Retire the misdesigned StepAttacks[] array.

StepAttacks[] is misdesigned, the color dependance is specific
to pawns, and trying to generalise to king and knights, proves
neither useful nor convinient in practice.

So this patch reformats the code with the following changes:

- Use PieceType instead of Piece in attacks_() functions

- Use PseudoAttacks for KING and KNIGHT

- Rename StepAttacks[] into PawnAttacks[]

Original patch and idea from Alain Savard.

No functional change.

Closes #1086

diff --git a/src/bitbase.cpp b/src/bitbase.cpp
index 0e4521c1eb9ac20306de568c7832b11415791c6b..d206210414846e3c3392ac655318080397c8b4a4 100644 (file)
--- a/src/bitbase.cpp
+++ b/src/bitbase.cpp
@@ -117,7 +117,7 @@ namespace {
     if (   distance(ksq[WHITE], ksq[BLACK]) <= 1
         || ksq[WHITE] == psq
         || ksq[BLACK] == psq
     if (   distance(ksq[WHITE], ksq[BLACK]) <= 1
         || ksq[WHITE] == psq
         || ksq[BLACK] == psq

-        || (us == WHITE && (StepAttacksBB[W_PAWN][psq] & ksq[BLACK])))
+        || (us == WHITE && (PawnAttacks[WHITE][psq] & ksq[BLACK])))

         result = INVALID;
 
     // Immediate win if a pawn can be promoted without getting captured
         result = INVALID;
 
     // Immediate win if a pawn can be promoted without getting captured


@@ -125,13 +125,13 @@ namespace {
              && rank_of(psq) == RANK_7
              && ksq[us] != psq + NORTH
              && (    distance(ksq[~us], psq + NORTH) > 1
              && rank_of(psq) == RANK_7
              && ksq[us] != psq + NORTH
              && (    distance(ksq[~us], psq + NORTH) > 1

-                 || (StepAttacksBB[KING][ksq[us]] & (psq + NORTH))))
+                 || (PseudoAttacks[KING][ksq[us]] & (psq + NORTH))))

         result = WIN;
 
     // Immediate draw if it is a stalemate or a king captures undefended pawn
     else if (   us == BLACK
         result = WIN;
 
     // Immediate draw if it is a stalemate or a king captures undefended pawn
     else if (   us == BLACK

-             && (  !(StepAttacksBB[KING][ksq[us]] & ~(StepAttacksBB[KING][ksq[~us]] | StepAttacksBB[W_PAWN][psq]))
-                 || (StepAttacksBB[KING][ksq[us]] & psq & ~StepAttacksBB[KING][ksq[~us]])))
+             && (  !(PseudoAttacks[KING][ksq[us]] & ~(PseudoAttacks[KING][ksq[~us]] | PawnAttacks[~us][psq]))
+                 || (PseudoAttacks[KING][ksq[us]] & psq & ~PseudoAttacks[KING][ksq[~us]])))

         result = DRAW;
 
     // Position will be classified later
         result = DRAW;
 
     // Position will be classified later


@@ -157,7 +157,7 @@ namespace {
     const Result Bad  = (Us == WHITE ? DRAW  : WIN);
 
     Result r = INVALID;
     const Result Bad  = (Us == WHITE ? DRAW  : WIN);
 
     Result r = INVALID;

-    Bitboard b = StepAttacksBB[KING][ksq[Us]];
+    Bitboard b = PseudoAttacks[KING][ksq[Us]];

 
     while (b)
         r |= Us == WHITE ? db[index(Them, ksq[Them]  , pop_lsb(&b), psq)]
 
     while (b)
         r |= Us == WHITE ? db[index(Them, ksq[Them]  , pop_lsb(&b), psq)]

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index 3f05d8bee52fde649bb36d06a3df7814033aaec9..1f6dab9df64de1394d6784b6d84983cd378d5ead 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -41,7 +41,6 @@ Bitboard FileBB[FILE_NB];
 Bitboard RankBB[RANK_NB];
 Bitboard AdjacentFilesBB[FILE_NB];
 Bitboard InFrontBB[COLOR_NB][RANK_NB];
 Bitboard RankBB[RANK_NB];
 Bitboard AdjacentFilesBB[FILE_NB];
 Bitboard InFrontBB[COLOR_NB][RANK_NB];

-Bitboard StepAttacksBB[PIECE_NB][SQUARE_NB];

 Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 Bitboard LineBB[SQUARE_NB][SQUARE_NB];
 Bitboard DistanceRingBB[SQUARE_NB][8];
 Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 Bitboard LineBB[SQUARE_NB][SQUARE_NB];
 Bitboard DistanceRingBB[SQUARE_NB][8];


@@ -49,6 +48,7 @@ Bitboard ForwardBB[COLOR_NB][SQUARE_NB];
 Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
 Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
 Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
 Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
 Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
 Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];

+Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];

 
 namespace {
 
 
 namespace {
 


@@ -191,21 +191,25 @@ void Bitboards::init() {
               DistanceRingBB[s1][SquareDistance[s1][s2] - 1] |= s2;
           }
 
               DistanceRingBB[s1][SquareDistance[s1][s2] - 1] |= s2;
           }
 

-  int steps[][9] = { {}, { 7, 9 }, { 17, 15, 10, 6, -6, -10, -15, -17 },
-                     {}, {}, {}, { 9, 7, -7, -9, 8, 1, -1, -8 } };
+  int steps[][5] = { {}, { 7, 9 }, { 6, 10, 15, 17 }, {}, {}, {}, { 1, 7, 8, 9 } };

 
   for (Color c = WHITE; c <= BLACK; ++c)
 
   for (Color c = WHITE; c <= BLACK; ++c)

-      for (PieceType pt = PAWN; pt <= KING; ++pt)
+      for (PieceType pt : { PAWN, KNIGHT, KING })

           for (Square s = SQ_A1; s <= SQ_H8; ++s)
               for (int i = 0; steps[pt][i]; ++i)
               {
                   Square to = s + Square(c == WHITE ? steps[pt][i] : -steps[pt][i]);
 
                   if (is_ok(to) && distance(s, to) < 3)
           for (Square s = SQ_A1; s <= SQ_H8; ++s)
               for (int i = 0; steps[pt][i]; ++i)
               {
                   Square to = s + Square(c == WHITE ? steps[pt][i] : -steps[pt][i]);
 
                   if (is_ok(to) && distance(s, to) < 3)

-                      StepAttacksBB[make_piece(c, pt)][s] |= to;
+                  {
+                      if (pt == PAWN)
+                          PawnAttacks[c][s] |= to;
+                      else
+                          PseudoAttacks[pt][s] |= to;
+                  }

               }
 
               }
 

-  Square RookDeltas[] = { NORTH,  EAST,  SOUTH,  WEST  };
+  Square RookDeltas[] = { NORTH,  EAST,  SOUTH,  WEST };

   Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
 
   init_magics(RookTable, RookAttacks, RookMagics, RookMasks, RookShifts, RookDeltas, magic_index<ROOK>);
   Square BishopDeltas[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
 
   init_magics(RookTable, RookAttacks, RookMagics, RookMasks, RookShifts, RookDeltas, magic_index<ROOK>);


@@ -216,14 +220,14 @@ void Bitboards::init() {
       PseudoAttacks[QUEEN][s1]  = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);
       PseudoAttacks[QUEEN][s1] |= PseudoAttacks[  ROOK][s1] = attacks_bb<  ROOK>(s1, 0);
 
       PseudoAttacks[QUEEN][s1]  = PseudoAttacks[BISHOP][s1] = attacks_bb<BISHOP>(s1, 0);
       PseudoAttacks[QUEEN][s1] |= PseudoAttacks[  ROOK][s1] = attacks_bb<  ROOK>(s1, 0);
 

-      for (Piece pc = W_BISHOP; pc <= W_ROOK; ++pc)
+      for (PieceType pt : { BISHOP, ROOK })

           for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
           {
           for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
           {

-              if (!(PseudoAttacks[pc][s1] & s2))
+              if (!(PseudoAttacks[pt][s1] & s2))

                   continue;
 
                   continue;
 

-              LineBB[s1][s2] = (attacks_bb(pc, s1, 0) & attacks_bb(pc, s2, 0)) | s1 | s2;
-              BetweenBB[s1][s2] = attacks_bb(pc, s1, SquareBB[s2]) & attacks_bb(pc, s2, SquareBB[s1]);
+              LineBB[s1][s2] = (attacks_bb(pt, s1, 0) & attacks_bb(pt, s2, 0)) | s1 | s2;
+              BetweenBB[s1][s2] = attacks_bb(pt, s1, SquareBB[s2]) & attacks_bb(pt, s2, SquareBB[s1]);

           }
   }
 }
           }
   }
 }

diff --git a/src/bitboard.h b/src/bitboard.h
index bef6467560bc7efcb122514954686ea5c61b3e93..c957a40fe23d61296a0e094bf36bd44581cda5d6 100644 (file)
--- a/src/bitboard.h
+++ b/src/bitboard.h
@@ -66,7 +66,6 @@ extern Bitboard FileBB[FILE_NB];
 extern Bitboard RankBB[RANK_NB];
 extern Bitboard AdjacentFilesBB[FILE_NB];
 extern Bitboard InFrontBB[COLOR_NB][RANK_NB];
 extern Bitboard RankBB[RANK_NB];
 extern Bitboard AdjacentFilesBB[FILE_NB];
 extern Bitboard InFrontBB[COLOR_NB][RANK_NB];

-extern Bitboard StepAttacksBB[PIECE_NB][SQUARE_NB];

 extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
 extern Bitboard DistanceRingBB[SQUARE_NB][8];
 extern Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 extern Bitboard LineBB[SQUARE_NB][SQUARE_NB];
 extern Bitboard DistanceRingBB[SQUARE_NB][8];


@@ -74,6 +73,7 @@ extern Bitboard ForwardBB[COLOR_NB][SQUARE_NB];
 extern Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
 extern Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
 extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];
 extern Bitboard PassedPawnMask[COLOR_NB][SQUARE_NB];
 extern Bitboard PawnAttackSpan[COLOR_NB][SQUARE_NB];
 extern Bitboard PseudoAttacks[PIECE_TYPE_NB][SQUARE_NB];

+extern Bitboard PawnAttacks[COLOR_NB][SQUARE_NB];

 
 
 /// Overloads of bitwise operators between a Bitboard and a Square for testing
 
 
 /// Overloads of bitwise operators between a Bitboard and a Square for testing


@@ -246,14 +246,16 @@ inline Bitboard attacks_bb(Square s, Bitboard occupied) {
   return (Pt == ROOK ? RookAttacks : BishopAttacks)[s][magic_index<Pt>(s, occupied)];
 }
 
   return (Pt == ROOK ? RookAttacks : BishopAttacks)[s][magic_index<Pt>(s, occupied)];
 }
 

-inline Bitboard attacks_bb(Piece pc, Square s, Bitboard occupied) {
+inline Bitboard attacks_bb(PieceType pt, Square s, Bitboard occupied) {

 
 

-  switch (type_of(pc))
+  assert(pt != PAWN);
+
+  switch (pt)

   {
   case BISHOP: return attacks_bb<BISHOP>(s, occupied);
   case ROOK  : return attacks_bb<ROOK>(s, occupied);
   case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);
   {
   case BISHOP: return attacks_bb<BISHOP>(s, occupied);
   case ROOK  : return attacks_bb<ROOK>(s, occupied);
   case QUEEN : return attacks_bb<BISHOP>(s, occupied) | attacks_bb<ROOK>(s, occupied);

-  default    : return StepAttacksBB[pc][s];
+  default    : return PseudoAttacks[pt][s];

   }
 }
 
   }
 }
 

diff --git a/src/movegen.cpp b/src/movegen.cpp
index ac5f565c1bfd0f9a51c342415868879a9a615ada..465d616ca6aca9013c8786e9f6c3abd7bf77cc25 100644 (file)
--- a/src/movegen.cpp
+++ b/src/movegen.cpp
@@ -80,7 +80,7 @@ namespace {
 
     // Knight promotion is the only promotion that can give a direct check
     // that's not already included in the queen promotion.
 
     // Knight promotion is the only promotion that can give a direct check
     // that's not already included in the queen promotion.

-    if (Type == QUIET_CHECKS && (StepAttacksBB[W_KNIGHT][to] & ksq))
+    if (Type == QUIET_CHECKS && (PseudoAttacks[KNIGHT][to] & ksq))

         *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
     else
         (void)ksq; // Silence a warning under MSVC
         *moveList++ = make<PROMOTION>(to - D, to, KNIGHT);
     else
         (void)ksq; // Silence a warning under MSVC


@@ -346,7 +346,7 @@ ExtMove* generate<QUIET_CHECKS>(const Position& pos, ExtMove* moveList) {
      if (pt == PAWN)
          continue; // Will be generated together with direct checks
 
      if (pt == PAWN)
          continue; // Will be generated together with direct checks
 

-     Bitboard b = pos.attacks_from(Piece(pt), from) & ~pos.pieces();
+     Bitboard b = pos.attacks_from(pt, from) & ~pos.pieces();

 
      if (pt == KING)
          b &= ~PseudoAttacks[QUEEN][pos.square<KING>(~us)];
 
      if (pt == KING)
          b &= ~PseudoAttacks[QUEEN][pos.square<KING>(~us)];

diff --git a/src/pawns.cpp b/src/pawns.cpp
index 0e57f01fffc089c2b00dc60b776800467f7c93f0..17a96670911dc414b351ca7f2197dada32a510a7 100644 (file)
--- a/src/pawns.cpp
+++ b/src/pawns.cpp
@@ -104,7 +104,6 @@ namespace {
     bool opposed, backward;
     Score score = SCORE_ZERO;
     const Square* pl = pos.squares<PAWN>(Us);
     bool opposed, backward;
     Score score = SCORE_ZERO;
     const Square* pl = pos.squares<PAWN>(Us);

-    const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)];

 
     Bitboard ourPawns   = pos.pieces(Us  , PAWN);
     Bitboard theirPawns = pos.pieces(Them, PAWN);
 
     Bitboard ourPawns   = pos.pieces(Us  , PAWN);
     Bitboard theirPawns = pos.pieces(Them, PAWN);


@@ -129,8 +128,8 @@ namespace {
         // Flag the pawn
         opposed    = theirPawns & forward_bb(Us, s);
         stoppers   = theirPawns & passed_pawn_mask(Us, s);
         // Flag the pawn
         opposed    = theirPawns & forward_bb(Us, s);
         stoppers   = theirPawns & passed_pawn_mask(Us, s);

-        lever      = theirPawns & pawnAttacksBB[s];
-        leverPush  = theirPawns & pawnAttacksBB[s + Up];
+        lever      = theirPawns & PawnAttacks[Us][s];
+        leverPush  = theirPawns & PawnAttacks[Us][s + Up];

         doubled    = ourPawns   & (s - Up);
         neighbours = ourPawns   & adjacent_files_bb(f);
         phalanx    = neighbours & rank_bb(s);
         doubled    = ourPawns   & (s - Up);
         neighbours = ourPawns   & adjacent_files_bb(f);
         phalanx    = neighbours & rank_bb(s);

diff --git a/src/position.cpp b/src/position.cpp
index e20c822f5998902ba2149d13504bd9846a1833d0..69a756d9ce9b0b68ab0eecce7758a4ced1e05401 100644 (file)
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -595,7 +595,7 @@ bool Position::pseudo_legal(const Move m) const {
                && empty(to - pawn_push(us))))
           return false;
   }
                && empty(to - pawn_push(us))))
           return false;
   }

-  else if (!(attacks_from(pc, from) & to))
+  else if (!(attacks_from(type_of(pc), from) & to))

       return false;
 
   // Evasions generator already takes care to avoid some kind of illegal moves
       return false;
 
   // Evasions generator already takes care to avoid some kind of illegal moves


@@ -648,7 +648,7 @@ bool Position::gives_check(Move m) const {
       return false;
 
   case PROMOTION:
       return false;
 
   case PROMOTION:

-      return attacks_bb(Piece(promotion_type(m)), to, pieces() ^ from) & square<KING>(~sideToMove);
+      return attacks_bb(promotion_type(m), to, pieces() ^ from) & square<KING>(~sideToMove);

 
   // En passant capture with check? We have already handled the case
   // of direct checks and ordinary discovered check, so the only case we
 
   // En passant capture with check? We have already handled the case
   // of direct checks and ordinary discovered check, so the only case we

diff --git a/src/position.h b/src/position.h
index 5a07193b9c5e9226986f789977f9b27e22d519fe..2361132fac4e5596cbb08ca369c7fd7364c0d614 100644 (file)
--- a/src/position.h
+++ b/src/position.h
@@ -109,7 +109,7 @@ public:
   // Attacks to/from a given square
   Bitboard attackers_to(Square s) const;
   Bitboard attackers_to(Square s, Bitboard occupied) const;
   // Attacks to/from a given square
   Bitboard attackers_to(Square s) const;
   Bitboard attackers_to(Square s, Bitboard occupied) const;

-  Bitboard attacks_from(Piece pc, Square s) const;
+  Bitboard attacks_from(PieceType pt, Square s) const;

   template<PieceType> Bitboard attacks_from(Square s) const;
   template<PieceType> Bitboard attacks_from(Square s, Color c) const;
   Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
   template<PieceType> Bitboard attacks_from(Square s) const;
   template<PieceType> Bitboard attacks_from(Square s, Color c) const;
   Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;


@@ -276,16 +276,16 @@ inline Bitboard Position::attacks_from(Square s) const {
   assert(Pt != PAWN);
   return  Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
         : Pt == QUEEN  ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)
   assert(Pt != PAWN);
   return  Pt == BISHOP || Pt == ROOK ? attacks_bb<Pt>(s, byTypeBB[ALL_PIECES])
         : Pt == QUEEN  ? attacks_from<ROOK>(s) | attacks_from<BISHOP>(s)

-        : StepAttacksBB[Pt][s];
+        : PseudoAttacks[Pt][s];

 }
 
 template<>
 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {
 }
 
 template<>
 inline Bitboard Position::attacks_from<PAWN>(Square s, Color c) const {

-  return StepAttacksBB[make_piece(c, PAWN)][s];
+  return PawnAttacks[c][s];

 }
 
 }
 

-inline Bitboard Position::attacks_from(Piece pc, Square s) const {
-  return attacks_bb(pc, s, byTypeBB[ALL_PIECES]);
+inline Bitboard Position::attacks_from(PieceType pt, Square s) const {
+  return attacks_bb(pt, s, byTypeBB[ALL_PIECES]);

 }
 
 inline Bitboard Position::attackers_to(Square s) const {
 }
 
 inline Bitboard Position::attackers_to(Square s) const {

diff --git a/src/syzygy/tbprobe.cpp b/src/syzygy/tbprobe.cpp
index d56ba05a7cd222d14c4cfba9aa35971d0397680c..5d08549e5046f29f2876e6b3439ab0f8e041f794 100644 (file)
--- a/src/syzygy/tbprobe.cpp
+++ b/src/syzygy/tbprobe.cpp
@@ -1292,7 +1292,7 @@ void Tablebases::init(const std::string& paths) {
             if (MapA1D1D4[s1] == idx && (idx || s1 == SQ_B1)) // SQ_B1 is mapped to 0
             {
                 for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
             if (MapA1D1D4[s1] == idx && (idx || s1 == SQ_B1)) // SQ_B1 is mapped to 0
             {
                 for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)

-                    if ((StepAttacksBB[KING][s1] | s1) & s2)
+                    if ((PseudoAttacks[KING][s1] | s1) & s2)

                         continue; // Illegal position
 
                     else if (!off_A1H8(s1) && off_A1H8(s2) > 0)
                         continue; // Illegal position
 
                     else if (!off_A1H8(s1) && off_A1H8(s2) > 0)