Bonus for double attacks on unsupported pawns

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 2b4f039ecf334857702fefd7edf2952aefcad675..5474850494cbb98036b2c307e172791b3ca3f099 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -36,6 +36,7 @@ namespace {
   constexpr Score Doubled  = S(11, 56);
   constexpr Score Isolated = S( 5, 15);
   constexpr Score WeakUnopposed = S( 13, 27);
+  constexpr Score Attacked2Unsupported = S( 0, 20);
 
   // Connected pawn bonus
   constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
@@ -79,8 +80,13 @@ namespace {
     Bitboard theirPawns = pos.pieces(Them, PAWN);
 
     e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0;
-    e->kingSquares[Us]   = SQ_NONE;
-    e->pawnAttacks[Us]   = pawn_attacks_bb<Us>(ourPawns);
+    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)
@@ -110,9 +116,8 @@ namespace {
         // 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 ^ leverPush)
-            && (support || !more_than_one(lever))
-            && popcount(phalanx) >= popcount(leverPush))
+        if (   !(stoppers ^ lever) ||
+              (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush)))
             e->passedPawns[Us] |= s;
 
         else if (stoppers == square_bb(s + Up) && r >= RANK_5)
@@ -191,7 +196,7 @@ void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) {
   for (File f = File(center - 1); f <= File(center + 1); ++f)
   {
       b = ourPawns & file_bb(f);
-      Rank ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1;
+      Rank ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;
 
       b = theirPawns & file_bb(f);
       Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1;