Add min pawn-king distance to endgame evaluation

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 049e73bf9fb3e41e41ee5e1ee325d93b8b82143a..73a9b904b347757fda1ba601344dfd69f913259b 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -261,9 +261,14 @@ Score PawnEntry::update_safety(const Position& pos, Square ksq) {
 
   kingSquares[Us] = ksq;
   castleRights[Us] = pos.can_castle(Us);
+  minKPdistance[Us] = 0;
+
+  Bitboard pawns = pos.pieces(Us, PAWN);
+  if (pawns)
+      while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
 
   if (relative_rank(Us, ksq) > RANK_4)
-      return kingSafety[Us] = SCORE_ZERO;
+      return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
 
   Value bonus = shelter_storm<Us>(pos, ksq);
 
@@ -274,7 +279,7 @@ Score PawnEntry::update_safety(const Position& pos, Square ksq) {
   if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE)))
       bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
 
-  return kingSafety[Us] = make_score(bonus, 0);
+  return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
 }
 
 // Explicit template instantiation