+
+
+/// 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) {
+ Square s;
+ File f;
+ Rank r;
+ bool passed, isolated, doubled, chain, backward, candidate;
+ int bonus;
+ 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));
+
+ // Passed, isolated or doubled pawn?
+ passed = Position::pawn_is_passed(theirPawns, Us, s);
+ isolated = Position::pawn_is_isolated(ourPawns, s);
+ doubled = Position::pawn_is_doubled(ourPawns, Us, s);
+
+ // We calculate kingside and queenside pawn storm
+ // scores for both colors. These are used when evaluating
+ // middle game positions with opposite side castling.
+ //
+ // Each pawn is given a base score given by a piece square table
+ // (KStormTable[] or QStormTable[]). Pawns which seem to have good
+ // chances of creating an open file by exchanging itself against an
+ // enemy pawn on an adjacent file gets an additional bonus.
+
+ // Kingside pawn storms
+ bonus = KStormTable[relative_square(Us, s)];
+ if (f >= FILE_F)
+ {
+ Bitboard b = outpost_mask(Us, s) & theirPawns & (FileFBB | FileGBB | FileHBB);
+ while (b)
+ {
+ // Give a bonus according to the distance of the nearest enemy pawn
+ Square s2 = pop_1st_bit(&b);
+ int v = StormLeverBonus[f] - 2 * square_distance(s, s2);
+
+ // 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) == FILE_H ? 4 : 2);
+
+ bonus += v;
+ }
+ }
+ pi->ksStormValue[Us] += bonus;
+
+ // Queenside pawn storms
+ bonus = QStormTable[relative_square(Us, s)];
+ if (f <= FILE_C)
+ {
+ Bitboard b = outpost_mask(Us, s) & theirPawns & (FileABB | FileBBB | FileCBB);
+ while (b)
+ {
+ // Give a bonus according to the distance of the nearest enemy pawn
+ Square s2 = pop_1st_bit(&b);
+ int v = StormLeverBonus[f] - 4 * square_distance(s, s2);
+
+ // 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) == FILE_A ? 4 : 2);
+
+ bonus += v;
+ }
+ }
+ pi->qsStormValue[Us] += bonus;
+
+ // Member of a pawn chain (but not the backward one)? We could speed up
+ // the test a little by introducing an array of masks indexed by color
+ // and square for doing the test, but because everything is hashed,
+ // it probably won't make any noticable difference.
+ chain = ourPawns
+ & neighboring_files_bb(f)
+ & (rank_bb(r) | rank_bb(r - (Us == WHITE ? 1 : -1)));
+
+ // Test for backward pawn
+ //
+ // 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 & behind_bb(Us, r) & neighboring_files_bb(f))
+ || (pos.attacks_from<PAWN>(s, Us) & theirPawns))
+ backward = false;
+ else
+ {
+ // 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.
+ Bitboard 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;
+ }
+
+ // Test for candidate passed pawn
+ candidate = !passed
+ && !(theirPawns & file_bb(f))
+ && ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(Us, r) | rank_bb(r)) & ourPawns)
+ - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(Us, r) & theirPawns)
+ >= 0);
+
+ // 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;
+
+ // Score this pawn
+ if (passed)
+ set_bit(&(pi->passedPawns), s);
+
+ if (isolated)
+ {
+ value -= IsolatedPawnPenalty[f];
+ if (!(theirPawns & file_bb(f)))
+ value -= IsolatedPawnPenalty[f] / 2;
+ }
+ if (doubled)
+ value -= DoubledPawnPenalty[f];
+
+ if (backward)
+ {
+ value -= BackwardPawnPenalty[f];
+ if (!(theirPawns & file_bb(f)))
+ value -= BackwardPawnPenalty[f] / 2;
+ }
+ if (chain)
+ value += ChainBonus[f];
+
+ if (candidate)
+ value += CandidateBonus[relative_rank(Us, s)];
+ }
+
+ return value;
+}
+
+
+/// 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) {
+
+ unsigned shelter = 0;
+ Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq);
+ 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;
+}