Improve handling of queen imbalance

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ca6ea5c44fd6da373d4e1cf9bf10deca66d2771f..b34d82f66d42d8d24446502a8b7125ad27cf1c76 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -74,7 +74,8 @@ using namespace Trace;
 namespace {
 
   // Threshold for lazy and space evaluation
-  constexpr Value LazyThreshold  = Value(1400);
+  constexpr Value LazyThreshold1  = Value(1400);
+  constexpr Value LazyThreshold2  = Value(1300);
   constexpr Value SpaceThreshold = Value(12222);
 
   // KingAttackWeights[PieceType] contains king attack weights by piece type
@@ -309,13 +310,15 @@ namespace {
 
         if (Pt == BISHOP || Pt == KNIGHT)
         {
-            // Bonus if piece is on an outpost square or can reach one
+            // Bonus if the piece is on an outpost square or can reach one
+            // Reduced bonus for knights (BadOutpost) if few relevant targets
             bb = OutpostRanks & attackedBy[Us][PAWN] & ~pe->pawn_attacks_span(Them);
+            Bitboard targets = pos.pieces(Them) & ~pos.pieces(PAWN);
+
             if (   Pt == KNIGHT
-                && bb & s & ~CenterFiles
-                && !(b & pos.pieces(Them) & ~pos.pieces(PAWN))
-                && !conditional_more_than_two(
-                      pos.pieces(Them) & ~pos.pieces(PAWN) & (s & QueenSide ? QueenSide : KingSide)))
+                && bb & s & ~CenterFiles // on a side outpost
+                && !(b & targets)        // no relevant attacks
+                && (!more_than_one(targets & (s & QueenSide ? QueenSide : KingSide))))
                 score += BadOutpost;
             else if (bb & s)
                 score += Outpost[Pt == BISHOP];
@@ -576,17 +579,21 @@ namespace {
     // Bonus for threats on the next moves against enemy queen
     if (pos.count<QUEEN>(Them) == 1)
     {
+        bool queenImbalance = pos.count<QUEEN>() == 1;
+
         Square s = pos.square<QUEEN>(Them);
-        safe = mobilityArea[Us] & ~stronglyProtected;
+        safe =   mobilityArea[Us]
+              & ~pos.pieces(Us, PAWN)
+              & ~stronglyProtected;
 
         b = attackedBy[Us][KNIGHT] & attacks_bb<KNIGHT>(s);
 
-        score += KnightOnQueen * popcount(b & safe);
+        score += KnightOnQueen * popcount(b & safe) * (1 + queenImbalance);
 
         b =  (attackedBy[Us][BISHOP] & attacks_bb<BISHOP>(s, pos.pieces()))
            | (attackedBy[Us][ROOK  ] & attacks_bb<ROOK  >(s, pos.pieces()));
 
-        score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]);
+        score += SliderOnQueen * popcount(b & safe & attackedBy2[Us]) * (1 + queenImbalance);
     }
 
     if (T)
@@ -786,7 +793,7 @@ namespace {
                 && pos.non_pawn_material(BLACK) == RookValueMg
                 && pos.count<PAWN>(strongSide) - pos.count<PAWN>(~strongSide) <= 1
                 && bool(KingSide & pos.pieces(strongSide, PAWN)) != bool(QueenSide & pos.pieces(strongSide, PAWN))
-                && (attackedBy[~strongSide][KING] & pos.pieces(~strongSide, PAWN)))
+                && (attacks_bb<KING>(pos.square<KING>(~strongSide)) & pos.pieces(~strongSide, PAWN)))
             sf = 36;
         else if (pos.count<QUEEN>() == 1)
             sf = 37 + 3 * (pos.count<QUEEN>(WHITE) == 1 ? pos.count<BISHOP>(BLACK) + pos.count<KNIGHT>(BLACK)
@@ -837,9 +844,12 @@ namespace {
     score += pe->pawn_score(WHITE) - pe->pawn_score(BLACK);
 
     // Early exit if score is high
-    Value v = (mg_value(score) + eg_value(score)) / 2;
-    if (abs(v) > LazyThreshold + pos.non_pawn_material() / 64)
-       return pos.side_to_move() == WHITE ? v : -v;
+    auto lazy_skip = [&](Value lazyThreshold) {
+        return abs(mg_value(score) + eg_value(score)) / 2 > lazyThreshold + pos.non_pawn_material() / 64;
+    };
+
+    if (lazy_skip(LazyThreshold1))
+        goto make_v;
 
     // Main evaluation begins here
     initialize<WHITE>();
@@ -856,12 +866,17 @@ namespace {
 
     // More complex interactions that require fully populated attack bitboards
     score +=  king<   WHITE>() - king<   BLACK>()
-            + threats<WHITE>() - threats<BLACK>()
-            + passed< WHITE>() - passed< BLACK>()
+            + passed< WHITE>() - passed< BLACK>();
+
+    if (lazy_skip(LazyThreshold2))
+        goto make_v;
+
+    score +=  threats<WHITE>() - threats<BLACK>()
             + space<  WHITE>() - space<  BLACK>();
 
+make_v:
     // Derive single value from mg and eg parts of score
-    v = winnable(score);
+    Value v = winnable(score);
 
     // In case of tracing add all remaining individual evaluation terms
     if (T)