#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
- };
-
- // Tables used to drive a piece towards or away from another piece
- constexpr int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
- constexpr int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
-
- // Pawn Rank based scaling factors used in KRPPKRP endgame
- constexpr int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 };
+ 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.
+ 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); }
#ifndef NDEBUG
bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {
assert(pos.count<PAWN>(strongSide) == 1);
if (file_of(pos.square<PAWN>(strongSide)) >= FILE_E)
- sq = Square(int(sq) ^ 7); // Mirror SQ_H1 -> SQ_A1
+ sq = flip_file(sq);
- return strongSide == WHITE ? sq : ~sq;
+ return strongSide == WHITE ? sq : flip_rank(sq);
}
} // namespace
Value result = pos.non_pawn_material(strongSide)
+ pos.count<PAWN>(strongSide) * PawnValueEg
- + PushToEdges[loserKSq]
- + PushClose[distance(winnerKSq, loserKSq)];
+ + push_to_edge(loserKSq)
+ + push_close(winnerKSq, loserKSq);
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_MATE_IN_MAX_PLY - 1);
+ result = std::min(result + VALUE_KNOWN_WIN, VALUE_TB_WIN_IN_MAX_PLY - 1);
return strongSide == pos.side_to_move() ? result : -result;
}
// 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
- + PushClose[distance(winnerKSq, loserKSq)]
- + PushToCorners[opposite_colors(bishopSq, SQ_A1) ? ~loserKSq : loserKSq];
+ Value result = (VALUE_KNOWN_WIN + 3520)
+ + push_close(winnerKSq, loserKSq)
+ + 420 * push_to_corner(opposite_colors(bishopSq, SQ_A1) ? flip_file(loserKSq) : loserKSq);
- assert(abs(result) < VALUE_MATE_IN_MAX_PLY);
+ assert(abs(result) < VALUE_TB_WIN_IN_MAX_PLY);
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;
}
Square bksq = pos.square<KING>(weakSide);
Square bnsq = pos.square<KNIGHT>(weakSide);
- Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]);
+ Value result = Value(push_to_edge(bksq) + push_away(bksq, bnsq));
return strongSide == pos.side_to_move() ? result : -result;
}
Square loserKSq = pos.square<KING>(weakSide);
Square pawnSq = pos.square<PAWN>(weakSide);
- Value result = Value(PushClose[distance(winnerKSq, loserKSq)]);
+ Value result = Value(push_close(winnerKSq, loserKSq));
if ( relative_rank(weakSide, pawnSq) != RANK_7
|| distance(loserKSq, pawnSq) != 1
- || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq))
+ || ((FileBBB | FileDBB | FileEBB | FileGBB) & pawnSq))
result += QueenValueEg - PawnValueEg;
return strongSide == pos.side_to_move() ? result : -result;
Value result = QueenValueEg
- RookValueEg
- + PushToEdges[loserKSq]
- + PushClose[distance(winnerKSq, loserKSq)];
+ + push_to_edge(loserKSq)
+ + push_close(winnerKSq, loserKSq);
return strongSide == pos.side_to_move() ? result : -result;
}
-/// KNN vs KP. Simply push the opposing king to the corner
+/// 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 {
assert(verify_material(pos, strongSide, 2 * KnightValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- Value result = 2 * KnightValueEg
- - PawnValueEg
- + PushToEdges[pos.square<KING>(weakSide)];
+ Value result = PawnValueEg
+ + 2 * push_to_edge(pos.square<KING>(weakSide))
+ - 10 * relative_rank(weakSide, pos.square<PAWN>(weakSide));
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 pawns = pos.pieces(strongSide, PAWN);
- File pawnsFile = file_of(lsb(pawns));
+ Bitboard strongPawns = pos.pieces(strongSide, PAWN);
+ Bitboard allPawns = pos.pieces(PAWN);
- // All pawns are on a single rook file?
- if ( (pawnsFile == FILE_A || pawnsFile == FILE_H)
- && !(pawns & ~file_bb(pawnsFile)))
+ // All strongSide pawns are on a single rook file?
+ if (!(strongPawns & ~FileABB) || !(strongPawns & ~FileHBB))
{
Square bishopSq = pos.square<BISHOP>(strongSide);
- Square queeningSq = relative_square(strongSide, make_square(pawnsFile, RANK_8));
- Square kingSq = pos.square<KING>(weakSide);
+ Square queeningSq = relative_square(strongSide, make_square(file_of(lsb(strongPawns)), RANK_8));
+ Square weakKingSq = pos.square<KING>(weakSide);
if ( opposite_colors(queeningSq, bishopSq)
- && distance(queeningSq, kingSq) <= 1)
+ && distance(queeningSq, weakKingSq) <= 1)
return SCALE_FACTOR_DRAW;
}
// If all the pawns are on the same B or G file, then it's potentially a draw
- if ( (pawnsFile == FILE_B || pawnsFile == FILE_G)
- && !(pos.pieces(PAWN) & ~file_bb(pawnsFile))
+ if ((!(allPawns & ~FileBBB) || !(allPawns & ~FileGBB))
&& pos.non_pawn_material(weakSide) == 0
&& pos.count<PAWN>(weakSide) >= 1)
{
- // Get weakSide pawn that is closest to the home rank
+ // Get the least advanced weakSide pawn
Square weakPawnSq = frontmost_sq(strongSide, pos.pieces(weakSide, PAWN));
Square strongKingSq = pos.square<KING>(strongSide);
// There's potential for a draw if our pawn is blocked on the 7th rank,
// the bishop cannot attack it or they only have one pawn left
if ( relative_rank(strongSide, weakPawnSq) == RANK_7
- && (pos.pieces(strongSide, PAWN) & (weakPawnSq + pawn_push(weakSide)))
- && (opposite_colors(bishopSq, weakPawnSq) || pos.count<PAWN>(strongSide) == 1))
+ && (strongPawns & (weakPawnSq + pawn_push(weakSide)))
+ && (opposite_colors(bishopSq, weakPawnSq) || !more_than_one(strongPawns)))
{
int strongKingDist = distance(weakPawnSq, strongKingSq);
int weakKingDist = distance(weakPawnSq, weakKingSq);
&& relative_rank(strongSide, bksq) > r)
{
assert(r > RANK_1 && r < RANK_7);
- return ScaleFactor(KRPPKRPScaleFactors[r]);
+ return ScaleFactor(7 * r);
}
return SCALE_FACTOR_NONE;
}
Square ksq = pos.square<KING>(weakSide);
Bitboard pawns = 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 (!((pawns & ~FileABB) || (pawns & ~FileHBB)) &&
+ !(pawns & ~passed_pawn_span(weakSide, ksq)))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
Square weakKingSq = 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)
+ if ( (forward_file_bb(strongSide, pawnSq) & weakKingSq)
&& ( opposite_colors(weakKingSq, strongBishopSq)
|| relative_rank(strongSide, weakKingSq) <= RANK_6))
return SCALE_FACTOR_DRAW;
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