Simplify scale factor computation

Minor non-functional simplifications in computing the scale factor.

In my opinion, the code is now slightly more readable:

- remove one condition which can never be satisfied.
- immediately return instead of assigning the sf variable.

Tested for non-regression:

LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 62162 W: 11166 L: 11115 D: 39881

No functional change

Closes #992

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 9e0629ef66686f816cc81041f801ebc3feb52829..2c5f130343ecc1f58bbe02a0eaaaad1928faa7eb 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -755,8 +755,7 @@ namespace {
 
     // If we don't already have an unusual scale factor, check for certain
     // types of endgames, and use a lower scale for those.
-    if (    ei.me->game_phase() < PHASE_MIDGAME
-        && (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN))
+    if (sf == SCALE_FACTOR_NORMAL || sf == SCALE_FACTOR_ONEPAWN)
     {
         if (pos.opposite_bishops())
         {
@@ -764,19 +763,18 @@ namespace {
             // is almost a draw, in case of KBP vs KB, it is even more a draw.
             if (   pos.non_pawn_material(WHITE) == BishopValueMg
                 && pos.non_pawn_material(BLACK) == BishopValueMg)
-                sf = more_than_one(pos.pieces(PAWN)) ? ScaleFactor(31) : ScaleFactor(9);
+                return more_than_one(pos.pieces(PAWN)) ? ScaleFactor(31) : ScaleFactor(9);
 
             // Endgame with opposite-colored bishops, but also other pieces. Still
             // a bit drawish, but not as drawish as with only the two bishops.
-            else
-                sf = ScaleFactor(46);
+            return ScaleFactor(46);
         }
         // Endings where weaker side can place his king in front of the opponent's
         // pawns are drawish.
         else if (    abs(eg) <= BishopValueEg
                  &&  pos.count<PAWN>(strongSide) <= 2
                  && !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
-            sf = ScaleFactor(37 + 7 * pos.count<PAWN>(strongSide));
+            return ScaleFactor(37 + 7 * pos.count<PAWN>(strongSide));
     }
 
     return sf;