intbitcount

intbitcount is a term used in various programming libraries and codebases to denote a function that computes the number of set bits in an unsigned integer, i.e., the population count or Hamming weight of the value. The function returns how many bits are equal to one in the binary representation of the input.

Typically, intbitcount takes an unsigned integer and returns an integer in the range from zero up to the number of bits in the type (for example, 0 to 32 on a 32-bit unsigned int). It is widely used in algorithms that require density calculations, parity checks, cryptography, bitmap processing, and combinatorial enumeration, where counting ones efficiently matters.

Implementation approaches vary. Modern processors provide hardware support for population count, such as the POPCNT instruction on x86-64, which can be accessed via compiler intrinsics like __builtin_popcount or similar. In portable code, intbitcount may be implemented in software using algorithms such as Kernighan’s method, which repeatedly clears the least-significant set bit, or a parallel counting routine that aggregates bits in stages with bit masks. Example (conceptual, not language-specific): a loop that increments a counter while flipping off the least-significant 1 bit, or a sequence of bit-twiddling steps that sums bits in groups of increasing size.

In modern practice, languages may expose equivalent functionality under different names, such as popcount, bitcount, or using standard library facilities (for example, C++20’s bit operations or language-specific intrinsics). The term intbitcount emphasizes counting set bits within an integer value and is essentially a historical or alias name for the same underlying operation.

See also: population count, popcount, Hamming weight, bit twiddling hacks.