X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fevaluate.cpp;h=2903c4b375da81736478ee3fb6439e6f2f749c08;hp=5e3a3ff24daf28de218928466d85de70c87d8243;hb=d4c9abb9675586c680433f498f12551fec4e4ecd;hpb=4220f191d8c1d597ff66e41f90af11367b0ebd7f

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 5e3a3ff2..2903c4b3 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 a minor piece that is not defended by anything
+  const Score UndefendedMinorPenalty = 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
@@ -547,9 +550,9 @@ Value do_evaluate(const Position& pos, Value& margin) {
         if (Piece == KNIGHT || Piece == QUEEN)
             b = pos.attacks_from<Piece>(s);
         else if (Piece == BISHOP)
-            b = attacks_bb<BISHOP>(s, pos.occupied_squares() & ~pos.pieces(QUEEN, Us));
+            b = attacks_bb<BISHOP>(s, pos.pieces() ^ pos.pieces(QUEEN, Us));
         else if (Piece == ROOK)
-            b = attacks_bb<ROOK>(s, pos.occupied_squares() & ~pos.pieces(ROOK, QUEEN, Us));
+            b = attacks_bb<ROOK>(s, pos.pieces() ^ pos.pieces(ROOK, QUEEN, Us));
         else
             assert(false);
 
@@ -573,7 +576,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
         if (   (Piece == BISHOP || Piece == ROOK || Piece == QUEEN)
             && (PseudoAttacks[Piece][pos.king_square(Them)] & s))
         {
-            b = BetweenBB[s][pos.king_square(Them)] & pos.occupied_squares();
+            b = BetweenBB[s][pos.king_square(Them)] & pos.pieces();
 
             assert(b);
 
@@ -679,12 +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
+    Bitboard undefended =  pos.pieces(Them)
+                         & (pos.pieces(BISHOP) | pos.pieces(KNIGHT))
+                         & ~ei.attackedBy[Them][0];
+    if (undefended)
+        score += single_bit(undefended) ? UndefendedMinorPenalty
+                                        : UndefendedMinorPenalty * 2;
+
     // Enemy pieces not defended by a pawn and under our attack
     Bitboard weakEnemies =  pos.pieces(Them)
                           & ~ei.attackedBy[Them][PAWN]
                           & ei.attackedBy[Us][0];
     if (!weakEnemies)
-        return SCORE_ZERO;
+        return score;
 
     // Add bonus according to type of attacked enemy piece and to the
     // type of attacking piece, from knights to queens. Kings are not
@@ -977,7 +988,7 @@ Value do_evaluate(const Position& pos, Value& margin) {
             // Opponent king cannot block because path is defended and position
             // is not in check. So only friendly pieces can be blockers.
             assert(!pos.in_check());
-            assert((queeningPath & pos.occupied_squares()) == (queeningPath & pos.pieces(c)));
+            assert((queeningPath & pos.pieces()) == (queeningPath & pos.pieces(c)));
 
             // Add moves needed to free the path from friendly pieces and retest condition
             movesToGo += popcount<Max15>(queeningPath & pos.pieces(c));