Simplify KingProtector penalty.

[stockfish] / src / endgame.cpp

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 55e4483dbe84a22c0d456b2a2994fc7e0256ca3d..3e01259c9745b01d90c0e9731f5bf2a6727fdf20 100644 (file)
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -214,7 +214,7 @@ Value Endgame<KRKP>::operator()(const Position& pos) const {
   Value result;
 
   // If the stronger side's king is in front of the pawn, it's a win
-  if (wksq < psq && file_of(wksq) == file_of(psq))
+  if (forward_file_bb(WHITE, wksq) & psq)
       result = RookValueEg - distance(wksq, psq);
 
   // If the weaker side's king is too far from the pawn and the rook,
@@ -631,29 +631,8 @@ ScaleFactor Endgame<KBPKB>::operator()(const Position& pos) const {
 
   // Case 2: Opposite colored bishops
   if (opposite_colors(strongBishopSq, weakBishopSq))
-  {
-      // We assume that the position is drawn in the following three situations:
-      //
-      //   a. The pawn is on rank 5 or further back.
-      //   b. The defending king is somewhere in the pawn's path.
-      //   c. The defending bishop attacks some square along the pawn's path,
-      //      and is at least three squares away from the pawn.
-      //
-      // These rules are probably not perfect, but in practice they work
-      // reasonably well.
-
-      if (relative_rank(strongSide, pawnSq) <= RANK_5)
-          return SCALE_FACTOR_DRAW;
-
-      Bitboard path = forward_file_bb(strongSide, pawnSq);
-
-      if (path & pos.pieces(weakSide, KING))
-          return SCALE_FACTOR_DRAW;
+      return SCALE_FACTOR_DRAW;
 
-      if (  (pos.attacks_from<BISHOP>(weakBishopSq) & path)
-          && distance(weakBishopSq, pawnSq) >= 3)
-          return SCALE_FACTOR_DRAW;
-  }
   return SCALE_FACTOR_NONE;
 }