Mark all compile-time constants as constexpr.

To more clearly distinguish them from "const" local variables, this patch
defines compile-time local constants as constexpr. This is consistent with
the definition of PvNode as constexpr in search() and qsearch(). It also
makes the code more robust, since the compiler will now check that those
constants are indeed compile-time constants.

We can go even one step further and define all the evaluation and search
compile-time constants as constexpr.

In generate_castling() I replaced "K" with "step", since K was incorrectly
capitalised (in the Chess960 case).

In timeman.cpp I had to make the non-local constants MaxRatio and StealRatio
constepxr, since otherwise gcc would complain when calculating TMaxRatio and
TStealRatio. (Strangely, I did not have to make Is64Bit constexpr even though
it is used in ucioption.cpp in the calculation of constexpr MaxHashMB.)

I have renamed PieceCount to pieceCount in material.h, since the values of
the array are not compile-time constants.

Some compile-time constants in tbprobe.cpp were overlooked. Sides and MaxFile
are not compile-time constants, so were renamed to sides and maxFile.

Non-functional change.

diff --git a/src/bitbase.cpp b/src/bitbase.cpp
index 3c9bf6e89e03c9aab7cd83a8948c0c914c4e2e49..60048289218b907f07005ee38446d4e4dc4e7556 100644 (file)
--- a/src/bitbase.cpp
+++ b/src/bitbase.cpp
@@ -29,7 +29,7 @@
 namespace {
 
   // There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7
-  const unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
+  constexpr unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
 
   // Each uint32_t stores results of 32 positions, one per bit
   uint32_t KPKBitbase[MAX_INDEX / 32];
@@ -152,9 +152,9 @@ namespace {
     // as WIN, the position is classified as WIN, otherwise the current position is
     // classified as UNKNOWN.
 
-    const Color  Them = (Us == WHITE ? BLACK : WHITE);
-    const Result Good = (Us == WHITE ? WIN   : DRAW);
-    const Result Bad  = (Us == WHITE ? DRAW  : WIN);
+    constexpr Color  Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Result Good = (Us == WHITE ? WIN   : DRAW);
+    constexpr Result Bad  = (Us == WHITE ? DRAW  : WIN);
 
     Result r = INVALID;
     Bitboard b = PseudoAttacks[KING][ksq[Us]];

diff --git a/src/bitboard.h b/src/bitboard.h
index ed01eada8fafe158dcb3a701e323afed5638dc6e..6032f47f6294b385847716154fe145009dfb5604 100644 (file)
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -39,26 +39,26 @@ const std::string pretty(Bitboard b);
 
 }
 
-const Bitboard AllSquares = ~Bitboard(0);
-const Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
-
-const Bitboard FileABB = 0x0101010101010101ULL;
-const Bitboard FileBBB = FileABB << 1;
-const Bitboard FileCBB = FileABB << 2;
-const Bitboard FileDBB = FileABB << 3;
-const Bitboard FileEBB = FileABB << 4;
-const Bitboard FileFBB = FileABB << 5;
-const Bitboard FileGBB = FileABB << 6;
-const Bitboard FileHBB = FileABB << 7;
-
-const Bitboard Rank1BB = 0xFF;
-const Bitboard Rank2BB = Rank1BB << (8 * 1);
-const Bitboard Rank3BB = Rank1BB << (8 * 2);
-const Bitboard Rank4BB = Rank1BB << (8 * 3);
-const Bitboard Rank5BB = Rank1BB << (8 * 4);
-const Bitboard Rank6BB = Rank1BB << (8 * 5);
-const Bitboard Rank7BB = Rank1BB << (8 * 6);
-const Bitboard Rank8BB = Rank1BB << (8 * 7);
+constexpr Bitboard AllSquares = ~Bitboard(0);
+constexpr Bitboard DarkSquares = 0xAA55AA55AA55AA55ULL;
+
+constexpr Bitboard FileABB = 0x0101010101010101ULL;
+constexpr Bitboard FileBBB = FileABB << 1;
+constexpr Bitboard FileCBB = FileABB << 2;
+constexpr Bitboard FileDBB = FileABB << 3;
+constexpr Bitboard FileEBB = FileABB << 4;
+constexpr Bitboard FileFBB = FileABB << 5;
+constexpr Bitboard FileGBB = FileABB << 6;
+constexpr Bitboard FileHBB = FileABB << 7;
+
+constexpr Bitboard Rank1BB = 0xFF;
+constexpr Bitboard Rank2BB = Rank1BB << (8 * 1);
+constexpr Bitboard Rank3BB = Rank1BB << (8 * 2);
+constexpr Bitboard Rank4BB = Rank1BB << (8 * 3);
+constexpr Bitboard Rank5BB = Rank1BB << (8 * 4);
+constexpr Bitboard Rank6BB = Rank1BB << (8 * 5);
+constexpr Bitboard Rank7BB = Rank1BB << (8 * 6);
+constexpr Bitboard Rank8BB = Rank1BB << (8 * 7);
 
 extern int SquareDistance[SQUARE_NB][SQUARE_NB];
 

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 39db219ed85a2c26f3f61f38f5999c51e5339bee..55e4483dbe84a22c0d456b2a2994fc7e0256ca3d 100644 (file)
--- a/src/endgame.cpp
+++ b/src/endgame.cpp
@@ -31,7 +31,7 @@ namespace {
 
   // Table used to drive the king towards the edge of the board
   // in KX vs K and KQ vs KR endgames.
-  const int PushToEdges[SQUARE_NB] = {
+  constexpr int PushToEdges[SQUARE_NB] = {
     100, 90, 80, 70, 70, 80, 90, 100,
      90, 70, 60, 50, 50, 60, 70,  90,
      80, 60, 40, 30, 30, 40, 60,  80,
@@ -44,7 +44,7 @@ namespace {
 
   // Table used to drive the king towards a corner square of the
   // right color in KBN vs K endgames.
-  const int PushToCorners[SQUARE_NB] = {
+  constexpr int PushToCorners[SQUARE_NB] = {
     200, 190, 180, 170, 160, 150, 140, 130,
     190, 180, 170, 160, 150, 140, 130, 140,
     180, 170, 155, 140, 140, 125, 140, 150,
@@ -56,11 +56,11 @@ namespace {
   };
 
   // Tables used to drive a piece towards or away from another piece
-  const int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
-  const int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
+  constexpr int PushClose[8] = { 0, 0, 100, 80, 60, 40, 20, 10 };
+  constexpr int PushAway [8] = { 0, 5, 20, 40, 60, 80, 90, 100 };
 
   // Pawn Rank based scaling factors used in KRPPKRP endgame
-  const int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 };
+  constexpr int KRPPKRPScaleFactors[RANK_NB] = { 0, 9, 10, 14, 21, 44, 0, 0 };
 
 #ifndef NDEBUG
   bool verify_material(const Position& pos, Color c, Value npm, int pawnsCnt) {

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index bb60107dc42ea069aa754c617bdfa11691535879..64e0eca40d748b335086d40100906ddd718fcd62 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -74,35 +74,35 @@ using namespace Trace;
 
 namespace {
 
-  const Bitboard QueenSide   = FileABB | FileBBB | FileCBB | FileDBB;
-  const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
-  const Bitboard KingSide    = FileEBB | FileFBB | FileGBB | FileHBB;
-  const Bitboard Center      = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
+  constexpr Bitboard QueenSide   = FileABB | FileBBB | FileCBB | FileDBB;
+  constexpr Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
+  constexpr Bitboard KingSide    = FileEBB | FileFBB | FileGBB | FileHBB;
+  constexpr Bitboard Center      = (FileDBB | FileEBB) & (Rank4BB | Rank5BB);
 
-  const Bitboard KingFlank[FILE_NB] = {
+  constexpr Bitboard KingFlank[FILE_NB] = {
     QueenSide,   QueenSide, QueenSide,
     CenterFiles, CenterFiles,
     KingSide,    KingSide,  KingSide
   };
 
   // Threshold for lazy and space evaluation
-  const Value LazyThreshold  = Value(1500);
-  const Value SpaceThreshold = Value(12222);
+  constexpr Value LazyThreshold  = Value(1500);
+  constexpr Value SpaceThreshold = Value(12222);
 
   // KingAttackWeights[PieceType] contains king attack weights by piece type
-  const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
+  constexpr int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 78, 56, 45, 11 };
 
   // Penalties for enemy's safe checks
-  const int QueenSafeCheck  = 780;
-  const int RookSafeCheck   = 880;
-  const int BishopSafeCheck = 435;
-  const int KnightSafeCheck = 790;
+  constexpr int QueenSafeCheck  = 780;
+  constexpr int RookSafeCheck   = 880;
+  constexpr int BishopSafeCheck = 435;
+  constexpr int KnightSafeCheck = 790;
 
 #define S(mg, eg) make_score(mg, eg)
 
   // MobilityBonus[PieceType-2][attacked] contains bonuses for middle and end game,
   // indexed by piece type and number of attacked squares in the mobility area.
-  const Score MobilityBonus[][32] = {
+  constexpr Score MobilityBonus[][32] = {
     { S(-75,-76), S(-57,-54), S( -9,-28), S( -2,-10), S(  6,  5), S( 14, 12), // Knights
       S( 22, 26), S( 29, 29), S( 36, 29) },
     { S(-48,-59), S(-20,-23), S( 16, -3), S( 26, 13), S( 38, 24), S( 51, 42), // Bishops
@@ -121,66 +121,66 @@ namespace {
   // Outpost[knight/bishop][supported by pawn] contains bonuses for minor
   // pieces if they occupy or can reach an outpost square, bigger if that
   // square is supported by a pawn.
-  const Score Outpost[][2] = {
+  constexpr Score Outpost[][2] = {
     { S(22, 6), S(36,12) }, // Knight
     { S( 9, 2), S(15, 5) }  // Bishop
   };
 
   // RookOnFile[semiopen/open] contains bonuses for each rook when there is
   // no (friendly) pawn on the rook file.
-  const Score RookOnFile[] = { S(20, 7), S(45, 20) };
+  constexpr Score RookOnFile[] = { S(20, 7), S(45, 20) };
 
   // ThreatByMinor/ByRook[attacked PieceType] contains bonuses according to
   // which piece type attacks which one. Attacks on lesser pieces which are
   // pawn-defended are not considered.
-  const Score ThreatByMinor[PIECE_TYPE_NB] = {
+  constexpr Score ThreatByMinor[PIECE_TYPE_NB] = {
     S(0, 0), S(0, 31), S(39, 42), S(57, 44), S(68, 112), S(47, 120)
   };
 
-  const Score ThreatByRook[PIECE_TYPE_NB] = {
+  constexpr Score ThreatByRook[PIECE_TYPE_NB] = {
     S(0, 0), S(0, 24), S(38, 71), S(38, 61), S(0, 38), S(36, 38)
   };
 
   // ThreatByKing[on one/on many] contains bonuses for king attacks on
   // pawns or pieces which are not pawn-defended.
-  const Score ThreatByKing[] = { S(3, 65), S(9, 145) };
+  constexpr Score ThreatByKing[] = { S(3, 65), S(9, 145) };
 
   // PassedRank[Rank] contains a bonus according to the rank of a passed pawn
-  const Score PassedRank[RANK_NB] = {
+  constexpr Score PassedRank[RANK_NB] = {
     S(0, 0), S(5, 7), S(5, 13), S(32, 42), S(70, 70), S(172, 170), S(217, 269)
   };
 
   // PassedFile[File] contains a bonus according to the file of a passed pawn
-  const Score PassedFile[FILE_NB] = {
+  constexpr Score PassedFile[FILE_NB] = {
     S(  9, 10), S(2, 10), S(1, -8), S(-20,-12),
     S(-20,-12), S(1, -8), S(2, 10), S(  9, 10)
   };
 
   // PassedDanger[Rank] contains a term to weight the passed score
-  const int PassedDanger[RANK_NB] = { 0, 0, 0, 2, 7, 12, 19 };
+  constexpr int PassedDanger[RANK_NB] = { 0, 0, 0, 2, 7, 12, 19 };
 
   // KingProtector[PieceType-2] contains a penalty according to distance from king
-  const Score KingProtector[] = { S(3, 5), S(4, 3), S(3, 0), S(1, -1) };
+  constexpr Score KingProtector[] = { S(3, 5), S(4, 3), S(3, 0), S(1, -1) };
 
   // Assorted bonuses and penalties
-  const Score BishopPawns        = S(  8, 12);
-  const Score CloseEnemies       = S(  7,  0);
-  const Score Connectivity       = S(  3,  1);
-  const Score CorneredBishop     = S( 50, 50);
-  const Score Hanging            = S( 52, 30);
-  const Score HinderPassedPawn   = S(  8,  1);
-  const Score KnightOnQueen      = S( 21, 11);
-  const Score LongDiagonalBishop = S( 22,  0);
-  const Score MinorBehindPawn    = S( 16,  0);
-  const Score PawnlessFlank      = S( 20, 80);
-  const Score RookOnPawn         = S(  8, 24);
-  const Score SliderOnQueen      = S( 42, 21);
-  const Score ThreatByPawnPush   = S( 47, 26);
-  const Score ThreatByRank       = S( 16,  3);
-  const Score ThreatBySafePawn   = S(175,168);
-  const Score TrappedRook        = S( 92,  0);
-  const Score WeakQueen          = S( 50, 10);
-  const Score WeakUnopposedPawn  = S(  5, 25);
+  constexpr Score BishopPawns        = S(  8, 12);
+  constexpr Score CloseEnemies       = S(  7,  0);
+  constexpr Score Connectivity       = S(  3,  1);
+  constexpr Score CorneredBishop     = S( 50, 50);
+  constexpr Score Hanging            = S( 52, 30);
+  constexpr Score HinderPassedPawn   = S(  8,  1);
+  constexpr Score KnightOnQueen      = S( 21, 11);
+  constexpr Score LongDiagonalBishop = S( 22,  0);
+  constexpr Score MinorBehindPawn    = S( 16,  0);
+  constexpr Score PawnlessFlank      = S( 20, 80);
+  constexpr Score RookOnPawn         = S(  8, 24);
+  constexpr Score SliderOnQueen      = S( 42, 21);
+  constexpr Score ThreatByPawnPush   = S( 47, 26);
+  constexpr Score ThreatByRank       = S( 16,  3);
+  constexpr Score ThreatBySafePawn   = S(175,168);
+  constexpr Score TrappedRook        = S( 92,  0);
+  constexpr Score WeakQueen          = S( 50, 10);
+  constexpr Score WeakUnopposedPawn  = S(  5, 25);
 
 #undef S
 
@@ -250,10 +250,10 @@ namespace {
   template<Tracing T> template<Color Us>
   void Evaluation<T>::initialize() {
 
-    const Color     Them = (Us == WHITE ? BLACK : WHITE);
-    const Direction Up   = (Us == WHITE ? NORTH : SOUTH);
-    const Direction Down = (Us == WHITE ? SOUTH : NORTH);
-    const Bitboard LowRanks = (Us == WHITE ? Rank2BB | Rank3BB: Rank7BB | Rank6BB);
+    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);
 
     // Find our pawns that are blocked or on the first two ranks
     Bitboard b = pos.pieces(Us, PAWN) & (shift<Down>(pos.pieces()) | LowRanks);
@@ -287,8 +287,8 @@ namespace {
   template<Tracing T> template<Color Us, PieceType Pt>
   Score Evaluation<T>::pieces() {
 
-    const Color Them = (Us == WHITE ? BLACK : WHITE);
-    const Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
+    constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Bitboard OutpostRanks = (Us == WHITE ? Rank4BB | Rank5BB | Rank6BB
                                                : Rank5BB | Rank4BB | Rank3BB);
     const Square* pl = pos.squares<Pt>(Us);
 
@@ -404,8 +404,8 @@ namespace {
   template<Tracing T> template<Color Us>
   Score Evaluation<T>::king() const {
 
-    const Color    Them = (Us == WHITE ? BLACK : WHITE);
-    const Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
+    constexpr Color    Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Bitboard Camp = (Us == WHITE ? AllSquares ^ Rank6BB ^ Rank7BB ^ Rank8BB
                                        : AllSquares ^ Rank1BB ^ Rank2BB ^ Rank3BB);
 
     const Square ksq = pos.square<KING>(Us);
@@ -506,9 +506,9 @@ namespace {
   template<Tracing T> template<Color Us>
   Score Evaluation<T>::threats() const {
 
-    const Color     Them     = (Us == WHITE ? BLACK   : WHITE);
-    const Direction Up       = (Us == WHITE ? NORTH   : SOUTH);
-    const Bitboard  TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
+    constexpr Color     Them     = (Us == WHITE ? BLACK   : WHITE);
+    constexpr Direction Up       = (Us == WHITE ? NORTH   : SOUTH);
+    constexpr Bitboard  TRank3BB = (Us == WHITE ? Rank3BB : Rank6BB);
 
     Bitboard b, weak, defended, nonPawnEnemies, stronglyProtected, safeThreats;
     Score score = SCORE_ZERO;
@@ -617,8 +617,8 @@ namespace {
   template<Tracing T> template<Color Us>
   Score Evaluation<T>::passed() const {
 
-    const Color     Them = (Us == WHITE ? BLACK : WHITE);
-    const Direction Up   = (Us == WHITE ? NORTH : SOUTH);
+    constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Direction Up   = (Us == WHITE ? NORTH : SOUTH);
 
     auto king_proximity = [&](Color c, Square s) {
       return std::min(distance(pos.square<KING>(c), s), 5);
@@ -715,8 +715,8 @@ namespace {
   template<Tracing T> template<Color Us>
   Score Evaluation<T>::space() const {
 
-    const Color Them = (Us == WHITE ? BLACK : WHITE);
-    const Bitboard SpaceMask =
+    constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Bitboard SpaceMask =
       Us == WHITE ? CenterFiles & (Rank2BB | Rank3BB | Rank4BB)
                   : CenterFiles & (Rank7BB | Rank6BB | Rank5BB);
 

diff --git a/src/evaluate.h b/src/evaluate.h
index 0004dd6319defab08530ed1aa10646e3bb9ff060..c3b0b2b9e2bab40f15e739211270d2f359c2f79e 100644 (file)
--- a/src/evaluate.h
+++ b/src/evaluate.h
@@ -30,7 +30,7 @@ class Position;
 
 namespace Eval {
 
-const Value Tempo = Value(20); // Must be visible to search
+constexpr Value Tempo = Value(20); // Must be visible to search
 
 extern std::atomic<Score> Contempt;
 

diff --git a/src/material.cpp b/src/material.cpp
index 4cfda03e4f3dcab3ee3bfed56553ea379e775826..921e3007d0733788de389a676da524919ab06016 100644 (file)
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -31,7 +31,7 @@ namespace {
 
   // Polynomial material imbalance parameters
 
-  const int QuadraticOurs[][PIECE_TYPE_NB] = {
+  constexpr int QuadraticOurs[][PIECE_TYPE_NB] = {
     //            OUR PIECES
     // pair pawn knight bishop rook queen
     {1667                               }, // Bishop pair
@@ -42,7 +42,7 @@ namespace {
     {-189,   24, 117,   133,  -134, -10 }  // Queen
   };
 
-  const int QuadraticTheirs[][PIECE_TYPE_NB] = {
+  constexpr int QuadraticTheirs[][PIECE_TYPE_NB] = {
     //           THEIR PIECES
     // pair pawn knight bishop rook queen
     {   0                               }, // Bishop pair
@@ -87,7 +87,7 @@ namespace {
   template<Color Us>
   int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
 
-    const Color Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Color Them = (Us == WHITE ? BLACK : WHITE);
 
     int bonus = 0;
 
@@ -215,13 +215,13 @@ Entry* probe(const Position& pos) {
   // Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
   // for the bishop pair "extended piece", which allows us to be more flexible
   // in defining bishop pair bonuses.
-  const int PieceCount[COLOR_NB][PIECE_TYPE_NB] = {
+  const int pieceCount[COLOR_NB][PIECE_TYPE_NB] = {
   { pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),
     pos.count<BISHOP>(WHITE)    , pos.count<ROOK>(WHITE), pos.count<QUEEN >(WHITE) },
   { pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
     pos.count<BISHOP>(BLACK)    , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
 
-  e->value = int16_t((imbalance<WHITE>(PieceCount) - imbalance<BLACK>(PieceCount)) / 16);
+  e->value = int16_t((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
   return e;
 }
 

diff --git a/src/movegen.cpp b/src/movegen.cpp
index cb221d95e178e1833c00fb414e183561b02a9924..ed8745e863d264b88bc14aecda1140a67414bdc7 100644 (file)
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -28,7 +28,7 @@ namespace {
   template<CastlingRight Cr, bool Checks, bool Chess960>
   ExtMove* generate_castling(const Position& pos, ExtMove* moveList, Color us) {
 
-    static const bool KingSide = (Cr == WHITE_OO || Cr == BLACK_OO);
+    static constexpr bool KingSide = (Cr == WHITE_OO || Cr == BLACK_OO);
 
     if (pos.castling_impeded(Cr) || !pos.can_castle(Cr))
         return moveList;
@@ -42,10 +42,10 @@ namespace {
 
     assert(!pos.checkers());
 
-    const Direction K = Chess960 ? kto > kfrom ? WEST : EAST
-                                 : KingSide    ? WEST : EAST;
+    const Direction step = Chess960 ? kto > kfrom ? WEST : EAST
+                                    : KingSide    ? WEST : EAST;
 
-    for (Square s = kto; s != kfrom; s += K)
+    for (Square s = kto; s != kfrom; s += step)
         if (pos.attackers_to(s) & enemies)
             return moveList;
 
@@ -94,13 +94,13 @@ namespace {
 
     // Compute our parametrized parameters at compile time, named according to
     // the point of view of white side.
-    const Color     Them     = (Us == WHITE ? BLACK      : WHITE);
-    const Bitboard  TRank8BB = (Us == WHITE ? Rank8BB    : Rank1BB);
-    const Bitboard  TRank7BB = (Us == WHITE ? Rank7BB    : Rank2BB);
-    const Bitboard  TRank3BB = (Us == WHITE ? Rank3BB    : Rank6BB);
-    const Direction Up       = (Us == WHITE ? NORTH      : SOUTH);
-    const Direction UpRight  = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
-    const Direction UpLeft   = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
+    constexpr Color     Them     = (Us == WHITE ? BLACK      : WHITE);
+    constexpr Bitboard  TRank8BB = (Us == WHITE ? Rank8BB    : Rank1BB);
+    constexpr Bitboard  TRank7BB = (Us == WHITE ? Rank7BB    : Rank2BB);
+    constexpr Bitboard  TRank3BB = (Us == WHITE ? Rank3BB    : Rank6BB);
+    constexpr Direction Up       = (Us == WHITE ? NORTH      : SOUTH);
+    constexpr Direction UpRight  = (Us == WHITE ? NORTH_EAST : SOUTH_WEST);
+    constexpr Direction UpLeft   = (Us == WHITE ? NORTH_WEST : SOUTH_EAST);
 
     Bitboard emptySquares;
 
@@ -261,7 +261,7 @@ namespace {
   template<Color Us, GenType Type>
   ExtMove* generate_all(const Position& pos, ExtMove* moveList, Bitboard target) {
 
-    const bool Checks = Type == QUIET_CHECKS;
+    constexpr bool Checks = Type == QUIET_CHECKS;
 
     moveList = generate_pawn_moves<Us, Type>(pos, moveList, target);
     moveList = generate_moves<KNIGHT, Checks>(pos, moveList, Us, target);

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 67bf59d183325a52fd2cfc3a200a5d0e60d18f7b..56f5d7239594b391e13ddd6b3edd80432632297f 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -32,20 +32,20 @@ namespace {
   #define S(mg, eg) make_score(mg, eg)
 
   // Isolated pawn penalty
-  const Score Isolated = S(13, 18);
+  constexpr Score Isolated = S(13, 18);
 
   // Backward pawn penalty
-  const Score Backward = S(24, 12);
+  constexpr Score Backward = S(24, 12);
 
   // Connected pawn bonus by opposed, phalanx, #support and rank
   Score Connected[2][2][3][RANK_NB];
 
   // Doubled pawn penalty
-  const Score Doubled = S(18, 38);
+  constexpr Score Doubled = S(18, 38);
 
   // Weakness of our pawn shelter in front of the king by [isKingFile][distance from edge][rank].
   // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king.
-  const Value ShelterWeakness[][int(FILE_NB) / 2][RANK_NB] = {
+  constexpr Value ShelterWeakness[][int(FILE_NB) / 2][RANK_NB] = {
     { { V( 98), V(20), V(11), V(42), V( 83), V( 84), V(101) }, // Not On King file
       { V(103), V( 8), V(33), V(86), V( 87), V(105), V(113) },
       { V(100), V( 2), V(65), V(95), V( 59), V( 89), V(115) },
@@ -59,7 +59,7 @@ namespace {
   // Danger of enemy pawns moving toward our king by [type][distance from edge][rank].
   // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has
   // no pawn on the given file, or their pawn is behind our king.
-  const Value StormDanger[][4][RANK_NB] = {
+  constexpr Value StormDanger[][4][RANK_NB] = {
     { { V( 0),  V(-290), V(-274), V(57), V(41) },  // BlockedByKing
       { V( 0),  V(  60), V( 144), V(39), V(13) },
       { V( 0),  V(  65), V( 141), V(41), V(34) },
@@ -80,7 +80,7 @@ namespace {
 
   // Max bonus for king safety. Corresponds to start position with all the pawns
   // in front of the king and no enemy pawn on the horizon.
-  const Value MaxSafetyBonus = V(258);
+  constexpr Value MaxSafetyBonus = V(258);
 
   #undef S
   #undef V
@@ -88,8 +88,8 @@ namespace {
   template<Color Us>
   Score evaluate(const Position& pos, Pawns::Entry* e) {
 
-    const Color     Them = (Us == WHITE ? BLACK : WHITE);
-    const Direction Up   = (Us == WHITE ? NORTH : SOUTH);
+    constexpr Color     Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Direction Up   = (Us == WHITE ? NORTH : SOUTH);
 
     Bitboard b, neighbours, stoppers, doubled, supported, phalanx;
     Bitboard lever, leverPush;
@@ -191,7 +191,7 @@ namespace Pawns {
 
 void init() {
 
-  static const int Seed[RANK_NB] = { 0, 13, 24, 18, 76, 100, 175, 330 };
+  static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 76, 100, 175, 330 };
 
   for (int opposed = 0; opposed <= 1; ++opposed)
       for (int phalanx = 0; phalanx <= 1; ++phalanx)

diff --git a/src/position.cpp b/src/position.cpp
index 9cec2c14ff9646882a06f3abd02290248196d8f2..c0e2232c08dee5c92c235d24408c99866dee88a3 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -52,8 +52,8 @@ namespace {
 
 const string PieceToChar(" PNBRQK  pnbrqk");
 
-const Piece Pieces[] = { W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
-                         B_PAWN, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING };
+constexpr Piece Pieces[] = { W_PAWN, W_KNIGHT, W_BISHOP, W_ROOK, W_QUEEN, W_KING,
+                             B_PAWN, B_KNIGHT, B_BISHOP, B_ROOK, B_QUEEN, B_KING };
 
 // min_attacker() is a helper function used by see_ge() to locate the least
 // valuable attacker for the side to move, remove the attacker we just found
@@ -1146,7 +1146,7 @@ void Position::flip() {
 
 bool Position::pos_is_ok() const {
 
-  const bool Fast = true; // Quick (default) or full check?
+  constexpr bool Fast = true; // Quick (default) or full check?
 
   if (   (sideToMove != WHITE && sideToMove != BLACK)
       || piece_on(square<KING>(WHITE)) != W_KING

diff --git a/src/psqt.cpp b/src/psqt.cpp
index cbdce81a26ed4da3c9b03f4cba5ed93f5c7325d9..e0f15c0636042b49da4268577203fc0d8b02e384 100644 (file)
--- a/src/psqt.cpp
+++ b/src/psqt.cpp
@@ -35,7 +35,7 @@ namespace PSQT {
 // type on a given square a (middlegame, endgame) score pair is assigned. Table
 // is defined for files A..D and white side: it is symmetric for black side and
 // second half of the files.
-const Score Bonus[][RANK_NB][int(FILE_NB) / 2] = {
+constexpr Score Bonus[][RANK_NB][int(FILE_NB) / 2] = {
   { },
   { // Pawn
    { S(  0, 0), S(  0, 0), S(  0, 0), S( 0, 0) },

diff --git a/src/search.cpp b/src/search.cpp
index afc4a671251b03c196d1d07a565561158f9524df..176006fcc1073ea837b04b27dcdcc8d3ace22e0e 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -63,12 +63,12 @@ namespace {
   enum NodeType { NonPV, PV };
 
   // Sizes and phases of the skip-blocks, used for distributing search depths across the threads
-  const int SkipSize[]  = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
-  const int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
+  constexpr int SkipSize[]  = { 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
+  constexpr int SkipPhase[] = { 0, 1, 0, 1, 2, 3, 0, 1, 2, 3, 4, 5, 0, 1, 2, 3, 4, 5, 6, 7 };
 
   // Razor and futility margins
-  const int RazorMargin1 = 590;
-  const int RazorMargin2 = 604;
+  constexpr int RazorMargin1 = 590;
+  constexpr int RazorMargin2 = 604;
   Value futility_margin(Depth d, bool improving) {
     return Value((175 - 50 * improving) * d / ONE_PLY);
   }

diff --git a/src/search.h b/src/search.h
index 1274b9681958fce4d2cbf53b6695c33505c1ab67..22f9f0d766ae0ce839b493ac91219f75f03247e0 100644 (file)
--- a/src/search.h
+++ b/src/search.h
@@ -32,7 +32,7 @@ class Position;
 namespace Search {
 
 /// Threshold used for countermoves based pruning
-const int CounterMovePruneThreshold = 0;
+constexpr int CounterMovePruneThreshold = 0;
 
 
 /// Stack struct keeps track of the information we need to remember from nodes

diff --git a/src/syzygy/tbprobe.cpp b/src/syzygy/tbprobe.cpp
index b50275e30f7e26baaad3bed17db6e5495a64c43d..722679fd948a169ed516a34e39da87c629bafa94 100644 (file)
--- a/src/syzygy/tbprobe.cpp
+++ b/src/syzygy/tbprobe.cpp
@@ -102,7 +102,7 @@ struct LR {
 
 static_assert(sizeof(LR) == 3, "LR tree entry must be 3 bytes");
 
-const int TBPIECES = 6;
+constexpr int TBPIECES = 6;
 
 struct PairsData {
     int flags;
@@ -208,7 +208,7 @@ int MapKK[10][SQUARE_NB]; // [MapA1D1D4][SQUARE_NB]
 bool pawns_comp(Square i, Square j) { return MapPawns[i] < MapPawns[j]; }
 int off_A1H8(Square sq) { return int(rank_of(sq)) - file_of(sq); }
 
-const Value WDL_to_value[] = {
+constexpr Value WDL_to_value[] = {
    -VALUE_MATE + MAX_PLY + 1,
     VALUE_DRAW - 2,
     VALUE_DRAW,
@@ -255,8 +255,8 @@ class HashTable {
     typedef std::pair<WDLEntry*, DTZEntry*> EntryPair;
     typedef std::pair<Key, EntryPair> Entry;
 
-    static const int TBHASHBITS = 10;
-    static const int HSHMAX     = 5;
+    static constexpr int TBHASHBITS = 10;
+    static constexpr int HSHMAX     = 5;
 
     Entry hashTable[1 << TBHASHBITS][HSHMAX];
 
@@ -315,9 +315,9 @@ public:
     TBFile(const std::string& f) {
 
 #ifndef _WIN32
-        const char SepChar = ':';
+        constexpr char SepChar = ':';
 #else
-        const char SepChar = ';';
+        constexpr char SepChar = ';';
 #endif
         std::stringstream ss(Paths);
         std::string path;
@@ -649,7 +649,7 @@ WDLScore map_score(WDLEntry*, File, int value, WDLScore) { return WDLScore(value
 
 int map_score(DTZEntry* entry, File f, int value, WDLScore wdl) {
 
-    const int WDLMap[] = { 1, 3, 0, 2, 0 };
+    constexpr int WDLMap[] = { 1, 3, 0, 2, 0 };
 
     int flags = entry->hasPawns ? entry->pawnTable.file[f].precomp->flags
                                 : entry->pieceTable.precomp->flags;
@@ -682,7 +682,7 @@ int map_score(DTZEntry* entry, File f, int value, WDLScore wdl) {
 template<typename Entry, typename T = typename Ret<Entry>::type>
 T do_probe_table(const Position& pos, Entry* entry, WDLScore wdl, ProbeState* result) {
 
-    const bool IsWDL = std::is_same<Entry, WDLEntry>::value;
+    constexpr bool IsWDL = std::is_same<Entry, WDLEntry>::value;
 
     Square squares[TBPIECES];
     Piece pieces[TBPIECES];
@@ -1081,16 +1081,16 @@ void do_init(Entry& e, T& p, uint8_t* data) {
 
     data++; // First byte stores flags
 
-    const int Sides = IsWDL && (e.key != e.key2) ? 2 : 1;
-    const File MaxFile = e.hasPawns ? FILE_D : FILE_A;
+    const int sides = IsWDL && (e.key != e.key2) ? 2 : 1;
+    const File maxFile = e.hasPawns ? FILE_D : FILE_A;
 
     bool pp = e.hasPawns && e.pawnTable.pawnCount[1]; // Pawns on both sides
 
     assert(!pp || e.pawnTable.pawnCount[0]);
 
-    for (File f = FILE_A; f <= MaxFile; ++f) {
+    for (File f = FILE_A; f <= maxFile; ++f) {
 
-        for (int i = 0; i < Sides; i++)
+        for (int i = 0; i < sides; i++)
             item(p, i, f).precomp = new PairsData();
 
         int order[][2] = { { *data & 0xF, pp ? *(data + 1) & 0xF : 0xF },
@@ -1098,36 +1098,36 @@ void do_init(Entry& e, T& p, uint8_t* data) {
         data += 1 + pp;
 
         for (int k = 0; k < e.pieceCount; ++k, ++data)
-            for (int i = 0; i < Sides; i++)
+            for (int i = 0; i < sides; i++)
                 item(p, i, f).precomp->pieces[k] = Piece(i ? *data >>  4 : *data & 0xF);
 
-        for (int i = 0; i < Sides; ++i)
+        for (int i = 0; i < sides; ++i)
             set_groups(e, item(p, i, f).precomp, order[i], f);
     }
 
     data += (uintptr_t)data & 1; // Word alignment
 
-    for (File f = FILE_A; f <= MaxFile; ++f)
-        for (int i = 0; i < Sides; i++)
+    for (File f = FILE_A; f <= maxFile; ++f)
+        for (int i = 0; i < sides; i++)
             data = set_sizes(item(p, i, f).precomp, data);
 
     if (!IsWDL)
-        data = set_dtz_map(e, p, data, MaxFile);
+        data = set_dtz_map(e, p, data, maxFile);
 
-    for (File f = FILE_A; f <= MaxFile; ++f)
-        for (int i = 0; i < Sides; i++) {
+    for (File f = FILE_A; f <= maxFile; ++f)
+        for (int i = 0; i < sides; i++) {
             (d = item(p, i, f).precomp)->sparseIndex = (SparseEntry*)data;
             data += d->sparseIndexSize * sizeof(SparseEntry);
         }
 
-    for (File f = FILE_A; f <= MaxFile; ++f)
-        for (int i = 0; i < Sides; i++) {
+    for (File f = FILE_A; f <= maxFile; ++f)
+        for (int i = 0; i < sides; i++) {
             (d = item(p, i, f).precomp)->blockLength = (uint16_t*)data;
             data += d->blockLengthSize * sizeof(uint16_t);
         }
 
-    for (File f = FILE_A; f <= MaxFile; ++f)
-        for (int i = 0; i < Sides; i++) {
+    for (File f = FILE_A; f <= maxFile; ++f)
+        for (int i = 0; i < sides; i++) {
             data = (uint8_t*)(((uintptr_t)data + 0x3F) & ~0x3F); // 64 byte alignment
             (d = item(p, i, f).precomp)->data = data;
             data += d->blocksNum * d->sizeofBlock;
@@ -1137,7 +1137,7 @@ void do_init(Entry& e, T& p, uint8_t* data) {
 template<typename Entry>
 void* init(Entry& e, const Position& pos) {
 
-    const bool IsWDL = std::is_same<Entry, WDLEntry>::value;
+    constexpr bool IsWDL = std::is_same<Entry, WDLEntry>::value;
 
     static Mutex mutex;
 
@@ -1158,7 +1158,7 @@ void* init(Entry& e, const Position& pos) {
         b += std::string(popcount(pos.pieces(BLACK, pt)), PieceToChar[pt]);
     }
 
-    const uint8_t TB_MAGIC[][4] = { { 0xD7, 0x66, 0x0C, 0xA5 },
+    constexpr uint8_t TB_MAGIC[][4] = { { 0xD7, 0x66, 0x0C, 0xA5 },
                                     { 0x71, 0xE8, 0x23, 0x5D } };
 
     fname =  (e.key == pos.material_key() ? w + 'v' + b : b + 'v' + w)

diff --git a/src/timeman.cpp b/src/timeman.cpp
index f6ead0b2a7acf18b8a076c04a5138b428aad52a7..e63454ebd7b3f85f4d6dedaafbe4df949e7133d2 100644 (file)
--- a/src/timeman.cpp
+++ b/src/timeman.cpp
@@ -32,9 +32,9 @@ namespace {
 
   enum TimeType { OptimumTime, MaxTime };
 
-  const int MoveHorizon   = 50;   // Plan time management at most this many moves ahead
-  const double MaxRatio   = 7.3; // When in trouble, we can step over reserved time with this ratio
-  const double StealRatio = 0.34; // However we must not steal time from remaining moves over this ratio
+  constexpr int MoveHorizon   = 50;   // Plan time management at most this many moves ahead
+  constexpr double MaxRatio   = 7.3;  // When in trouble, we can step over reserved time with this ratio
+  constexpr double StealRatio = 0.34; // However we must not steal time from remaining moves over this ratio
 
 
   // move_importance() is a skew-logistic function based on naive statistical
@@ -44,9 +44,9 @@ namespace {
 
   double move_importance(int ply) {
 
-    const double XScale = 6.85;
-    const double XShift = 64.5;
-    const double Skew   = 0.171;
+    constexpr double XScale = 6.85;
+    constexpr double XShift = 64.5;
+    constexpr double Skew   = 0.171;
 
     return pow((1 + exp((ply - XShift) / XScale)), -Skew) + DBL_MIN; // Ensure non-zero
   }
@@ -54,8 +54,8 @@ namespace {
   template<TimeType T>
   int remaining(int myTime, int movesToGo, int ply, int slowMover) {
 
-    const double TMaxRatio   = (T == OptimumTime ? 1 : MaxRatio);
-    const double TStealRatio = (T == OptimumTime ? 0 : StealRatio);
+    constexpr double TMaxRatio   = (T == OptimumTime ? 1 : MaxRatio);
+    constexpr double TStealRatio = (T == OptimumTime ? 0 : StealRatio);
 
     double moveImportance = (move_importance(ply) * slowMover) / 100;
     double otherMovesImportance = 0;
@@ -106,12 +106,12 @@ void TimeManagement::init(Search::LimitsType& limits, Color us, int ply) {
   startTime = limits.startTime;
   optimumTime = maximumTime = std::max(limits.time[us], minThinkingTime);
 
-  const int MaxMTG = limits.movestogo ? std::min(limits.movestogo, MoveHorizon) : MoveHorizon;
+  const int maxMTG = limits.movestogo ? std::min(limits.movestogo, MoveHorizon) : MoveHorizon;
 
   // We calculate optimum time usage for different hypothetical "moves to go"-values
   // and choose the minimum of calculated search time values. Usually the greatest
   // hypMTG gives the minimum values.
-  for (int hypMTG = 1; hypMTG <= MaxMTG; ++hypMTG)
+  for (int hypMTG = 1; hypMTG <= maxMTG; ++hypMTG)
   {
       // Calculate thinking time for hypothetical "moves to go"-value
       int hypMyTime =  limits.time[us]

diff --git a/src/tt.h b/src/tt.h
index ca7dfbfee539f8b3ed52facb2950aa27b14ddaff..5f9c29e4a389745c38639e984b11b8df61cc4126 100644 (file)
--- a/src/tt.h
+++ b/src/tt.h
@@ -85,8 +85,8 @@ private:
 
 class TranspositionTable {
 
-  static const int CacheLineSize = 64;
-  static const int ClusterSize = 3;
+  static constexpr int CacheLineSize = 64;
+  static constexpr int ClusterSize = 3;
 
   struct Cluster {
     TTEntry entry[ClusterSize];

diff --git a/src/types.h b/src/types.h
index 3415a6208abde95b2a5ac7009c856a5c962ed646..2cf52ef123ef9694d9aca8772ed4b9f0183295b8 100644 (file)
--- a/src/types.h
+++ b/src/types.h
@@ -80,28 +80,28 @@
 #endif
 
 #ifdef USE_POPCNT
-const bool HasPopCnt = true;
+constexpr bool HasPopCnt = true;
 #else
-const bool HasPopCnt = false;
+constexpr bool HasPopCnt = false;
 #endif
 
 #ifdef USE_PEXT
-const bool HasPext = true;
+constexpr bool HasPext = true;
 #else
-const bool HasPext = false;
+constexpr bool HasPext = false;
 #endif
 
 #ifdef IS_64BIT
-const bool Is64Bit = true;
+constexpr bool Is64Bit = true;
 #else
-const bool Is64Bit = false;
+constexpr bool Is64Bit = false;
 #endif
 
 typedef uint64_t Key;
 typedef uint64_t Bitboard;
 
-const int MAX_MOVES = 256;
-const int MAX_PLY   = 128;
+constexpr int MAX_MOVES = 256;
+constexpr int MAX_PLY   = 128;
 
 /// A move needs 16 bits to be stored
 ///

diff --git a/src/ucioption.cpp b/src/ucioption.cpp
index f648c017de26e934134e7585319a68c2a629878d..bca4a1f1adb2276cfa76100f870198496ad3cb5b 100644 (file)
--- a/src/ucioption.cpp
+++ b/src/ucioption.cpp
@@ -56,7 +56,7 @@ bool CaseInsensitiveLess::operator() (const string& s1, const string& s2) const
 void init(OptionsMap& o) {
 
   // at most 2^32 clusters.
-  const int MaxHashMB = Is64Bit ? 131072 : 2048;
+  constexpr int MaxHashMB = Is64Bit ? 131072 : 2048;
 
   o["Debug Log File"]        << Option("", on_logger);
   o["Contempt"]              << Option(12, -100, 100);