2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
6 Stockfish is free software: you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation, either version 3 of the License, or
9 (at your option) any later version.
12 Stockfish is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>.
21 #ifndef BITCOUNT_H_INCLUDED
22 #define BITCOUNT_H_INCLUDED
36 /// Determine at compile time the best popcount<> specialization according to
37 /// whether the platform is 32 or 64 bit, the maximum number of non-zero
38 /// bits to count and if the hardware popcnt instruction is available.
39 const BitCountType Full = HasPopCnt ? CNT_HW_POPCNT : Is64Bit ? CNT_64 : CNT_32;
40 const BitCountType Max15 = HasPopCnt ? CNT_HW_POPCNT : Is64Bit ? CNT_64_MAX15 : CNT_32_MAX15;
43 /// popcount() counts the number of non-zero bits in a bitboard
44 template<BitCountType> inline int popcount(Bitboard);
47 inline int popcount<CNT_64>(Bitboard b) {
48 b -= (b >> 1) & 0x5555555555555555ULL;
49 b = ((b >> 2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
50 b = ((b >> 4) + b) & 0x0F0F0F0F0F0F0F0FULL;
51 return (b * 0x0101010101010101ULL) >> 56;
55 inline int popcount<CNT_64_MAX15>(Bitboard b) {
56 b -= (b >> 1) & 0x5555555555555555ULL;
57 b = ((b >> 2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
58 return (b * 0x1111111111111111ULL) >> 60;
62 inline int popcount<CNT_32>(Bitboard b) {
63 unsigned w = unsigned(b >> 32), v = unsigned(b);
64 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
65 w -= (w >> 1) & 0x55555555;
66 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
67 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
68 v = ((v >> 4) + v + (w >> 4) + w) & 0x0F0F0F0F;
69 return (v * 0x01010101) >> 24;
73 inline int popcount<CNT_32_MAX15>(Bitboard b) {
74 unsigned w = unsigned(b >> 32), v = unsigned(b);
75 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
76 w -= (w >> 1) & 0x55555555;
77 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
78 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
79 return ((v + w) * 0x11111111) >> 28;
83 inline int popcount<CNT_HW_POPCNT>(Bitboard b) {
88 return b != 0; // Avoid 'b not used' warning
90 #elif defined(_MSC_VER) && defined(__INTEL_COMPILER)
92 return _mm_popcnt_u64(b);
94 #elif defined(_MSC_VER)
96 return (int)__popcnt64(b);
98 #else // Assumed gcc or compatible compiler
100 return __builtin_popcountll(b);
105 #endif // #ifndef BITCOUNT_H_INCLUDED