X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fevaluate.cpp;h=c03aa99f51940f0f0ec96fcbc7dce8b5ec9b4e69;hp=2193eb6be797805b6aa46a4f510bbc9c14c4a38c;hb=dbe5e28eaa284aeaa4927ddde8a4341200e0e601;hpb=3c6a4bfbed219b220535bcbaaa76636d3f4879e8

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 2193eb6b..c03aa99f 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -167,6 +167,9 @@ namespace {
   // happen in Chess960 games.
   const Score TrappedBishopA1H1Penalty = make_score(100, 100);
 
+  // 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
   // based on how many squares inside this area are safe and available for
@@ -679,12 +682,15 @@ Value do_evaluate(const Position& pos, Value& margin) {
     Bitboard b;
     Score score = SCORE_ZERO;
 
-    // Undefended minors get penalized even if not under attack
-    Bitboard undefended =  pos.pieces(Them)
-                         & (pos.pieces(BISHOP) | pos.pieces(KNIGHT))
-                         & ~ei.attackedBy[Them][0];
-    if (undefended)
-        score += make_score(25, 10) * popcount<Max15>(undefended);
+    // 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
     Bitboard weakEnemies =  pos.pieces(Them)