There was already a penalty for squares only defended by King (undefended)
This test records a penalty for completely undefended squares in the so called extended king-ring
(so if we exclude squares defended by a Kg8 for example, we only look at h6 g6 and f6)
We also exclude squares occupied by opponent pieces in this computation,
based on the following results
Was yellow at STC
LLR: -2.97 (-2.94,2.94) [0.00,5.00]
Total: 112499 W: 20649 L: 20293 D: 71557
and passed LTC
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 36805 W: 5100 L: 4857 D: 26848
Bench:
8430233
Resolves: #619
// Main king safety evaluation
if (ei.kingAttackersCount[Them])
{
// Main king safety evaluation
if (ei.kingAttackersCount[Them])
{
- // Find the attacked squares around the king which have no defenders
- // apart from the king itself.
+ // Find the attacked squares which are defended only by the king...
undefended = ei.attackedBy[Them][ALL_PIECES]
& ei.attackedBy[Us][KING]
& ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
| ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
| ei.attackedBy[Us][QUEEN]);
undefended = ei.attackedBy[Them][ALL_PIECES]
& ei.attackedBy[Us][KING]
& ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
| ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
| ei.attackedBy[Us][QUEEN]);
+ // ... and those which are not defended at all in the larger king ring
+ b = ei.attackedBy[Them][ALL_PIECES] & ~ei.attackedBy[Us][ALL_PIECES]
+ & ei.kingRing[Us] & ~pos.pieces(Them);
+
// Initialize the 'attackUnits' variable, which is used later on as an
// index into the KingDanger[] array. The initial value is based on the
// number and types of the enemy's attacking pieces, the number of
// Initialize the 'attackUnits' variable, which is used later on as an
// index into the KingDanger[] array. The initial value is based on the
// number and types of the enemy's attacking pieces, the number of
attackUnits = std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
+ 9 * ei.kingAdjacentZoneAttacksCount[Them]
+ 27 * popcount(undefended)
attackUnits = std::min(72, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
+ 9 * ei.kingAdjacentZoneAttacksCount[Them]
+ 27 * popcount(undefended)
- + 11 * !!ei.pinnedPieces[Us]
+ + 11 * (popcount(b) + !!ei.pinnedPieces[Us])
- 64 * !pos.count<QUEEN>(Them)
- mg_value(score) / 8;
- 64 * !pos.count<QUEEN>(Them)
- mg_value(score) / 8;