tviigg. (#2238)

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index acc3d77096dd10f79742c4be15e69d2baa76fa9c..0d3a57bfa6eabb2866ad6c6a6f60a36d6acdc10f 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -32,11 +32,11 @@ namespace {
   #define S(mg, eg) make_score(mg, eg)
 
   // Pawn penalties
-  constexpr Score Backward = S( 9, 24);
-  constexpr Score Doubled  = S(11, 56);
-  constexpr Score Isolated = S( 5, 15);
-  constexpr Score WeakUnopposed = S( 13, 27);
-  constexpr Score Attacked2Unsupported = S( 0, 20);
+  constexpr Score Backward      = S( 9, 24);
+  constexpr Score Doubled       = S(11, 56);
+  constexpr Score Isolated      = S( 5, 15);
+  constexpr Score WeakUnopposed = S(13, 27);
+  constexpr Score Attacked2Unsupported = S(0, 56);
 
   // Connected pawn bonus
   constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
@@ -84,11 +84,6 @@ namespace {
     e->kingSquares[Us] = SQ_NONE;
     e->pawnAttacks[Us] = pawn_attacks_bb<Us>(ourPawns);
 
-    // Unsupported enemy pawns attacked twice by us
-    score += Attacked2Unsupported * popcount(  theirPawns
-                                             & pawn_double_attacks_bb<Us>(ourPawns)
-                                             & ~pawn_attacks_bb<Them>(theirPawns));
-
     // Loop through all pawns of the current color and score each pawn
     while ((s = *pl++) != SQ_NONE)
     {
@@ -108,17 +103,18 @@ namespace {
         phalanx    = neighbours & rank_bb(s);
         support    = neighbours & rank_bb(s - Up);
 
-        // A pawn is backward when it is behind all pawns of the same color
-        // on the adjacent files and cannot be safely advanced.
-        backward =  !(ourPawns & pawn_attack_span(Them, s + Up))
+        // A pawn is backward when it is behind all pawns of the same color on
+        // the adjacent files and cannot safely advance. Phalanx and isolated
+        // pawns will be excluded when the pawn is scored.
+        backward =  !(neighbours & forward_ranks_bb(Them, s))
                   && (stoppers & (leverPush | (s + Up)));
 
         // Passed pawns will be properly scored in evaluation because we need
         // full attack info to evaluate them. Include also not passed pawns
-        // which could become passed after one or two pawn pushes when are
-        // not attacked more times than defended.
-        if (   !(stoppers ^ lever) ||
-              (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush)))
+        // which could become passed after one or two pawn pushes when they
+        // are not attacked more times than defended.
+        if ( !(stoppers ^ lever) ||
+            (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush)))
             e->passedPawns[Us] |= s;
 
         else if (stoppers == square_bb(s + Up) && r >= RANK_5)
@@ -137,6 +133,7 @@ namespace {
 
             score += make_score(v, v * (r - 2) / 4);
         }
+
         else if (!neighbours)
             score -= Isolated + WeakUnopposed * int(!opposed);
 
@@ -147,6 +144,12 @@ namespace {
             score -= Doubled;
     }
 
+    // Unsupported friendly pawns attacked twice by the enemy
+    score -= Attacked2Unsupported * popcount(  ourPawns
+                                             & pawn_double_attacks_bb<Them>(theirPawns)
+                                             & ~pawn_attacks_bb<Us>(ourPawns)
+                                             & ~e->passedPawns[Us]);
+
     return score;
   }