Reduce penalty for doubled pawns further away from each other

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 1e62557784199b1a4a135ef796d93bd053233762..6d90f6b5858f9fb314a8f2bf61092a7ef7142a23 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -89,10 +89,10 @@ namespace {
     const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW);
     const Square Left  = (Us == WHITE ? DELTA_NW : DELTA_SE);
 
-    Bitboard b, p;
+    Bitboard b, p, doubled;
     Square s;
     File f;
-    bool passed, isolated, doubled, opposed, connected, backward, candidate, unsupported;
+    bool passed, isolated, opposed, connected, backward, candidate, unsupported;
     Score value = SCORE_ZERO;
     const Square* pl = pos.list<PAWN>(Us);
 
@@ -177,7 +177,7 @@ namespace {
             value -= UnsupportedPawnPenalty;
 
         if (doubled)
-            value -= Doubled[f];
+            value -= Doubled[f] / rank_distance(s, lsb(doubled));
 
         if (backward)
             value -= Backward[opposed][f];