Simplify backward pawn scoring

STC

LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 52322 W: 10011 L: 9945 D: 32366

LTC

LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 14143 W: 2334 L: 2203 D: 9606

Bench: 7976423

Resolves #354

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 6236c216df9f29379553dedca2b204bc919c6380..8e3e7815ec60bdf8193979a015fc57abfb645db1 100644 (file)
--- 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, 56), S(49, 40) };
 
   // Connected pawn bonus by opposed, phalanx, twice supported and rank
   Score Connected[2][2][2][RANK_NB];
@@ -182,7 +178,7 @@ namespace {
             score -= Isolated[opposed][f];
 
         else if (backward)
-            score -= Backward[opposed][f];
+            score -= Backward[opposed];
 
         else if (!supported)
             score -= UnsupportedPawnPenalty;