Linear Protector bonus by distance

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 4351fe2eb7795500b2b44b84c4ffc537f4eb2179..9202c9ed3d861d58c5cda2b45be52b9bb6b2557a 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -174,14 +174,8 @@ namespace {
     S(-20,-12), S( 1, -8), S( 2, 10), S(  9, 10)
   };
 
     S(-20,-12), S( 1, -8), S( 2, 10), S(  9, 10)
   };
 

-  // Protector[PieceType-2][distance] contains a protecting bonus for our king,
-  // indexed by piece type and distance between the piece and the king.
-  const Score Protector[][8] = {
-    { S(0, 0), S( 7, 9), S( 7, 1), S( 1, 5), S(-10,-4), S( -1,-4), S( -7,-3), S(-16,-10) }, // Knight
-    { S(0, 0), S(11, 8), S(-7,-1), S(-1,-2), S( -1,-7), S(-11,-3), S( -9,-1), S(-16, -1) }, // Bishop
-    { S(0, 0), S(10, 0), S(-2, 2), S(-5, 4), S( -6, 2), S(-14,-3), S( -2,-9), S(-12, -7) }, // Rook
-    { S(0, 0), S( 3,-5), S( 2,-5), S(-4, 0), S( -9,-6), S( -4, 7), S(-13,-7), S(-10, -7) }  // Queen
-  };
+  // KingProtector[PieceType-2] * "distance to own king" determines a bonus for each piece.
+  const Score KingProtector[] = {S(-3, -5), S(-4, -3), S(-3, 0), S(-1, 1) };

 
   // Assorted bonuses and penalties used by evaluation
   const Score MinorBehindPawn     = S( 16,  0);
 
   // Assorted bonuses and penalties used by evaluation
   const Score MinorBehindPawn     = S( 16,  0);


@@ -299,8 +293,7 @@ namespace {
 
         mobility[Us] += MobilityBonus[Pt-2][mob];
 
 
         mobility[Us] += MobilityBonus[Pt-2][mob];
 

-        // Bonus for this piece as a king protector
-        score += Protector[Pt-2][distance(s, pos.square<KING>(Us))];
+        score += KingProtector[Pt-2] * distance(s, pos.square<KING>(Us));

 
         if (Pt == BISHOP || Pt == KNIGHT)
         {
 
         if (Pt == BISHOP || Pt == KNIGHT)
         {