X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=ee46279d8957a757f0877421c003c6df2b2020e5;hp=5290efb2c70c2eb4fcd72cfe60ff774ced77000a;hb=4502a1934f2d624288b635b5901ecda8cefa342c;hpb=8463fa479ee2841f852fdf57374b08c87b61e227

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 5290efb2..ee46279d 100644
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -43,12 +43,8 @@ namespace {
   { S(25, 30), S(36, 35), S(40, 35), S(40, 35),
     S(40, 35), S(40, 35), S(36, 35), S(25, 30) } };
 
-  // Backward pawn penalty by opposed flag and file
-  const Score Backward[2][FILE_NB] = {
-  { S(50, 52), S(63, 56), S(69, 56), S(69, 56),
-    S(69, 56), S(69, 56), S(63, 56), S(50, 52) },
-  { S(40, 38), S(49, 41), S(53, 41), S(53, 41),
-    S(53, 41), S(53, 41), S(49, 41), S(40, 38) } };
+  // Backward pawn penalty by opposed flag
+  const Score Backward[2] = { S(67, 42), S(49, 24) };
 
   // Connected pawn bonus by opposed, phalanx, twice supported and rank
   Score Connected[2][2][2][RANK_NB];
@@ -151,9 +147,10 @@ namespace {
         // Test for backward pawn.
         // If the pawn is passed, isolated, lever or connected it cannot be
         // backward. If there are friendly pawns behind on adjacent files
-        // it cannot be backward either.
+        // or if it is sufficiently advanced, it cannot be backward either.
         if (   (passed | isolated | lever | connected)
-            || (ourPawns & pawn_attack_span(Them, s)))
+            || (ourPawns & pawn_attack_span(Them, s))
+            || (relative_rank(Us, s) >= RANK_5))
             backward = false;
         else
         {
@@ -180,17 +177,19 @@ namespace {
         // Score this pawn
         if (isolated)
             score -= Isolated[opposed][f];
+
         else if (backward)
-            score -= Backward[opposed][f];
+            score -= Backward[opposed];
+
         else if (!supported)
             score -= UnsupportedPawnPenalty;
 
         if (connected)
             score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)];
- 
+
         if (doubled)
             score -= Doubled[f] / distance<Rank>(s, frontmost_sq(Us, doubled));
-                    
+
         if (lever)
             score += Lever[relative_rank(Us, s)];
     }