Always scale using pawn contribution

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ad63e21630126499e168dba7fef10a550909e8ec..c98a83fc81a777806b111d80200946eaeb271da7 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -698,7 +698,7 @@ namespace {
         } // w != 0
 
         // Scale down bonus for candidate passers which need more than one
-        // pawn push to become passed or have a pawn in front of them.
+        // pawn push to become passed, or have a pawn in front of them.
         if (   !pos.pawn_passed(Us, s + Up)
             || (pos.pieces(PAWN) & forward_file_bb(Us, s)))
             bonus = bonus / 2;
@@ -731,9 +731,7 @@ namespace {
     if (pos.non_pawn_material() < SpaceThreshold)
         return SCORE_ZERO;
 
-    // Find the safe squares for our pieces inside the area defined by
-    // SpaceMask. A square is unsafe if it is attacked by an enemy
-    // pawn, or if it is undefended and attacked by an enemy piece.
+    // Find the available squares for our pieces inside the area defined by SpaceMask
     Bitboard safe =   SpaceMask
                    & ~pos.pieces(Us, PAWN)
                    & ~attackedBy[Them][PAWN];
@@ -796,9 +794,8 @@ namespace {
     Color strongSide = eg > VALUE_DRAW ? WHITE : BLACK;
     int sf = me->scale_factor(pos, strongSide);
 
-    // If we don't already have an unusual scale factor, check for certain
-    // types of endgames, and use a lower scale for those.
-    if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
+    // If scale is not already specific, scale down the endgame via general heuristics
+    if (sf == SCALE_FACTOR_NORMAL)
     {
         if (pos.opposite_bishops())
         {
@@ -812,12 +809,8 @@ namespace {
             else
                 sf = 46;
         }
-        // Endings where weaker side can place his king in front of the enemy's
-        // pawns are drawish.
-        else if (    abs(eg) <= BishopValueEg
-                 &&  pos.count<PAWN>(strongSide) <= 2
-                 && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
-            sf = 37 + 7 * pos.count<PAWN>(strongSide);
+        else
+            sf = std::min(40 + 7 * pos.count<PAWN>(strongSide), sf);
     }
 
     return ScaleFactor(sf);