/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad
+ Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
Stockfish is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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
+ // 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 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);
- }
-}
+ // 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) } };
+ // 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);
+
+ #undef S
+ #undef V
+}
-/// PawnInfoTable::get_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.
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
+/// 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.
- assert(pos.is_ok());
+PawnEntry* PawnTable::probe(const Position& pos) {
- Key key = pos.get_pawn_key();
- PawnInfo* pi = probe(key);
+ Key key = pos.pawn_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);
+ 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 BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b;
Rank r;
bool passed, isolated, doubled, opposed, chain, backward, candidate;
Score value = SCORE_ZERO;
- const Square* ptr = pos.piece_list_begin(Us, PAWN);
+ const Square* pl = pos.piece_list(Us, PAWN);
// Loop through all pawns of the current color and score each pawn
- while ((s = *ptr++) != SQ_NONE)
+ while ((s = *pl++) != SQ_NONE)
{
assert(pos.piece_on(s) == make_piece(Us, PAWN));
- f = square_file(s);
- r = square_rank(s);
+ f = file_of(s);
+ 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));
+ chain = ourPawns & adjacent_files_bb(f) & b;
+ isolated = !(ourPawns & adjacent_files_bb(f));
doubled = ourPawns & squares_in_front_of(Us, s);
opposed = theirPawns & squares_in_front_of(Us, s);
- isolated = !(ourPawns & neighboring_files_bb(f));
- chain = ourPawns & neighboring_files_bb(f) & b;
+ passed = !(theirPawns & passed_pawn_mask(Us, s));
// Test for backward pawn
backward = false;
// If the pawn is passed, isolated, or member of a pawn chain it cannot
- // be backward. If there are friendly pawns behind on neighboring files
+ // be backward. If there are friendly pawns behind on adjacent files
// or if can capture an enemy pawn it cannot be backward either.
if ( !(passed | isolated | chain)
&& !(ourPawns & attack_span_mask(Them, 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
+ // pawn on adjacent files. We now check whether the pawn is
+ // backward by looking in the forward direction on the adjacent
// files, and seeing whether we meet a friendly or an enemy pawn first.
b = pos.attacks_from<PAWN>(s, Us);
// A not passed pawn is a candidate to become passed if it is free to
// advance and if the number of friendly pawns beside or behind this
- // pawn on neighboring files is higher or equal than the number of
- // enemy pawns in the forward direction on the neighboring files.
+ // pawn on adjacent files is higher or equal than the number of
+ // enemy pawns in the forward direction on the adjacent files.
candidate = !(opposed | passed | backward | isolated)
- && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != EmptyBoardBB
- && count_1s<Max15>(b) >= count_1s<Max15>(attack_span_mask(Us, s) & theirPawns);
+ && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0
+ && popcount<Max15>(b) >= popcount<Max15>(attack_span_mask(Us, s) & theirPawns);
// Passed pawns will be properly scored in evaluation because we need
// full attack info to evaluate passed pawns. Only the frontmost passed
// pawn on each file is considered a true passed pawn.
if (passed && !doubled)
- set_bit(&(pi->passedPawns[Us]), s);
+ e->passedPawns[Us] |= s;
// Score this pawn
if (isolated)
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 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) {
+Value PawnEntry::shelter_storm(const Position& pos, Square ksq) {
- const int Shift = (Us == WHITE ? 8 : -8);
+ 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);
- Bitboard pawns;
- int r, shelter = 0;
+ kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf;
- if (relative_rank(Us, ksq) <= RANK_4)
+ for (int f = kf - 1; f <= kf + 1; f++)
{
- pawns = pos.pieces(PAWN, Us) & this_and_neighboring_files_bb(ksq);
- r = ksq & (7 << 3);
- for (int i = 0; i < 3; i++)
- {
- r += Shift;
- shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (64 >> i);
- }
+ // 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];
+
+ if (relative_rank(Us, ksq) > RANK_4)
+ return kingSafety[Us] = SCORE_ZERO;
+
+ 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, 0);
}
// 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