Simplify ThreatByKing to be a single Score.

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index de9574fba5611be5d3282490ea42c3b3b6cba80f..ef69ee6cc1b47c921f6ccf89271cd21333dd2bcc 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -140,10 +140,6 @@ namespace {
     S(0, 0), S(0, 24), S(38, 71), S(38, 61), S(0, 38), S(36, 38)
   };
 
-  // ThreatByKing[on one/on many] contains bonuses for king attacks on
-  // pawns or pieces which are not pawn-defended.
-  constexpr Score ThreatByKing[] = { S(30, 62), S(-9, 160) };
-
   // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
   constexpr Score PassedRank[RANK_NB] = {
     S(0, 0), S(4, 17), S(7, 20), S(14, 36), S(42, 62), S(165, 171), S(279, 252)
@@ -158,8 +154,8 @@ namespace {
   // PassedDanger[Rank] contains a term to weight the passed score
   constexpr int PassedDanger[RANK_NB] = { 0, 0, 0, 2, 7, 12, 19 };
 
-  // KingProtector[PieceType-2] contains a penalty according to distance from king
-  constexpr Score KingProtector[] = { S(4, 6), S(6, 3), S(1, 0), S(0, -2) };
+  // KingProtector[knight/bishop] contains a penalty according to distance from king
+  constexpr Score KingProtector[] = { S(4, 6), S(6, 3) };
 
   // Assorted bonuses and penalties
   constexpr Score BishopPawns        = S(  3,  5);
@@ -175,6 +171,7 @@ namespace {
   constexpr Score PawnlessFlank      = S( 20, 80);
   constexpr Score RookOnPawn         = S(  8, 24);
   constexpr Score SliderOnQueen      = S( 42, 21);
+  constexpr Score ThreatByKing       = S( 31, 75);
   constexpr Score ThreatByPawnPush   = S( 49, 30);
   constexpr Score ThreatByRank       = S( 16,  3);
   constexpr Score ThreatBySafePawn   = S(165,133);
@@ -330,9 +327,6 @@ namespace {
 
         mobility[Us] += MobilityBonus[Pt - 2][mob];
 
-        // Penalty if the piece is far from the king
-        score -= KingProtector[Pt - 2] * distance(s, pos.square<KING>(Us));
-
         if (Pt == BISHOP || Pt == KNIGHT)
         {
             // Bonus if piece is on an outpost square or can reach one
@@ -348,6 +342,9 @@ namespace {
                 && (pos.pieces(PAWN) & (s + pawn_push(Us))))
                 score += MinorBehindPawn;
 
+            // Penalty if the piece is far from the king
+            score -= KingProtector[Pt == BISHOP] * distance(s, pos.square<KING>(Us));
+
             if (Pt == BISHOP)
             {
                 // Penalty according to number of pawns on the same color square as the
@@ -558,9 +555,9 @@ namespace {
                 score += ThreatByRank * (int)relative_rank(Them, s);
         }
 
-        b = weak & attackedBy[Us][KING];
-        if (b)
-            score += ThreatByKing[more_than_one(b)];
+        // Bonus for king attacks on pawns or pieces which are not pawn-defended
+        if (weak & attackedBy[Us][KING])
+            score += ThreatByKing;
 
         score += Hanging * popcount(weak & ~attackedBy[Them][ALL_PIECES]);
 
@@ -647,7 +644,7 @@ namespace {
 
         assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
 
-        bb = forward_file_bb(Us, s) & (attackedBy[Them][ALL_PIECES] | pos.pieces(Them));
+        bb = forward_file_bb(Us, s) & pos.pieces(Them);
         score -= HinderPassedPawn * popcount(bb);
 
         int r = relative_rank(Us, s);