namespace {
+ #define V Value
#define S(mg, eg) make_score(mg, eg)
// Doubled pawn penalty by opposed flag and file
const Score PawnStructureWeight = S(233, 201);
- #undef S
-
- const File ShelterFile[8] = { FILE_B, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_G };
+ // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank]
+ const Value ShelterWeakness[2][8] =
+ { { V(141), V(0), V(38), V(102), V(128), V(141), V(141) },
+ { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61) } };
- inline Value score_non_center_file(const Value v) {
- return Value(v * 7 / 16);
- }
+ // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank]
+ const Value StormDanger[2][8] =
+ { { V(26), V(0), V(128), V(51), V(26) },
+ { V(13), V(0), V( 64), V(25), V(13) } };
- typedef Value V;
- // Arrays are indexed by rank. Zeroth value is for when no pawn on that file.
- const Value PawnShelter[8] = { V(141), V(0), V( 38), V(102), V(128), V(141), V(141), V(141) };
- const Value PawnStorm[8] = { V( 26), V(0), V(128), V( 51), V( 26), V( 0), V( 0), V( 0) };
- // We compute shelter as a penalty for the given color, but shelter is used as a bonus, so we invert it using this as the basis.
- const Value PawnShelterBasis = PawnShelter[0] + score_non_center_file(PawnShelter[0]) * 2;
+ // Max bonus for king safety. Corresponds to start position with all the pawns
+ // in front of the king and no enemy pawn on the horizont.
+ const Value MaxSafetyBonus = V(263);
- inline Score apply_weight(Score v, Score w) {
- return make_score((int(mg_value(v)) * mg_value(w)) / 0x100,
- (int(eg_value(v)) * eg_value(w)) / 0x100);
- }
+ #undef S
+ #undef V
}
-/// PawnInfoTable::pawn_info() takes a position object as input, computes
-/// a PawnInfo object, and returns a pointer to it. The result is also stored
-/// in an hash table, so we don't have to recompute everything when the same
-/// pawn structure occurs again.
+/// PawnTable::probe() takes a position object as input, computes a PawnEntry
+/// object, and returns a pointer to it. The result is also stored in a hash
+/// table, so we don't have to recompute everything when the same pawn structure
+/// occurs again.
-PawnInfo* PawnInfoTable::pawn_info(const Position& pos) const {
+PawnEntry* PawnTable::probe(const Position& pos) {
Key key = pos.pawn_key();
- PawnInfo* pi = probe(key);
+ PawnEntry* e = entries[key];
- // If pi->key matches the position's pawn hash key, it means that we
+ // If e->key matches the position's pawn hash key, it means that we
// have analysed this pawn structure before, and we can simply return
// the information we found the last time instead of recomputing it.
- if (pi->key == key)
- return pi;
+ if (e->key == key)
+ return e;
- // Initialize PawnInfo entry
- pi->key = key;
- pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0;
- pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE;
- pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF;
+ e->key = key;
+ e->passedPawns[WHITE] = e->passedPawns[BLACK] = 0;
+ e->kingSquares[WHITE] = e->kingSquares[BLACK] = SQ_NONE;
+ e->halfOpenFiles[WHITE] = e->halfOpenFiles[BLACK] = 0xFF;
- // Calculate pawn attacks
- Bitboard wPawns = pos.pieces(PAWN, WHITE);
- Bitboard bPawns = pos.pieces(PAWN, BLACK);
- pi->pawnAttacks[WHITE] = ((wPawns << 9) & ~FileABB) | ((wPawns << 7) & ~FileHBB);
- pi->pawnAttacks[BLACK] = ((bPawns >> 7) & ~FileABB) | ((bPawns >> 9) & ~FileHBB);
+ Bitboard wPawns = pos.pieces(WHITE, PAWN);
+ Bitboard bPawns = pos.pieces(BLACK, PAWN);
+ e->pawnAttacks[WHITE] = ((wPawns & ~FileHBB) << 9) | ((wPawns & ~FileABB) << 7);
+ e->pawnAttacks[BLACK] = ((bPawns & ~FileHBB) >> 7) | ((bPawns & ~FileABB) >> 9);
- // Evaluate pawns for both colors and weight the result
- pi->value = evaluate_pawns<WHITE>(pos, wPawns, bPawns, pi)
- - evaluate_pawns<BLACK>(pos, bPawns, wPawns, pi);
+ e->value = evaluate_pawns<WHITE>(pos, wPawns, bPawns, e)
+ - evaluate_pawns<BLACK>(pos, bPawns, wPawns, e);
- pi->value = apply_weight(pi->value, PawnStructureWeight);
+ e->value = apply_weight(e->value, PawnStructureWeight);
- return pi;
+ return e;
}
-/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color
+/// PawnTable::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) {
+Score PawnTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
+ Bitboard theirPawns, PawnEntry* e) {
const Color Them = (Us == WHITE ? BLACK : WHITE);
r = rank_of(s);
// This file cannot be half open
- pi->halfOpenFiles[Us] &= ~(1 << f);
+ e->halfOpenFiles[Us] &= ~(1 << f);
// Our rank plus previous one. Used for chain detection
b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1));
// Flag the pawn as passed, isolated, doubled or member of a pawn
// chain (but not the backward one).
- passed = !(theirPawns & passed_pawn_mask(Us, s));
- doubled = ourPawns & squares_in_front_of(Us, s);
- opposed = theirPawns & squares_in_front_of(Us, s);
- isolated = !(ourPawns & adjacent_files_bb(f));
chain = 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));
// Test for backward pawn
backward = false;
// full attack info to evaluate passed pawns. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
if (passed && !doubled)
- pi->passedPawns[Us] |= s;
+ e->passedPawns[Us] |= s;
// Score this pawn
if (isolated)
if (candidate)
value += CandidateBonus[relative_rank(Us, s)];
}
+
return value;
}
-template<Color Us>
-int computePawnShelter(const Position &pos, Square ksq) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
- const File kingFile = ShelterFile[file_of(ksq)];
- const Bitboard ourPawns = pos.pieces(PAWN, Us) & in_front_bb(Us, ksq);
- const Bitboard theirPawns = pos.pieces(PAWN, Them) & (RankBB[rank_of(ksq)] | in_front_bb(Us, ksq));
-
- int shelter = 0;
-
- // Compute king shelter and storm values for the file the king is on, as well as the two adjacent files.
- for (int fileOffset = -1; fileOffset <= 1; fileOffset++) {
- // Shelter takes full penalty for center file, otherwise it's half penalty
- Bitboard shelterFile = ourPawns & FileBB[kingFile + fileOffset];
- Rank shelterClosest = shelterFile ? relative_rank<Us>(shelterFile)
- : RANK_1;
-
- shelter += fileOffset == 0 ? PawnShelter[shelterClosest]
- : score_non_center_file(PawnShelter[shelterClosest]);
-
- // Storm takes full penalty, unless there is an enemy pawn blocking us
- Bitboard stormFile = theirPawns & FileBB[kingFile + fileOffset];
- Rank stormClosest = stormFile ? relative_rank<Us>(stormFile)
- : RANK_1;
-
- shelter += shelterClosest + 1 == stormClosest ? PawnStorm[stormClosest] / 2
- : PawnStorm[stormClosest];
- }
-
- return shelter;
-}
-/// PawnInfo::updateShelter() calculates and caches king shelter. It is called
-/// only when king square changes, about 20% of total king_shelter() calls.
+/// PawnEntry::shelter_storm() calculates shelter and storm penalties for the file
+/// the king is on, as well as the two adjacent files.
+
template<Color Us>
-Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
- int shelter = 0;
+Value PawnEntry::shelter_storm(const Position& pos, Square ksq) {
+
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+
+ Value safety = MaxSafetyBonus;
+ Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | rank_bb(ksq));
+ Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq);
+ Bitboard theirPawns = b & pos.pieces(Them);
+ Rank rkUs, rkThem;
+ File kf = file_of(ksq);
- if (relative_rank(Us, ksq) <= RANK_4)
+ kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf;
+
+ for (int f = kf - 1; f <= kf + 1; f++)
{
- shelter = computePawnShelter<Us>(pos, ksq);
- if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO))
- shelter = std::min(shelter, computePawnShelter<Us>(pos, relative_square(Us, SQ_G1)));
- if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO))
- shelter = std::min(shelter, computePawnShelter<Us>(pos, relative_square(Us, SQ_C1)));
- shelter = PawnShelterBasis - shelter;
+ // Shelter penalty is higher for the pawn in front of the king
+ b = ourPawns & FileBB[f];
+ rkUs = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1;
+ safety -= ShelterWeakness[f != kf][rkUs];
+
+ // Storm danger is smaller if enemy pawn is blocked
+ b = theirPawns & FileBB[f];
+ rkThem = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1;
+ safety -= StormDanger[rkThem == rkUs + 1][rkThem];
}
+ return safety;
+}
+
+
+/// PawnEntry::update_safety() calculates and caches a bonus for king safety. It is
+/// called only when king square changes, about 20% of total king_safety() calls.
+
+template<Color Us>
+Score PawnEntry::update_safety(const Position& pos, Square ksq) {
+
kingSquares[Us] = ksq;
- kingShelters[Us] = make_score(shelter, 0);
- return kingShelters[Us];
+ castleRights[Us] = pos.can_castle(Us);
+ minKPdistance[Us] = 0;
+
+ Bitboard pawns = pos.pieces(Us, PAWN);
+ if (pawns)
+ while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
+
+ if (relative_rank(Us, ksq) > RANK_4)
+ return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
+
+ Value bonus = shelter_storm<Us>(pos, ksq);
+
+ // If we can castle use the bonus after the castle if is bigger
+ if (pos.can_castle(make_castle_right(Us, KING_SIDE)))
+ bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
+ bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
+
+ return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
}
// Explicit template instantiation
-template Score PawnInfo::updateShelter<WHITE>(const Position& pos, Square ksq);
-template Score PawnInfo::updateShelter<BLACK>(const Position& pos, Square ksq);
+template Score PawnEntry::update_safety<WHITE>(const Position& pos, Square ksq);
+template Score PawnEntry::update_safety<BLACK>(const Position& pos, Square ksq);
projects / stockfish / blobdiff