Good bishops on the main diagonals

Bonus in midgame for bishops on long diagonals when the central squares are not occupied by pawns.

Author: ElbertoOne

Passed STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 10801 W: 1955 L: 1786 D: 7060
http://tests.stockfishchess.org/tests/view/59cf5c1d0ebc5916ff64b9da

and LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 83978 W: 10685 L: 10303 D: 62990
http://tests.stockfishchess.org/tests/view/59cf6f6c0ebc5916ff64b9e4

Bench: 5620312

src/evaluate.cpp

@@ -31,6 +31,16 @@
 
 namespace {
 
+ const Bitboard LongDiagonals = 0x8142241818244281ULL; // A1..H8 | H1..A8
+ const Bitboard Center = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
+ const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
+ const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
+ const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
+
+ const Bitboard KingFlank[FILE_NB] = {
+ QueenSide, QueenSide, QueenSide, CenterFiles, CenterFiles, KingSide, KingSide, KingSide
+ };
+
  namespace Trace {
 
  enum Tracing {NO_TRACE, TRACE};
@@ -204,6 +214,7 @@ namespace {
  // Assorted bonuses and penalties used by evaluation
  const Score MinorBehindPawn = S( 16, 0);
  const Score BishopPawns = S( 8, 12);
+ const Score LongRangedBishop = S( 22, 0);
  const Score RookOnPawn = S( 8, 24);
  const Score TrappedRook = S( 92, 0);
  const Score WeakQueen = S( 50, 10);
@@ -338,10 +349,18 @@ namespace {
  && (pos.pieces(PAWN) & (s + pawn_push(Us))))
  score += MinorBehindPawn;
 
- // Penalty for pawns on the same color square as the bishop
  if (Pt == BISHOP)
+ {
+ // Penalty for pawns on the same color square as the bishop
  score -= BishopPawns * pe->pawns_on_same_color_squares(Us, s);
 
+ // Bonus for bishop on a long diagonal without pawns in the center
+ if ( (LongDiagonals & s)
+ && !(attackedBy[Them][PAWN] & s)
+ && !(Center & PseudoAttacks[BISHOP][s] & pos.pieces(PAWN)))
+ score += LongRangedBishop;
+ }
+
  // An important Chess960 pattern: A cornered bishop blocked by a friendly
  // pawn diagonally in front of it is a very serious problem, especially
  // when that pawn is also blocked.
@@ -396,14 +415,6 @@ namespace {
 
  // evaluate_king() assigns bonuses and penalties to a king of a given color
 
- const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
- const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
- const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
-
- const Bitboard KingFlank[FILE_NB] = {
- QueenSide, QueenSide, QueenSide, CenterFiles, CenterFiles, KingSide, KingSide, KingSide
- };
-
  template<Tracing T> template<Color Us>
  Score Evaluation<T>::evaluate_king() {