Add doubled isolated pawn penalty.

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index a2063a8f8323cd9ad420e81d8cfe60cd93099ff6..c20cb5293c009ee2a2538318965be79156ba5d4b 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -32,12 +32,13 @@ namespace {
   #define S(mg, eg) make_score(mg, eg)
 
   // Pawn penalties
-  constexpr Score Backward      = S( 9, 24);
-  constexpr Score BlockedStorm  = S(82, 82);
-  constexpr Score Doubled       = S(11, 56);
-  constexpr Score Isolated      = S( 5, 15);
-  constexpr Score WeakLever     = S( 0, 56);
-  constexpr Score WeakUnopposed = S(13, 27);
+  constexpr Score Backward        = S( 9, 24);
+  constexpr Score BlockedStorm    = S(82, 82);
+  constexpr Score Doubled         = S(11, 56);
+  constexpr Score DoubledIsolated = S(15, 57);
+  constexpr Score Isolated        = S( 5, 15);
+  constexpr Score WeakLever       = S( 0, 56);
+  constexpr Score WeakUnopposed   = S(13, 27);
 
   // Connected pawn bonus
   constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 };
@@ -86,7 +87,6 @@ namespace {
     e->passedPawns[Us] = 0;
     e->kingSquares[Us] = SQ_NONE;
     e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb<Us>(ourPawns);
-    e->blockedCount[Us] = 0;
 
     // Loop through all pawns of the current color and score each pawn
     while ((s = *pl++) != SQ_NONE)
@@ -106,7 +106,7 @@ namespace {
         phalanx    = neighbours & rank_bb(s);
         support    = neighbours & rank_bb(s - Up);
 
-        e->blockedCount[Us] += bool(blocked);
+        e->blockedCount += blocked || more_than_one(leverPush);
 
         // A pawn is backward when it is behind all pawns of the same color on
         // the adjacent files and cannot safely advance.
@@ -145,9 +145,16 @@ namespace {
         }
 
         else if (!neighbours)
+        {
             score -=   Isolated
                      + WeakUnopposed * !opposed;
 
+            if (   (ourPawns & forward_file_bb(Them, s))
+                && popcount(opposed) == 1
+                && !(theirPawns & adjacent_files_bb(s)))
+                score -= DoubledIsolated;
+        }
+
         else if (backward)
             score -=   Backward
                      + WeakUnopposed * !opposed;
@@ -178,6 +185,7 @@ Entry* probe(const Position& pos) {
       return e;
 
   e->key = key;
+  e->blockedCount = 0;
   e->scores[WHITE] = evaluate<WHITE>(pos, e);
   e->scores[BLACK] = evaluate<BLACK>(pos, e);
 
@@ -244,7 +252,7 @@ Score Entry::do_king_safety(const Position& pos) {
 
   // In endgame we like to bring our king near our closest pawn
   Bitboard pawns = pos.pieces(Us, PAWN);
-  int minPawnDist = pawns ? 8 : 0;
+  int minPawnDist = 6;
 
   if (pawns & PseudoAttacks[KING][ksq])
       minPawnDist = 1;