// Bonus for file distance of the two outermost pawns
const Score PawnsFileSpan = S(0, 15);
+ // Unsupported pawn penalty
+ const Score UnsupportedPawnPenalty = S(20, 10);
+
// Weakness of our pawn shelter in front of the king indexed by [rank]
const Value ShelterWeakness[RANK_NB] =
{ V(100), V(0), V(27), V(73), V(92), V(101), V(101) };
const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE);
- Bitboard b;
+ Bitboard b, p, doubled;
Square s;
File f;
- bool passed, isolated, doubled, opposed, connected, backward, candidate;
+ bool passed, isolated, opposed, connected, backward, candidate, unsupported;
Score value = SCORE_ZERO;
const Square* pl = pos.list<PAWN>(Us);
// This file cannot be semi-open
e->semiopenFiles[Us] &= ~(1 << f);
+ // Previous rank
+ p = rank_bb(s - pawn_push(Us));
+
// Our rank plus previous one
- b = rank_bb(s) | rank_bb(s - pawn_push(Us));
+ b = rank_bb(s) | p;
- // Flag the pawn as passed, isolated, doubled or
- // connected (but not the backward one).
- connected = ourPawns & adjacent_files_bb(f) & b;
- isolated = !(ourPawns & adjacent_files_bb(f));
- doubled = ourPawns & forward_bb(Us, s);
- opposed = theirPawns & forward_bb(Us, s);
- passed = !(theirPawns & passed_pawn_mask(Us, s));
+ // Flag the pawn as passed, isolated, doubled,
+ // unsupported or connected (but not the backward one).
+ connected = ourPawns & adjacent_files_bb(f) & b;
+ unsupported = !(ourPawns & adjacent_files_bb(f) & p);
+ isolated = !(ourPawns & adjacent_files_bb(f));
+ doubled = ourPawns & forward_bb(Us, s);
+ opposed = theirPawns & forward_bb(Us, s);
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn.
// If the pawn is passed, isolated, or connected it cannot be
if (isolated)
value -= Isolated[opposed][f];
+ if (unsupported && !isolated)
+ value -= UnsupportedPawnPenalty;
+
if (doubled)
- value -= Doubled[f];
+ value -= Doubled[f] / rank_distance(s, lsb(doubled));
if (backward)
value -= Backward[opposed][f];
}
-/// Entry::update_safety() calculates and caches a bonus for king safety.
-/// It is called only when king square changes, which is about 20% of total
-/// king_safety() calls.
+/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
+/// when king square changes, which is about 20% of total king_safety() calls.
template<Color Us>
-Score Entry::update_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
kingSquares[Us] = ksq;
castlingRights[Us] = pos.can_castle(Us);
while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
if (relative_rank(Us, ksq) > RANK_4)
- return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
+ return make_score(0, -16 * minKPdistance[Us]);
Value bonus = shelter_storm<Us>(pos, ksq);
if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
- return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
+ return make_score(bonus, -16 * minKPdistance[Us]);
}
// Explicit template instantiation
-template Score Entry::update_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::update_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
} // namespace Pawns