/*
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) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+ Copyright (C) 2004-2022 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
#include "position.h"
#include "thread.h"
+namespace Stockfish {
+
namespace {
#define V Value
#define S(mg, eg) make_score(mg, eg)
// Pawn penalties
- constexpr Score Backward = S( 9, 24);
- constexpr Score BlockedStorm = S(82, 82);
- constexpr Score Doubled = S(11, 56);
- constexpr Score Isolated = S( 5, 15);
- constexpr Score WeakLever = S( 0, 56);
- constexpr Score WeakUnopposed = S(13, 27);
+ constexpr Score Backward = S( 6, 19);
+ constexpr Score Doubled = S(11, 51);
+ constexpr Score DoubledEarly = S(17, 7);
+ constexpr Score Isolated = S( 1, 20);
+ constexpr Score WeakLever = S( 2, 57);
+ constexpr Score WeakUnopposed = S(15, 18);
+
+ // Bonus for blocked pawns at 5th or 6th rank
+ constexpr Score BlockedPawn[2] = { S(-19, -8), S(-7, 3) };
+
+ constexpr Score BlockedStorm[RANK_NB] = {
+ S(0, 0), S(0, 0), S(64, 75), S(-3, 14), S(-12, 19), S(-7, 4), S(-10, 5)
+ };
// Connected pawn bonus
- constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
+ constexpr int Connected[RANK_NB] = { 0, 3, 7, 7, 15, 54, 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( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) },
- { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) },
- { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) },
- { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) }
+ { V(-2), V(85), V(95), V(53), V(39), V(23), V(25) },
+ { V(-55), V(64), V(32), V(-55), V(-30), V(-11), V(-61) },
+ { V(-11), V(75), V(19), V(-6), V(26), V(9), V(-47) },
+ { V(-41), V(-11), V(-27), V(-58), V(-42), V(-66), V(-163) }
};
// Danger of enemy pawns moving toward our king by [distance from edge][rank].
// 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( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) },
- { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) },
- { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) },
- { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) }
+ { V(94), V(-280), V(-170), V(90), V(59), V(47), V(53) },
+ { V(43), V(-17), V(128), V(39), V(26), V(-17), V(15) },
+ { V(-9), V(62), V(170), V(34), V(-5), V(-20), V(-11) },
+ { V(-27), V(-19), V(106), V(10), V(2), V(-13), V(-24) }
};
+
+ // 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(-18,11), S(-6,-3) },
+ { S( 0, 0), S( 5,-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;
constexpr Direction Up = pawn_push(Us);
+ constexpr Direction Down = -Up;
Bitboard neighbours, stoppers, support, phalanx, opposed;
Bitboard lever, leverPush, blocked;
Square s;
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] = 0;
e->kingSquares[Us] = SQ_NONE;
e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
- e->blockedCount[Us] = 0;
+ 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)
+ while (b)
{
+ s = pop_lsb(b);
+
assert(pos.piece_on(s) == make_piece(Us, PAWN));
Rank r = relative_rank(Us, s);
opposed = theirPawns & forward_file_bb(Us, s);
blocked = theirPawns & (s + Up);
stoppers = theirPawns & passed_pawn_span(Us, s);
- lever = theirPawns & PawnAttacks[Us][s];
- leverPush = theirPawns & PawnAttacks[Us][s + Up];
+ lever = theirPawns & pawn_attacks_bb(Us, s);
+ leverPush = theirPawns & pawn_attacks_bb(Us, s + Up);
doubled = ourPawns & (s - Up);
neighbours = ourPawns & adjacent_files_bb(s);
phalanx = neighbours & rank_bb(s);
support = neighbours & rank_bb(s - Up);
- e->blockedCount[Us] += blocked || more_than_one(leverPush);
+ if (doubled)
+ {
+ // 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.
// Score this pawn
if (support | phalanx)
{
- int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2
- + 21 * popcount(support);
+ 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
- + WeakUnopposed * !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
- + WeakUnopposed * !opposed;
+ score -= Backward
+ + WeakUnopposed * !opposed * bool(~(FileABB | FileHBB) & s);
if (!support)
- score -= Doubled * doubled
- + WeakLever * more_than_one(lever);
+ score -= Doubled * doubled
+ + WeakLever * more_than_one(lever);
+
+ if (blocked && r >= RANK_5)
+ score += BlockedPawn[r - RANK_5];
}
return score;
namespace Pawns {
+
/// 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
/// is found. Otherwise a new Entry is computed and stored there, so we don't
return e;
e->key = key;
+ e->blockedCount = 0;
e->scores[WHITE] = evaluate<WHITE>(pos, e);
e->scores[BLACK] = evaluate<BLACK>(pos, e);
/// penalty for a king, looking at the king file and the two closest files.
template<Color Us>
-Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) const {
constexpr Color Them = ~Us;
Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
- Bitboard ourPawns = b & pos.pieces(Us);
+ Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them];
Bitboard theirPawns = b & pos.pieces(Them);
Score bonus = make_score(5, 5);
- File center = Utility::clamp(file_of(ksq), FILE_B, FILE_G);
+ 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);
b = theirPawns & file_bb(f);
int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
- File d = File(edge_distance(f));
+ int d = edge_distance(f);
bonus += make_score(ShelterStrength[d][ourRank], 0);
if (ourRank && (ourRank == theirRank - 1))
- bonus -= BlockedStorm * int(theirRank == RANK_3);
+ bonus -= BlockedStorm[theirRank];
else
bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
+ // King On File
+ bonus -= KingOnFile[pos.is_on_semiopen_file(Us, ksq)][pos.is_on_semiopen_file(Them, ksq)];
+
return bonus;
}
// In endgame we like to bring our king near our closest pawn
Bitboard pawns = pos.pieces(Us, PAWN);
- int minPawnDist = pawns ? 8 : 0;
+ int minPawnDist = 6;
- if (pawns & PseudoAttacks[KING][ksq])
+ if (pawns & attacks_bb<KING>(ksq))
minPawnDist = 1;
else while (pawns)
- minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(pawns)));
return shelter - make_score(0, 16 * minPawnDist);
}
template Score Entry::do_king_safety<BLACK>(const Position& pos);
} // namespace Pawns
+
+} // namespace Stockfish