- // 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)
- {
- Square s2 = pop_1st_bit(&b);
- if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2)))
- {
- // The enemy pawn has no pawn beside itself, which makes it
- // particularly vulnerable. Big bonus, especially against a
- // weakness on the rook file.
- if (square_file(s2) == FILE_A)
- bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2);
- else
- bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2);
- } else
- // There is at least one enemy pawn beside the enemy pawn we look
- // at, which means that the pawn has somewhat better chances of
- // defending itself by advancing. Smaller bonus.
- bonus += StormLeverBonus[f] - 4*square_distance(s, s2);
- }
- }
- 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.
- bool 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.
- bool backward;
- if ( passed
- || isolated
- || chain
- || (pos.pawn_attacks(us, s) & theirPawns)
- || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f)))
- 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.pawn_attacks(us, s);
- if (us == WHITE)
- {
- for ( ; !(b & (ourPawns | theirPawns)); b <<= 8);
- backward = (b | (b << 8)) & theirPawns;
- }
- else
- {
- for ( ; !(b & (ourPawns | theirPawns)); b >>= 8);
- backward = (b | (b >> 8)) & theirPawns;
- }
- }