Tweak initiative formula

Give more weight to the pawns number and
the vertical king distance in evaluate_initiative()

Passed STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 26729 W: 5067 L: 4825 D: 16837

and LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 60480 W: 8338 L: 8016 D: 44126

Bench: 8295162

Resolves #594

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 826e860a5c22d3441424f63fd674c2aaa5b624d1..e8d3834343bc33215357310f3eedf304dce62260 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -679,11 +679,12 @@ namespace {
   // status of the players.
   Score evaluate_initiative(const Position& pos, int asymmetry, Value eg) {
 
   // status of the players.
   Score evaluate_initiative(const Position& pos, int asymmetry, Value eg) {
 

-    int kingDistance = distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));
+    int kingDistance =   distance<File>(pos.square<KING>(WHITE), pos.square<KING>(BLACK))
+                       - distance<Rank>(pos.square<KING>(WHITE), pos.square<KING>(BLACK));

     int pawns = pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK);
 
     // Compute the initiative bonus for the attacking side
     int pawns = pos.count<PAWN>(WHITE) + pos.count<PAWN>(BLACK);
 
     // Compute the initiative bonus for the attacking side

-    int initiative = 8 * (pawns + asymmetry + kingDistance - 15);
+    int initiative = 8 * (asymmetry + kingDistance) + 12 * pawns - 120;

 
     // Now apply the bonus: note that we find the attacking side by extracting
     // the sign of the endgame value, and that we carefully cap the bonus so
 
     // Now apply the bonus: note that we find the attacking side by extracting
     // the sign of the endgame value, and that we carefully cap the bonus so