
- return ScaleFactor(0);
- else if ( square_file(ksq) == FILE_H
- && (in_front_bb(strongerSide, ksq) & pawns) == EmptyBoardBB)
- return ScaleFactor(0);
- else
- return SCALE_FACTOR_NONE;
- }
- else
+ // Does the stronger side have a passed pawn?
+ if (pos.pawn_passed(strongSide, strongPawn1) || pos.pawn_passed(strongSide, strongPawn2))
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.
-ScaleFactor KBPKBScalingFunction::apply(const Position &pos) {
+ Rank pawnRank = std::max(relative_rank(strongSide, strongPawn1), relative_rank(strongSide, strongPawn2));
- assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
-
- Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
- Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
- Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP, 0);
- Square weakerKingSq = pos.king_square(weakerSide);
-
- // Case 1: Defending king blocks the pawn, and cannot be driven away
- if ( square_file(weakerKingSq) == square_file(pawnSq)
- && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( square_color(weakerKingSq) != square_color(strongerBishopSq)
- || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return ScaleFactor(0);
-
- // Case 2: Opposite colored bishops
- if (square_color(strongerBishopSq) != square_color(weakerBishopSq))
+ if ( distance<File>(weakKing, strongPawn1) <= 1
+ && distance<File>(weakKing, strongPawn2) <= 1
+ && relative_rank(strongSide, weakKing) > pawnRank)
{
- // 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 ScaleFactor(0);
- else
- {
- Bitboard ray = ray_bb(pawnSq, (strongerSide == WHITE)? SIGNED_DIR_N : SIGNED_DIR_S);
- if (ray & pos.kings(weakerSide))
- return ScaleFactor(0);
- if( (pos.piece_attacks<BISHOP>(weakerBishopSq) & ray)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
- return ScaleFactor(0);
- }
+ assert(pawnRank > RANK_1 && pawnRank < RANK_7);
+ return ScaleFactor(7 * pawnRank);
}
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 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 {
-ScaleFactor KBPKNScalingFunction::apply(const Position &pos) {
+ assert(pos.non_pawn_material(strongSide) == VALUE_ZERO);
+ assert(pos.count<PAWN>(strongSide) >= 2);
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- 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 weakKing = pos.square<KING>(weakSide);
+ Bitboard strongPawns = pos.pieces(strongSide, PAWN);
- Square pawnSq = pos.piece_list(strongerSide, PAWN, 0);
- Square strongerBishopSq = pos.piece_list(strongerSide, BISHOP, 0);
- Square weakerKingSq = pos.king_square(weakerSide);
-
- if ( square_file(weakerKingSq) == square_file(pawnSq)
- && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( square_color(weakerKingSq) != square_color(strongerBishopSq)
- || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
- return ScaleFactor(0);
+ // 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;
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.
-
-ScaleFactor KNPKScalingFunction::apply(const Position &pos) {
+/// 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) == KnightValueMidgame);
- assert(pos.piece_count(strongerSide, KNIGHT) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- 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 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);
- if ( pawnSq == relative_square(strongerSide, SQ_A7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
- return ScaleFactor(0);
+ // Case 1: Defending king blocks the pawn, and cannot be driven away
+ if ( (forward_file_bb(strongSide, strongPawn) & weakKing)
+ && ( opposite_colors(weakKing, strongBishop)
+ || relative_rank(strongSide, weakKing) <= RANK_6))
+ return SCALE_FACTOR_DRAW;
- if ( pawnSq == relative_square(strongerSide, SQ_H7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
- return ScaleFactor(0);
+ // Case 2: Opposite colored bishops
+ if (opposite_colors(strongBishop, weakBishop))
+ 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).
+/// KBPP vs KB. It detects a few basic draws with opposite-colored bishops
+template<>
+ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
-ScaleFactor KPKPScalingFunction::apply(const Position &pos) {
+ assert(verify_material(pos, strongSide, BishopValueMg, 2));
+ assert(verify_material(pos, weakSide, BishopValueMg, 0));
- assert(pos.non_pawn_material(strongerSide) == Value(0));
- assert(pos.non_pawn_material(weakerSide) == Value(0));
- assert(pos.piece_count(WHITE, PAWN) == 1);
- assert(pos.piece_count(BLACK, PAWN) == 1);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakBishop = pos.square<BISHOP>(weakSide);
+
+ if (!opposite_colors(strongBishop, weakBishop))
+ return SCALE_FACTOR_NONE;
- Square wksq, bksq, wpsq;
- Color stm;
+ Square weakKing = pos.square<KING>(weakSide);
+ Square strongPawn1 = pos.squares<PAWN>(strongSide)[0];
+ Square strongPawn2 = pos.squares<PAWN>(strongSide)[1];
+ Square blockSq1, blockSq2;
- if (strongerSide == WHITE)
+ if (relative_rank(strongSide, strongPawn1) > relative_rank(strongSide, strongPawn2))
{
- wksq = pos.king_square(WHITE);
- bksq = pos.king_square(BLACK);
- wpsq = pos.piece_list(WHITE, PAWN, 0);
- stm = pos.side_to_move();
+ blockSq1 = strongPawn1 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(strongPawn2), rank_of(strongPawn1));
}
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());
+ blockSq1 = strongPawn2 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(strongPawn1), rank_of(strongPawn2));
}
- if (square_file(wpsq) >= FILE_E)
+ switch (distance<File>(strongPawn1, strongPawn2))
{
- wksq = flop_square(wksq);
- bksq = flop_square(bksq);
- wpsq = flop_square(wpsq);
- }
+ case 0:
+ // 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;
- // 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;
+ case 1:
+ // 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 ( 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;
- // 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.
- if (probe_kpk(wksq, wpsq, bksq, stm))
- return SCALE_FACTOR_NONE;
- else
- return ScaleFactor(0);
+ default:
+ // The pawns are not on the same file or adjacent files. No scaling.
+ return SCALE_FACTOR_NONE;
+ }
}
-/// 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.
+/// 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(verify_material(pos, strongSide, BishopValueMg, 1));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
+
+ Square strongPawn = pos.square<PAWN>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
-void init_bitbases() {
- generate_kpk_bitbase(KPKBitbase);
+ 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;
}
-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 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));
- int wp = int(square_file(wpsq)) + (int(square_rank(wpsq)) - 1) * 4;
- int index = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*wp;
+ Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
- assert(index >= 0 && index < 24576*8);
- return KPKBitbase[index/8] & (1 << (index&7));
- }
+ // 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(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 Bitbases::probe(strongKing, strongPawn, weakKing, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}