Assorted trivial cleanups 3/2019 (#2030)

[stockfish] / src / bitboard.cpp

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index b3aeed854b70ce656fda25215c213967b3b6ddcc..2adf27794209a4e89d175eca412453a2beda2f48 100644 (file)
--- a/src/bitboard.cpp
+++ b/src/bitboard.cpp
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -18,27 +18,27 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <bitset>
 #include <algorithm>
 
 #include "bitboard.h"
 #include "misc.h"
 
 uint8_t PopCnt16[1 << 16];
-int SquareDistance[SQUARE_NB][SQUARE_NB];
+uint8_t SquareDistance[SQUARE_NB][SQUARE_NB];
 
-Bitboard SquareBB[SQUARE_NB];
-Bitboard FileBB[FILE_NB];
-Bitboard RankBB[RANK_NB];
-Bitboard AdjacentFilesBB[FILE_NB];
-Bitboard ForwardRanksBB[COLOR_NB][RANK_NB];
 Bitboard BetweenBB[SQUARE_NB][SQUARE_NB];
 Bitboard LineBB[SQUARE_NB][SQUARE_NB];
 Bitboard DistanceRingBB[SQUARE_NB][8];
-Bitboard ForwardFileBB[COLOR_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];
+Bitboard SquareBB[SQUARE_NB];
+
+Bitboard KingFlank[FILE_NB] = {
+  QueenSide ^ FileDBB, QueenSide, QueenSide,
+  CenterFiles, CenterFiles,
+  KingSide, KingSide, KingSide ^ FileEBB
+};
 
 Magic RookMagics[SQUARE_NB];
 Magic BishopMagics[SQUARE_NB];
@@ -49,15 +49,6 @@ namespace {
   Bitboard BishopTable[0x1480]; // To store bishop attacks
 
   void init_magics(Bitboard table[], Magic magics[], Direction directions[]);
-
-  // popcount16() counts the non-zero bits using SWAR-Popcount algorithm
-
-  unsigned popcount16(unsigned u) {
-    u -= (u >> 1) & 0x5555U;
-    u = ((u >> 2) & 0x3333U) + (u & 0x3333U);
-    u = ((u >> 4) + u) & 0x0F0FU;
-    return (u * 0x0101U) >> 8;
-  }
 }
 
 
@@ -86,37 +77,16 @@ const std::string Bitboards::pretty(Bitboard b) {
 void Bitboards::init() {
 
   for (unsigned i = 0; i < (1 << 16); ++i)
-      PopCnt16[i] = (uint8_t) popcount16(i);
+      PopCnt16[i] = std::bitset<16>(i).count();
 
   for (Square s = SQ_A1; s <= SQ_H8; ++s)
       SquareBB[s] = (1ULL << s);
 
-  for (File f = FILE_A; f <= FILE_H; ++f)
-      FileBB[f] = f > FILE_A ? FileBB[f - 1] << 1 : FileABB;
-
-  for (Rank r = RANK_1; r <= RANK_8; ++r)
-      RankBB[r] = r > RANK_1 ? RankBB[r - 1] << 8 : Rank1BB;
-
-  for (File f = FILE_A; f <= FILE_H; ++f)
-      AdjacentFilesBB[f] = (f > FILE_A ? FileBB[f - 1] : 0) | (f < FILE_H ? FileBB[f + 1] : 0);
-
-  for (Rank r = RANK_1; r < RANK_8; ++r)
-      ForwardRanksBB[WHITE][r] = ~(ForwardRanksBB[BLACK][r + 1] = ForwardRanksBB[BLACK][r] | RankBB[r]);
-
-  for (Color c = WHITE; c <= BLACK; ++c)
-      for (Square s = SQ_A1; s <= SQ_H8; ++s)
-      {
-          ForwardFileBB [c][s] = ForwardRanksBB[c][rank_of(s)] & FileBB[file_of(s)];
-          PawnAttackSpan[c][s] = ForwardRanksBB[c][rank_of(s)] & AdjacentFilesBB[file_of(s)];
-          PassedPawnMask[c][s] = ForwardFileBB [c][s] | PawnAttackSpan[c][s];
-      }
-
   for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
       for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
-          if (s1 != s2)
           {
               SquareDistance[s1][s2] = std::max(distance<File>(s1, s2), distance<Rank>(s1, s2));
-              DistanceRingBB[s1][SquareDistance[s1][s2] - 1] |= s2;
+              DistanceRingBB[s1][SquareDistance[s1][s2]] |= s2;
           }
 
   int steps[][5] = { {}, { 7, 9 }, { 6, 10, 15, 17 }, {}, {}, {}, { 1, 7, 8, 9 } };
@@ -150,13 +120,11 @@ void Bitboards::init() {
 
       for (PieceType pt : { BISHOP, ROOK })
           for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
-          {
-              if (!(PseudoAttacks[pt][s1] & s2))
-                  continue;
-
-              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]);
-          }
+              if (PseudoAttacks[pt][s1] & s2)
+              {
+                  LineBB[s1][s2] = (attacks_bb(pt, s1, 0) & attacks_bb(pt, s2, 0)) | s1 | s2;
+                  BetweenBB[s1][s2] = attacks_bb(pt, s1, square_bb(s2)) & attacks_bb(pt, s2, square_bb(s1));
+              }
   }
 }
 
@@ -184,8 +152,8 @@ namespace {
 
   // init_magics() computes all rook and bishop attacks at startup. Magic
   // bitboards are used to look up attacks of sliding pieces. As a reference see
-  // chessprogramming.wikispaces.com/Magic+Bitboards. In particular, here we
-  // use the so called "fancy" approach.
+  // www.chessprogramming.org/Magic_Bitboards. In particular, here we use the so
+  // called "fancy" approach.
 
   void init_magics(Bitboard table[], Magic magics[], Direction directions[]) {