2 Stockfish, a UCI chess playing engine derived from Glaurung 2.1
3 Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
4 Copyright (C) 2008-2010 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 #if !defined(BITCOUNT_H_INCLUDED)
22 #define BITCOUNT_H_INCLUDED
34 /// count_1s() counts the number of nonzero bits in a bitboard.
35 /// We have different optimized versions according if platform
36 /// is 32 or 64 bits, and to the maximum number of nonzero bits.
37 /// We also support hardware popcnt instruction. See Readme.txt
38 /// on how to pgo compile with popcnt support.
39 template<BitCountType> inline int count_1s(Bitboard);
42 inline int count_1s<CNT64>(Bitboard b) {
43 b -= ((b>>1) & 0x5555555555555555ULL);
44 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
45 b = ((b>>4) + b) & 0x0F0F0F0F0F0F0F0FULL;
46 b *= 0x0101010101010101ULL;
51 inline int count_1s<CNT64_MAX15>(Bitboard b) {
52 b -= (b>>1) & 0x5555555555555555ULL;
53 b = ((b>>2) & 0x3333333333333333ULL) + (b & 0x3333333333333333ULL);
54 b *= 0x1111111111111111ULL;
59 inline int count_1s<CNT32>(Bitboard b) {
60 unsigned w = unsigned(b >> 32), v = unsigned(b);
61 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
62 w -= (w >> 1) & 0x55555555;
63 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
64 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
65 v = ((v >> 4) + v) & 0x0F0F0F0F; // 0-8 in 8 bits
66 v += (((w >> 4) + w) & 0x0F0F0F0F); // 0-16 in 8 bits
67 v *= 0x01010101; // mul is fast on amd procs
72 inline int count_1s<CNT32_MAX15>(Bitboard b) {
73 unsigned w = unsigned(b >> 32), v = unsigned(b);
74 v -= (v >> 1) & 0x55555555; // 0-2 in 2 bits
75 w -= (w >> 1) & 0x55555555;
76 v = ((v >> 2) & 0x33333333) + (v & 0x33333333); // 0-4 in 4 bits
77 w = ((w >> 2) & 0x33333333) + (w & 0x33333333);
78 v += w; // 0-8 in 4 bits
84 inline int count_1s<CNT_POPCNT>(Bitboard b) {
85 #if !defined(USE_POPCNT)
86 return int(b != 0); // Avoid 'b not used' warning
87 #elif defined(_MSC_VER) && defined(__INTEL_COMPILER)
88 return _mm_popcnt_u64(b);
89 #elif defined(_MSC_VER)
90 return (int)__popcnt64(b);
91 #elif defined(__GNUC__)
93 __asm__("popcnt %1, %0" : "=r" (ret) : "r" (b));
98 #endif // !defined(BITCOUNT_H_INCLUDED)