Add a penalty for low mobility pieces

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index e96e635c876f44901a456b41189c98eddbcb85e9..9c5c12b8b7003c62d31d66064f2840bf1355cece 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -171,6 +171,7 @@ namespace {
   const Score UndefendedMinor  = make_score(25, 10);
   const Score TrappedRook      = make_score(90,  0);
   const Score Unstoppable      = make_score( 0, 20);
+  const Score LowMobPenalty    = make_score(40, 20);
 
   // Penalty for a bishop on a1/h1 (a8/h8 for black) which is trapped by
   // a friendly pawn on b2/g2 (b7/g7 for black). This can obviously only
@@ -186,6 +187,8 @@ namespace {
     (FileCBB | FileDBB | FileEBB | FileFBB) & (Rank7BB | Rank6BB | Rank5BB)
   };
 
+  const Bitboard EdgeBB = Rank1BB | Rank8BB | FileABB | FileHBB;
+
   // King danger constants and variables. The king danger scores are taken
   // from KingDanger[]. Various little "meta-bonuses" measuring the strength
   // of the enemy attack are added up into an integer, which is used as an
@@ -491,6 +494,9 @@ Value do_evaluate(const Position& pos) {
 
         mobility[Us] += MobilityBonus[Pt][mob];
 
+        if (mob <= 1 && (EdgeBB & s))
+            score -= LowMobPenalty;
+
         // Decrease score if we are attacked by an enemy pawn. The remaining part
         // of threat evaluation must be done later when we have full attack info.
         if (ei.attackedBy[Them][PAWN] & s)