+
+
+/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+
+template<Color Us>
+Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
+ Bitboard theirPawns, PawnInfo* pi) const {
+ Bitboard b;
+ Square s;
+ File f;
+ Rank r;
+ int bonus;
+ bool passed, isolated, doubled, opposed, chain, backward, candidate;
+ Score value = make_score(0, 0);
+ const Square* ptr = pos.piece_list_begin(Us, PAWN);
+
+ // Initialize pawn storm scores by giving bonuses for open files
+ for (f = FILE_A; f <= FILE_H; f++)
+ if (!(ourPawns & file_bb(f)))
+ {
+ pi->ksStormValue[Us] += KStormOpenFileBonus[f];
+ pi->qsStormValue[Us] += QStormOpenFileBonus[f];
+ pi->halfOpenFiles[Us] |= (1 << f);
+ }
+
+ // Loop through all pawns of the current color and score each pawn
+ while ((s = *ptr++) != SQ_NONE)
+ {
+ f = square_file(s);
+ r = square_rank(s);
+
+ assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN));
+
+ // Calculate kingside and queenside pawn storm scores for both colors to be
+ // used when evaluating middle game positions with opposite side castling.
+ bonus = (f >= FILE_F ? evaluate_pawn_storm<Us, KingSide>(s, r, f, theirPawns) : 0);
+ pi->ksStormValue[Us] += KStormTable[relative_square(Us, s)] + bonus;
+
+ bonus = (f <= FILE_C ? evaluate_pawn_storm<Us, QueenSide>(s, r, f, theirPawns) : 0);
+ pi->qsStormValue[Us] += QStormTable[relative_square(Us, s)] + bonus;
+
+ // Our rank plus previous one. Used for chain detection.
+ b = rank_bb(r) | rank_bb(Us == WHITE ? r - 1 : r + 1);
+
+ // Passed, isolated, doubled or member of a pawn
+ // chain (but not the backward one) ?
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
+ doubled = ourPawns & squares_behind(Us, s);
+ opposed = theirPawns & squares_in_front_of(Us, s);
+ isolated = !(ourPawns & neighboring_files_bb(f));
+ chain = ourPawns & neighboring_files_bb(f) & b;
+
+ // Test for backward pawn
+ //
+ backward = false;
+
+ // If the pawn is passed, isolated, or member of a pawn chain
+ // it cannot be backward. If can capture an enemy pawn or if
+ // there are friendly pawns behind on neighboring files it cannot
+ // be backward either.
+ if ( !(passed | isolated | chain)
+ && !(ourPawns & attack_span_mask(opposite_color(Us), s))
+ && !(pos.attacks_from<PAWN>(s, Us) & theirPawns))
+ {
+ // We now know that there are no friendly pawns beside or behind this
+ // pawn on neighboring files. We now check whether the pawn is
+ // backward by looking in the forward direction on the neighboring
+ // files, and seeing whether we meet a friendly or an enemy pawn first.
+ b = pos.attacks_from<PAWN>(s, Us);
+
+ // Note that we are sure to find something because pawn is not passed
+ // nor isolated, so loop is potentially infinite, but it isn't.
+ while (!(b & (ourPawns | theirPawns)))
+ Us == WHITE ? b <<= 8 : b >>= 8;
+
+ // The friendly pawn needs to be at least two ranks closer than the enemy
+ // pawn in order to help the potentially backward pawn advance.
+ backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns;
+ }
+
+ assert(passed | opposed | (attack_span_mask(Us, s) & theirPawns));
+
+ // Test for candidate passed pawn
+ candidate = !(opposed | passed)
+ && (b = attack_span_mask(opposite_color(Us), s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
+ && count_1s_max_15(b) >= count_1s_max_15(attack_span_mask(Us, s) & theirPawns);
+
+ // In order to prevent doubled passed pawns from receiving a too big
+ // bonus, only the frontmost passed pawn on each file is considered as
+ // a true passed pawn.
+ if (passed && (ourPawns & squares_in_front_of(Us, s)))
+ passed = false;
+
+ // Mark the pawn as passed. Pawn will be properly scored in evaluation
+ // because we need full attack info to evaluate passed pawns.
+ if (passed)
+ set_bit(&(pi->passedPawns), s);
+
+ // Score this pawn
+ if (isolated)
+ {
+ value -= IsolatedPawnPenalty[f];
+ if (!opposed)
+ value -= IsolatedPawnPenalty[f] / 2;
+ }
+ if (doubled)
+ value -= DoubledPawnPenalty[f];
+
+ if (backward)
+ {
+ value -= BackwardPawnPenalty[f];
+ if (!opposed)
+ value -= BackwardPawnPenalty[f] / 2;
+ }
+ if (chain)
+ value += ChainBonus[f];
+
+ if (candidate)
+ value += CandidateBonus[relative_rank(Us, s)];
+ }
+
+ return value;
+}
+
+
+/// PawnInfoTable::evaluate_pawn_storm() evaluates each pawn which seems
+/// to have good chances of creating an open file by exchanging itself
+/// against an enemy pawn on an adjacent file.
+
+template<Color Us, PawnInfoTable::SideType Side>
+int PawnInfoTable::evaluate_pawn_storm(Square s, Rank r, File f, Bitboard theirPawns) const {
+
+ const Bitboard StormFilesBB = (Side == KingSide ? FileFBB | FileGBB | FileHBB
+ : FileABB | FileBBB | FileCBB);
+ const int K = (Side == KingSide ? 2 : 4);
+ const File RookFile = (Side == KingSide ? FILE_H : FILE_A);
+
+ Bitboard b = attack_span_mask(Us, s) & theirPawns & StormFilesBB;
+ int bonus = 0;
+
+ while (b)
+ {
+ // Give a bonus according to the distance of the nearest enemy pawn
+ Square s2 = pop_1st_bit(&b);
+ Rank r2 = square_rank(s2);
+ int v = StormLeverBonus[f] - K * rank_distance(r, r2);
+
+ // If enemy pawn has no pawn beside itself is particularly vulnerable.
+ // Big bonus, especially against a weakness on the rook file
+ if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
+ v *= (square_file(s2) == RookFile ? 4 : 2);
+
+ bonus += v;
+ }
+ return bonus;
+}
+
+
+/// PawnInfo::updateShelter calculates and caches king shelter. It is called
+/// only when king square changes, about 20% of total get_king_shelter() calls.
+int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {
+
+ Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq);
+ unsigned shelter = 0;
+ unsigned r = ksq & (7 << 3);
+
+ for (int i = 1, k = (c ? -8 : 8); i < 4; i++)
+ {
+ r += k;
+ shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i);
+ }
+ kingSquares[c] = ksq;
+ kingShelters[c] = shelter;
+ return shelter;
+}