Assorted trivial cleanups June 2019

No functional change.

src/evaluate.cpp

@@ -142,7 +142,7 @@ namespace {
   constexpr Score KnightOnQueen      = S( 16, 12);
   constexpr Score LongDiagonalBishop = S( 45,  0);
   constexpr Score MinorBehindPawn    = S( 18,  3);
-  constexpr Score Outpost            = S( 36, 12);
+  constexpr Score Outpost            = S( 18,  6);
   constexpr Score PawnlessFlank      = S( 17, 95);
   constexpr Score RestrictedPiece    = S(  7,  7);
   constexpr Score RookOnPawn         = S( 10, 32);
@@ -222,7 +222,7 @@ namespace {
     constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
     constexpr Direction Up   = (Us == WHITE ? NORTH : SOUTH);
     constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH);
-    constexpr Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
+    constexpr Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB : Rank7BB | Rank6BB);
 
     const Square ksq = pos.square<KING>(Us);
 
@@ -305,10 +305,10 @@ namespace {
             // Bonus if piece is on an outpost square or can reach one
             bb = OutpostRanks & attackedBy[Us][PAWN] & ~pe->pawn_attacks_span(Them);
             if (bb & s)
-                score += Outpost * (Pt == KNIGHT ? 2 : 1);
+                score += Outpost * (Pt == KNIGHT ? 4 : 2);
 
             else if (bb & b & ~pos.pieces(Us))
-                score += Outpost / (Pt == KNIGHT ? 1 : 2);
+                score += Outpost * (Pt == KNIGHT ? 2 : 1);
 
             // Knight and Bishop bonus for being right behind a pawn
             if (shift<Down>(pos.pieces(PAWN)) & s)
@@ -561,7 +561,7 @@ namespace {
     b &= ~attackedBy[Them][PAWN] & safe;
 
     // Bonus for safe pawn threats on the next move
-    b = pawn_attacks_bb<Us>(b) & pos.pieces(Them);
+    b = pawn_attacks_bb<Us>(b) & nonPawnEnemies;
     score += ThreatByPawnPush * popcount(b);
 
     // Our safe or protected pawns

src/pawns.cpp

@@ -32,9 +32,9 @@ namespace {
   #define S(mg, eg) make_score(mg, eg)
 
   // Pawn penalties
-  constexpr Score Backward = S( 9, 24);
-  constexpr Score Doubled  = S(11, 56);
-  constexpr Score Isolated = S( 5, 15);
+  constexpr Score Backward      = S( 9, 24);
+  constexpr Score Doubled       = S(11, 56);
+  constexpr Score Isolated      = S( 5, 15);
   constexpr Score WeakUnopposed = S( 13, 27);
   constexpr Score Attacked2Unsupported = S( 0, 20);
 
@@ -108,17 +108,18 @@ namespace {
         phalanx    = neighbours & rank_bb(s);
         support    = neighbours & rank_bb(s - Up);
 
-        // A pawn is backward when it is behind all pawns of the same color
-        // on the adjacent files and cannot be safely advanced.
-        backward =  !(ourPawns & pawn_attack_span(Them, s + Up))
+        // A pawn is backward when it is behind all pawns of the same color on
+        // the adjacent files and cannot safely advance. Phalanx and isolated
+        // pawns will be excluded when the pawn is scored.
+        backward =  !(neighbours & forward_ranks_bb(Them, s))
                   && (stoppers & (leverPush | (s + Up)));
 
         // Passed pawns will be properly scored in evaluation because we need
         // full attack info to evaluate them. Include also not passed pawns
         // which could become passed after one or two pawn pushes when are
         // not attacked more times than defended.
-        if (   !(stoppers ^ lever) ||
-              (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush)))
+        if ( !(stoppers ^ lever) ||
+            (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush)))
             e->passedPawns[Us] |= s;
 
         else if (stoppers == square_bb(s + Up) && r >= RANK_5)
@@ -137,6 +138,7 @@ namespace {
 
             score += make_score(v, v * (r - 2) / 4);
         }
+
         else if (!neighbours)
             score -= Isolated + WeakUnopposed * int(!opposed);
 

src/position.cpp

@@ -55,13 +55,13 @@ constexpr Piece Pieces[] = { W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING
 // valuable attacker for the side to move, remove the attacker we just found
 // from the bitboards and scan for new X-ray attacks behind it.
 
-template<int Pt>
+template<PieceType Pt>
 PieceType min_attacker(const Bitboard* byTypeBB, Square to, Bitboard stmAttackers,
                        Bitboard& occupied, Bitboard& attackers) {
 
   Bitboard b = stmAttackers & byTypeBB[Pt];
   if (!b)
-      return min_attacker<Pt + 1>(byTypeBB, to, stmAttackers, occupied, attackers);
+      return min_attacker<PieceType(Pt + 1)>(byTypeBB, to, stmAttackers, occupied, attackers);
 
   occupied ^= lsb(b); // Remove the attacker from occupied
 
@@ -77,7 +77,7 @@ PieceType min_attacker(const Bitboard* byTypeBB, Square to, Bitboard stmAttacker
   // X-ray may add already processed pieces because byTypeBB[] is constant: in
   // the rook example, now attackers contains _again_ rook in a7, so remove it.
   attackers &= occupied;
-  return (PieceType)Pt;
+  return Pt;
 }
 
 template<>

src/position.h

@@ -108,6 +108,7 @@ class Position {
   Bitboard checkers() const;
   Bitboard blockers_for_king(Color c) const;
   Bitboard check_squares(PieceType pt) const;
+  bool is_discovery_check_on_king(Color c, Move m) const;
 
   // Attacks to/from a given square
   Bitboard attackers_to(Square s) const;
@@ -316,6 +317,10 @@ inline Bitboard Position::check_squares(PieceType pt) const {
   return st->checkSquares[pt];
 }
 
+inline bool Position::is_discovery_check_on_king(Color c, Move m) const {
+  return st->blockersForKing[c] & from_sq(m);
+}
+
 inline bool Position::pawn_passed(Color c, Square s) const {
   return !(pieces(~c, PAWN) & passed_pawn_span(c, s));
 }

src/search.cpp

@@ -739,7 +739,7 @@ namespace {
     }
     else if (ttHit)
     {
-        // Never assume anything on values stored in TT
+        // Never assume anything about values stored in TT
         ss->staticEval = eval = tte->eval();
         if (eval == VALUE_NONE)
             ss->staticEval = eval = evaluate(pos);
@@ -978,7 +978,7 @@ namespace {
 
       // Check extension (~2 Elo)
       else if (    givesCheck
-               && (pos.blockers_for_king(~us) & from_sq(move) || pos.see_ge(move)))
+               && (pos.is_discovery_check_on_king(~us, move) || pos.see_ge(move)))
           extension = ONE_PLY;
 
       // Castling extension
@@ -1013,7 +1013,7 @@ namespace {
               && !givesCheck
               && (!pos.advanced_pawn_push(move) || pos.non_pawn_material(~us) > BishopValueMg))
           {
-              // Move count based pruning (~30 Elo)
+              // Move count based pruning
               if (moveCountPruning)
                   continue;
 
@@ -1037,8 +1037,8 @@ namespace {
               if (!pos.see_ge(move, Value(-29 * lmrDepth * lmrDepth)))
                   continue;
           }
-          else if ((!givesCheck || !extension)
-                  && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
+          else if (  (!givesCheck || !extension)
+                   && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY))) // (~20 Elo)
                   continue;
       }
 
@@ -1341,7 +1341,7 @@ namespace {
     {
         if (ttHit)
         {
-            // Never assume anything on values stored in TT
+            // Never assume anything about values stored in TT
             if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE)
                 ss->staticEval = bestValue = evaluate(pos);