Merge Gary's bishop_pin patch
[stockfish] / src / evaluate.cpp
index 5140c4932ab022ab53b94268188363b4404eba4b..3ba405ccf28ff378192bed7b905ef1fc9f9686c9 100644 (file)
@@ -150,6 +150,8 @@ namespace {
 
   #undef S
 
+  const Score BishopPinBonus = make_score(66, 11);
+
   // Bonus for having the side to move (modified by Joona Kiiski)
   const Score Tempo = make_score(24, 11);
 
@@ -577,23 +579,18 @@ Value do_evaluate(const Position& pos, Value& margin) {
 
         mobility += MobilityBonus[Piece][mob];
 
-        // Add a bonus if a slider is pinning an enemy piece
-        if (   (Piece == BISHOP || Piece == ROOK || Piece == QUEEN)
-            && (PseudoAttacks[Piece][pos.king_square(Them)] & s))
-        {
-            b = BetweenBB[s][pos.king_square(Them)] & pos.pieces();
-
-            assert(b);
-
-            if (!more_than_one(b) && (b & pos.pieces(Them)))
-                score += ThreatBonus[Piece][type_of(pos.piece_on(lsb(b)))];
-        }
-
         // Decrease score if we are attacked by an enemy pawn. Remaining part
         // of threat evaluation must be done later when we have full attack info.
         if (ei.attackedBy[Them][PAWN] & s)
             score -= ThreatenedByPawnPenalty[Piece];
 
+        // Otherwise give a bonus if we are a bishop and can pin a piece or
+        // can give a discovered check through an x-ray attack.
+        else if (    Piece == BISHOP
+                 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
+                 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
+                 score += BishopPinBonus;
+
         // Bishop and knight outposts squares
         if (    (Piece == BISHOP || Piece == KNIGHT)
             && !(pos.pieces(Them, PAWN) & attack_span_mask(Us, s)))
@@ -699,8 +696,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
                       & ~ei.attackedBy[Them][0];
 
     if (undefendedMinors)
-        score += more_than_one(undefendedMinors) ? UndefendedMinorPenalty * 2
-                                                 : UndefendedMinorPenalty;
+        score += UndefendedMinorPenalty;
 
     // Enemy pieces not defended by a pawn and under our attack
     weakEnemies =  pos.pieces(Them)