/*
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
#undef S
+ const File ShelterFile[8] = { FILE_B, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_G };
+
+ inline Value score_non_center_file(const Value v) {
+ return Value(v * 7 / 16);
+ }
+
+ 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;
+
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);
}
-/// PawnInfoTable::get_pawn_info() takes a position object as input, computes
+/// 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.
-PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const {
+PawnInfo* PawnInfoTable::pawn_info(const Position& pos) const {
- Key key = pos.get_pawn_key();
+ Key key = pos.pawn_key();
PawnInfo* pi = probe(key);
// If pi->key matches the position's pawn hash key, it means that we
Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
Bitboard theirPawns, PawnInfo* pi) {
- const BitCountType Max15 = CpuIs64Bit ? CNT64_MAX15 : CNT32_MAX15;
const Color Them = (Us == WHITE ? BLACK : WHITE);
Bitboard b;
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 & neighboring_files_bb(f));
- chain = ourPawns & neighboring_files_bb(f) & b;
+ isolated = !(ourPawns & adjacent_files_bb(f));
+ chain = ourPawns & adjacent_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 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);
+ pi->passedPawns[Us] |= s;
// Score this pawn
if (isolated)
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.
template<Color Us>
Score PawnInfo::updateShelter(const Position& pos, Square ksq) {
-
- const int Shift = (Us == WHITE ? 8 : -8);
-
- Bitboard pawns;
- int r, shelter = 0;
+ int shelter = 0;
if (relative_rank(Us, ksq) <= RANK_4)
{
- 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] << (6 - i);
- }
+ 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;
}
+
kingSquares[Us] = ksq;
kingShelters[Us] = make_score(shelter, 0);
return kingShelters[Us];