Bishop Pawns based on Files

Passed STC:
https://tests.stockfishchess.org/tests/view/5f8cc8145a4eacb45305da3c
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 132544 W: 27795 L: 27328 D: 77421
Ptnml(0-2): 2756, 15558, 29272, 15835, 2851

Passed LTC:
https://tests.stockfishchess.org/tests/view/5f8df614bacb75a4f9a4721e
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 169608 W: 23257 L: 22622 D: 123729
Ptnml(0-2): 1408, 16316, 48758, 16877, 1445

closes https://github.com/official-stockfish/Stockfish/pull/3194

Bench: 4067106

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 425ba6f8faead8b61e22d6713d815c5d3624b962..030d10175790190033a41be8ba67b35f2c0fe176 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -222,6 +222,12 @@ namespace {
       S(112,178), S(114,185), S(114,187), S(119,221) }
   };
 
+  // BishopPawns[distance from edge] contains a file-dependent penalty for pawns on
+  // squares of the same color as our bishop.
+  constexpr Score BishopPawns[int(FILE_NB) / 2] = {
+    S(3, 8), S(3, 9), S(1, 8), S(3, 7)
+  };
+
   // KingProtector[knight/bishop] contains penalty for each distance unit to own king
   constexpr Score KingProtector[] = { S(8, 9), S(6, 9) };
 
@@ -252,7 +258,6 @@ namespace {
   // Assorted bonuses and penalties
   constexpr Score BadOutpost          = S( -7, 36);
   constexpr Score BishopOnKingRing    = S( 24,  0);
-  constexpr Score BishopPawns         = S(  3,  7);
   constexpr Score BishopXRayPawns     = S(  4,  5);
   constexpr Score CorneredBishop      = S( 50, 50);
   constexpr Score FlankAttacks        = S(  8,  0);
@@ -453,7 +458,7 @@ namespace {
                 // when the bishop is outside the pawn chain.
                 Bitboard blocked = pos.pieces(Us, PAWN) & shift<Down>(pos.pieces());
 
-                score -= BishopPawns * pos.pawns_on_same_color_squares(Us, s)
+                score -= BishopPawns[edge_distance(file_of(s))] * pos.pawns_on_same_color_squares(Us, s)
                                      * (!(attackedBy[Us][PAWN] & s) + popcount(blocked & CenterFiles));
 
                 // Penalty for all enemy pawns x-rayed
@@ -906,7 +911,7 @@ namespace {
                                                         : pos.count<BISHOP>(WHITE) + pos.count<KNIGHT>(WHITE));
         else
             sf = std::min(sf, 36 + 7 * pos.count<PAWN>(strongSide)) - 4 * !pawnsOnBothFlanks;
-      
+
         sf -= 4 * !pawnsOnBothFlanks;
     }