along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
+#include <algorithm>
#include <cassert>
#include "bitboard.h"
#define S(mg, eg) make_score(mg, eg)
// Pawn penalties
- constexpr Score Backward = S( 9, 24);
- constexpr Score Doubled = S(11, 56);
- constexpr Score Isolated = S( 5, 15);
+ constexpr Score Backward = S( 9, 24);
+ constexpr Score Doubled = S(11, 56);
+ constexpr Score Isolated = S( 5, 15);
+ constexpr Score WeakLever = S( 0, 56);
+ constexpr Score WeakUnopposed = S(13, 27);
// Connected pawn bonus
- constexpr int Connected[RANK_NB] = { 0, 13, 17, 24, 59, 96, 171 };
+ constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 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.
// 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.
+ // [0][1-2] accommodate opponent pawn on edge (likely blocked by our king)
constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = {
- { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) },
- { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) },
- { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) },
- { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) }
+ { V( 89), V(-285), V(-185), V(93), V(57), V( 45), V( 51) },
+ { V( 44), V( -18), V( 123), V(46), V(39), V( -7), V( 23) },
+ { V( 4), V( 52), V( 162), V(37), V( 7), V(-14), V( -2) },
+ { V(-10), V( -14), V( 90), V(15), V( 2), V( -7), V(-16) }
};
#undef S
constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH);
- Bitboard b, neighbours, stoppers, doubled, support, phalanx;
+ Bitboard neighbours, stoppers, doubled, support, phalanx;
Bitboard lever, leverPush;
Square s;
- bool opposed, backward;
+ bool opposed, backward, passed;
Score score = SCORE_ZERO;
const Square* pl = pos.squares<PAWN>(Us);
Bitboard ourPawns = pos.pieces( Us, PAWN);
Bitboard theirPawns = pos.pieces(Them, PAWN);
- e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0;
- 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] = e->pawnAttacksSpan[Us] = 0;
+ e->kingSquares[Us] = SQ_NONE;
+ e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
// 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));
- File f = file_of(s);
Rank r = relative_rank(Us, s);
e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s);
lever = theirPawns & PawnAttacks[Us][s];
leverPush = theirPawns & PawnAttacks[Us][s + Up];
doubled = ourPawns & (s - Up);
- neighbours = ourPawns & adjacent_files_bb(f);
+ neighbours = ourPawns & adjacent_files_bb(s);
phalanx = neighbours & rank_bb(s);
support = 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))
+ // A pawn is backward when it is behind all pawns of the same color on
+ // the adjacent files and cannot safely advance. Phalanx and isolated
+ // pawns will be excluded when the pawn is scored.
+ backward = !(neighbours & forward_ranks_bb(Them, s))
&& (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)
- && (support || !more_than_one(lever))
- && popcount(phalanx) >= popcount(leverPush))
+ // 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.
+ passed = !(stoppers ^ lever)
+ || ( !(stoppers ^ leverPush)
+ && popcount(phalanx) >= popcount(leverPush))
+ || ( stoppers == square_bb(s + Up) && r >= RANK_5
+ && (shift<Up>(support) & ~(theirPawns | doubleAttackThem)));
+
+ // Passed pawns will be properly scored later in evaluation when we have
+ // full attack info.
+ if (passed)
e->passedPawns[Us] |= s;
- else if (stoppers == square_bb(s + Up) && r >= RANK_5)
- {
- b = shift<Up>(support) & ~theirPawns;
- while (b)
- if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)]))
- e->passedPawns[Us] |= s;
- }
-
// Score this pawn
if (support | phalanx)
{
- int v = (phalanx ? 3 : 2) * Connected[r];
- v = 17 * popcount(support) + (v >> (opposed + 1));
+ int v = Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1)
+ + 17 * popcount(support);
+
score += make_score(v, v * (r - 2) / 4);
}
+
else if (!neighbours)
- score -= Isolated, e->weakUnopposed[Us] += !opposed;
+ score -= Isolated + WeakUnopposed * int(!opposed);
else if (backward)
- score -= Backward, e->weakUnopposed[Us] += !opposed;
+ score -= Backward + WeakUnopposed * int(!opposed);
if (doubled && !support)
score -= Doubled;
}
+ // Penalize our unsupported pawns attacked twice by enemy pawns
+ score -= WeakLever * popcount( ourPawns
+ & doubleAttackThem
+ & ~e->pawnAttacks[Us]);
+
return score;
}
/// 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) {
+void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) {
- 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 == WHITE ? BLACK : WHITE);
Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq);
Bitboard ourPawns = b & pos.pieces(Us);
Bitboard theirPawns = b & pos.pieces(Them);
- Value safety = (shift<Down>(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ?
- Value(374) : Value(5);
+ Score bonus = make_score(5, 5);
File center = clamp(file_of(ksq), FILE_B, FILE_G);
for (File f = File(center - 1); f <= File(center + 1); ++f)
{
b = ourPawns & file_bb(f);
- Rank ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+ Rank ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
b = theirPawns & file_bb(f);
Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
int d = std::min(f, ~f);
- safety += ShelterStrength[d][ourRank];
- safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3)
- : UnblockedStorm[d][theirRank];
+ bonus += make_score(ShelterStrength[d][ourRank], 0);
+
+ if (ourRank && (ourRank == theirRank - 1))
+ bonus -= make_score(82 * (theirRank == RANK_3), 82 * (theirRank == RANK_3));
+ else
+ bonus -= make_score(UnblockedStorm[d][theirRank], 0);
}
- return safety;
+ if (mg_value(bonus) > mg_value(shelter))
+ shelter = bonus;
}
Square ksq = pos.square<KING>(Us);
kingSquares[Us] = ksq;
castlingRights[Us] = pos.castling_rights(Us);
- int minKingPawnDistance = 0;
Bitboard pawns = pos.pieces(Us, PAWN);
- if (pawns)
- while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {}
+ int minPawnDist = pawns ? 8 : 0;
+
+ if (pawns & PseudoAttacks[KING][ksq])
+ minPawnDist = 1;
+
+ else while (pawns)
+ minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
- Value bonus = evaluate_shelter<Us>(pos, ksq);
+ Score shelter = make_score(-VALUE_INFINITE, VALUE_ZERO);
+ evaluate_shelter<Us>(pos, ksq, shelter);
// If we can castle use the bonus after the castling if it is bigger
if (pos.can_castle(Us | KING_SIDE))
- bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1)));
+ evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1), shelter);
if (pos.can_castle(Us | QUEEN_SIDE))
- bonus = std::max(bonus, evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1)));
+ evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1), shelter);
- return make_score(bonus, -16 * minKingPawnDistance);
+ return shelter - make_score(VALUE_ZERO, 16 * minPawnDist);
}
// Explicit template instantiation
projects / stockfish / blobdiff