Popcount comes up in chess engine programming, where boards are regularly represented as a series of bits for each type of piece. The Chess Programming Wiki has

Popcount comes up in chess engine programming, where boards are regularly represented as a series of bits for each type of piece. The Chess Programming Wiki has a lot of information about both usage and implementation: https://www.chessprogramming.org/Population_Count https://www.chessprogramming.org/Population_Count