Simplify move_importance(): take 3

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 7d57dddbe6e62a4701a8bc3c461ad6e84e2056e4..13bc515f4cfa4d7df9fb683dae637bde8b5581d1 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -150,11 +150,8 @@ namespace {
   // Threat[attacking][attacked] contains bonuses according to which piece
   // type attacks which one.
   const Score Threat[][PIECE_TYPE_NB] = {
-    {}, {},
-    { S(0, 0), S( 7, 39), S( 0,  0), S(24, 49), S(41,100), S(41,100) }, // KNIGHT
-    { S(0, 0), S( 7, 39), S(24, 49), S( 0,  0), S(41,100), S(41,100) }, // BISHOP
-    { S(0, 0), S( 0, 22), S(15, 49), S(15, 49), S( 0,  0), S(24, 49) }, // ROOK
-    { S(0, 0), S(15, 39), S(15, 39), S(15, 39), S(15, 39), S( 0,  0) }  // QUEEN
+    { S(0, 0), S( 7, 39), S(24, 49), S(24, 49), S(41,100), S(41,100) }, // Minor
+    { S(0, 0), S(15, 39), S(15, 45), S(15, 45), S(15, 45), S(24, 49) }, // Major
   };
 
   // ThreatenedByPawn[PieceType] contains a penalty according to which piece
@@ -166,7 +163,6 @@ namespace {
   #undef S
 
   const Score Tempo            = make_score(24, 11);
-  const Score BishopPin        = make_score(66, 11);
   const Score RookOn7th        = make_score(11, 20);
   const Score QueenOn7th       = make_score( 3,  8);
   const Score RookOnPawn       = make_score(10, 28);
@@ -210,19 +206,6 @@ namespace {
   const int BishopCheck       = 2;
   const int KnightCheck       = 3;
 
-  // KingExposed[Square] contains penalties based on the position of the
-  // defending king, indexed by king's square (from white's point of view).
-  const int KingExposed[] = {
-     2,  0,  2,  5,  5,  2,  0,  2,
-     2,  2,  4,  8,  8,  4,  2,  2,
-     7, 10, 12, 12, 12, 12, 10,  7,
-    15, 15, 15, 15, 15, 15, 15, 15,
-    15, 15, 15, 15, 15, 15, 15, 15,
-    15, 15, 15, 15, 15, 15, 15, 15,
-    15, 15, 15, 15, 15, 15, 15, 15,
-    15, 15, 15, 15, 15, 15, 15, 15
-  };
-
   // KingDanger[Color][attackUnits] contains the actual king danger weighted
   // scores, indexed by color and by a calculated integer number.
   Score KingDanger[COLOR_NB][128];
@@ -437,7 +420,7 @@ Value do_evaluate(const Position& pos) {
     {
         ei.kingRing[Them] = b | shift_bb<Down>(b);
         b &= ei.attackedBy[Us][PAWN];
-        ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) / 2 : 0;
+        ei.kingAttackersCount[Us] = b ? popcount<Max15>(b) : 0;
         ei.kingAdjacentZoneAttacksCount[Us] = ei.kingAttackersWeight[Us] = 0;
     }
     else
@@ -517,13 +500,6 @@ Value do_evaluate(const Position& pos) {
         if (ei.attackedBy[Them][PAWN] & s)
             score -= ThreatenedByPawn[Piece];
 
-        // Otherwise give a bonus if we are a bishop and can pin a piece or can
-        // give a discovered check through an x-ray attack.
-        else if (    Piece == BISHOP
-                 && (PseudoAttacks[Piece][pos.king_square(Them)] & s)
-                 && !more_than_one(BetweenBB[s][pos.king_square(Them)] & pos.pieces()))
-                 score += BishopPin;
-
         // Penalty for bishop with same coloured pawns
         if (Piece == BISHOP)
             score -= BishopPawns * ei.pi->pawns_on_same_color_squares(Us, s);
@@ -643,8 +619,7 @@ Value do_evaluate(const Position& pos) {
     Score score = ei.pi->king_safety<Us>(pos, ksq);
 
     // Main king safety evaluation
-    if (   ei.kingAttackersCount[Them] >= 2
-        && ei.kingAdjacentZoneAttacksCount[Them])
+    if (ei.kingAttackersCount[Them])
     {
         // Find the attacked squares around the king which have no defenders
         // apart from the king itself
@@ -657,11 +632,10 @@ Value do_evaluate(const Position& pos) {
         // Initialize the 'attackUnits' variable, which is used later on as an
         // index to the KingDanger[] array. The initial value is based on the
         // number and types of the enemy's attacking pieces, the number of
-        // attacked and undefended squares around our king, the square of the
-        // king, and the quality of the pawn shelter.
+        // attacked and undefended squares around our king and the quality of
+        // the pawn shelter (current 'score' value).
         attackUnits =  std::min(20, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2)
                      + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount<Max15>(undefended))
-                     + KingExposed[relative_square(Us, ksq)]
                      - mg_value(score) / 32;
 
         // Analyse the enemy's safe queen contact checks. Firstly, find the
@@ -762,18 +736,17 @@ Value do_evaluate(const Position& pos) {
                  & ~ei.attackedBy[Them][PAWN]
                  & ei.attackedBy[Us][ALL_PIECES];
 
-    // Add bonus according to type of attacked enemy piece and to the
-    // type of attacking piece, from knights to queens. Kings are not
-    // considered because they are already handled in king evaluation.
+    // Add a bonus according if the attacking pieces are minor or major
     if (weakEnemies)
-        for (PieceType pt1 = KNIGHT; pt1 < KING; ++pt1)
-        {
-            b = ei.attackedBy[Us][pt1] & weakEnemies;
-            if (b)
-                for (PieceType pt2 = PAWN; pt2 < KING; ++pt2)
-                    if (b & pos.pieces(pt2))
-                        score += Threat[pt1][pt2];
-        }
+    {
+        b = weakEnemies & (ei.attackedBy[Us][KNIGHT] | ei.attackedBy[Us][BISHOP]);
+        if (b)
+            score += Threat[0][type_of(pos.piece_on(lsb(b)))];
+
+        b = weakEnemies & (ei.attackedBy[Us][ROOK] | ei.attackedBy[Us][QUEEN]);
+        if (b)
+            score += Threat[1][type_of(pos.piece_on(lsb(b)))];
+    }
 
     if (Trace)
         Tracing::scores[Us][THREAT] = score;