Clarify the mapping of files to queenside

[stockfish] / src / pawns.cpp

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 5df175b233c8092a1f2c41ba66f3f0d4c7de6c64..d822ef4ef85e8387d7a206db3f85714646844ee2 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -33,6 +33,7 @@ namespace {
 
   // 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);
@@ -70,10 +71,10 @@ namespace {
     constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
     constexpr Direction Up   = (Us == WHITE ? NORTH : SOUTH);
 
-    Bitboard neighbours, stoppers, doubled, support, phalanx;
+    Bitboard neighbours, stoppers, support, phalanx;
     Bitboard lever, leverPush;
     Square s;
-    bool opposed, backward, passed;
+    bool opposed, backward, passed, doubled;
     Score score = SCORE_ZERO;
     const Square* pl = pos.squares<PAWN>(Us);
 
@@ -129,27 +130,23 @@ namespace {
         // Score this pawn
         if (support | phalanx)
         {
-            int v =  Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1)
+            int v =  Connected[r] * (2 + bool(phalanx) - opposed)
                    + 17 * popcount(support);
 
             score += make_score(v, v * (r - 2) / 4);
         }
 
         else if (!neighbours)
-            score -= Isolated + WeakUnopposed * int(!opposed);
+            score -= Isolated + WeakUnopposed * !opposed;
 
         else if (backward)
-            score -= Backward + WeakUnopposed * int(!opposed);
+            score -= Backward + WeakUnopposed * !opposed;
 
-        if (doubled && !support)
-            score -= Doubled;
+        if (!support)
+            score -=   Doubled * doubled
+                     + WeakLever * more_than_one(lever);
     }
 
-    // Penalize our unsupported pawns attacked twice by enemy pawns
-    score -= WeakLever * popcount(  ourPawns
-                                  & doubleAttackThem
-                                  & ~e->pawnAttacks[Us]);
-
     return score;
   }
 
@@ -182,7 +179,7 @@ Entry* probe(const Position& pos) {
 /// penalty for a king, looking at the king file and the two closest files.
 
 template<Color Us>
-void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) {
+Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
 
   constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
 
@@ -201,17 +198,16 @@ void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) {
       b = theirPawns & file_bb(f);
       int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
 
-      int d = std::min(f, ~f);
+      int d = map_to_queenside(f);
       bonus += make_score(ShelterStrength[d][ourRank], 0);
 
       if (ourRank && (ourRank == theirRank - 1))
-          bonus -= make_score(82 * (theirRank == RANK_3), 82 * (theirRank == RANK_3));
+          bonus -= BlockedStorm * int(theirRank == RANK_3);
       else
           bonus -= make_score(UnblockedStorm[d][theirRank], 0);
   }
 
-  if (mg_value(bonus) > mg_value(shelter))
-      shelter = bonus;
+  return bonus;
 }
 
 
@@ -225,26 +221,31 @@ Score Entry::do_king_safety(const Position& pos) {
   kingSquares[Us] = ksq;
   castlingRights[Us] = pos.castling_rights(Us);
 
+  Score shelters[3] = { evaluate_shelter<Us>(pos, ksq),
+                        make_score(-VALUE_INFINITE, 0),
+                        make_score(-VALUE_INFINITE, 0) };
+
+  // If we can castle use the bonus after castling if it is bigger
+  if (pos.can_castle(Us & KING_SIDE))
+      shelters[1] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1));
+
+  if (pos.can_castle(Us & QUEEN_SIDE))
+      shelters[2] = evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1));
+
+  for (int i : {1, 2})
+     if (mg_value(shelters[i]) > mg_value(shelters[0]))
+         shelters[0] = shelters[i];
+
+  // In endgame we like to bring our king near our closest pawn
   Bitboard pawns = pos.pieces(Us, PAWN);
   int minPawnDist = pawns ? 8 : 0;
 
   if (pawns & PseudoAttacks[KING][ksq])
       minPawnDist = 1;
-
   else while (pawns)
       minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns)));
 
-  Score shelter = make_score(-VALUE_INFINITE, 0);
-  evaluate_shelter<Us>(pos, ksq, shelter);
-
-  // If we can castle use the bonus after the castling if it is bigger
-  if (pos.can_castle(Us | KING_SIDE))
-      evaluate_shelter<Us>(pos, relative_square(Us, SQ_G1), shelter);
-
-  if (pos.can_castle(Us | QUEEN_SIDE))
-      evaluate_shelter<Us>(pos, relative_square(Us, SQ_C1), shelter);
-
-  return shelter - make_score(0, 16 * minPawnDist);
+  return shelters[0] - make_score(0, 16 * minPawnDist);
 }
 
 // Explicit template instantiation