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Optimize undefended minor check.

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Gary Linscott
2012-03-21 08:19:21 -04:00
parent 3c6a4bfbed
commit d1e18fc7dd
1 changed files with 14 additions and 8 deletions
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22
src/evaluate.cpp
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@@ -167,6 +167,9 @@ namespace {
// happen in Chess960 games. // happen in Chess960 games.
const Score TrappedBishopA1H1Penalty = make_score(100, 100); const Score TrappedBishopA1H1Penalty = make_score(100, 100);
// Penalty for a minor piece that is not defended by anything
const Score UndefendedMinorPenalty = make_score(25, 10);
// The SpaceMask[Color] contains the area of the board which is considered // The SpaceMask[Color] contains the area of the board which is considered
// by the space evaluation. In the middle game, each side is given a bonus // by the space evaluation. In the middle game, each side is given a bonus
// based on how many squares inside this area are safe and available for // based on how many squares inside this area are safe and available for
@@ -680,16 +683,19 @@ Value do_evaluate(const Position& pos, Value& margin) {
Score score = SCORE_ZERO; Score score = SCORE_ZERO;
// Undefended minors get penalized even if not under attack // Undefended minors get penalized even if not under attack
Bitboard undefended = pos.pieces(Them) const Bitboard undefended = pos.pieces(Them)
& (pos.pieces(BISHOP) | pos.pieces(KNIGHT)) & (pos.pieces(BISHOP) | pos.pieces(KNIGHT))
& ~ei.attackedBy[Them][0]; & ~ei.attackedBy[Them][0];
if (undefended) if (undefended) {
score += make_score(25, 10) * popcount<Max15>(undefended); score += UndefendedMinorPenalty;
if (!single_bit(undefended))
score += UndefendedMinorPenalty;
}
// Enemy pieces not defended by a pawn and under our attack // Enemy pieces not defended by a pawn and under our attack
Bitboard weakEnemies = pos.pieces(Them) const Bitboard weakEnemies = pos.pieces(Them)
& ~ei.attackedBy[Them][PAWN] & ~ei.attackedBy[Them][PAWN]
& ei.attackedBy[Us][0]; & ei.attackedBy[Us][0];
if (!weakEnemies) if (!weakEnemies)
return score; return score;