Simplify some kingring penalties expressions

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ee93f11f13cda2b3e776221282534969c18512ed..39dac6d14ffb5481b74986ec41660cf5aebac6f0 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -421,7 +421,7 @@ namespace {
                                        : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);
-    Bitboard kingOnlyDefended, undefended, b, b1, b2, safe, other;
+    Bitboard weak, b, b1, b2, safe, other;
     int kingDanger;
 
     // King shelter and enemy pawns storm
@@ -430,16 +430,10 @@ namespace {
     // Main king safety evaluation
     if (kingAttackersCount[Them] > (1 - pos.count<QUEEN>(Them)))
     {
-        // Find the attacked squares which are defended only by our king...
-        kingOnlyDefended =   attackedBy[Them][ALL_PIECES]
-                          &  attackedBy[Us][KING]
-                          & ~attackedBy2[Us];
-
-        // ... and those which are not defended at all in the larger king ring
-        undefended =   attackedBy[Them][ALL_PIECES]
-                    & ~attackedBy[Us][ALL_PIECES]
-                    &  kingRing[Us]
-                    & ~pos.pieces(Them);
+        // Attacked squares defended at most once by our queen or king
+        weak =  attackedBy[Them][ALL_PIECES]
+              & ~attackedBy2[Us]
+              & (attackedBy[Us][KING] | attackedBy[Us][QUEEN] | ~attackedBy[Us][ALL_PIECES]);
 
         // Initialize the 'kingDanger' variable, which will be transformed
         // later into a king danger score. The initial value is based on the
@@ -448,7 +442,7 @@ namespace {
         // the quality of the pawn shelter (current 'score' value).
         kingDanger =        kingAttackersCount[Them] * kingAttackersWeight[Them]
                     + 102 * kingAdjacentZoneAttacksCount[Them]
-                    + 191 * popcount(kingOnlyDefended | undefended)
+                    + 191 * popcount(kingRing[Us] & weak)
                     + 143 * !!pos.pinned_pieces(Us)
                     - 848 * !pos.count<QUEEN>(Them)
                     -   9 * mg_value(score) / 8
@@ -456,21 +450,15 @@ namespace {
 
         // Analyse the safe enemy's checks which are possible on next move
         safe  = ~pos.pieces(Them);
-        safe &= ~attackedBy[Us][ALL_PIECES] | (kingOnlyDefended & attackedBy2[Them]);
+        safe &= ~attackedBy[Us][ALL_PIECES] | (weak & attackedBy2[Them]);
 
         b1 = pos.attacks_from<  ROOK>(ksq);
         b2 = pos.attacks_from<BISHOP>(ksq);
 
         // Enemy queen safe checks
-        if ((b1 | b2) & attackedBy[Them][QUEEN] & safe)
+        if ((b1 | b2) & attackedBy[Them][QUEEN] & safe & ~attackedBy[Us][QUEEN])
             kingDanger += QueenCheck;
 
-        // For minors and rooks, also consider the square safe if attacked twice,
-        // and only defended by our queen.
-        safe |=  attackedBy2[Them]
-               & ~(attackedBy2[Us] | pos.pieces(Them))
-               & attackedBy[Us][QUEEN];
-
         // Some other potential checks are also analysed, even from squares
         // currently occupied by the opponent own pieces, as long as the square
         // is not attacked by our pawns, and is not occupied by a blocked pawn.