-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;
-}