/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2020 The Stockfish developers (see AUTHORS file)
+ Copyright (C) 2004-2021 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
namespace {
// Threshold for lazy and space evaluation
- constexpr Value LazyThreshold1 = Value(1400);
- constexpr Value LazyThreshold2 = Value(1300);
- constexpr Value SpaceThreshold = Value(12222);
- constexpr Value NNUEThreshold1 = Value(550);
- constexpr Value NNUEThreshold2 = Value(150);
+ constexpr Value LazyThreshold1 = Value(1565);
+ constexpr Value LazyThreshold2 = Value(1102);
+ constexpr Value SpaceThreshold = Value(11551);
+ constexpr Value NNUEThreshold1 = Value(682);
+ constexpr Value NNUEThreshold2 = Value(176);
// KingAttackWeights[PieceType] contains king attack weights by piece type
constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 81, 52, 44, 10 };
// BishopPawns[distance from edge] contains a file-dependent penalty for pawns on
// squares of the same color as our bishop.
constexpr Score BishopPawns[int(FILE_NB) / 2] = {
- S(3, 8), S(3, 9), S(1, 8), S(3, 7)
+ S(3, 8), S(3, 9), S(2, 8), S(3, 8)
};
// KingProtector[knight/bishop] contains penalty for each distance unit to own king
// Outpost[knight/bishop] contains bonuses for each knight or bishop occupying a
// pawn protected square on rank 4 to 6 which is also safe from a pawn attack.
- constexpr Score Outpost[] = { S(56, 34), S(31, 23) };
+ constexpr Score Outpost[] = { S(57, 38), S(31, 24) };
// PassedRank[Rank] contains a bonus according to the rank of a passed pawn
constexpr Score PassedRank[RANK_NB] = {
- S(0, 0), S(9, 28), S(15, 31), S(17, 39), S(64, 70), S(171, 177), S(277, 260)
+ S(0, 0), S(7, 27), S(16, 32), S(17, 40), S(64, 71), S(170, 174), S(278, 262)
};
- // RookOnFile[semiopen/open] contains bonuses for each rook when there is
- // no (friendly) pawn on the rook file.
- constexpr Score RookOnFile[] = { S(19, 7), S(48, 27) };
+ constexpr Score RookOnClosedFile = S(10, 5);
+ constexpr Score RookOnOpenFile[] = { S(19, 6), S(47, 26) };
// ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
// which piece type attacks which one. Attacks on lesser pieces which are
};
// Assorted bonuses and penalties
- constexpr Score BadOutpost = S( -7, 36);
+ constexpr Score UncontestedOutpost = S( 1, 10);
constexpr Score BishopOnKingRing = S( 24, 0);
constexpr Score BishopXRayPawns = S( 4, 5);
constexpr Score CorneredBishop = S( 50, 50);
constexpr Direction Down = -pawn_push(Us);
constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
: Rank5BB | Rank4BB | Rank3BB);
- const Square* pl = pos.squares<Pt>(Us);
-
+ Bitboard b1 = pos.pieces(Us, Pt);
Bitboard b, bb;
Score score = SCORE_ZERO;
attackedBy[Us][Pt] = 0;
- for (Square s = *pl; s != SQ_NONE; s = *++pl)
- {
+ while (b1) {
+ Square s = pop_lsb(&b1);
+
// Find attacked squares, including x-ray attacks for bishops and rooks
b = Pt == BISHOP ? attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN))
: Pt == ROOK ? attacks_bb< ROOK>(s, pos.pieces() ^ pos.pieces(QUEEN) ^ pos.pieces(Us, ROOK))
if (Pt == BISHOP || Pt == KNIGHT)
{
// Bonus if the piece is on an outpost square or can reach one
- // Reduced bonus for knights (BadOutpost) if few relevant targets
+ // Bonus for knights (UncontestedOutpost) if few relevant targets
bb = OutpostRanks & (attackedBy[Us][PAWN] | shift<Down>(pos.pieces(PAWN)))
& ~pe->pawn_attacks_span(Them);
Bitboard targets = pos.pieces(Them) & ~pos.pieces(PAWN);
&& bb & s & ~CenterFiles // on a side outpost
&& !(b & targets) // no relevant attacks
&& (!more_than_one(targets & (s & QueenSide ? QueenSide : KingSide))))
- score += BadOutpost;
+ score += UncontestedOutpost * popcount(pos.pieces(PAWN) & (s & QueenSide ? QueenSide : KingSide));
else if (bb & s)
score += Outpost[Pt == BISHOP];
else if (Pt == KNIGHT && bb & b & ~pos.pieces(Us))
if (Pt == ROOK)
{
- // Bonus for rook on an open or semi-open file
+ // Bonuses for rook on a (semi-)open or closed file
if (pos.is_on_semiopen_file(Us, s))
- score += RookOnFile[pos.is_on_semiopen_file(Them, s)];
-
- // Penalty when trapped by the king, even more if the king cannot castle
- else if (mob <= 3)
{
- File kf = file_of(pos.square<KING>(Us));
- if ((kf < FILE_E) == (file_of(s) < kf))
- score -= TrappedRook * (1 + !pos.castling_rights(Us));
+ score += RookOnOpenFile[pos.is_on_semiopen_file(Them, s)];
+ }
+ else
+ {
+ // If our pawn on this file is blocked, increase penalty
+ if ( pos.pieces(Us, PAWN)
+ & shift<Down>(pos.pieces())
+ & file_bb(s))
+ {
+ score -= RookOnClosedFile;
+ }
+
+ // Penalty when trapped by the king, even more if the king cannot castle
+ if (mob <= 3)
+ {
+ File kf = file_of(pos.square<KING>(Us));
+ if ((kf < FILE_E) == (file_of(s) < kf))
+ score -= TrappedRook * (1 + !pos.castling_rights(Us));
+ }
}
}
int kingFlankDefense = popcount(b3);
kingDanger += kingAttackersCount[Them] * kingAttackersWeight[Them] // (~10 Elo)
- + 185 * popcount(kingRing[Us] & weak) // (~15 Elo)
+ + 183 * popcount(kingRing[Us] & weak) // (~15 Elo)
+ 148 * popcount(unsafeChecks) // (~4 Elo)
+ 98 * popcount(pos.blockers_for_king(Us)) // (~2 Elo)
+ 69 * kingAttacksCount[Them] // (~0.5 Elo)
bb = forward_file_bb(Them, s) & pos.pieces(ROOK, QUEEN);
if (!(pos.pieces(Them) & bb))
- unsafeSquares &= attackedBy[Them][ALL_PIECES];
+ unsafeSquares &= attackedBy[Them][ALL_PIECES] | pos.pieces(Them);
- // If there are no enemy attacks on passed pawn span, assign a big bonus.
+ // If there are no enemy pieces or attacks on passed pawn span, assign a big bonus.
+ // Or if there is some, but they are all attacked by our pawns, assign a bit smaller bonus.
// Otherwise assign a smaller bonus if the path to queen is not attacked
// and even smaller bonus if it is attacked but block square is not.
- int k = !unsafeSquares ? 35 :
- !(unsafeSquares & squaresToQueen) ? 20 :
- !(unsafeSquares & blockSq) ? 9 :
+ int k = !unsafeSquares ? 36 :
+ !(unsafeSquares & ~attackedBy[Us][PAWN]) ? 30 :
+ !(unsafeSquares & squaresToQueen) ? 17 :
+ !(unsafeSquares & blockSq) ? 7 :
0 ;
// Assign a larger bonus if the block square is defended
behind |= shift<Down>(behind);
behind |= shift<Down+Down>(behind);
+ // Compute space score based on the number of safe squares and number of our pieces
+ // increased with number of total blocked pawns in position.
int bonus = popcount(safe) + popcount(behind & safe & ~attackedBy[Them][ALL_PIECES]);
int weight = pos.count<ALL_PIECES>(Us) - 3 + std::min(pe->blocked_count(), 9);
Score score = make_score(bonus * weight * weight / 16, 0);
Value Evaluation<T>::winnable(Score score) const {
int outflanking = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
- - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
+ + int(rank_of(pos.square<KING>(WHITE)) - rank_of(pos.square<KING>(BLACK)));
bool pawnsOnBothFlanks = (pos.pieces(PAWN) & QueenSide)
&& (pos.pieces(PAWN) & KingSide);
{
if (pos.opposite_bishops())
{
+ // For pure opposite colored bishops endgames use scale factor
+ // based on the number of passed pawns of the strong side.
if ( pos.non_pawn_material(WHITE) == BishopValueMg
&& pos.non_pawn_material(BLACK) == BishopValueMg)
sf = 18 + 4 * popcount(pe->passed_pawns(strongSide));
+ // For every other opposite colored bishops endgames use scale factor
+ // based on the number of all pieces of the strong side.
else
sf = 22 + 3 * pos.count<ALL_PIECES>(strongSide);
}
+ // For rook endgames with strong side not having overwhelming pawn number advantage
+ // and its pawns being on one flank and weak side protecting its pieces with a king
+ // use lower scale factor.
else if ( pos.non_pawn_material(WHITE) == RookValueMg
&& pos.non_pawn_material(BLACK) == RookValueMg
&& pos.count<PAWN>(strongSide) - pos.count<PAWN>(~strongSide) <= 1
&& bool(KingSide & pos.pieces(strongSide, PAWN)) != bool(QueenSide & pos.pieces(strongSide, PAWN))
&& (attacks_bb<KING>(pos.square<KING>(~strongSide)) & pos.pieces(~strongSide, PAWN)))
sf = 36;
+ // For queen vs no queen endgames use scale factor
+ // based on number of minors of side that doesn't have queen.
else if (pos.count<QUEEN>() == 1)
sf = 37 + 3 * (pos.count<QUEEN>(WHITE) == 1 ? pos.count<BISHOP>(BLACK) + pos.count<KNIGHT>(BLACK)
: pos.count<BISHOP>(WHITE) + pos.count<KNIGHT>(WHITE));
+ // In every other case use scale factor based on
+ // the number of pawns of the strong side reduced if pawns are on a single flank.
else
sf = std::min(sf, 36 + 7 * pos.count<PAWN>(strongSide)) - 4 * !pawnsOnBothFlanks;
+ // Reduce scale factor in case of pawns being on a single flank
sf -= 4 * !pawnsOnBothFlanks;
}
{
// Scale and shift NNUE for compatibility with search and classical evaluation
auto adjusted_NNUE = [&](){
- int mat = pos.non_pawn_material() + PieceValue[MG][PAWN] * pos.count<PAWN>();
- return NNUE::evaluate(pos) * (720 + mat / 32) / 1024 + Tempo;
+ int mat = pos.non_pawn_material() + PawnValueMg * pos.count<PAWN>();
+ return NNUE::evaluate(pos) * (679 + mat / 32) / 1024 + Tempo;
};
// If there is PSQ imbalance use classical eval, with small probability if it is small
bool largePsq = psq * 16 > (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50;
bool classical = largePsq || (psq > PawnValueMg / 4 && !(pos.this_thread()->nodes & 0xB));
- v = classical ? Evaluation<NO_TRACE>(pos).value() : adjusted_NNUE();
+ // Use classical evaluation for really low piece endgames.
+ // The most critical case is a bishop + A/H file pawn vs naked king draw.
+ bool strongClassical = pos.non_pawn_material() < 2 * RookValueMg && pos.count<PAWN>() < 2;
+
+ v = classical || strongClassical ? Evaluation<NO_TRACE>(pos).value() : adjusted_NNUE();
// If the classical eval is small and imbalance large, use NNUE nevertheless.
// For the case of opposite colored bishops, switch to NNUE eval with
// small probability if the classical eval is less than the threshold.
- if ( largePsq
- && (abs(v) * 16 < NNUEThreshold2 * r50
- || ( pos.opposite_bishops()
- && abs(v) * 16 < (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50
- && !(pos.this_thread()->nodes & 0xB))))
+ if ( largePsq && !strongClassical
+ && ( abs(v) * 16 < NNUEThreshold2 * r50
+ || ( pos.opposite_bishops()
+ && abs(v) * 16 < (NNUEThreshold1 + pos.non_pawn_material() / 64) * r50
+ && !(pos.this_thread()->nodes & 0xB))))
v = adjusted_NNUE();
}