Manual Reference Pages - popcnt (3fortran)

NAME

POPCNT(3) - [BIT:COUNT] Number of bits set

SYNOPSIS

result = popcnt(i)

         elemental integer function popcnt(i)

          integer(kind=KIND), intent(in) :: i

CHARACTERISTICS

o I may be an integer of any kind.

o The return value is an integer of the default integer kind.

DESCRIPTION

POPCNT(3) returns the number of bits set to one in the binary representation of an integer.

OPTIONS

o I : value to count set bits in

RESULT

The number of bits set to one in I.

EXAMPLES

Sample program:

    program demo_popcnt
    use, intrinsic :: iso_fortran_env, only : integer_kinds, &
       & int8, int16, int32, int64
    implicit none
    character(len=*),parameter :: pretty=’(b64,1x,i0)’
      ! basic usage
       print pretty, 127,     popcnt(127)
       print pretty, int(b"01010"), popcnt(int(b"01010"))

      ! any kind of an integer can be used
       print pretty, huge(0_int8),  popcnt(huge(0_int8))
       print pretty, huge(0_int16), popcnt(huge(0_int16))
       print pretty, huge(0_int32), popcnt(huge(0_int32))
       print pretty, huge(0_int64), popcnt(huge(0_int64))
    end program demo_popcnt

Results:

Note that on most machines the first bit is the sign bit, and a zero is used for positive values; but that this is system-dependent. These are typical values, where the huge(3f) function has set all but the first bit to 1.

> 1111111 7 > 1010 2 > 1111111 7 > 111111111111111 15 > 1111111111111111111111111111111 31 > 111111111111111111111111111111111111111111111111111111111111111 63

STANDARD

Fortran 2008

There are many procedures that operator or query values at the bit level:
POPPAR(3), LEADZ(3), TRAILZ(3) ATOMIC_AND(3), ATOMIC_FETCH_AND(3), ATOMIC_FETCH_OR(3), ATOMIC_FETCH_XOR(3), ATOMIC_OR(3), ATOMIC_XOR(3), BGE(3), BGT(3), BIT_SIZE(3), BLE(3), BLT(3), BTEST(3), DSHIFTL(3), DSHIFTR(3), IALL(3), IAND(3), IANY(3), IBCLR(3), IBITS(3), IBSET(3), IEOR(3), IOR(3), IPARITY(3), ISHFTC(3), ISHFT(3), MASKL(3), MASKR(3), MERGE_BITS(3), MVBITS(3), NOT(3), SHIFTA(3), SHIFTL(3), SHIFTR(3), STORAGE_SIZE(3)
fortran-lang intrinsic descriptions (license: MIT) @urbanjost

Nemo Release 3.1

popcnt (3fortran)

April 28, 2024

Generated by manServer 1.08 from b1045c89-cf6b-4a2e-9c72-b5cd1feb667a using man macros.

o	I may be an integer of any kind.
o	The return value is an integer of the default integer kind.