Fix isolated and backward pawns scoring

It is more clear and also more correct because we
consider enemy pawns only in fornt of us and not just
on our file.

Very small functional change, almost not measurable, but
keep the patch for documenting purposes.

Spotted by Marek Kwiatkowski.

Signed-off-by: Marco Costalba <mcostalba@gmail.com>

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 1cdeb46..34c2595 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -274,7 +274,7 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
       if (isolated)
       {
           value -= IsolatedPawnPenalty[f];
-          if (!(theirPawns & file_bb(f)))
+          if (!opposed)
               value -= IsolatedPawnPenalty[f] / 2;
       }
       if (doubled)
@@ -283,7 +283,7 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns,
       if (backward)
       {
           value -= BackwardPawnPenalty[f];
-          if (!(theirPawns & file_bb(f)))
+          if (!opposed)
               value -= BackwardPawnPenalty[f] / 2;
       }
       if (chain)