/*
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
+ 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
#define V Value
#define S(mg, eg) make_score(mg, eg)
- // Isolated pawn penalty
- constexpr Score Isolated = S(13, 16);
+ // Pawn penalties
+ constexpr Score Backward = S( 6, 23);
+ constexpr Score Doubled = S(13, 53);
+ constexpr Score DoubledEarly = S(20, 10);
+ constexpr Score Isolated = S( 2, 15);
+ constexpr Score WeakLever = S( 5, 57);
+ constexpr Score WeakUnopposed = S(16, 22);
- // Backward pawn penalty
- constexpr Score Backward = S(17, 11);
+ // Bonus for blocked pawns at 5th or 6th rank
+ constexpr Score BlockedPawn[2] = { S(-15, -3), S(-6, 3) };
- // Connected pawn bonus by opposed, phalanx, #support and rank
- Score Connected[2][2][3][RANK_NB];
+ constexpr Score BlockedStorm[RANK_NB] = {
+ S(0, 0), S(0, 0), S(75, 78), S(-8, 16), S(-6, 10), S(-6, 6), S(0, 2)
+ };
- // Doubled pawn penalty
- constexpr Score Doubled = S(13, 40);
+ // Connected pawn bonus
+ constexpr int Connected[RANK_NB] = { 0, 5, 7, 11, 24, 48, 86 };
// Strength of pawn shelter for our king by [distance from edge][rank].
// RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king.
constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = {
- { V( 7), V(76), V( 84), V( 38), V( 7), V( 30), V(-19) },
- { V(-13), V(83), V( 42), V(-27), V( 2), V(-32), V(-45) },
- { V(-26), V(63), V( 5), V(-44), V( -5), V( 2), V(-59) },
- { V(-19), V(53), V(-11), V(-22), V(-12), V(-51), V(-60) }
+ { V( -5), V( 82), V( 92), V( 54), V( 36), V( 22), V( 28) },
+ { V(-44), V( 63), V( 33), V(-50), V(-30), V(-12), V( -62) },
+ { V(-11), V( 77), V( 22), V( -6), V( 31), V( 8), V( -45) },
+ { V(-39), V(-12), V(-29), V(-50), V(-43), V(-68), V(-164) }
};
// Danger of enemy pawns moving toward our king by [distance from edge][rank].
- // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn
- // is behind our king.
+ // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn
+ // is behind our king. Note that UnblockedStorm[0][1-2] accommodate opponent pawn
+ // on edge, likely blocked by our king.
constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
- { V( 25), V( 79), V(107), V( 51), V( 27), V( 0), V( 0) },
- { V( 5), V( 35), V(121), V( -2), V( 15), V(-10), V(-10) },
- { V(-20), V( 22), V( 98), V( 36), V( 7), V(-20), V(-20) },
- { V(-27), V( 24), V( 80), V( 25), V( -4), V(-30), V(-30) }
+ { V( 87), V(-288), V(-168), V( 96), V( 47), V( 44), V( 46) },
+ { V( 42), V( -25), V( 120), V( 45), V( 34), V( -9), V( 24) },
+ { V( -8), V( 51), V( 167), V( 35), V( -4), V(-16), V(-12) },
+ { V(-17), V( -13), V( 100), V( 4), V( 9), V(-16), V(-31) }
};
- // Danger of blocked enemy pawns storming our king, by rank
- constexpr Value BlockedStorm[RANK_NB] =
- { V( 0), V( 0), V( 75), V(-10), V(-20), V(-20), V(-20) };
+
+ // KingOnFile[semi-open Us][semi-open Them] contains bonuses/penalties
+ // for king when the king is on a semi-open or open file.
+ constexpr Score KingOnFile[2][2] = {{ S(-21,10), S(-7, 1) },
+ { S( 0,-3), S( 9,-4) }};
#undef S
#undef V
+
+ /// evaluate() calculates a score for the static pawn structure of the given position.
+ /// We cannot use the location of pieces or king in this function, as the evaluation
+ /// of the pawn structure will be stored in a small cache for speed reasons, and will
+ /// be re-used even when the pieces have moved.
+
template<Color Us>
Score evaluate(const Position& pos, Pawns::Entry* e) {
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
+ constexpr Color Them = ~Us;
+ constexpr Direction Up = pawn_push(Us);
+ constexpr Direction Down = -Up;
- Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
- Bitboard lever, leverPush;
+ Bitboard neighbours, stoppers, support, phalanx, opposed;
+ Bitboard lever, leverPush, blocked;
Square s;
- bool opposed, backward;
+ bool backward, passed, doubled;
Score score = SCORE_ZERO;
- const Square* pl = pos.squares<PAWN>(Us);
+ Bitboard b = pos.pieces(Us, PAWN);
Bitboard ourPawns = pos.pieces( Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
- e->semiopenFiles[Us] = 0xFF;
- e->kingSquares[Us] = SQ_NONE;
- e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
- e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares);
- e->pawnsOnSquares[Us][WHITE] = pos.count<PAWN>(Us) - e->pawnsOnSquares[Us][BLACK];
+ Bitboard doubleAttackThem = pawn_double_attacks_bb<Them>(theirPawns);
+
+ e->passedPawns[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
+ e->blockedCount += popcount(shift<Up>(ourPawns) & (theirPawns | doubleAttackThem));
// Loop through all pawns of the current color and score each pawn
- while ((s = *pl++) != SQ_NONE)
- {
- assert(pos.piece_on(s) == make_piece(Us, PAWN));
+ while (b) {
+ s = pop_lsb(&b);
- File f = file_of(s);
+ assert(pos.piece_on(s) == make_piece(Us, PAWN));
- e->semiopenFiles[Us] &= ~(1 << f);
- e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+ Rank r = relative_rank(Us, s);
// Flag the pawn
opposed = theirPawns & forward_file_bb(Us, s);
- stoppers = theirPawns & passed_pawn_mask(Us, s);
- lever = theirPawns & PawnAttacks[Us][s];
- leverPush = theirPawns & PawnAttacks[Us][s + Up];
+ blocked = theirPawns & (s + Up);
+ stoppers = theirPawns & passed_pawn_span(Us, s);
+ lever = theirPawns & pawn_attacks_bb(Us, s);
+ leverPush = theirPawns & pawn_attacks_bb(Us, s + Up);
doubled = ourPawns & (s - Up);
- neighbours = ourPawns & adjacent_files_bb(f);
+ neighbours = ourPawns & adjacent_files_bb(s);
phalanx = neighbours & rank_bb(s);
- supported = neighbours & rank_bb(s - Up);
-
- // A pawn is backward when it is behind all pawns of the same color
- // on the adjacent files and cannot be safely advanced.
- backward = !(ourPawns & pawn_attack_span(Them, s + Up))
- && (stoppers & (leverPush | (s + Up)));
-
- // Passed pawns will be properly scored in evaluation because we need
- // full attack info to evaluate them. Include also not passed pawns
- // which could become passed after one or two pawn pushes when are
- // not attacked more times than defended.
- if ( !(stoppers ^ lever ^ leverPush)
- && !(ourPawns & forward_file_bb(Us, s))
- && popcount(supported) >= popcount(lever) - 1
- && popcount(phalanx) >= popcount(leverPush))
- e->passedPawns[Us] |= s;
+ support = neighbours & rank_bb(s - Up);
- else if ( stoppers == SquareBB[s + Up]
- && relative_rank(Us, s) >= RANK_5)
+ if (doubled)
{
- b = shift<Up>(supported) & ~theirPawns;
- while (b)
- if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
- e->passedPawns[Us] |= s;
+ // Additional doubled penalty if none of their pawns is fixed
+ if (!(ourPawns & shift<Down>(theirPawns | pawn_attacks_bb<Them>(theirPawns))))
+ score -= DoubledEarly;
}
+ // A pawn is backward when it is behind all pawns of the same color on
+ // the adjacent files and cannot safely advance.
+ backward = !(neighbours & forward_ranks_bb(Them, s + Up))
+ && (leverPush | blocked);
+
+ // Compute additional span if pawn is not backward nor blocked
+ if (!backward && !blocked)
+ e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
+
+ // A pawn is passed if one of the three following conditions is true:
+ // (a) there is no stoppers except some levers
+ // (b) the only stoppers are the leverPush, but we outnumber them
+ // (c) there is only one front stopper which can be levered.
+ // (Refined in Evaluation::passed)
+ passed = !(stoppers ^ lever)
+ || ( !(stoppers ^ leverPush)
+ && popcount(phalanx) >= popcount(leverPush))
+ || ( stoppers == blocked && r >= RANK_5
+ && (shift<Up>(support) & ~(theirPawns | doubleAttackThem)));
+
+ passed &= !(forward_file_bb(Us, s) & ourPawns);
+
+ // Passed pawns will be properly scored later in evaluation when we have
+ // full attack info.
+ if (passed)
+ e->passedPawns[Us] |= s;
+
// Score this pawn
- if (supported | phalanx)
- score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)];
+ if (support | phalanx)
+ {
+ int v = Connected[r] * (2 + bool(phalanx) - bool(opposed))
+ + 22 * popcount(support);
+
+ score += make_score(v, v * (r - 2) / 4);
+ }
else if (!neighbours)
- score -= Isolated, e->weakUnopposed[Us] += !opposed;
+ {
+ if ( opposed
+ && (ourPawns & forward_file_bb(Them, s))
+ && !(theirPawns & adjacent_files_bb(s)))
+ score -= Doubled;
+ else
+ score -= Isolated
+ + WeakUnopposed * !opposed;
+ }
else if (backward)
- score -= Backward, e->weakUnopposed[Us] += !opposed;
+ score -= Backward
+ + WeakUnopposed * !opposed * bool(~(FileABB | FileHBB) & s);
+
+ if (!support)
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
- if (doubled && !supported)
- score -= Doubled;
+ if (blocked && r >= RANK_5)
+ score += BlockedPawn[r - RANK_5];
}
return score;
namespace Pawns {
-/// Pawns::init() initializes some tables needed by evaluation. Instead of using
-/// hard-coded tables, when makes sense, we prefer to calculate them with a formula
-/// to reduce independent parameters and to allow easier tuning and better insight.
-
-void init() {
-
- static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 };
-
- for (int opposed = 0; opposed <= 1; ++opposed)
- for (int phalanx = 0; phalanx <= 1; ++phalanx)
- for (int support = 0; support <= 2; ++support)
- for (Rank r = RANK_2; r < RANK_8; ++r)
- {
- int v = 17 * support;
- v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed;
-
- Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4);
- }
-}
-
/// Pawns::probe() looks up the current position's pawns configuration in
/// the pawns hash table. It returns a pointer to the Entry if the position
return e;
e->key = key;
+ e->blockedCount = 0;
e->scores[WHITE] = evaluate<WHITE>(pos, e);
e->scores[BLACK] = evaluate<BLACK>(pos, e);
- e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]);
- e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK])
- | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]));
return e;
}
/// penalty for a king, looking at the king file and the two closest files.
template<Color Us>
-Value Entry::evaluate_shelter(const Position& pos, Square ksq) {
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) const {
- constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
- constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
- constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB);
+ constexpr Color Them = ~Us;
- Bitboard b = pos.pieces(PAWN) & (forward_ranks_bb(Us, ksq) | rank_bb(ksq));
- Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
+ Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them];
Bitboard theirPawns = b & pos.pieces(Them);
- Value safety = (ourPawns & file_bb(ksq)) ? Value(5) : Value(-5);
+ Score bonus = make_score(5, 5);
- if (shift<Down>(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq)
- safety += Value(374);
-
- File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq)));
+ File center = std::clamp(file_of(ksq), FILE_B, FILE_G);
for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0;
+ int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
b = theirPawns & file_bb(f);
int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
- int d = std::min(f, ~f);
- safety += ShelterStrength[d][ourRank];
- safety -= (ourRank && (ourRank == theirRank - 1)) ? BlockedStorm[theirRank]
- : UnblockedStorm[d][theirRank];
+ int d = edge_distance(f);
+ bonus += make_score(ShelterStrength[d][ourRank], 0);
+
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus -= BlockedStorm[theirRank];
+ else
+ bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
- return safety;
+ // King On File
+ bonus -= KingOnFile[pos.is_on_semiopen_file(Us, ksq)][pos.is_on_semiopen_file(Them, ksq)];
+
+ return bonus;
}
/// when king square changes, which is about 20% of total king_safety() calls.
template<Color Us>
-Score Entry::do_king_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos) {
+ Square ksq = pos.square<KING>(Us);
kingSquares[Us] = ksq;
- castlingRights[Us] = pos.can_castle(Us);
- int minKingPawnDistance = 0;
+ castlingRights[Us] = pos.castling_rights(Us);
+ auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); };
- Bitboard pawns = pos.pieces(Us, PAWN);
- if (pawns)
- while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {}
+ Score shelter = evaluate_shelter<Us>(pos, ksq);
- Value bonus = evaluate_shelter<Us>(pos, ksq);
+ // If we can castle use the bonus after castling if it is bigger
- // If we can castle use the bonus after the castling if it is bigger
- if (pos.can_castle(MakeCastling<Us, KING_SIDE>::right))
- bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)));
+ if (pos.can_castle(Us & KING_SIDE))
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)), compare);
+
+ if (pos.can_castle(Us & QUEEN_SIDE))
+ shelter = std::max(shelter, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)), compare);
+
+ // In endgame we like to bring our king near our closest pawn
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ int minPawnDist = 6;
- if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
- bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
+ if (pawns & attacks_bb<KING>(ksq))
+ minPawnDist = 1;
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- return make_score(bonus, -16 * minKingPawnDistance);
+ return shelter - make_score(0, 16 * minPawnDist);
}
// Explicit template instantiation
-template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos);
+template Score Entry::do_king_safety<BLACK>(const Position& pos);
} // namespace Pawns
projects / stockfish / blobdiff