Account for double pawn push in evaluate_unstoppable_pawns()

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6c563f72cf1cddf509dfcbb9e2c2f1c145948e88..4987a53122d153e30ec6e87c727ba38e681a9426 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -148,6 +148,10 @@ namespace {
 
   #undef S
 
+  // Threats weights indexed by sente (side to move has a bigger weight)
+  const int ConcurrentThreatsWeight[2] = { 3, 15 };
+  const int ThreatsWeight[2] = { 249, 267 };
+
   // Bonus for unstoppable passed pawns
   const Value UnstoppablePawnValue = Value(0x500);
 
@@ -348,23 +352,23 @@ Value do_evaluate(const Position& pos, EvalInfo& ei, int threadID) {
   // Middle-game specific evaluation terms
   if (phase > PHASE_ENDGAME)
   {
-    // Pawn storms in positions with opposite castling
-    if (   square_file(pos.king_square(WHITE)) >= FILE_E
-        && square_file(pos.king_square(BLACK)) <= FILE_D)
+      // Pawn storms in positions with opposite castling
+      if (   square_file(pos.king_square(WHITE)) >= FILE_E
+          && square_file(pos.king_square(BLACK)) <= FILE_D)
 
-        ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
+          ei.value += make_score(ei.pi->queenside_storm_value(WHITE) - ei.pi->kingside_storm_value(BLACK), 0);
 
-    else if (   square_file(pos.king_square(WHITE)) <= FILE_D
-             && square_file(pos.king_square(BLACK)) >= FILE_E)
+      else if (   square_file(pos.king_square(WHITE)) <= FILE_D
+               && square_file(pos.king_square(BLACK)) >= FILE_E)
 
-        ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
+          ei.value += make_score(ei.pi->kingside_storm_value(WHITE) - ei.pi->queenside_storm_value(BLACK), 0);
 
-    // Evaluate space for both sides
-    if (ei.mi->space_weight() > 0)
-    {
-        evaluate_space<WHITE, HasPopCnt>(pos, ei);
-        evaluate_space<BLACK, HasPopCnt>(pos, ei);
-    }
+      // Evaluate space for both sides
+      if (ei.mi->space_weight() > 0)
+      {
+          evaluate_space<WHITE, HasPopCnt>(pos, ei);
+          evaluate_space<BLACK, HasPopCnt>(pos, ei);
+      }
   }
 
   // Mobility
@@ -636,6 +640,8 @@ namespace {
     const Color Them = (Us == WHITE ? BLACK : WHITE);
 
     Bitboard b;
+    Value mg, eg;
+    int sente, threatCount = 0;
     Score bonus = make_score(0, 0);
 
     // Enemy pieces not defended by a pawn and under our attack
@@ -654,9 +660,20 @@ namespace {
         if (b)
             for (PieceType pt2 = PAWN; pt2 < KING; pt2++)
                 if (b & pos.pieces(pt2))
+                {
                     bonus += ThreatBonus[pt1][pt2];
+                    threatCount++;
+                }
     }
-    ei.value += Sign[Us] * bonus;
+
+    sente = (Us == pos.side_to_move());
+
+    // Non linear threat evaluation. Increase threats score according to the
+    // number of concurrent threats and to the side to move.
+    mg = (mg_value(bonus) + mg_value(bonus) * ConcurrentThreatsWeight[sente] * threatCount / 256) * ThreatsWeight[sente] / 256;
+    eg = (eg_value(bonus) + eg_value(bonus) * ConcurrentThreatsWeight[sente] * threatCount / 256) * ThreatsWeight[sente] / 256;
+
+    ei.value += Sign[Us] * make_score(mg, eg);
   }
 
 
@@ -820,9 +837,6 @@ namespace {
                 squaresToQueen = squares_in_front_of(Us, s);
                 defendedSquares = squaresToQueen & ei.attacked_by(Us);
 
-                // There are no enemy pawns in the pawn's path
-                assert(!(squaresToQueen & pos.pieces(PAWN, Them)));
-
                 // If there is an enemy rook or queen attacking the pawn from behind,
                 // add all X-ray attacks by the rook or queen. Otherwise consider only
                 // the squares in the pawn's path attacked or occupied by the enemy.
@@ -900,6 +914,7 @@ namespace {
             Square s = pop_1st_bit(&b);
             Square queeningSquare = relative_square(c, make_square(square_file(s), RANK_8));
             int d =  square_distance(s, queeningSquare)
+                   - (relative_rank(c, s) == RANK_2) // Double pawn push
                    - square_distance(pos.king_square(opposite_color(c)), queeningSquare)
                    + int(c != pos.side_to_move());