If the opponent has a cramped position, opening a file often
helps him/her to exchange pieces, so it makes sense to reduce
the space bonus if there are open files.
Credits: Leonardo Ljubičić for the strategic idea, Alain Savard for the
implementation of the open files calculation, "CrunchyNYC" for the
compensation of the numerator.
STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 49112 W: 9239 L: 8900 D: 30973
LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 89415 W: 12014 L: 11601 D: 65800
Bench:
7591630
// ...count safe + (behind & safe) with a single popcount
int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
bonus = std::min(16, bonus);
- int weight = pos.count<ALL_PIECES>(Us);
+ int weight = pos.count<ALL_PIECES>(Us) - 2 * ei.pi->open_files();
- return make_score(bonus * weight * weight / 22, 0);
+ return make_score(bonus * weight * weight / 18, 0);
}
e->key = key;
e->score = evaluate<WHITE>(pos, e) - evaluate<BLACK>(pos, e);
e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]);
+ e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]);
return e;
}
Bitboard passed_pawns(Color c) const { return passedPawns[c]; }
Bitboard pawn_attacks_span(Color c) const { return pawnAttacksSpan[c]; }
int pawn_asymmetry() const { return asymmetry; }
+ int open_files() const { return openFiles; }
int semiopen_file(Color c, File f) const {
return semiopenFiles[c] & (1 << f);
int semiopenFiles[COLOR_NB];
int pawnsOnSquares[COLOR_NB][COLOR_NB]; // [color][light/dark squares]
int asymmetry;
+ int openFiles;
};
typedef HashTable<Entry, 16384> Table;