X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fevaluate.cpp;h=db08b1c49e22179fee74b556741104ec3c5d1567;hb=dd8a07612843f32d4073135fc9e17b8814aa34a5;hp=1c215dc0d4a19b586189676331751e7e43845c9b;hpb=4350d9e8a6c979c5631d05ecb645834882701e4c;p=stockfish

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 1c215dc0..db08b1c4 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -200,6 +200,7 @@ namespace {
 
   // Bonuses for enemy's safe checks
   const int QueenContactCheckBonus = 6;
+  const int RookContactCheckBonus  = 4;
   const int QueenCheckBonus        = 3;
   const int RookCheckBonus         = 2;
   const int BishopCheckBonus       = 1;
@@ -710,6 +711,24 @@ namespace {
                               * (Them == pos.side_to_move() ? 2 : 1);
         }
 
+        // Analyse enemy's safe rook contact checks. First find undefended
+        // squares around the king attacked by enemy rooks...
+        b = undefended & ei.attackedBy[Them][ROOK] & ~pos.pieces_of_color(Them);
+
+        // Consider only squares where the enemy rook gives check
+        b &= RookPseudoAttacks[ksq];
+
+        if (b)
+        {
+            // ...then remove squares not supported by another enemy piece
+            b &= (  ei.attackedBy[Them][PAWN]   | ei.attackedBy[Them][KNIGHT]
+                  | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][QUEEN]);
+            if (b)
+                attackUnits +=  RookContactCheckBonus
+                              * count_1s_max_15<HasPopCnt>(b)
+                              * (Them == pos.side_to_move() ? 2 : 1);
+        }
+
         // Analyse enemy's safe distance checks for sliders and knights
         safe = ~(pos.pieces_of_color(Them) | ei.attackedBy[Us][0]);