More readable trapped rook condition

Prefer

file_of(s) < file_of(ksq)

to the inidrect

file_of(ksq) < FILE_E

To evaluate if semiopen side to check is the left side.

Also other small touches while there.

No functional change.

src/evaluate.cpp

@@ -379,10 +379,10 @@ namespace {
             }
 
             // Give a bonus for a rook on a open or semi-open file
-            if (ei.pi->semiopen(Us, file_of(s)))
-                score += ei.pi->semiopen(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
+            if (ei.pi->semiopen_file(Us, file_of(s)))
+                score += ei.pi->semiopen_file(Them, file_of(s)) ? RookOpenFile : RookSemiopenFile;
 
-            if (mob > 3 || ei.pi->semiopen(Us, file_of(s)))
+            if (mob > 3 || ei.pi->semiopen_file(Us, file_of(s)))
                 continue;
 
             Square ksq = pos.king_square(Us);
@@ -391,8 +391,8 @@ namespace {
             // king has lost its castling capability.
             if (   ((file_of(ksq) < FILE_E) == (file_of(s) < file_of(ksq)))
                 && (rank_of(ksq) == rank_of(s) || relative_rank(Us, ksq) == RANK_1)
-                && !ei.pi->semiopen_on_side(Us, file_of(ksq), file_of(ksq) < FILE_E))
-                score -= (TrappedRook - make_score(mob * 8, 0)) * (pos.can_castle(Us) ? 1 : 2);
+                && !ei.pi->semiopen_side(Us, file_of(ksq), file_of(s) < file_of(ksq)))
+                score -= (TrappedRook - make_score(mob * 8, 0)) * (1 + !pos.can_castle(Us));
         }
 
         // An important Chess960 pattern: A cornered bishop blocked by a friendly

src/pawns.cpp

@@ -280,12 +280,11 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) {
 }
 
 
-/// Entry::update_safety() calculates and caches a bonus for king safety.
-/// It is called only when king square changes, which is about 20% of total
-/// king_safety() calls.
+/// Entry::do_king_safety() calculates a bonus for king safety. It is called only
+/// when king square changes, which is about 20% of total king_safety() calls.
 
 template<Color Us>
-Score Entry::update_safety(const Position& pos, Square ksq) {
+Score Entry::do_king_safety(const Position& pos, Square ksq) {
 
   kingSquares[Us] = ksq;
   castlingRights[Us] = pos.can_castle(Us);
@@ -296,7 +295,7 @@ Score Entry::update_safety(const Position& pos, Square ksq) {
       while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {}
 
   if (relative_rank(Us, ksq) > RANK_4)
-      return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]);
+      return make_score(0, -16 * minKPdistance[Us]);
 
   Value bonus = shelter_storm<Us>(pos, ksq);
 
@@ -307,11 +306,11 @@ Score Entry::update_safety(const Position& pos, Square ksq) {
   if (pos.can_castle(MakeCastling<Us, QUEEN_SIDE>::right))
       bonus = std::max(bonus, shelter_storm<Us>(pos, relative_square(Us, SQ_C1)));
 
-  return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);
+  return make_score(bonus, -16 * minKPdistance[Us]);
 }
 
 // Explicit template instantiation
-template Score Entry::update_safety<WHITE>(const Position& pos, Square ksq);
-template Score Entry::update_safety<BLACK>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<WHITE>(const Position& pos, Square ksq);
+template Score Entry::do_king_safety<BLACK>(const Position& pos, Square ksq);
 
 } // namespace Pawns

src/pawns.h

@@ -26,56 +26,59 @@
 
 namespace Pawns {
 
-/// Pawns::Entry contains various information about a pawn structure. Currently,
-/// it only includes a middlegame and endgame pawn structure evaluation, and a
-/// bitboard of passed pawns. We may want to add further information in the future.
-/// A lookup to the pawn hash table (performed by calling the probe function)
-/// returns a pointer to an Entry object.
+/// Pawns::Entry contains various information about a pawn structure. A lookup
+/// to the pawn hash table (performed by calling the probe function) returns a
+/// pointer to an Entry object.
 
 struct Entry {
 
   Score pawns_value() const { return value; }
   Bitboard pawn_attacks(Color c) const { return pawnAttacks[c]; }
   Bitboard passed_pawns(Color c) const { return passedPawns[c]; }
   Bitboard candidate_pawns(Color c) const { return candidatePawns[c]; }
-  int pawns_on_same_color_squares(Color c, Square s) const { return pawnsOnSquares[c][!!(DarkSquares & s)]; }
-  int semiopen(Color c, File f) const { return semiopenFiles[c] & (1 << int(f)); }
-  int semiopen_on_side(Color c, File f, bool left) const {
 
-    return semiopenFiles[c] & (left ? ((1 << int(f)) - 1) : ~((1 << int(f+1)) - 1));
+  int semiopen_file(Color c, File f) const {
+    return semiopenFiles[c] & (1 << f);
+  }
+
+  int semiopen_side(Color c, File f, bool leftSide) const {
+    return semiopenFiles[c] & (leftSide ? (1 << f) - 1 : ~((1 << (f + 1)) - 1));
+  }
+
+  int pawns_on_same_color_squares(Color c, Square s) const {
+    return pawnsOnSquares[c][!!(DarkSquares & s)];
   }
 
   template<Color Us>
   Score king_safety(const Position& pos, Square ksq)  {
-
-    return kingSquares[Us] == ksq && castlingRights[Us] == pos.can_castle(Us)
-         ? kingSafety[Us] : update_safety<Us>(pos, ksq);
+    return  kingSquares[Us] == ksq && castlingRights[Us] == pos.can_castle(Us)
+          ? kingSafety[Us] : (kingSafety[Us] = do_king_safety<Us>(pos, ksq));
   }
 
   template<Color Us>
-  Score update_safety(const Position& pos, Square ksq);
+  Score do_king_safety(const Position& pos, Square ksq);
 
   template<Color Us>
   Value shelter_storm(const Position& pos, Square ksq);
 
   Key key;
+  Score value;
   Bitboard passedPawns[COLOR_NB];
   Bitboard candidatePawns[COLOR_NB];
   Bitboard pawnAttacks[COLOR_NB];
   Square kingSquares[COLOR_NB];
+  Score kingSafety[COLOR_NB];
   int minKPdistance[COLOR_NB];
   int castlingRights[COLOR_NB];
-  Score value;
   int semiopenFiles[COLOR_NB];
-  Score kingSafety[COLOR_NB];
-  int pawnsOnSquares[COLOR_NB][COLOR_NB];
+  int pawnsOnSquares[COLOR_NB][COLOR_NB]; // [color][light/dark squares]
 };
 
 typedef HashTable<Entry, 16384> Table;
 
 void init();
 Entry* probe(const Position& pos, Table& entries);
 
-}
+} // namespace Pawns
 
 #endif // #ifndef PAWNS_H_INCLUDED