HCha/Stockfish
1
0
Fork 0
mirror of https://github.com/HChaZZY/Stockfish.git synced 2025-12-25 11:36:51 +08:00
Code Issues Packages Projects Releases Wiki Activity

Add more detailed pawn shelter/storm evaluation

Browse Source
This commit is contained in:
Gary Linscott
2012-03-26 07:52:10 -04:00
parent 32d3a07c67
commit 374c9e6b63
3 changed files with 102 additions and 16 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
src/pawns.cpp
View File

@@ -65,6 +65,19 @@ namespace {
#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);
@@ -209,27 +222,53 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
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_adjacent_files_bb(file_of(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];