Introduce bonus for queen infiltration

Idea is that queen feels much better when it can't be kicked away now
or later by pawn moves, especially in endgame. Special thanks to
Linmiao Xu for the original idea of this patch.

passed STC:
LLR: 2.94 (-2.94,2.94) {-0.50,1.50}
Total: 84008 W: 16271 L: 15958 D: 51779
Ptnml(0-2): 1476, 9688, 19420, 9887, 1533
https://tests.stockfishchess.org/tests/view/5eee7ca0447c5b640047a439

passed LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.75}
Total: 11720 W: 1522 L: 1328 D: 8870
Ptnml(0-2): 52, 1021, 3574, 1107, 106
https://tests.stockfishchess.org/tests/view/5eefc588122d6514328d75f9

closes https://github.com/official-stockfish/Stockfish/pull/2759

Bench: 4471740

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 3b0891a2d4fbfc1af9c10b8b84ea04309746c9fe..8b4a27bc112b3cad6d9997b3ea11209a5445edce 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -143,16 +143,17 @@ namespace {
   constexpr Score ReachableOutpost    = S( 31, 22);
   constexpr Score PassedFile          = S( 11,  8);
   constexpr Score PawnlessFlank       = S( 17, 95);
+  constexpr Score QueenInfiltration   = S( -2, 14);
   constexpr Score RestrictedPiece     = S(  7,  7);
   constexpr Score RookOnKingRing      = S( 16,  0);
-  constexpr Score RookOnQueenFile     = S(  5,  9);
-  constexpr Score SliderOnQueen       = S( 59, 18);
+  constexpr Score RookOnQueenFile     = S(  6, 11);
+  constexpr Score SliderOnQueen       = S( 60, 18);
   constexpr Score ThreatByKing        = S( 24, 89);
   constexpr Score ThreatByPawnPush    = S( 48, 39);
   constexpr Score ThreatBySafePawn    = S(173, 94);
   constexpr Score TrappedRook         = S( 55, 13);
-  constexpr Score WeakQueen           = S( 51, 14);
-  constexpr Score WeakQueenProtection = S( 15,  0);
+  constexpr Score WeakQueen           = S( 56, 15);
+  constexpr Score WeakQueenProtection = S( 14,  0);
 
 #undef S
 
@@ -373,6 +374,10 @@ namespace {
             Bitboard queenPinners;
             if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s, queenPinners))
                 score -= WeakQueen;
+
+            // Bonus for queen on weak square in enemy camp
+            if (relative_rank(Us, s) > RANK_4 && (~pe->pawn_attacks_span(Them) & s))
+                score += QueenInfiltration;    
         }
     }
     if (T)