Use int8_t instead of int for SquareDistance[]

[stockfish] / src / bitboard.cpp

diff --git a/src/bitboard.cpp b/src/bitboard.cpp
index ccde19057c0893106789f10df6c659dc9f629401..105d201f1c17de3ca2cfc9a1cad5a2d9aab4efd7 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) 2015-2017 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
@@ -24,12 +24,11 @@
 #include "misc.h"
 
 uint8_t PopCnt16[1 << 16];
-int SquareDistance[SQUARE_NB][SQUARE_NB];
+int8_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];
@@ -45,27 +44,11 @@ Magic BishopMagics[SQUARE_NB];
 
 namespace {
 
-  // De Bruijn sequences. See chessprogramming.wikispaces.com/BitScan
-  const uint64_t DeBruijn64 = 0x3F79D71B4CB0A89ULL;
-  const uint32_t DeBruijn32 = 0x783A9B23;
-
-  int MSBTable[256];            // To implement software msb()
-  Square BSFTable[SQUARE_NB];   // To implement software bitscan
   Bitboard RookTable[0x19000];  // To store rook attacks
   Bitboard BishopTable[0x1480]; // To store bishop attacks
 
   void init_magics(Bitboard table[], Magic magics[], Direction directions[]);
 
-  // bsf_index() returns the index into BSFTable[] to look up the bitscan. Uses
-  // Matt Taylor's folding for 32 bit case, extended to 64 bit by Kim Walisch.
-
-  unsigned bsf_index(Bitboard b) {
-    b ^= b - 1;
-    return Is64Bit ? (b * DeBruijn64) >> 58
-                   : ((unsigned(b) ^ unsigned(b >> 32)) * DeBruijn32) >> 26;
-  }
-
-
   // popcount16() counts the non-zero bits using SWAR-Popcount algorithm
 
   unsigned popcount16(unsigned u) {
@@ -76,46 +59,6 @@ namespace {
   }
 }
 
-#ifdef NO_BSF
-
-/// Software fall-back of lsb() and msb() for CPU lacking hardware support
-
-Square lsb(Bitboard b) {
-  assert(b);
-  return BSFTable[bsf_index(b)];
-}
-
-Square msb(Bitboard b) {
-
-  assert(b);
-  unsigned b32;
-  int result = 0;
-
-  if (b > 0xFFFFFFFF)
-  {
-      b >>= 32;
-      result = 32;
-  }
-
-  b32 = unsigned(b);
-
-  if (b32 > 0xFFFF)
-  {
-      b32 >>= 16;
-      result += 16;
-  }
-
-  if (b32 > 0xFF)
-  {
-      b32 >>= 8;
-      result += 8;
-  }
-
-  return Square(result + MSBTable[b32]);
-}
-
-#endif // ifdef NO_BSF
-
 
 /// Bitboards::pretty() returns an ASCII representation of a bitboard suitable
 /// to be printed to standard output. Useful for debugging.
@@ -145,13 +88,7 @@ void Bitboards::init() {
       PopCnt16[i] = (uint8_t) popcount16(i);
 
   for (Square s = SQ_A1; s <= SQ_H8; ++s)
-  {
-      SquareBB[s] = 1ULL << s;
-      BSFTable[bsf_index(SquareBB[s])] = s;
-  }
-
-  for (Bitboard b = 2; b < 256; ++b)
-      MSBTable[b] = MSBTable[b - 1] + !more_than_one(b);
+      SquareBB[s] = (1ULL << s);
 
   for (File f = FILE_A; f <= FILE_H; ++f)
       FileBB[f] = f > FILE_A ? FileBB[f - 1] << 1 : FileABB;
@@ -159,9 +96,6 @@ void Bitboards::init() {
   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]);
 
@@ -169,7 +103,7 @@ void Bitboards::init() {
       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)];
+          PawnAttackSpan[c][s] = ForwardRanksBB[c][rank_of(s)] & adjacent_files_bb(file_of(s));
           PassedPawnMask[c][s] = ForwardFileBB [c][s] | PawnAttackSpan[c][s];
       }
 
@@ -178,7 +112,7 @@ void Bitboards::init() {
           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 } };
@@ -199,7 +133,7 @@ void Bitboards::init() {
                   }
               }
 
-  Direction RookDirections[] = { NORTH,  EAST,  SOUTH,  WEST };
+  Direction RookDirections[] = { NORTH, EAST, SOUTH, WEST };
   Direction BishopDirections[] = { NORTH_EAST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST };
 
   init_magics(RookTable, RookMagics, RookDirections);
@@ -246,8 +180,8 @@ 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[]) {