Small cleanups

closes https://github.com/official-stockfish/Stockfish/pull/2606

No functional change

src/bitboard.cpp

@@ -84,23 +84,16 @@ void Bitboards::init() {
   init_magics(RookTable, RookMagics, RookDirections);
   init_magics(BishopTable, BishopMagics, BishopDirections);
 
-  // Helper returning the target bitboard of a step from a square
-  auto landing_square_bb = [&](Square s, int step)
-  {
-      Square to = Square(s + step);
-      return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
-  };
-
   for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
   {
       PawnAttacks[WHITE][s1] = pawn_attacks_bb<WHITE>(square_bb(s1));
       PawnAttacks[BLACK][s1] = pawn_attacks_bb<BLACK>(square_bb(s1));
 
       for (int step : {-9, -8, -7, -1, 1, 7, 8, 9} )
-         PseudoAttacks[KING][s1] |= landing_square_bb(s1, step);
+         PseudoAttacks[KING][s1] |= safe_destination(s1, step);
 
       for (int step : {-17, -15, -10, -6, 6, 10, 15, 17} )
-         PseudoAttacks[KNIGHT][s1] |= landing_square_bb(s1, step);
+         PseudoAttacks[KNIGHT][s1] |= safe_destination(s1, step);
 
       PseudoAttacks[QUEEN][s1]  = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);
       PseudoAttacks[QUEEN][s1] |= PseudoAttacks[  ROOK][s1] = attacks_bb<  ROOK>(s1, 0);
@@ -117,20 +110,16 @@ namespace {
 
   Bitboard sliding_attack(Direction directions[], Square sq, Bitboard occupied) {
 
-    Bitboard attack = 0;
+    Bitboard attacks = 0;
 
     for (int i = 0; i < 4; ++i)
-        for (Square s = sq + directions[i];
+    {
-             is_ok(s) && distance(s, s - directions[i]) == 1;
+        Square s = sq;
-             s += directions[i])
+        while(safe_destination(s, directions[i]) && !(occupied & s))
-        {
+            attacks |= (s += directions[i]);
-            attack |= s;
+    }
 
-            if (occupied & s)
+    return attacks;
-                break;
-        }
-
-    return attack;
   }
 
 

src/bitboard.h

@@ -106,7 +106,7 @@ extern Magic RookMagics[SQUARE_NB];
 extern Magic BishopMagics[SQUARE_NB];
 
 inline Bitboard square_bb(Square s) {
-  assert(s >= SQ_A1 && s <= SQ_H8);
+  assert(is_ok(s));
   return SquareBB[s];
 }
 
@@ -123,7 +123,7 @@ inline Bitboard  operator&(Square s, Bitboard b) { return b & s; }
 inline Bitboard  operator|(Square s, Bitboard b) { return b | s; }
 inline Bitboard  operator^(Square s, Bitboard b) { return b ^ s; }
 
-inline Bitboard  operator|(Square s, Square s2) { return square_bb(s) | square_bb(s2); }
+inline Bitboard  operator|(Square s, Square s2) { return square_bb(s) | s2; }
 
 constexpr bool more_than_one(Bitboard b) {
   return b & (b - 1);
@@ -209,8 +209,8 @@ inline Bitboard between_bb(Square s1, Square s2) {
 /// forward_ranks_bb(BLACK, SQ_D3) will return the 16 squares on ranks 1 and 2.
 
 inline Bitboard forward_ranks_bb(Color c, Square s) {
-  return c == WHITE ? ~Rank1BB << 8 * (rank_of(s) - RANK_1)
+  return c == WHITE ? ~Rank1BB << 8 * relative_rank(WHITE, s)
-                    : ~Rank8BB >> 8 * (RANK_8 - rank_of(s));
+                    : ~Rank8BB >> 8 * relative_rank(BLACK, s);
 }
 
 
@@ -255,8 +255,16 @@ template<> inline int distance<File>(Square x, Square y) { return std::abs(file_
 template<> inline int distance<Rank>(Square x, Square y) { return std::abs(rank_of(x) - rank_of(y)); }
 template<> inline int distance<Square>(Square x, Square y) { return SquareDistance[x][y]; }
 
-inline File edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
+inline int edge_distance(File f) { return std::min(f, File(FILE_H - f)); }
-inline Rank edge_distance(Rank r) { return std::min(r, Rank(RANK_8 - r)); }
+inline int edge_distance(Rank r) { return std::min(r, Rank(RANK_8 - r)); }
+
+/// Return the target square bitboard if we do not step off the board, empty otherwise
+
+inline Bitboard safe_destination(Square s, int step)
+{
+    Square to = Square(s + step);
+    return is_ok(to) && distance(s, to) <= 2 ? square_bb(to) : Bitboard(0);
+}
 
 /// attacks_bb() returns a bitboard representing all the squares attacked by a
 /// piece of type Pt (bishop or rook) placed on 's'.

src/evaluate.cpp

@@ -746,7 +746,7 @@ namespace {
     {
         if (   pos.opposite_bishops()
             && pos.non_pawn_material() == 2 * BishopValueMg)
-            sf = 22 ;
+            sf = 22;
         else
             sf = std::min(sf, 36 + (pos.opposite_bishops() ? 2 : 7) * pos.count<PAWN>(strongSide));
 

src/movegen.cpp

@@ -277,16 +277,13 @@ ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
   assert(!pos.checkers());
 
   Color us = pos.side_to_move();
-  Bitboard dc = pos.blockers_for_king(~us) & pos.pieces(us);
+  Bitboard dc = pos.blockers_for_king(~us) & pos.pieces(us) & ~pos.pieces(PAWN);
 
   while (dc)
   {
      Square from = pop_lsb(&dc);
      PieceType pt = type_of(pos.piece_on(from));
 
-     if (pt == PAWN)
-         continue; // Will be generated together with direct checks
-
      Bitboard b = pos.attacks_from(pt, from) & ~pos.pieces();
 
      if (pt == KING)
@@ -317,10 +314,7 @@ ExtMove* generate<EVASIONS>(const Position& pos, ExtMove* moveList) {
   // the king evasions in order to skip known illegal moves, which avoids any
   // useless legality checks later on.
   while (sliders)
-  {
+      sliderAttacks |= LineBB[ksq][pop_lsb(&sliders)] & ~pos.checkers();
-      Square checksq = pop_lsb(&sliders);
-      sliderAttacks |= LineBB[ksq][checksq] ^ checksq;
-  }
 
   // Generate evasions for king, capture and non capture moves
   Bitboard b = pos.attacks_from<KING>(ksq) & ~pos.pieces(us) & ~sliderAttacks;

src/pawns.cpp

@@ -204,7 +204,7 @@ Score Entry::evaluate_shelter(const Position& pos, Square ksq) {
       b = theirPawns & file_bb(f);
       int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0;
 
-      File d = edge_distance(f);
+      File d = File(edge_distance(f));
       bonus += make_score(ShelterStrength[d][ourRank], 0);
 
       if (ourRank && (ourRank == theirRank - 1))

src/psqt.cpp

@@ -112,7 +112,7 @@ void init() {
 
       for (Square s = SQ_A1; s <= SQ_H8; ++s)
       {
-          File f = edge_distance(file_of(s));
+          File f = File(edge_distance(file_of(s)));
           psq[ pc][ s] = score + (type_of(pc) == PAWN ? PBonus[rank_of(s)][file_of(s)]
                                                       : Bonus[pc][rank_of(s)][f]);
           psq[~pc][flip_rank(s)] = -psq[pc][s];

src/search.cpp

@@ -303,7 +303,7 @@ void MainThread::search() {
       }
   }
 
-  previousScore = bestThread->rootMoves[0].score;
+  bestPreviousScore = bestThread->rootMoves[0].score;
 
   // Send again PV info if we have a new best thread
   if (bestThread != this)
@@ -349,12 +349,12 @@ void Thread::search() {
 
   if (mainThread)
   {
-      if (mainThread->previousScore == VALUE_INFINITE)
+      if (mainThread->bestPreviousScore == VALUE_INFINITE)
           for (int i=0; i<4; ++i)
               mainThread->iterValue[i] = VALUE_ZERO;
       else
           for (int i=0; i<4; ++i)
-              mainThread->iterValue[i] = mainThread->previousScore;
+              mainThread->iterValue[i] = mainThread->bestPreviousScore;
   }
 
   size_t multiPV = Options["MultiPV"];
@@ -433,13 +433,13 @@ void Thread::search() {
           // Reset aspiration window starting size
           if (rootDepth >= 4)
           {
-              Value previousScore = rootMoves[pvIdx].previousScore;
+              Value prev = rootMoves[pvIdx].previousScore;
               delta = Value(21);
-              alpha = std::max(previousScore - delta,-VALUE_INFINITE);
+              alpha = std::max(prev - delta,-VALUE_INFINITE);
-              beta  = std::min(previousScore + delta, VALUE_INFINITE);
+              beta  = std::min(prev + delta, VALUE_INFINITE);
 
               // Adjust contempt based on root move's previousScore (dynamic contempt)
-              int dct = ct + (102 - ct / 2) * previousScore / (abs(previousScore) + 157);
+              int dct = ct + (102 - ct / 2) * prev / (abs(prev) + 157);
 
               contempt = (us == WHITE ?  make_score(dct, dct / 2)
                                       : -make_score(dct, dct / 2));
@@ -537,7 +537,7 @@ void Thread::search() {
           && !Threads.stop
           && !mainThread->stopOnPonderhit)
       {
-          double fallingEval = (332 +  6 * (mainThread->previousScore - bestValue)
+          double fallingEval = (332 +  6 * (mainThread->bestPreviousScore - bestValue)
                                     +  6 * (mainThread->iterValue[iterIdx]  - bestValue)) / 704.0;
           fallingEval = Utility::clamp(fallingEval, 0.5, 1.5);
 
@@ -626,7 +626,7 @@ namespace {
     Move ttMove, move, excludedMove, bestMove;
     Depth extension, newDepth;
     Value bestValue, value, ttValue, eval, maxValue;
-    bool ttHit, ttPv, inCheck, givesCheck, improving, didLMR, priorCapture;
+    bool ttHit, ttPv, formerPv, inCheck, givesCheck, improving, didLMR, priorCapture;
     bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture, singularLMR;
     Piece movedPiece;
     int moveCount, captureCount, quietCount;
@@ -696,6 +696,7 @@ namespace {
     ttMove =  rootNode ? thisThread->rootMoves[thisThread->pvIdx].pv[0]
             : ttHit    ? tte->move() : MOVE_NONE;
     ttPv = PvNode || (ttHit && tte->is_pv());
+    formerPv = ttPv && !PvNode;
 
     if (ttPv && depth > 12 && ss->ply - 1 < MAX_LPH && !pos.captured_piece() && is_ok((ss-1)->currentMove))
         thisThread->lowPlyHistory[ss->ply - 1][from_to((ss-1)->currentMove)] << stat_bonus(depth - 5);
@@ -900,7 +901,8 @@ namespace {
         &&  depth >= 5
         &&  abs(beta) < VALUE_TB_WIN_IN_MAX_PLY)
     {
-        Value raisedBeta = std::min(beta + 189 - 45 * improving, VALUE_INFINITE);
+        Value raisedBeta = beta + 189 - 45 * improving;
+        assert(raisedBeta < VALUE_INFINITE);
         MovePicker mp(pos, ttMove, raisedBeta - ss->staticEval, &captureHistory);
         int probCutCount = 0;
 
@@ -965,7 +967,6 @@ moves_loop: // When in check, search starts from here
     value = bestValue;
     singularLMR = moveCountPruning = false;
     ttCapture = ttMove && pos.capture_or_promotion(ttMove);
-    bool formerPv = ttPv && !PvNode;
 
     // Mark this node as being searched
     ThreadHolding th(thisThread, posKey, ss->ply);
@@ -1039,11 +1040,13 @@ moves_loop: // When in check, search starts from here
           }
           else
           {
+              // Capture history based pruning when the move doesn't give check
               if (   !givesCheck
                   && lmrDepth < 1
                   && captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] < 0)
                   continue;
 
+              // See based pruning
               if (!pos.see_ge(move, Value(-194) * depth)) // (~25 Elo)
                   continue;
           }

src/syzygy/tbprobe.cpp

@@ -705,7 +705,7 @@ Ret do_probe_table(const Position& pos, T* entry, WDLScore wdl, ProbeState* resu
 
         std::swap(squares[0], *std::max_element(squares, squares + leadPawnsCnt, pawns_comp));
 
-        tbFile = edge_distance(file_of(squares[0]));
+        tbFile = File(edge_distance(file_of(squares[0])));
     }
 
     // DTZ tables are one-sided, i.e. they store positions only for white to

src/thread.cpp

@@ -166,7 +166,7 @@ void ThreadPool::clear() {
       th->clear();
 
   main()->callsCnt = 0;
-  main()->previousScore = VALUE_INFINITE;
+  main()->bestPreviousScore = VALUE_INFINITE;
   main()->previousTimeReduction = 1.0;
 }
 

src/thread.h

@@ -88,7 +88,7 @@ struct MainThread : public Thread {
   void check_time();
 
   double previousTimeReduction;
-  Value previousScore;
+  Value bestPreviousScore;
   Value iterValue[4];
   int callsCnt;
   bool stopOnPonderhit;

src/types.h

@@ -177,9 +177,9 @@ enum Value : int {
   VALUE_NONE      = 32002,
 
   VALUE_TB_WIN_IN_MAX_PLY  =  VALUE_MATE - 2 * MAX_PLY,
-  VALUE_TB_LOSS_IN_MAX_PLY = -VALUE_MATE + 2 * MAX_PLY,
+  VALUE_TB_LOSS_IN_MAX_PLY = -VALUE_TB_WIN_IN_MAX_PLY,
   VALUE_MATE_IN_MAX_PLY  =  VALUE_MATE - MAX_PLY,
-  VALUE_MATED_IN_MAX_PLY = -VALUE_MATE + MAX_PLY,
+  VALUE_MATED_IN_MAX_PLY = -VALUE_MATE_IN_MAX_PLY,
 
   PawnValueMg   = 128,   PawnValueEg   = 213,
   KnightValueMg = 781,   KnightValueEg = 854,
@@ -351,7 +351,7 @@ inline Score operator*(Score s, int i) {
 
 /// Multiplication of a Score by a boolean
 inline Score operator*(Score s, bool b) {
-  return Score(int(s) * int(b));
+  return b ? s : SCORE_ZERO;
 }
 
 constexpr Color operator~(Color c) {