Replace the PassedDanger array by an equation

[stockfish] / src / evaluate.cpp

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index 6128b45fcad597e7c2ddad68f2ca4b55364f622d..0f89a05ac7767f9a7199e1ed543d986482307c5b 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -151,9 +151,6 @@ namespace {
     S(-30,-14), S(-9, -8), S( 0,  9), S( -1,  7)
   };
 
-  // PassedDanger[Rank] contains a term to weight the passed score
-  constexpr int PassedDanger[RANK_NB] = { 0, 0, 0, 3, 7, 11, 20 };
-
   // Assorted bonuses and penalties
   constexpr Score BishopPawns        = S(  3,  7);
   constexpr Score CloseEnemies       = S(  6,  0);
@@ -629,12 +626,12 @@ namespace {
         assert(!(pos.pieces(Them, PAWN) & forward_file_bb(Us, s + Up)));
 
         int r = relative_rank(Us, s);
-        int w = PassedDanger[r];
 
         Score bonus = PassedRank[r];
 
-        if (w)
+        if (r > RANK_3)
         {
+            int w = (r-2) * (r-2) + 2;
             Square blockSq = s + Up;
 
             // Adjust bonus based on the king's proximity
@@ -675,7 +672,7 @@ namespace {
 
                 bonus += make_score(k * w, k * w);
             }
-        } // w != 0
+        } // rank > RANK_3
 
         // Scale down bonus for candidate passers which need more than one
         // pawn push to become passed, or have a pawn in front of them.