/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
- Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ 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
#include "endgame.h"
#include "movegen.h"
-using std::string;
-
namespace {
- // Table used to drive the 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.
- constexpr 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,
- 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 king towards a corner square of the
- // right color in KBN vs K endgames.
- constexpr int PushToCorners[SQUARE_NB] = {
- 6400, 6080, 5760, 5440, 5120, 4800, 4480, 4160,
- 6080, 5760, 5440, 5120, 4800, 4480, 4160, 4480,
- 5760, 5440, 4960, 4480, 4480, 4000, 4480, 4800,
- 5440, 5120, 4480, 3840, 3520, 4480, 4800, 5120,
- 5120, 4800, 4480, 3520, 3840, 4480, 5120, 5440,
- 4800, 4480, 4000, 4480, 4480, 4960, 5440, 5760,
- 4480, 4160, 4480, 4800, 5120, 5440, 5760, 6080,
- 4160, 4480, 4800, 5120, 5440, 5760, 6080, 6400
- };
+ // 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);
+ }
+
+ // 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));
+ }
// 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); }
- // Pawn Rank based scaling factors used in KRPPKRP endgame
- constexpr int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 };
-
#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;
add<KQKR>("KQKR");
add<KNNKP>("KNNKP");
- add<KNPK>("KNPK");
- add<KNPKB>("KNPKB");
add<KRPKR>("KRPKR");
add<KRPKB>("KRPKB");
add<KBPKB>("KBPKB");
if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
return VALUE_DRAW;
- Square winnerKSq = pos.square<KING>(strongSide);
- Square loserKSq = pos.square<KING>(weakSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
Value result = pos.non_pawn_material(strongSide)
+ pos.count<PAWN>(strongSide) * PawnValueEg
- + PushToEdges[loserKSq]
- + push_close(winnerKSq, loserKSq);
+ + push_to_edge(weakKing)
+ + push_close(strongKing, weakKing);
if ( pos.count<QUEEN>(strongSide)
|| pos.count<ROOK>(strongSide)
assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square winnerKSq = pos.square<KING>(strongSide);
- Square loserKSq = pos.square<KING>(weakSide);
- Square bishopSq = pos.square<BISHOP>(strongSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
// If our bishop does not attack A1/H8, we flip the enemy king square
// to drive to opposite corners (A8/H1).
- Value result = VALUE_KNOWN_WIN
- + push_close(winnerKSq, loserKSq)
- + PushToCorners[opposite_colors(bishopSq, SQ_A1) ? ~loserKSq : loserKSq];
+ Value result = (VALUE_KNOWN_WIN + 3520)
+ + push_close(strongKing, weakKing)
+ + 420 * push_to_corner(opposite_colors(strongBishop, SQ_A1) ? flip_file(weakKing) : weakKing);
assert(abs(result) < VALUE_TB_WIN_IN_MAX_PLY);
return strongSide == pos.side_to_move() ? result : -result;
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
// Assume strongSide is white and the pawn is on files A-D
- Square wksq = normalize(pos, strongSide, pos.square<KING>(strongSide));
- Square bksq = normalize(pos, strongSide, pos.square<KING>(weakSide));
- Square psq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
+ 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));
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
- if (!Bitbases::probe(wksq, psq, bksq, us))
+ if (!Bitbases::probe(strongKing, strongPawn, weakKing, us))
return VALUE_DRAW;
- Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq));
+ Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(strongPawn));
return strongSide == pos.side_to_move() ? result : -result;
}
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- Square wksq = relative_square(strongSide, pos.square<KING>(strongSide));
- Square bksq = relative_square(strongSide, pos.square<KING>(weakSide));
- Square rsq = relative_square(strongSide, pos.square<ROOK>(strongSide));
- Square psq = relative_square(strongSide, pos.square<PAWN>(weakSide));
-
- Square queeningSq = make_square(file_of(psq), 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 (forward_file_bb(WHITE, wksq) & psq)
- result = RookValueEg - distance(wksq, psq);
+ 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 ( distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
- && distance(bksq, rsq) >= 3)
- result = RookValueEg - distance(wksq, psq);
+ else if ( distance(weakKing, weakPawn) >= 3 + (pos.side_to_move() == weakSide)
+ && distance(weakKing, strongRook) >= 3)
+ result = RookValueEg - distance(strongKing, weakPawn);
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
- else if ( rank_of(bksq) <= RANK_3
- && 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 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) - 8 * ( distance(wksq, psq + SOUTH)
- - distance(bksq, psq + SOUTH)
- - distance(psq, queeningSq));
+ result = Value(200) - 8 * ( distance(strongKing, weakPawn + pawn_push(weakSide))
+ - distance(weakKing, weakPawn + pawn_push(weakSide))
+ - distance(weakPawn, queeningSquare));
return strongSide == pos.side_to_move() ? result : -result;
}
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Value result = Value(PushToEdges[pos.square<KING>(weakSide)]);
+ Value result = Value(push_to_edge(pos.square<KING>(weakSide)));
return strongSide == pos.side_to_move() ? result : -result;
}
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
- Square bksq = pos.square<KING>(weakSide);
- Square bnsq = pos.square<KNIGHT>(weakSide);
- Value result = Value(PushToEdges[bksq] + push_away(bksq, bnsq));
+ 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;
}
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- Square winnerKSq = pos.square<KING>(strongSide);
- Square loserKSq = pos.square<KING>(weakSide);
- Square
pawnSq = pos.square<PAWN>(weakSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square
weakPawn = pos.square<PAWN>(weakSide);
- Value result = Value(push_close(winnerKSq, loserKSq));
+ Value result = Value(push_close(strongKing, weakKing));
- if ( relative_rank(weakSide, pawnSq) != RANK_7
- || distance(loserKSq, pawnSq) != 1
- || ((FileBBB | FileDBB | FileEBB | FileGBB) & pawnSq))
+ if ( relative_rank(weakSide, weakPawn) != RANK_7
+ || distance(weakKing, weakPawn) != 1
+ || ((FileBBB | FileDBB | FileEBB | FileGBB) & weakPawn))
result += QueenValueEg - PawnValueEg;
return strongSide == pos.side_to_move() ? result : -result;
}
-/// KQ vs KR. This is almost identical to KX vs K: We give the attacking
+/// KQ vs KR. This is almost identical to KX vs K: we give the attacking
/// king a bonus for having the kings close together, and for forcing the
/// defending king towards the edge. If we also take care to avoid null move for
/// the defending side in the search, this is usually sufficient to win KQ vs KR.
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, RookValueMg, 0));
- Square winnerKSq = pos.square<KING>(strongSide);
- Square loserKSq = pos.square<KING>(weakSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
Value result = QueenValueEg
- RookValueEg
- + PushToEdges[loserKSq]
- + push_close(winnerKSq, loserKSq);
+ + push_to_edge(weakKing)
+ + push_close(strongKing, weakKing);
return strongSide == pos.side_to_move() ? result : -result;
}
/// 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.
+/// press the weakSide King to a corner before the pawn advances too much.
template<>
Value Endgame<KNNKP>::operator()(const Position& pos) const {
assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakPawn = pos.square<PAWN>(weakSide);
+
Value result = PawnValueEg
- + 2 * PushToEdges[pos.square<KING>(weakSide)]
- - 10 * relative_rank(weakSide, pos.square<PAWN>(weakSide));
+ + 2 * push_to_edge(weakKing)
+ - 10 * relative_rank(weakSide, weakPawn);
return strongSide == pos.side_to_move() ? result : -result;
}
// No assertions about the material of weakSide, because we want draws to
// be detected even when the weaker side has some pawns.
- Bitboard strongpawns = pos.pieces(strongSide, PAWN);
- Bitboard allpawns = pos.pieces(PAWN);
+ 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 strongSide pawns are on a single rook file?
- if (!(strongpawns & ~FileABB) || !(strongpawns & ~FileHBB))
+ if (!(strongPawns & ~FileABB) || !(strongPawns & ~FileHBB))
{
- Square bishopSq = pos.square<BISHOP>(strongSide);
- Square queeningSq = relative_square(strongSide, make_square(file_of(lsb(strongpawns)), RANK_8));
- Square weakkingSq = pos.square<KING>(weakSide);
+ Square queeningSquare = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8));
- if ( opposite_colors(queeningSq, bishopSq)
- && distance(queeningSq, weakkingSq) <= 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))
+ if ((!(allPawns & ~FileBBB) || !(allPawns & ~FileGBB))
&& pos.non_pawn_material(weakSide) == 0
&& pos.count<PAWN>(weakSide) >= 1)
{
// Get the least advanced weakSide pawn
- Square weakPawnSq = frontmost_sq(strongSide, pos.pieces(weakSide, PAWN));
-
- Square strongKingSq = pos.square<KING>(strongSide);
- Square weakKingSq = pos.square<KING>(weakSide);
- Square bishopSq = pos.square<BISHOP>(strongSide);
+ 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, weakPawnSq) == RANK_7
- && (strongpawns & (weakPawnSq + pawn_push(weakSide)))
- && (opposite_colors(bishopSq, weakPawnSq) || !more_than_one(strongpawns)))
+ // 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)))
{
- int strongKingDist = distance(weakPawnSq, strongKingSq);
- int weakKingDist = distance(weakPawnSq, weakKingSq);
+ 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, weakKingSq) >= RANK_7
+ // 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;
assert(pos.count<ROOK>(weakSide) == 1);
assert(pos.count<PAWN>(weakSide) >= 1);
- Square kingSq = pos.square<KING>(weakSide);
- Square rsq = pos.square<ROOK>(weakSide);
+ Square strongKing = pos.square<KING>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
+ Square weakRook = pos.square<ROOK>(weakSide);
- if ( relative_rank(weakSide, kingSq) <= RANK_2
- && relative_rank(weakSide, pos.square<KING>(strongSide)) >= RANK_4
- && relative_rank(weakSide, rsq) == RANK_3
+ if ( relative_rank(weakSide, weakKing) <= RANK_2
+ && relative_rank(weakSide, strongKing) >= RANK_4
+ && relative_rank(weakSide, weakRook) == RANK_3
&& ( pos.pieces(weakSide, PAWN)
- & pos.attacks_from<KING>(kingSq)
- & pos.attacks_from<PAWN>(rsq, strongSide)))
+ & attacks_bb<KING>(weakKing)
+ & pawn_attacks_bb(strongSide, weakRook)))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
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.square<KING>(strongSide));
- Square bksq = normalize(pos, strongSide, pos.square<KING>(weakSide));
- Square wrsq = normalize(pos, strongSide, pos.square<ROOK>(strongSide));
- Square wpsq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
- Square brsq = normalize(pos, strongSide, pos.square<ROOK>(weakSide));
-
- File f = file_of(wpsq);
- Rank r = rank_of(wpsq);
- Square queeningSq = make_square(f, RANK_8);
+ 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 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
- && distance(bksq, queeningSq) <= 1
- && wksq <= SQ_H5
- && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6)))
+ if ( pawnRank <= RANK_5
+ && distance(weakKing, queeningSquare) <= 1
+ && strongKing <= SQ_H5
+ && (rank_of(weakRook) == RANK_6 || (pawnRank <= RANK_3 && rank_of(strongRook) != RANK_6)))
return SCALE_FACTOR_DRAW;
// The defending side saves a draw by checking from behind in case the pawn
// has advanced to the 6th rank with the king behind.
- if ( r == RANK_6
- && distance(bksq, queeningSq) <= 1
- && rank_of(wksq) + tempo <= RANK_6
- && (rank_of(brsq) == RANK_1 || (!tempo && distance<File>(brsq, wpsq) >= 3)))
+ if ( pawnRank == RANK_6
+ && distance(weakKing, queeningSquare) <= 1
+ && rank_of(strongKing) + tempo <= RANK_6
+ && (rank_of(weakRook) == RANK_1 || (!tempo && distance<File>(weakRook, strongPawn) >= 3)))
return SCALE_FACTOR_DRAW;
- if ( r >= RANK_6
- && bksq == queeningSq
- && rank_of(brsq) == RANK_1
- && (!tempo || distance(wksq, wpsq) >= 2))
+ if ( pawnRank >= RANK_6
+ && weakKing == queeningSquare
+ && rank_of(weakRook) == RANK_1
+ && (!tempo || distance(strongKing, strongPawn) >= 2))
return SCALE_FACTOR_DRAW;
// White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7
// and the black rook is behind the pawn.
- if ( wpsq == SQ_A7
- && wrsq == SQ_A8
- && (bksq == SQ_H7 || bksq == SQ_G7)
- && file_of(brsq) == FILE_A
- && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5))
+ if ( strongPawn == SQ_A7
+ && strongRook == SQ_A8
+ && (weakKing == SQ_H7 || weakKing == SQ_G7)
+ && file_of(weakRook) == FILE_A
+ && (rank_of(weakRook) <= RANK_3 || file_of(strongKing) >= FILE_D || rank_of(strongKing) <= RANK_5))
return SCALE_FACTOR_DRAW;
// If the defending king blocks the pawn and the attacking king is too far
// away, it's a draw.
- if ( r <= RANK_5
- && bksq == wpsq + NORTH
- && distance(wksq, wpsq) - tempo >= 2
- && distance(wksq, brsq) - tempo >= 2)
+ if ( pawnRank <= RANK_5
+ && weakKing == strongPawn + NORTH
+ && distance(strongKing, strongPawn) - tempo >= 2
+ && distance(strongKing, weakRook) - tempo >= 2)
return SCALE_FACTOR_DRAW;
// Pawn on the 7th rank supported by the rook from behind usually wins if the
// attacking king is closer to the queening square than the defending king,
// and the defending king cannot gain tempi by threatening the attacking rook.
- if ( r == RANK_7
- && f != FILE_A
- && file_of(wrsq) == f
- && wrsq != queeningSq
- && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
- && (distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo))
- return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(wksq, queeningSq));
+ if ( pawnRank == RANK_7
+ && pawnFile != FILE_A
+ && file_of(strongRook) == pawnFile
+ && strongRook != queeningSquare
+ && (distance(strongKing, queeningSquare) < distance(weakKing, queeningSquare) - 2 + tempo)
+ && (distance(strongKing, queeningSquare) < distance(weakKing, strongRook) + tempo))
+ return ScaleFactor(SCALE_FACTOR_MAX - 2 * distance(strongKing, queeningSquare));
// Similar to the above, but with the pawn further back
- if ( f != FILE_A
- && file_of(wrsq) == f
- && wrsq < wpsq
- && (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
- && (distance(wksq, wpsq + NORTH) < distance(bksq, wpsq + NORTH) - 2 + tempo)
- && ( distance(bksq, wrsq) + tempo >= 3
- || ( distance(wksq, queeningSq) < distance(bksq, wrsq) + tempo
- && (distance(wksq, wpsq + NORTH) < 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 * distance(wpsq, queeningSq)
- - 2 * 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
// the pawn's path, it's probably a draw.
- if (r <= RANK_4 && bksq > wpsq)
+ if (pawnRank <= RANK_4 && weakKing > strongPawn)
{
- if (file_of(bksq) == file_of(wpsq))
+ if (file_of(weakKing) == file_of(strongPawn))
return ScaleFactor(10);
- if ( distance<File>(bksq, wpsq) == 1
- && distance(wksq, bksq) > 2)
- return ScaleFactor(24 - 2 * distance(wksq, bksq));
+ if ( distance<File>(weakKing, strongPawn) == 1
+ && distance(strongKing, weakKing) > 2)
+ return ScaleFactor(24 - 2 * distance(strongKing, weakKing));
}
return SCALE_FACTOR_NONE;
}
// Test for a rook pawn
if (pos.pieces(PAWN) & (FileABB | FileHBB))
{
- Square ksq = pos.square<KING>(weakSide);
- Square bsq = pos.square<BISHOP>(weakSide);
- Square psq = pos.square<PAWN>(strongSide);
- Rank rk = relative_rank(strongSide, psq);
+ 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
// 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))
+ if (pawnRank == RANK_5 && !opposite_colors(weakBishop, strongPawn))
{
- int d = distance(psq + 3 * push, ksq);
+ int d = distance(strongPawn + 3 * push, weakKing);
- if (d <= 2 && !(d == 0 && ksq == pos.square<KING>(strongSide) + 2 * push))
+ if (d <= 2 && !(d == 0 && weakKing == strongKing + 2 * push))
return ScaleFactor(24);
else
return ScaleFactor(48);
// 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)
+ if ( pawnRank == RANK_6
+ && distance(strongPawn + 2 * push, weakKing) <= 1
+ && (attacks_bb<BISHOP>(weakBishop) & (strongPawn + push))
+ && distance<File>(weakBishop, strongPawn) >= 2)
return ScaleFactor(8);
}
assert(verify_material(pos, strongSide, RookValueMg, 2));
assert(verify_material(pos, weakSide, RookValueMg, 1));
- Square
wpsq1 = pos.squares<PAWN>(strongSide)[0];
- Square
wpsq2 = pos.squares<PAWN>(strongSide)[1];
- Square bksq = pos.square<KING>(weakSide);
+ Square
strongPawn1 = pos.squares<PAWN>(strongSide)[0];
+ Square
strongPawn2 = pos.squares<PAWN>(strongSide)[1];
+ Square weakKing = pos.square<KING>(weakSide);
// Does the stronger side have a passed pawn?
- if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
+ if (pos.pawn_passed(strongSide, strongPawn1) || pos.pawn_passed(strongSide, strongPawn2))
return SCALE_FACTOR_NONE;
- Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2));
+ Rank pawnRank = std::max(relative_rank(strongSide, strongPawn1), relative_rank(strongSide, strongPawn2));
- if ( distance<File>(bksq, wpsq1) <= 1
- && distance<File>(bksq, wpsq2) <= 1
- && relative_rank(strongSide, bksq) > r)
+ if ( distance<File>(weakKing, strongPawn1) <= 1
+ && distance<File>(weakKing, strongPawn2) <= 1
+ && relative_rank(strongSide, weakKing) > pawnRank)
{
- assert(r > RANK_1 && r < RANK_7);
- return ScaleFactor(KRPPKRPScaleFactors[r]);
+ assert(pawnRank > RANK_1 && pawnRank < RANK_7);
+ return ScaleFactor(7 * pawnRank);
}
return SCALE_FACTOR_NONE;
}
-/// K and two or more pawns vs K. There is just a single rule here: If all pawns
+/// K and two or more pawns vs K. There is just a single rule here: if all pawns
/// are on the same rook file and are blocked by the defending king, it's a draw.
template<>
ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
assert(pos.count<PAWN>(strongSide) >= 2);
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square ksq = pos.square<KING>(weakSide);
- Bitboard pawns = pos.pieces(strongSide, PAWN);
+ Square weakKing = pos.square<KING>(weakSide);
+ Bitboard strongPawns = pos.pieces(strongSide, PAWN);
- // If all pawns are ahead of the king, on a single rook file and
- // the king is within one file of the pawns, it's a draw.
- if ( !(pawns & ~forward_ranks_bb(weakSide, ksq))
- && !((pawns & ~FileABB) && (pawns & ~FileHBB))
- && distance<File>(ksq, lsb(pawns)) <= 1)
+ // 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;
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Square
pawnSq = pos.square<PAWN>(strongSide);
- Square strongBishopSq = pos.square<BISHOP>(strongSide);
- Square weakBishopSq = pos.square<BISHOP>(weakSide);
- Square weakKingSq = pos.square<KING>(weakSide);
+ Square
strongPawn = pos.square<PAWN>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakBishop = pos.square<BISHOP>(weakSide);
+ Square weakKing = pos.square<KING>(weakSide);
// Case 1: Defending king blocks the pawn, and cannot be driven away
- if ( file_of(weakKingSq) == file_of(pawnSq)
- && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
- && ( opposite_colors(weakKingSq, strongBishopSq)
- || relative_rank(strongSide, weakKingSq) <= RANK_6))
+ if ( (forward_file_bb(strongSide, strongPawn) & weakKing)
+ && ( opposite_colors(weakKing, strongBishop)
+ || relative_rank(strongSide, weakKing) <= RANK_6))
return SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
- if (opposite_colors(strongBishopSq, weakBishopSq))
+ if (opposite_colors(strongBishop, weakBishop))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
assert(verify_material(pos, strongSide, BishopValueMg, 2));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Square wbsq = pos.square<BISHOP>(strongSide);
- Square bbsq = pos.square<BISHOP>(weakSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakBishop = pos.square<BISHOP>(weakSide);
- if (!opposite_colors(wbsq, bbsq))
+ if (!opposite_colors(strongBishop, weakBishop))
return SCALE_FACTOR_NONE;
- Square ksq = pos.square<KING>(weakSide);
- Square
psq1 = pos.squares<PAWN>(strongSide)[0];
- Square
psq2 = pos.squares<PAWN>(strongSide)[1];
+ Square weakKing = pos.square<KING>(weakSide);
+ Square
strongPawn1 = pos.squares<PAWN>(strongSide)[0];
+ Square
strongPawn2 = pos.squares<PAWN>(strongSide)[1];
Square blockSq1, blockSq2;
- if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
+ if (relative_rank(strongSide, strongPawn1) > relative_rank(strongSide, strongPawn2))
{
- blockSq1 = psq1 + pawn_push(strongSide);
- blockSq2 = make_square(file_of(psq2), rank_of(psq1));
+ blockSq1 = strongPawn1 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(strongPawn2), rank_of(strongPawn1));
}
else
{
- blockSq1 = psq2 + pawn_push(strongSide);
- blockSq2 = make_square(file_of(psq1), rank_of(psq2));
+ blockSq1 = strongPawn2 + pawn_push(strongSide);
+ blockSq2 = make_square(file_of(strongPawn1), rank_of(strongPawn2));
}
- switch (distance<File>(psq1, psq2))
+ switch (distance<File>(strongPawn1, strongPawn2))
{
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(ksq) == file_of(blockSq1)
- && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1)
- && opposite_colors(ksq, wbsq))
+ 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;
// 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
- && opposite_colors(ksq, wbsq)
- && ( bbsq == blockSq2
- || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
- || distance<Rank>(psq1, psq2) >= 2))
+ if ( weakKing == blockSq1
+ && opposite_colors(weakKing, strongBishop)
+ && ( weakBishop == blockSq2
+ || (attacks_bb<BISHOP>(blockSq2, pos.pieces()) & pos.pieces(weakSide, BISHOP))
+ || distance<Rank>(strongPawn1, strongPawn2) >= 2))
return SCALE_FACTOR_DRAW;
- else if ( ksq == blockSq2
- && opposite_colors(ksq, wbsq)
- && ( bbsq == blockSq1
- || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakSide, BISHOP))))
+ 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;
}
-/// KBP vs KN. There is a single rule: If the defending king is somewhere along
+/// 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<>
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
- Square
pawnSq = pos.square<PAWN>(strongSide);
- Square strongBishopSq = pos.square<BISHOP>(strongSide);
- Square weakKingSq = pos.square<KING>(weakSide);
+ Square
strongPawn = pos.square<PAWN>(strongSide);
+ Square strongBishop = pos.square<BISHOP>(strongSide);
+ Square weakKing = pos.square<KING>(weakSide);
- if ( file_of(weakKingSq) == file_of(pawnSq)
- && relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
- && ( opposite_colors(weakKingSq, strongBishopSq)
- || relative_rank(strongSide, weakKingSq) <= RANK_6))
+ 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;
}
-/// 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 Endgame<KNPK>::operator()(const Position& pos) const {
-
- assert(verify_material(pos, strongSide, KnightValueMg, 1));
- assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
-
- // Assume strongSide is white and the pawn is on files A-D
- Square pawnSq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
- Square weakKingSq = normalize(pos, strongSide, pos.square<KING>(weakSide));
-
- if (pawnSq == SQ_A7 && distance(SQ_A8, weakKingSq) <= 1)
- return SCALE_FACTOR_DRAW;
-
- return SCALE_FACTOR_NONE;
-}
-
-
-/// KNP vs KB. If knight can block bishop from taking pawn, it's a win.
-/// Otherwise the position is drawn.
-template<>
-ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
-
- assert(verify_material(pos, strongSide, KnightValueMg, 1));
- assert(verify_material(pos, weakSide, BishopValueMg, 0));
-
- Square pawnSq = pos.square<PAWN>(strongSide);
- Square bishopSq = pos.square<BISHOP>(weakSide);
- Square weakKingSq = pos.square<KING>(weakSide);
-
- // King needs to get close to promoting pawn to prevent knight from blocking.
- // Rules for this are very tricky, so just approximate.
- if (forward_file_bb(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
- return ScaleFactor(distance(weakKingSq, pawnSq));
-
- return SCALE_FACTOR_NONE;
-}
-
-
/// 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
+/// 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).
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
// Assume strongSide is white and the pawn is on files A-D
- Square wksq = normalize(pos, strongSide, pos.square<KING>(strongSide));
- Square bksq = normalize(pos, strongSide, pos.square<KING>(weakSide));
- Square
psq = normalize(pos, strongSide, pos.square<PAWN>(strongSide));
+ 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));
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
// If the pawn has advanced to the fifth rank or further, and is not a
// rook pawn, it's too dangerous to assume that it's at least a draw.
- if (rank_of(psq) >= RANK_5 && file_of(psq) != FILE_A)
+ if (rank_of(strongPawn) >= RANK_5 && file_of(strongPawn) != FILE_A)
return SCALE_FACTOR_NONE;
// Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw,
// it's probably at least a draw even with the pawn.
- return Bitbases::probe(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
+ return Bitbases::probe(strongKing, strongPawn, weakKing, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}
projects / stockfish / blobdiff