Raise penalty for knight attacked by pawn

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 40d59648f2ed10edf6660befbf0c2eb035feec35..c880b7c7845f3c881ba2d7600a662c393e6a9436 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -61,11 +61,11 @@ namespace {
     // KingAttackWeights array.
     int kingAttackersWeight[COLOR_NB];
 
-    // kingAdjacentZoneAttacksCount[color] is the number of attacks to squares
-    // directly adjacent to the king of the given color. Pieces which attack
-    // more than one square are counted multiple times. For instance, if black's
-    // king is on g8 and there's a white knight on g5, this knight adds
-    // 2 to kingAdjacentZoneAttacksCount[BLACK].
+    // kingAdjacentZoneAttacksCount[color] is the number of attacks by the given
+    // color to squares directly adjacent to the enemy king. Pieces which attack
+    // more than one square are counted multiple times. For instance, if there is
+    // a white knight on g5 and black's king is on g8, this white knight adds 2
+    // to kingAdjacentZoneAttacksCount[WHITE].
     int kingAdjacentZoneAttacksCount[COLOR_NB];
 
     Bitboard pinnedPieces[COLOR_NB];
@@ -148,7 +148,7 @@ namespace {
   // ThreatenedByPawn[PieceType] contains a penalty according to which piece
   // type is attacked by an enemy pawn.
   const Score ThreatenedByPawn[] = {
-    S(0, 0), S(0, 0), S(87, 118), S(84, 122), S(114, 203), S(121, 217)
+    S(0, 0), S(0, 0), S(107, 138), S(84, 122), S(114, 203), S(121, 217)
   };
 
   // Assorted bonuses and penalties used by evaluation
@@ -163,6 +163,7 @@ namespace {
   const Score Unstoppable        = S( 0, 20);
   const Score Hanging            = S(31, 26);
   const Score PawnAttackThreat   = S(20, 20);
+  const Score PawnSafePush       = S( 5,  5);
 
   // 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
@@ -413,10 +414,10 @@ namespace {
         // attacked and undefended squares around our king and the quality of
         // the pawn shelter (current 'score' value).
         attackUnits =  std::min(74, ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them])
-                     + 8 * ei.kingAdjacentZoneAttacksCount[Them]
+                     +  8 * ei.kingAdjacentZoneAttacksCount[Them]
                      + 25 * popcount<Max15>(undefended)
-                     +  11 * (ei.pinnedPieces[Us] != 0)
-                     - mg_value(score) * 31 / 256
+                     + 11 * (ei.pinnedPieces[Us] != 0)
+                     - mg_value(score) / 8
                      - !pos.count<QUEEN>(Them) * 60;
 
         // Analyse the enemy's safe queen contact checks. Firstly, find the
@@ -547,14 +548,18 @@ namespace {
             score += more_than_one(b) ? KingOnMany : KingOnOne;
     }
 
-    // Add bonus for safe pawn pushes which attacks an enemy piece
+    // Add a small bonus for safe pawn pushes
     b = pos.pieces(Us, PAWN) & ~TRank7BB;
     b = shift_bb<Up>(b | (shift_bb<Up>(b & TRank2BB) & ~pos.pieces()));
 
     b &=  ~pos.pieces()
         & ~ei.attackedBy[Them][PAWN]
-        & (ei.attackedBy[Us][PAWN] | ~ei.attackedBy[Them][ALL_PIECES]);
+        & (ei.attackedBy[Us][ALL_PIECES] | ~ei.attackedBy[Them][ALL_PIECES]);
 
+    if (b)
+        score += popcount<Full>(b) * PawnSafePush;
+
+    // Add another bonus if the pawn push attacks an enemy piece
     b =  (shift_bb<Left>(b) | shift_bb<Right>(b))
        &  pos.pieces(Them)
        & ~ei.attackedBy[Us][PAWN];
@@ -912,14 +917,14 @@ namespace Eval {
 
   void init() {
 
-    const int MaxSlope = 87;
-    const int Peak = 12800;
+    const int MaxSlope = 8700;
+    const int Peak = 1280000;
     int t = 0;
 
     for (int i = 0; i < 400; ++i)
     {
-        t = std::min(Peak, std::min(i * i * 27 / 100, t + MaxSlope));
-        KingDanger[i] = apply_weight(make_score(t / 10, 0), Weights[KingSafety]);
+        t = std::min(Peak, std::min(i * i * 27, t + MaxSlope));
+        KingDanger[i] = apply_weight(make_score(t / 1000, 0), Weights[KingSafety]);
     }
   }