Tidy up on Overload

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 69c3278556ab856026f556b49ec9614680fd5a1e..1505bf67facd53bcd028eac73d795b25d49ee8af 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -171,6 +171,7 @@ namespace {
   constexpr Score KnightOnQueen      = S( 21, 11);
   constexpr Score LongDiagonalBishop = S( 22,  0);
   constexpr Score MinorBehindPawn    = S( 16,  0);
+  constexpr Score Overload           = S( 10,  5);
   constexpr Score PawnlessFlank      = S( 20, 80);
   constexpr Score RookOnPawn         = S(  8, 24);
   constexpr Score SliderOnQueen      = S( 42, 21);
@@ -300,6 +301,7 @@ namespace {
     Bitboard b, bb;
     Square s;
     Score score = SCORE_ZERO;
+    int mob;
 
     attackedBy[Us][Pt] = 0;
 
@@ -324,7 +326,8 @@ namespace {
             kingAttacksCount[Us] += popcount(b & attackedBy[Them][KING]);
         }
 
-        int mob = popcount(b & mobilityArea[Us]);
+        mob = (Pt == KNIGHT || Pt == BISHOP) ? popcount(b & mobilityArea[Us] & ~pos.pieces(Us, QUEEN))
+                                             : popcount(b & mobilityArea[Us]);
 
         mobility[Us] += MobilityBonus[Pt - 2][mob];
 
@@ -373,7 +376,7 @@ namespace {
 
         if (Pt == ROOK)
         {
-            // Bonus for aligning rook with with enemy pawns on the same rank/file
+            // Bonus for aligning rook with enemy pawns on the same rank/file
             if (relative_rank(Us, s) >= RANK_5)
                 score += RookOnPawn * popcount(pos.pieces(Them, PAWN) & PseudoAttacks[ROOK][s]);
 
@@ -518,19 +521,8 @@ namespace {
     Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
     Score score = SCORE_ZERO;
 
-    // Non-pawn enemies attacked by a pawn
+    // Non-pawn enemies
     nonPawnEnemies = pos.pieces(Them) ^ pos.pieces(Them, PAWN);
-    weak = nonPawnEnemies & attackedBy[Us][PAWN];
-
-    if (weak)
-    {
-        // Our safe or protected pawns
-        b =  pos.pieces(Us, PAWN)
-           & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
-
-        safeThreats = pawn_attacks_bb<Us>(b) & weak;
-        score += ThreatBySafePawn * popcount(safeThreats);
-    }
 
     // Squares strongly protected by the enemy, either because they defend the
     // square with a pawn, or because they defend the square twice and we don't.
@@ -564,17 +556,30 @@ namespace {
                 score += ThreatByRank * (int)relative_rank(Them, s);
         }
 
-        score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
-
         b = weak & attackedBy[Us][KING];
         if (b)
             score += ThreatByKing[more_than_one(b)];
+
+        score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
+
+        // Bonus for overload (non-pawn enemies attacked and defended exactly once)
+        b =  nonPawnEnemies
+           & attackedBy[Us][ALL_PIECES]   & ~attackedBy2[Us]
+           & attackedBy[Them][ALL_PIECES] & ~attackedBy2[Them];
+        score += Overload * popcount(b);
     }
 
     // Bonus for enemy unopposed weak pawns
     if (pos.pieces(Us, ROOK, QUEEN))
         score += WeakUnopposedPawn * pe->weak_unopposed(Them);
 
+    // Our safe or protected pawns
+    b =   pos.pieces(Us, PAWN)
+       & (~attackedBy[Them][ALL_PIECES] | attackedBy[Us][ALL_PIECES]);
+
+    safeThreats = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
+    score += ThreatBySafePawn * popcount(safeThreats);
+
     // Find squares where our pawns can push on the next move
     b  = shift<Up>(pos.pieces(Us, PAWN)) & ~pos.pieces();
     b |= shift<Up>(b & TRank3BB) & ~pos.pieces();
@@ -692,7 +697,7 @@ namespace {
             }
             else if (pos.pieces(Us) & blockSq)
                 bonus += make_score(w + r * 2, w + r * 2);
-        } // rr != 0
+        } // w != 0
 
         // Scale down bonus for candidate passers which need more than one
         // pawn push to become passed or have a pawn in front of them.
@@ -733,8 +738,7 @@ namespace {
     // pawn, or if it is undefended and attacked by an enemy piece.
     Bitboard safe =   SpaceMask
                    & ~pos.pieces(Us, PAWN)
-                   & ~attackedBy[Them][PAWN]
-                   & (attackedBy[Us][ALL_PIECES] | ~attackedBy[Them][ALL_PIECES]);
+                   & ~attackedBy[Them][PAWN];
 
     // Find all squares which are at most three squares behind some friendly pawn
     Bitboard behind = pos.pieces(Us, PAWN);
@@ -800,11 +804,10 @@ namespace {
     {
         if (pos.opposite_bishops())
         {
-            // Endgame with opposite-colored bishops and no other pieces (ignoring pawns)
-            // is almost a draw, in case of KBP vs KB, it is even more a draw.
+            // Endgame with opposite-colored bishops and no other pieces is almost a draw
             if (   pos.non_pawn_material(WHITE) == BishopValueMg
                 && pos.non_pawn_material(BLACK) == BishopValueMg)
-                sf = more_than_one(pos.pieces(PAWN)) ? 31 : 9;
+                sf = 31;
 
             // Endgame with opposite-colored bishops, but also other pieces. Still
             // a bit drawish, but not as drawish as with only the two bishops.