Candidate passed pawns

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 03b422f8b1155252a7a8930eae5e87a5523fc377..fb91afcb7f7aedfde6a4c97c205b0981c92c460a 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -99,8 +99,9 @@ namespace {
     const Square Left  = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
 
     Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
+    Bitboard lever, leverPush, connected;
     Square s;
-    bool opposed, lever, connected, backward;
+    bool opposed, backward;
     Score score = SCORE_ZERO;
     const Square* pl = pos.squares<PAWN>(Us);
     const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];
@@ -129,6 +130,7 @@ namespace {
         opposed    = theirPawns & forward_bb(Us, s);
         stoppers   = theirPawns & passed_pawn_mask(Us, s);
         lever      = theirPawns & pawnAttacksBB[s];
+        leverPush  = theirPawns & pawnAttacksBB[s + Up];
         doubled    = ourPawns   & (s + Up);
         neighbours = ourPawns   & adjacent_files_bb(f);
         phalanx    = neighbours & rank_bb(s);
@@ -153,8 +155,13 @@ namespace {
         }
 
         // Passed pawns will be properly scored in evaluation because we need
-        // full attack info to evaluate them.
-        if (!stoppers && !(ourPawns & forward_bb(Us, s)))
+        // 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)
+            && !(ourPawns & forward_bb(Us, s))
+            && popcount(supported) >= popcount(lever)
+            && popcount(phalanx)   >= popcount(leverPush))
             e->passedPawns[Us] |= s;
 
         // Score this pawn