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) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
#include <cassert>
#include "bitboard.h"
-#include "bitcount.h"
#include "endgame.h"
#include "movegen.h"
// Table used to drive the king towards the edge of the board
// in KX vs K and KQ vs KR endgames.
- const int PushToEdges[SQUARE_NB] = {
+ 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,
80, 60, 40, 30, 30, 40, 60, 80,
90, 70, 60, 50, 50, 60, 70, 90,
- 100, 90, 80, 70, 70, 80, 90, 100,
+ 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.
- const int PushToCorners[SQUARE_NB] = {
+ constexpr int PushToCorners[SQUARE_NB] = {
200, 190, 180, 170, 160, 150, 140, 130,
190, 180, 170, 160, 150, 140, 130, 140,
180, 170, 155, 140, 140, 125, 140, 150,
};
// Tables used to drive a piece towards or away from another piece
- const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
- const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
+ 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 };
#ifndef NDEBUG
bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {
assert(pos.count<PAWN>(strongSide) == 1);
- if (file_of(pos.list<PAWN>(strongSide)[0]) >= FILE_E)
+ if (file_of(pos.square<PAWN>(strongSide)) >= FILE_E)
sq = Square(sq ^ 7); // Mirror SQ_H1 -> SQ_A1
if (strongSide == BLACK)
return sq;
}
- // Get the material key of Position out of the given endgame key code
- // like "KBPKN". The trick here is to first forge an ad-hoc FEN string
- // and then let a Position object do the work for us.
- Key key(const string& code, Color c) {
-
- assert(code.length() > 0 && code.length() < 8);
- assert(code[0] == 'K');
-
- string sides[] = { code.substr(code.find('K', 1)), // Weak
- code.substr(0, code.find('K', 1)) }; // Strong
-
- std::transform(sides[c].begin(), sides[c].end(), sides[c].begin(), tolower);
-
- string fen = sides[0] + char(8 - sides[0].length() + '0') + "/8/8/8/8/8/8/"
- + sides[1] + char(8 - sides[1].length() + '0') + " w - - 0 10";
-
- return Position(fen, false, nullptr).material_key();
- }
-
} // namespace
-/// Endgames members definitions
-
-Endgames::Endgames() {
-
- add<KPK>("KPK");
- add<KNNK>("KNNK");
- add<KBNK>("KBNK");
- add<KRKP>("KRKP");
- add<KRKB>("KRKB");
- add<KRKN>("KRKN");
- add<KQKP>("KQKP");
- add<KQKR>("KQKR");
-
- add<KNPK>("KNPK");
- add<KNPKB>("KNPKB");
- add<KRPKR>("KRPKR");
- add<KRPKB>("KRPKB");
- add<KBPKB>("KBPKB");
- add<KBPKN>("KBPKN");
- add<KBPPKB>("KBPPKB");
- add<KRPPKRP>("KRPPKRP");
-}
-
-
-template<EndgameType E, typename T>
-void Endgames::add(const string& code) {
- map<T>()[key(code, WHITE)] = std::unique_ptr<EndgameBase<T>>(new Endgame<E>(WHITE));
- map<T>()[key(code, BLACK)] = std::unique_ptr<EndgameBase<T>>(new Endgame<E>(BLACK));
-}
-
-
/// Mate with KX vs K. This function is used to evaluate positions with
/// king and plenty of material vs a lone king. It simply gives the
/// attacking side a bonus for driving the defending king towards the edge
if (pos.side_to_move() == weakSide && !MoveList<LEGAL>(pos).size())
return VALUE_DRAW;
- Square winnerKSq = pos.king_square(strongSide);
- Square loserKSq = pos.king_square(weakSide);
+ Square winnerKSq = pos.square<KING>(strongSide);
+ Square loserKSq = pos.square<KING>(weakSide);
Value result = pos.non_pawn_material(strongSide)
+ pos.count<PAWN>(strongSide) * PawnValueEg
if ( pos.count<QUEEN>(strongSide)
|| pos.count<ROOK>(strongSide)
||(pos.count<BISHOP>(strongSide) && pos.count<KNIGHT>(strongSide))
- ||(pos.count<BISHOP>(strongSide) > 1 && opposite_colors(pos.list<BISHOP>(strongSide)[0],
- pos.list<BISHOP>(strongSide)[1])))
- result += VALUE_KNOWN_WIN;
+ || ( (pos.pieces(strongSide, BISHOP) & ~DarkSquares)
+ && (pos.pieces(strongSide, BISHOP) & DarkSquares)))
+ result = std::min(result + VALUE_KNOWN_WIN, VALUE_MATE_IN_MAX_PLY - 1);
return strongSide == pos.side_to_move() ? result : -result;
}
assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square winnerKSq = pos.king_square(strongSide);
- Square loserKSq = pos.king_square(weakSide);
- Square bishopSq = pos.list<BISHOP>(strongSide)[0];
+ Square winnerKSq = pos.square<KING>(strongSide);
+ Square loserKSq = pos.square<KING>(weakSide);
+ Square bishopSq = pos.square<BISHOP>(strongSide);
// kbnk_mate_table() tries to drive toward corners A1 or H8. If we have a
// bishop that cannot reach the above squares, we flip the kings in order
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.king_square(strongSide));
- Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
- Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+ 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));
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- Square wksq = relative_square(strongSide, pos.king_square(strongSide));
- Square bksq = relative_square(strongSide, pos.king_square(weakSide));
- Square rsq = relative_square(strongSide, pos.list<ROOK>(strongSide)[0]);
- Square psq = relative_square(strongSide, pos.list<PAWN>(weakSide)[0]);
+ 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);
Value result;
// If the stronger side's king is in front of the pawn, it's a win
- if (wksq < psq && file_of(wksq) == file_of(psq))
+ if (forward_file_bb(WHITE, wksq) & psq)
result = RookValueEg - distance(wksq, psq);
// If the weaker side's king is too far from the pawn and the rook,
result = Value(80) - 8 * distance(wksq, psq);
else
- result = Value(200) - 8 * ( distance(wksq, psq + DELTA_S)
- - distance(bksq, psq + DELTA_S)
+ result = Value(200) - 8 * ( distance(wksq, psq + SOUTH)
+ - distance(bksq, psq + SOUTH)
- distance(psq, queeningSq));
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 {
assert(verify_material(pos, strongSide, RookValueMg, 0));
assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Value result = Value(PushToEdges[pos.king_square(weakSide)]);
+ Value result = Value(PushToEdges[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.king_square(weakSide);
- Square bnsq = pos.list<KNIGHT>(weakSide)[0];
+ Square bksq = pos.square<KING>(weakSide);
+ Square bnsq = pos.square<KNIGHT>(weakSide);
Value result = Value(PushToEdges[bksq] + PushAway[distance(bksq, bnsq)]);
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.king_square(strongSide);
- Square loserKSq = pos.king_square(weakSide);
- Square pawnSq = pos.list<PAWN>(weakSide)[0];
+ Square winnerKSq = pos.square<KING>(strongSide);
+ Square loserKSq = pos.square<KING>(weakSide);
+ Square pawnSq = pos.square<PAWN>(weakSide);
Value result = Value(PushClose[distance(winnerKSq, loserKSq)]);
assert(verify_material(pos, strongSide, QueenValueMg, 0));
assert(verify_material(pos, weakSide, RookValueMg, 0));
- Square winnerKSq = pos.king_square(strongSide);
- Square loserKSq = pos.king_square(weakSide);
+ Square winnerKSq = pos.square<KING>(strongSide);
+ Square loserKSq = pos.square<KING>(weakSide);
Value result = QueenValueEg
- RookValueEg
// be detected even when the weaker side has some pawns.
Bitboard pawns = pos.pieces(strongSide, PAWN);
- File pawnFile = file_of(pos.list<PAWN>(strongSide)[0]);
+ File pawnsFile = file_of(lsb(pawns));
- // All pawns are on a single rook file ?
- if ( (pawnFile == FILE_A || pawnFile == FILE_H)
- && !(pawns & ~file_bb(pawnFile)))
+ // All pawns are on a single rook file?
+ if ( (pawnsFile == FILE_A || pawnsFile == FILE_H)
+ && !(pawns & ~file_bb(pawnsFile)))
{
- Square bishopSq = pos.list<BISHOP>(strongSide)[0];
- Square queeningSq = relative_square(strongSide, make_square(pawnFile, RANK_8));
- Square kingSq = pos.king_square(weakSide);
+ Square bishopSq = pos.square<BISHOP>(strongSide);
+ Square queeningSq = relative_square(strongSide, make_square(pawnsFile, RANK_8));
+ Square kingSq = pos.square<KING>(weakSide);
if ( opposite_colors(queeningSq, bishopSq)
&& distance(queeningSq, kingSq) <= 1)
}
// If all the pawns are on the same B or G file, then it's potentially a draw
- if ( (pawnFile == FILE_B || pawnFile == FILE_G)
- && !(pos.pieces(PAWN) & ~file_bb(pawnFile))
+ if ( (pawnsFile == FILE_B || pawnsFile == FILE_G)
+ && !(pos.pieces(PAWN) & ~file_bb(pawnsFile))
&& pos.non_pawn_material(weakSide) == 0
&& pos.count<PAWN>(weakSide) >= 1)
{
// Get weakSide pawn that is closest to the home rank
Square weakPawnSq = backmost_sq(weakSide, pos.pieces(weakSide, PAWN));
- Square strongKingSq = pos.king_square(strongSide);
- Square weakKingSq = pos.king_square(weakSide);
- Square bishopSq = pos.list<BISHOP>(strongSide)[0];
+ Square strongKingSq = pos.square<KING>(strongSide);
+ Square weakKingSq = pos.square<KING>(weakSide);
+ Square bishopSq = pos.square<BISHOP>(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
assert(pos.count<ROOK>(weakSide) == 1);
assert(pos.count<PAWN>(weakSide) >= 1);
- Square kingSq = pos.king_square(weakSide);
- Square rsq = pos.list<ROOK>(weakSide)[0];
+ Square kingSq = pos.square<KING>(weakSide);
+ Square rsq = pos.square<ROOK>(weakSide);
if ( relative_rank(weakSide, kingSq) <= RANK_2
- && relative_rank(weakSide, pos.king_square(strongSide)) >= RANK_4
+ && relative_rank(weakSide, pos.square<KING>(strongSide)) >= RANK_4
&& relative_rank(weakSide, rsq) == RANK_3
&& ( pos.pieces(weakSide, PAWN)
& pos.attacks_from<KING>(kingSq)
assert(verify_material(pos, weakSide, RookValueMg, 0));
// Assume strongSide is white and the pawn is on files A-D
- Square wksq = normalize(pos, strongSide, pos.king_square(strongSide));
- Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
- Square wrsq = normalize(pos, strongSide, pos.list<ROOK>(strongSide)[0]);
- Square wpsq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
- Square brsq = normalize(pos, strongSide, pos.list<ROOK>(weakSide)[0]);
+ 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);
if ( r == RANK_6
&& distance(bksq, queeningSq) <= 1
&& rank_of(wksq) + tempo <= RANK_6
- && (rank_of(brsq) == RANK_1 || (!tempo && distance(file_of(brsq), f) >= 3)))
+ && (rank_of(brsq) == RANK_1 || (!tempo && distance<File>(brsq, wpsq) >= 3)))
return SCALE_FACTOR_DRAW;
if ( r >= RANK_6
// 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
+ && bksq == wpsq + NORTH
&& distance(wksq, wpsq) - tempo >= 2
&& distance(wksq, brsq) - tempo >= 2)
return SCALE_FACTOR_DRAW;
&& file_of(wrsq) == f
&& wrsq < wpsq
&& (distance(wksq, queeningSq) < distance(bksq, queeningSq) - 2 + tempo)
- && (distance(wksq, wpsq + DELTA_N) < distance(bksq, wpsq + DELTA_N) - 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 + DELTA_N) < distance(bksq, wrsq) + tempo))))
+ && (distance(wksq, wpsq + NORTH) < distance(bksq, wrsq) + tempo))))
return ScaleFactor( SCALE_FACTOR_MAX
- 8 * distance(wpsq, queeningSq)
- 2 * distance(wksq, queeningSq));
// Test for a rook pawn
if (pos.pieces(PAWN) & (FileABB | FileHBB))
{
- Square ksq = pos.king_square(weakSide);
- Square bsq = pos.list<BISHOP>(weakSide)[0];
- Square psq = pos.list<PAWN>(strongSide)[0];
+ 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 push = pawn_push(strongSide);
+ 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
{
int d = distance(psq + 3 * push, ksq);
- if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 2 * push))
+ if (d <= 2 && !(d == 0 && ksq == pos.square<KING>(strongSide) + 2 * push))
return ScaleFactor(24);
else
return ScaleFactor(48);
assert(verify_material(pos, strongSide, RookValueMg, 2));
assert(verify_material(pos, weakSide, RookValueMg, 1));
- Square wpsq1 = pos.list<PAWN>(strongSide)[0];
- Square wpsq2 = pos.list<PAWN>(strongSide)[1];
- Square bksq = pos.king_square(weakSide);
+ Square wpsq1 = pos.squares<PAWN>(strongSide)[0];
+ Square wpsq2 = pos.squares<PAWN>(strongSide)[1];
+ Square bksq = pos.square<KING>(weakSide);
// Does the stronger side have a passed pawn?
if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
&& distance<File>(bksq, wpsq2) <= 1
&& relative_rank(strongSide, bksq) > r)
{
- 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);
- }
+ assert(r > RANK_1 && r < RANK_7);
+ return ScaleFactor(KRPPKRPScaleFactors[r]);
}
return SCALE_FACTOR_NONE;
}
assert(pos.count<PAWN>(strongSide) >= 2);
assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square ksq = pos.king_square(weakSide);
+ Square ksq = pos.square<KING>(weakSide);
Bitboard pawns = pos.pieces(strongSide, PAWN);
- Square psq = pos.list<PAWN>(strongSide)[0];
// If all pawns are ahead of the king, on a single rook file and
// the king is within one file of the pawns, it's a draw.
- if ( !(pawns & ~in_front_bb(weakSide, rank_of(ksq)))
+ if ( !(pawns & ~forward_ranks_bb(weakSide, ksq))
&& !((pawns & ~FileABB) && (pawns & ~FileHBB))
- && distance<File>(ksq, psq) <= 1)
+ && distance<File>(ksq, lsb(pawns)) <= 1)
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.list<PAWN>(strongSide)[0];
- Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
- Square weakBishopSq = pos.list<BISHOP>(weakSide)[0];
- Square weakKingSq = pos.king_square(weakSide);
+ Square pawnSq = pos.square<PAWN>(strongSide);
+ Square strongBishopSq = pos.square<BISHOP>(strongSide);
+ Square weakBishopSq = pos.square<BISHOP>(weakSide);
+ 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)
// Case 2: Opposite colored bishops
if (opposite_colors(strongBishopSq, weakBishopSq))
- {
- // 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(strongSide, pawnSq) <= RANK_5)
- return SCALE_FACTOR_DRAW;
- else
- {
- Bitboard path = forward_bb(strongSide, pawnSq);
-
- if (path & pos.pieces(weakSide, KING))
- return SCALE_FACTOR_DRAW;
+ return SCALE_FACTOR_DRAW;
- if ( (pos.attacks_from<BISHOP>(weakBishopSq) & path)
- && distance(weakBishopSq, pawnSq) >= 3)
- 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.list<BISHOP>(strongSide)[0];
- Square bbsq = pos.list<BISHOP>(weakSide)[0];
+ Square wbsq = pos.square<BISHOP>(strongSide);
+ Square bbsq = pos.square<BISHOP>(weakSide);
if (!opposite_colors(wbsq, bbsq))
return SCALE_FACTOR_NONE;
- Square ksq = pos.king_square(weakSide);
- Square psq1 = pos.list<PAWN>(strongSide)[0];
- Square psq2 = pos.list<PAWN>(strongSide)[1];
+ Square ksq = pos.square<KING>(weakSide);
+ Square psq1 = pos.squares<PAWN>(strongSide)[0];
+ Square psq2 = pos.squares<PAWN>(strongSide)[1];
Rank r1 = rank_of(psq1);
Rank r2 = rank_of(psq2);
Square blockSq1, blockSq2;
assert(verify_material(pos, strongSide, BishopValueMg, 1));
assert(verify_material(pos, weakSide, KnightValueMg, 0));
- Square pawnSq = pos.list<PAWN>(strongSide)[0];
- Square strongBishopSq = pos.list<BISHOP>(strongSide)[0];
- Square weakKingSq = pos.king_square(weakSide);
+ Square pawnSq = pos.square<PAWN>(strongSide);
+ Square strongBishopSq = pos.square<BISHOP>(strongSide);
+ Square weakKingSq = pos.square<KING>(weakSide);
if ( file_of(weakKingSq) == file_of(pawnSq)
&& relative_rank(strongSide, pawnSq) < relative_rank(strongSide, weakKingSq)
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.list<PAWN>(strongSide)[0]);
- Square weakKingSq = normalize(pos, strongSide, pos.king_square(weakSide));
+ 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;
template<>
ScaleFactor Endgame<KNPKB>::operator()(const Position& pos) const {
- Square pawnSq = pos.list<PAWN>(strongSide)[0];
- Square bishopSq = pos.list<BISHOP>(weakSide)[0];
- Square weakKingSq = pos.king_square(weakSide);
+ 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_bb(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
+ if (forward_file_bb(strongSide, pawnSq) & pos.attacks_from<BISHOP>(bishopSq))
return ScaleFactor(distance(weakKingSq, pawnSq));
return SCALE_FACTOR_NONE;
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.king_square(strongSide));
- Square bksq = normalize(pos, strongSide, pos.king_square(weakSide));
- Square psq = normalize(pos, strongSide, pos.list<PAWN>(strongSide)[0]);
+ 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));
Color us = strongSide == pos.side_to_move() ? WHITE : BLACK;