Merge remote-tracking branch 'upstream/master'

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 9bd403e1bf8ab1100284eec6d27f791f5b3b6bcc..c03aa99f51940f0f0ec96fcbc7dce8b5ec9b4e69 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -167,8 +167,8 @@ namespace {
   // happen in Chess960 games.
   const Score TrappedBishopA1H1Penalty = make_score(100, 100);
 
-  // Penalty for a minor piece that is not defended by anything
-  const Score UndefendedMinorPenalty = make_score(25, 10);
+  // Penalty for BNR that is not defended by anything
+  const Score UndefendedPiecePenalty = make_score(25, 10);
 
   // The SpaceMask[Color] contains the area of the board which is considered
   // by the space evaluation. In the middle game, each side is given a bonus
@@ -682,20 +682,20 @@ Value do_evaluate(const Position& pos, Value& margin) {
     Bitboard b;
     Score score = SCORE_ZERO;
 
-    // Undefended minors get penalized even if not under attack
-    const Bitboard undefended =  pos.pieces(Them)
-                              & (pos.pieces(BISHOP) | pos.pieces(KNIGHT))
-                              & ~ei.attackedBy[Them][0];
-    if (undefended) {
-        score += UndefendedMinorPenalty;
-        if (!single_bit(undefended))
-            score += UndefendedMinorPenalty;
-    }
+    // Undefended pieces get penalized even if not under attack
+    Bitboard undefended = pos.pieces(Them) & ~ei.attackedBy[Them][0];
+    const Bitboard undefendedMinors = undefended & (pos.pieces(BISHOP) | pos.pieces(KNIGHT));
+    
+    if (undefendedMinors)
+        score += single_bit(undefendedMinors) ? UndefendedPiecePenalty
+                                              : UndefendedPiecePenalty * 2;
+    if (undefended & pos.pieces(ROOK))
+        score += UndefendedPiecePenalty;
 
     // Enemy pieces not defended by a pawn and under our attack
-    const Bitboard weakEnemies =  pos.pieces(Them)
-                               & ~ei.attackedBy[Them][PAWN]
-                               & ei.attackedBy[Us][0];
+    Bitboard weakEnemies =  pos.pieces(Them)
+                          & ~ei.attackedBy[Them][PAWN]
+                          & ei.attackedBy[Us][0];
     if (!weakEnemies)
         return score;