namespace {
- // Table used to drive the defending king towards the edge of the board
+ // Table used to drive the king towards the edge of the board
// in KX vs K and KQ vs KR endgames.
- const int MateTable[SQUARE_NB] = {
+ const 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,
100, 90, 80, 70, 70, 80, 90, 100,
};
- // Table used to drive the defending king towards a corner square of the
+ // Table used to drive the king towards a corner square of the
// right color in KBN vs K endgames.
- const int KBNKMateTable[SQUARE_NB] = {
+ const 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,
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 };
+ // 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 };
+
+#ifndef NDEBUG
+ bool verify_material(const Position& pos, Color c, Value npm, int num_pawns) {
+ return pos.non_pawn_material(c) == npm && pos.count<PAWN>(c) == num_pawns;
+ }
+#endif
// Get the material key of a Position out of the given endgame key code
// like "KBPKN". The trick here is to first forge an ad-hoc fen string
assert(code.length() > 0 && code.length() < 8);
assert(code[0] == 'K');
- string sides[] = { code.substr(code.find('K', 1)), // Weaker
- code.substr(0, code.find('K', 1)) }; // Stronger
+ 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);
add<KBBKN>("KBBKN");
add<KNPK>("KNPK");
+ add<KNPKB>("KNPKB");
add<KRPKR>("KRPKR");
+ add<KRPKB>("KRPKB");
add<KBPKB>("KBPKB");
add<KBPKN>("KBPKN");
add<KBPPKB>("KBPPKB");
template<>
Value Endgame<KXK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
+ assert(!pos.checkers()); // Eval is never called when in check
// Stalemate detection with lone king
- if ( pos.side_to_move() == weakerSide
- && !pos.checkers()
- && !MoveList<LEGAL>(pos).size()) {
- return VALUE_DRAW;
- }
+ 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 winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
- Value result = pos.non_pawn_material(strongerSide)
- + pos.piece_count(strongerSide, PAWN) * PawnValueEg
- + MateTable[loserKSq]
- + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+ Value result = pos.non_pawn_material(strongSide)
+ + pos.count<PAWN>(strongSide) * PawnValueEg
+ + PushToEdges[loserKSq]
+ + PushClose[square_distance(winnerKSq, loserKSq)];
- if ( pos.piece_count(strongerSide, QUEEN)
- || pos.piece_count(strongerSide, ROOK)
- || pos.bishop_pair(strongerSide)) {
- result += VALUE_KNOWN_WIN;
- }
+ if ( pos.count<QUEEN>(strongSide)
+ || pos.count<ROOK>(strongSide)
+ || pos.bishop_pair(strongSide))
+ result += VALUE_KNOWN_WIN;
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KBNK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == VALUE_ZERO);
- assert(pos.non_pawn_material(strongerSide) == KnightValueMg + BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, KNIGHT) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
+ assert(verify_material(pos, strongSide, KnightValueMg + BishopValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
- Square bishopSq = pos.piece_list(strongerSide, BISHOP)[0];
+ Square winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
+ Square bishopSq = pos.list<BISHOP>(strongSide)[0];
// kbnk_mate_table() tries to drive toward corners A1 or H8,
// if we have a bishop that cannot reach the above squares we
}
Value result = VALUE_KNOWN_WIN
- + DistanceBonus[square_distance(winnerKSq, loserKSq)]
- + KBNKMateTable[loserKSq];
+ + PushClose[square_distance(winnerKSq, loserKSq)]
+ + PushToCorners[loserKSq];
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KPK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(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 us;
+ Square wksq = pos.king_square(strongSide);
+ Square bksq = pos.king_square(weakSide);
+ Square psq = pos.list<PAWN>(strongSide)[0];
+ Color us = pos.side_to_move();
- if (strongerSide == WHITE)
- {
- wksq = pos.king_square(WHITE);
- bksq = pos.king_square(BLACK);
- wpsq = pos.piece_list(WHITE, PAWN)[0];
- us = pos.side_to_move();
- }
- else
+ if (strongSide == BLACK)
{
- wksq = ~pos.king_square(BLACK);
- bksq = ~pos.king_square(WHITE);
- wpsq = ~pos.piece_list(BLACK, PAWN)[0];
- us = ~pos.side_to_move();
+ wksq = ~wksq;
+ bksq = ~bksq;
+ psq = ~psq;
+ us = ~us;
}
- if (file_of(wpsq) >= FILE_E)
+ if (file_of(psq) >= FILE_E)
{
wksq = mirror(wksq);
bksq = mirror(bksq);
- wpsq = mirror(wpsq);
+ psq = mirror(psq);
}
- if (!Bitbases::probe_kpk(wksq, wpsq, bksq, us))
+ if (!Bitbases::probe_kpk(wksq, psq, bksq, us))
return VALUE_DRAW;
- Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(wpsq));
+ Value result = VALUE_KNOWN_WIN + PawnValueEg + Value(rank_of(psq));
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KRKP>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- 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);
+ Square wksq = pos.king_square(strongSide);
+ Square bksq = pos.king_square(weakSide);
+ Square rsq = pos.list<ROOK>(strongSide)[0];
+ Square psq = pos.list<PAWN>(weakSide)[0];
- 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)
+ if (strongSide == BLACK)
{
wksq = ~wksq;
- wrsq = ~wrsq;
bksq = ~bksq;
- bpsq = ~bpsq;
+ rsq = ~rsq;
+ psq = ~psq;
}
- Square queeningSq = file_of(bpsq) | RANK_1;
+ Square queeningSq = 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 < bpsq && file_of(wksq) == file_of(bpsq))
- result = RookValueEg - Value(square_distance(wksq, bpsq));
+ if (wksq < psq && file_of(wksq) == file_of(psq))
+ result = RookValueEg - Value(square_distance(wksq, psq));
// 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 = RookValueEg - Value(square_distance(wksq, bpsq));
+ // it's a win.
+ else if ( square_distance(bksq, psq) >= 3 + (pos.side_to_move() == weakSide)
+ && square_distance(bksq, rsq) >= 3)
+ result = RookValueEg - Value(square_distance(wksq, psq));
// If the pawn is far advanced and supported by the defending king,
// the position is drawish
else if ( rank_of(bksq) <= RANK_3
- && square_distance(bksq, bpsq) == 1
+ && square_distance(bksq, psq) == 1
&& rank_of(wksq) >= RANK_4
- && square_distance(wksq, bpsq) - tempo > 2)
- result = Value(80 - square_distance(wksq, bpsq) * 8);
+ && square_distance(wksq, psq) > 2 + (pos.side_to_move() == strongSide))
+ result = Value(80 - square_distance(wksq, psq) * 8);
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);
+ - Value(square_distance(wksq, psq + DELTA_S) * 8)
+ + Value(square_distance(bksq, psq + DELTA_S) * 8)
+ + Value(square_distance(psq, queeningSq) * 8);
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KRKB>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMg);
- 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 = Value(MateTable[pos.king_square(weakerSide)]);
- return strongerSide == pos.side_to_move() ? result : -result;
+ Value result = Value(PushToEdges[pos.king_square(weakSide)]);
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KRKN>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
+ assert(verify_material(pos, strongSide, RookValueMg, 0));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
- const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 };
-
- Square bksq = pos.king_square(weakerSide);
- Square bnsq = pos.piece_list(weakerSide, KNIGHT)[0];
- Value result = Value(MateTable[bksq] + penalty[square_distance(bksq, bnsq)]);
- return strongerSide == pos.side_to_move() ? result : -result;
+ Square bksq = pos.king_square(weakSide);
+ Square bnsq = pos.list<KNIGHT>(weakSide)[0];
+ Value result = Value(PushToEdges[bksq] + PushAway[square_distance(bksq, bnsq)]);
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KQKP>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
- 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, QueenValueMg, 0));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
- Square pawnSq = pos.piece_list(weakerSide, PAWN)[0];
+ Square winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
+ Square pawnSq = pos.list<PAWN>(weakSide)[0];
- Value result = QueenValueEg
- - PawnValueEg
- + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+ Value result = Value(PushClose[square_distance(winnerKSq, loserKSq)]);
- if ( square_distance(loserKSq, pawnSq) == 1
- && relative_rank(weakerSide, pawnSq) == RANK_7)
- {
- File f = file_of(pawnSq);
+ if ( relative_rank(weakSide, pawnSq) != RANK_7
+ || square_distance(loserKSq, pawnSq) != 1
+ || !((FileABB | FileCBB | FileFBB | FileHBB) & pawnSq))
+ result += QueenValueEg - PawnValueEg;
- if (f == FILE_A || f == FILE_C || f == FILE_F || f == FILE_H)
- result = Value(DistanceBonus[square_distance(winnerKSq, loserKSq)]);
- }
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
template<>
Value Endgame<KQKR>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 0);
- assert(pos.non_pawn_material(weakerSide) == RookValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(verify_material(pos, strongSide, QueenValueMg, 0));
+ assert(verify_material(pos, weakSide, RookValueMg, 0));
- Square winnerKSq = pos.king_square(strongerSide);
- Square loserKSq = pos.king_square(weakerSide);
+ Square winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
Value result = QueenValueEg
- RookValueEg
- + MateTable[loserKSq]
- + DistanceBonus[square_distance(winnerKSq, loserKSq)];
+ + PushToEdges[loserKSq]
+ + PushClose[square_distance(winnerKSq, loserKSq)];
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
-template<>
-Value Endgame<KBBKN>::operator()(const Position& pos) const {
- assert(pos.piece_count(strongerSide, BISHOP) == 2);
- assert(pos.non_pawn_material(strongerSide) == 2*BishopValueMg);
- assert(pos.piece_count(weakerSide, KNIGHT) == 1);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMg);
- assert(!pos.pieces(PAWN));
+/// KBB vs KN. This is almost always a win. We try to push enemy king to a corner
+/// and away from his knight. For a reference of this difficult endgame see:
+/// en.wikipedia.org/wiki/Chess_endgame#Effect_of_tablebases_on_endgame_theory
- Value result = BishopValueEg;
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square nsq = pos.piece_list(weakerSide, KNIGHT)[0];
+template<>
+Value Endgame<KBBKN>::operator()(const Position& pos) const {
- // Bonus for attacking king close to defending king
- result += Value(DistanceBonus[square_distance(wksq, bksq)]);
+ assert(verify_material(pos, strongSide, 2 * BishopValueMg, 0));
+ assert(verify_material(pos, weakSide, KnightValueMg, 0));
- // Bonus for driving the defending king and knight apart
- result += Value(square_distance(bksq, nsq) * 32);
+ Square winnerKSq = pos.king_square(strongSide);
+ Square loserKSq = pos.king_square(weakSide);
+ Square knightSq = pos.list<KNIGHT>(weakSide)[0];
- // Bonus for restricting the knight's mobility
- result += Value((8 - popcount<Max15>(pos.attacks_from<KNIGHT>(nsq))) * 8);
+ Value result = VALUE_KNOWN_WIN
+ + PushToCorners[loserKSq]
+ + PushClose[square_distance(winnerKSq, loserKSq)]
+ + PushAway[square_distance(loserKSq, knightSq)];
- return strongerSide == pos.side_to_move() ? result : -result;
+ return strongSide == pos.side_to_move() ? result : -result;
}
-/// K and two minors vs K and one or two minors or K and two knights against
-/// king alone are always draw.
-template<>
-Value Endgame<KmmKm>::operator()(const Position&) const {
- return VALUE_DRAW;
-}
+/// Some cases of trivial draws
+template<> Value Endgame<KNNK>::operator()(const Position&) const { return VALUE_DRAW; }
+template<> Value Endgame<KmmKm>::operator()(const Position&) const { return VALUE_DRAW; }
-template<>
-Value Endgame<KNNK>::operator()(const Position&) const {
- return VALUE_DRAW;
-}
/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and
/// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW
template<>
ScaleFactor Endgame<KBPsK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) >= 1);
+ assert(pos.non_pawn_material(strongSide) == BishopValueMg);
+ assert(pos.count<PAWN>(strongSide) >= 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.pieces(strongerSide, PAWN);
- File pawnFile = file_of(pos.piece_list(strongerSide, PAWN)[0]);
+ Bitboard pawns = pos.pieces(strongSide, PAWN);
+ File pawnFile = file_of(pos.list<PAWN>(strongSide)[0]);
// All pawns are on a single rook file ?
if ( (pawnFile == FILE_A || pawnFile == FILE_H)
&& !(pawns & ~file_bb(pawnFile)))
{
- Square bishopSq = pos.piece_list(strongerSide, BISHOP)[0];
- Square queeningSq = relative_square(strongerSide, pawnFile | RANK_8);
- Square kingSq = pos.king_square(weakerSide);
+ Square bishopSq = pos.list<BISHOP>(strongSide)[0];
+ Square queeningSq = relative_square(strongSide, pawnFile | RANK_8);
+ Square kingSq = pos.king_square(weakSide);
if ( opposite_colors(queeningSq, bishopSq)
&& abs(file_of(kingSq) - pawnFile) <= 1)
// The bishop has the wrong color, and the defending king is on the
// file of the pawn(s) or the adjacent file. Find the rank of the
// frontmost pawn.
- Rank rank;
- if (strongerSide == WHITE)
- {
- for (rank = RANK_7; !(rank_bb(rank) & pawns); rank--) {}
- assert(rank >= RANK_2 && rank <= RANK_7);
- }
- else
- {
- for (rank = RANK_2; !(rank_bb(rank) & pawns); rank++) {}
- rank = Rank(rank ^ 7); // HACK to get the relative rank
- assert(rank >= RANK_2 && rank <= RANK_7);
- }
+ Square pawnSq = frontmost_sq(strongSide, pawns);
+
// 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)
+ || relative_rank(weakSide, kingSq) <= relative_rank(weakSide, pawnSq))
return SCALE_FACTOR_DRAW;
}
}
// All pawns on same B or G file? Then potential draw
if ( (pawnFile == FILE_B || pawnFile == FILE_G)
&& !(pos.pieces(PAWN) & ~file_bb(pawnFile))
- && pos.non_pawn_material(weakerSide) == 0
- && pos.piece_count(weakerSide, PAWN) >= 1)
+ && pos.non_pawn_material(weakSide) == 0
+ && pos.count<PAWN>(weakSide) >= 1)
{
- // Get weaker pawn closest to opponent's queening square
- Bitboard wkPawns = pos.pieces(weakerSide, PAWN);
- Square weakerPawnSq = strongerSide == WHITE ? msb(wkPawns) : lsb(wkPawns);
-
- Square strongerKingSq = pos.king_square(strongerSide);
- Square weakerKingSq = pos.king_square(weakerSide);
- Square bishopSq = pos.piece_list(strongerSide, BISHOP)[0];
-
- // Draw if weaker pawn is on rank 7, bishop can't attack the pawn, and
- // weaker king can stop opposing opponent's king from penetrating.
- if ( relative_rank(strongerSide, weakerPawnSq) == RANK_7
- && opposite_colors(bishopSq, weakerPawnSq)
- && square_distance(weakerPawnSq, weakerKingSq) <= square_distance(weakerPawnSq, strongerKingSq))
- return SCALE_FACTOR_DRAW;
+ // Get weakSide pawn that is closest to 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];
+
+ // 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))
+ {
+ int strongKingDist = square_distance(weakPawnSq, strongKingSq);
+ int weakKingDist = square_distance(weakPawnSq, weakKingSq);
+
+ // Draw if the weak king is on it's 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
+ && weakKingDist <= 2
+ && weakKingDist <= strongKingDist)
+ return SCALE_FACTOR_DRAW;
+ }
}
return SCALE_FACTOR_NONE;
template<>
ScaleFactor Endgame<KQKRPs>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == QueenValueMg);
- 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 kingSq = pos.king_square(weakerSide);
- if ( relative_rank(weakerSide, kingSq) <= RANK_2
- && relative_rank(weakerSide, pos.king_square(strongerSide)) >= RANK_4
- && (pos.pieces(weakerSide, ROOK) & rank_bb(relative_rank(weakerSide, RANK_3)))
- && (pos.pieces(weakerSide, PAWN) & rank_bb(relative_rank(weakerSide, RANK_2)))
- && (pos.attacks_from<KING>(kingSq) & pos.pieces(weakerSide, PAWN)))
- {
- Square rsq = pos.piece_list(weakerSide, ROOK)[0];
- if (pos.attacks_from<PAWN>(rsq, strongerSide) & pos.pieces(weakerSide, PAWN))
+ assert(verify_material(pos, strongSide, QueenValueMg, 0));
+ 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];
+
+ if ( relative_rank(weakSide, kingSq) <= RANK_2
+ && relative_rank(weakSide, pos.king_square(strongSide)) >= RANK_4
+ && (pos.pieces(weakSide, ROOK) & rank_bb(relative_rank(weakSide, RANK_3)))
+ && (pos.pieces(weakSide, PAWN) & rank_bb(relative_rank(weakSide, RANK_2)))
+ && (pos.attacks_from<KING>(kingSq) & pos.pieces(weakSide, PAWN))
+ && (pos.attacks_from<PAWN>(rsq, strongSide) & pos.pieces(weakSide, PAWN)))
return SCALE_FACTOR_DRAW;
- }
+
return SCALE_FACTOR_NONE;
}
template<>
ScaleFactor Endgame<KRPKR>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == RookValueMg);
- 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];
+ Square wksq = pos.king_square(strongSide);
+ Square bksq = pos.king_square(weakSide);
+ Square wrsq = pos.list<ROOK>(strongSide)[0];
+ Square wpsq = pos.list<PAWN>(strongSide)[0];
+ Square brsq = pos.list<ROOK>(weakSide)[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)
+ if (strongSide == BLACK)
{
wksq = ~wksq;
wrsq = ~wrsq;
bksq = ~bksq;
brsq = ~brsq;
}
+
if (file_of(wpsq) > FILE_D)
{
wksq = mirror(wksq);
File f = file_of(wpsq);
Rank r = rank_of(wpsq);
Square queeningSq = f | RANK_8;
- int tempo = (pos.side_to_move() == strongerSide);
+ 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.
return SCALE_FACTOR_NONE;
}
+template<>
+ScaleFactor Endgame<KRPKB>::operator()(const Position& pos) const {
+
+ assert(verify_material(pos, strongSide, RookValueMg, 1));
+ assert(verify_material(pos, weakSide, BishopValueMg, 0));
+
+ // 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];
+ Rank rk = relative_rank(strongSide, psq);
+ Square 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 (rk == RANK_5 && !opposite_colors(bsq, psq))
+ {
+ int d = square_distance(psq + 3 * push, ksq);
+
+ if (d <= 2 && !(d == 0 && ksq == pos.king_square(strongSide) + 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 ( rk == RANK_6
+ && square_distance(psq + 2 * push, ksq) <= 1
+ && (PseudoAttacks[BISHOP][bsq] & (psq + push))
+ && file_distance(bsq, psq) >= 2)
+ return ScaleFactor(8);
+ }
+
+ return SCALE_FACTOR_NONE;
+}
/// K, rook and two pawns vs K, rook and one pawn. There is only a single
/// pattern: If the stronger side has no passed pawns and the defending king
template<>
ScaleFactor Endgame<KRPPKRP>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == RookValueMg);
- assert(pos.piece_count(strongerSide, PAWN) == 2);
- assert(pos.non_pawn_material(weakerSide) == RookValueMg);
- assert(pos.piece_count(weakerSide, PAWN) == 1);
+ assert(verify_material(pos, strongSide, RookValueMg, 2));
+ assert(verify_material(pos, weakSide, RookValueMg, 1));
- Square wpsq1 = pos.piece_list(strongerSide, PAWN)[0];
- Square wpsq2 = pos.piece_list(strongerSide, PAWN)[1];
- Square bksq = pos.king_square(weakerSide);
+ Square wpsq1 = pos.list<PAWN>(strongSide)[0];
+ Square wpsq2 = pos.list<PAWN>(strongSide)[1];
+ Square bksq = pos.king_square(weakSide);
// Does the stronger side have a passed pawn?
- if ( pos.pawn_is_passed(strongerSide, wpsq1)
- || pos.pawn_is_passed(strongerSide, wpsq2))
+ if (pos.pawn_passed(strongSide, wpsq1) || pos.pawn_passed(strongSide, wpsq2))
return SCALE_FACTOR_NONE;
- Rank r = std::max(relative_rank(strongerSide, wpsq1), relative_rank(strongerSide, wpsq2));
+ Rank r = std::max(relative_rank(strongSide, wpsq1), relative_rank(strongSide, wpsq2));
if ( file_distance(bksq, wpsq1) <= 1
&& file_distance(bksq, wpsq2) <= 1
- && relative_rank(strongerSide, bksq) > r)
+ && relative_rank(strongSide, bksq) > r)
{
switch (r) {
case RANK_2: return ScaleFactor(10);
template<>
ScaleFactor Endgame<KPsK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.piece_count(strongerSide, PAWN) >= 2);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(pos.non_pawn_material(strongSide) == VALUE_ZERO);
+ assert(pos.count<PAWN>(strongSide) >= 2);
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square ksq = pos.king_square(weakerSide);
- Bitboard pawns = pos.pieces(strongerSide, PAWN);
+ Square ksq = pos.king_square(weakSide);
+ Bitboard pawns = pos.pieces(strongSide, PAWN);
// Are all pawns on the 'a' file?
if (!(pawns & ~FileABB))
{
// Does the defending king block the pawns?
- if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1
+ if ( square_distance(ksq, relative_square(strongSide, SQ_A8)) <= 1
|| ( file_of(ksq) == FILE_A
- && !(in_front_bb(strongerSide, ksq) & pawns)))
+ && !(in_front_bb(strongSide, rank_of(ksq)) & pawns)))
return SCALE_FACTOR_DRAW;
}
// Are all pawns on the 'h' file?
else if (!(pawns & ~FileHBB))
{
// Does the defending king block the pawns?
- if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1
+ if ( square_distance(ksq, relative_square(strongSide, SQ_H8)) <= 1
|| ( file_of(ksq) == FILE_H
- && !(in_front_bb(strongerSide, ksq) & pawns)))
+ && !(in_front_bb(strongSide, rank_of(ksq)) & pawns)))
return SCALE_FACTOR_DRAW;
}
return SCALE_FACTOR_NONE;
template<>
ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMg);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
- 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 strongerBishopSq = pos.piece_list(strongerSide, BISHOP)[0];
- Square weakerBishopSq = pos.piece_list(weakerSide, BISHOP)[0];
- Square weakerKingSq = pos.king_square(weakerSide);
+ 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);
// Case 1: Defending king blocks the pawn, and cannot be driven away
- if ( file_of(weakerKingSq) == file_of(pawnSq)
- && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( opposite_colors(weakerKingSq, strongerBishopSq)
- || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
+ 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))
return SCALE_FACTOR_DRAW;
// Case 2: Opposite colored bishops
- if (opposite_colors(strongerBishopSq, weakerBishopSq))
+ if (opposite_colors(strongBishopSq, weakBishopSq))
{
// We assume that the position is drawn in the following three situations:
//
// These rules are probably not perfect, but in practice they work
// reasonably well.
- if (relative_rank(strongerSide, pawnSq) <= RANK_5)
+ if (relative_rank(strongSide, pawnSq) <= RANK_5)
return SCALE_FACTOR_DRAW;
else
{
- Bitboard path = forward_bb(strongerSide, pawnSq);
+ Bitboard path = forward_bb(strongSide, pawnSq);
- if (path & pos.pieces(weakerSide, KING))
+ if (path & pos.pieces(weakSide, KING))
return SCALE_FACTOR_DRAW;
- if ( (pos.attacks_from<BISHOP>(weakerBishopSq) & path)
- && square_distance(weakerBishopSq, pawnSq) >= 3)
+ if ( (pos.attacks_from<BISHOP>(weakBishopSq) & path)
+ && square_distance(weakBishopSq, pawnSq) >= 3)
return SCALE_FACTOR_DRAW;
}
}
template<>
ScaleFactor Endgame<KBPPKB>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 2);
- assert(pos.non_pawn_material(weakerSide) == BishopValueMg);
- assert(pos.piece_count(weakerSide, BISHOP) == 1);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(verify_material(pos, strongSide, BishopValueMg, 2));
+ assert(verify_material(pos, weakSide, BishopValueMg, 0));
- Square wbsq = pos.piece_list(strongerSide, BISHOP)[0];
- Square bbsq = pos.piece_list(weakerSide, BISHOP)[0];
+ Square wbsq = pos.list<BISHOP>(strongSide)[0];
+ Square bbsq = pos.list<BISHOP>(weakSide)[0];
if (!opposite_colors(wbsq, bbsq))
return SCALE_FACTOR_NONE;
- Square ksq = pos.king_square(weakerSide);
- Square psq1 = pos.piece_list(strongerSide, PAWN)[0];
- Square psq2 = pos.piece_list(strongerSide, PAWN)[1];
+ Square ksq = pos.king_square(weakSide);
+ Square psq1 = pos.list<PAWN>(strongSide)[0];
+ Square psq2 = pos.list<PAWN>(strongSide)[1];
Rank r1 = rank_of(psq1);
Rank r2 = rank_of(psq2);
Square blockSq1, blockSq2;
- if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
+ if (relative_rank(strongSide, psq1) > relative_rank(strongSide, psq2))
{
- blockSq1 = psq1 + pawn_push(strongerSide);
+ blockSq1 = psq1 + pawn_push(strongSide);
blockSq2 = file_of(psq2) | rank_of(psq1);
}
else
{
- blockSq1 = psq2 + pawn_push(strongerSide);
+ blockSq1 = psq2 + pawn_push(strongSide);
blockSq2 = file_of(psq1) | rank_of(psq2);
}
// Both pawns are on the same file. Easy draw if defender firmly controls
// some square in the frontmost pawn's path.
if ( file_of(ksq) == file_of(blockSq1)
- && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
+ && relative_rank(strongSide, ksq) >= relative_rank(strongSide, blockSq1)
&& opposite_colors(ksq, wbsq))
return SCALE_FACTOR_DRAW;
else
if ( ksq == blockSq1
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq2
- || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakerSide, BISHOP))
+ || (pos.attacks_from<BISHOP>(blockSq2) & pos.pieces(weakSide, BISHOP))
|| abs(r1 - r2) >= 2))
return SCALE_FACTOR_DRAW;
else if ( ksq == blockSq2
&& opposite_colors(ksq, wbsq)
&& ( bbsq == blockSq1
- || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakerSide, BISHOP))))
+ || (pos.attacks_from<BISHOP>(blockSq1) & pos.pieces(weakSide, BISHOP))))
return SCALE_FACTOR_DRAW;
else
return SCALE_FACTOR_NONE;
template<>
ScaleFactor Endgame<KBPKN>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == BishopValueMg);
- assert(pos.piece_count(strongerSide, BISHOP) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == KnightValueMg);
- assert(pos.piece_count(weakerSide, KNIGHT) == 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 weakerKingSq = pos.king_square(weakerSide);
-
- if ( file_of(weakerKingSq) == file_of(pawnSq)
- && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq)
- && ( opposite_colors(weakerKingSq, strongerBishopSq)
- || relative_rank(strongerSide, weakerKingSq) <= RANK_6))
+ 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);
+
+ 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))
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
template<>
ScaleFactor Endgame<KNPK>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == KnightValueMg);
- assert(pos.piece_count(strongerSide, KNIGHT) == 1);
- assert(pos.piece_count(strongerSide, PAWN) == 1);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(weakerSide, PAWN) == 0);
+ assert(verify_material(pos, strongSide, KnightValueMg, 1));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 0));
- Square pawnSq = pos.piece_list(strongerSide, PAWN)[0];
- Square weakerKingSq = pos.king_square(weakerSide);
+ Square pawnSq = pos.list<PAWN>(strongSide)[0];
+ Square weakKingSq = pos.king_square(weakSide);
- if ( pawnSq == relative_square(strongerSide, SQ_A7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1)
+ if ( pawnSq == relative_square(strongSide, SQ_A7)
+ && square_distance(weakKingSq, relative_square(strongSide, SQ_A8)) <= 1)
return SCALE_FACTOR_DRAW;
- if ( pawnSq == relative_square(strongerSide, SQ_H7)
- && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1)
+ if ( pawnSq == relative_square(strongSide, SQ_H7)
+ && square_distance(weakKingSq, relative_square(strongSide, SQ_H8)) <= 1)
return SCALE_FACTOR_DRAW;
return SCALE_FACTOR_NONE;
}
+/// K, knight and a pawn vs K and bishop. If knight can block bishop from taking
+/// pawn, it's a win. Otherwise, drawn.
+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);
+
+ // 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))
+ return ScaleFactor(square_distance(weakKingSq, pawnSq));
+
+ return SCALE_FACTOR_NONE;
+}
+
+
/// K and a pawn vs K and a pawn. This is done by removing the weakest side's
/// pawn and probing the KP vs K bitbase: If the weakest side has a draw without
/// the pawn, she probably has at least a draw with the pawn as well. The exception
template<>
ScaleFactor Endgame<KPKP>::operator()(const Position& pos) const {
- assert(pos.non_pawn_material(strongerSide) == VALUE_ZERO);
- assert(pos.non_pawn_material(weakerSide) == VALUE_ZERO);
- assert(pos.piece_count(WHITE, PAWN) == 1);
- assert(pos.piece_count(BLACK, PAWN) == 1);
+ assert(verify_material(pos, strongSide, VALUE_ZERO, 1));
+ assert(verify_material(pos, weakSide, VALUE_ZERO, 1));
- Square wksq = pos.king_square(strongerSide);
- Square bksq = pos.king_square(weakerSide);
- Square wpsq = pos.piece_list(strongerSide, PAWN)[0];
- Color us = pos.side_to_move();
+ Square wksq = pos.king_square(strongSide);
+ Square bksq = pos.king_square(weakSide);
+ Square psq = pos.list<PAWN>(strongSide)[0];
+ Color us = pos.side_to_move();
- if (strongerSide == BLACK)
+ if (strongSide == BLACK)
{
wksq = ~wksq;
bksq = ~bksq;
- wpsq = ~wpsq;
+ psq = ~psq;
us = ~us;
}
- if (file_of(wpsq) >= FILE_E)
+ if (file_of(psq) >= FILE_E)
{
wksq = mirror(wksq);
bksq = mirror(bksq);
- wpsq = mirror(wpsq);
+ psq = mirror(psq);
}
// 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(wpsq) >= RANK_5
- && file_of(wpsq) != FILE_A)
+ if (rank_of(psq) >= RANK_5 && file_of(psq) != 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_kpk(wksq, wpsq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
+ return Bitbases::probe_kpk(wksq, psq, bksq, us) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW;
}
projects / stockfish / blobdiff