Rank threats on pinned pawns

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index df3f89698fb1c7ef1048a4961e51f19a18ac78ce..ac9cf90bdcb314aad1198af283f0ab8d9662eb6c 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -164,7 +164,7 @@ namespace {
   constexpr Score KnightOnQueen      = S( 21, 11);
   constexpr Score LongDiagonalBishop = S( 22,  0);
   constexpr Score MinorBehindPawn    = S( 16,  0);
-  constexpr Score Overload           = S( 16,  7);
+  constexpr Score Overload           = S( 13,  6);
   constexpr Score PawnlessFlank      = S( 20, 80);
   constexpr Score RookOnPawn         = S(  8, 24);
   constexpr Score SliderOnQueen      = S( 42, 21);
@@ -540,6 +540,9 @@ namespace {
             score += ThreatByMinor[type_of(pos.piece_on(s))];
             if (type_of(pos.piece_on(s)) != PAWN)
                 score += ThreatByRank * (int)relative_rank(Them, s);
+
+            else if (pos.blockers_for_king(Them) & s)
+                score += ThreatByRank * (int)relative_rank(Them, s) / 2;
         }
 
         b = weak & attackedBy[Us][ROOK];
@@ -549,9 +552,11 @@ namespace {
             score += ThreatByRook[type_of(pos.piece_on(s))];
             if (type_of(pos.piece_on(s)) != PAWN)
                 score += ThreatByRank * (int)relative_rank(Them, s);
+
+            else if (pos.blockers_for_king(Them) & s)
+                score += ThreatByRank * (int)relative_rank(Them, s) / 2;
         }
 
-        // Bonus for king attacks on pawns or pieces which are not pawn-defended
         if (weak & attackedBy[Us][KING])
             score += ThreatByKing;
 
@@ -576,7 +581,7 @@ namespace {
     b  = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
     b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
 
-    // Keep only the squares which are not completely unsafe
+    // Keep only the squares which are relatively safe
     b &= ~attackedBy[Them][PAWN]
         & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);