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shumon84/crazy_count_bits.c

Created March 25, 2017 05:04
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crazy_count_bits.c
#define count_bits(n) (0x0000ffff&((0x00ff00ff&((0x0f0f0f0f&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))+((0xf0f0f0f0&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))>>4)))+((0xff00ff00&((0x0f0f0f0f&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))+((0xf0f0f0f0&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))>>4)))>>8)))+((0xffff0000&((0x00ff00ff&((0x0f0f0f0f&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))+((0xf0f0f0f0&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))>>4)))+((0xff00ff00&((0x0f0f0f0f&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))+((0xf0f0f0f0&((0x33333333&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))+((0xcccccccc&((0x55555555&(n))+((0xaaaaaaaa&(n))>>1)))>>2)))>>4)))>>8)))>>16)
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