From: Gary Linscott <glinscott@gmail.com>
Date: Thu, 22 Mar 2012 11:33:47 +0000 (-0400)
Subject: Penalty for undefended rook as well
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=f41a21fefd3ceadc6d17205573e6fd4fd805a4c5;hp=d4c9abb9675586c680433f498f12551fec4e4ecd

Penalty for undefended rook as well
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 2903c4b3..c03aa99f 100644
--- 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
@@ -682,13 +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 += single_bit(undefended) ? UndefendedMinorPenalty
-                                        : UndefendedMinorPenalty * 2;
+    // 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)