ExPopcount

Popcount, or population count, is a function that determines the number of set bits (bits with a value of 1) in a binary representation of an integer.

ExPopcount is an Erlang NIF library that exposes a popcount/1 operation over arbitrary integers and binaries/bitstrings.

The performance of the underlying operation relies mostly on the performance of the Rust stdlib u64::count_ones operation.

Installation

The package can be installed by adding ex_popcount to your list of dependencies in mix.exs:

def deps do
  [
    {:ex_popcount, "~> 0.1.0"}
  ]
end

Force compilation

This library includes pre-compiled binaries for the native Rust code. If you want to force-compile the Rust code, you can add the following configuration to your application:

config :rustler_precompiled, :force_build, ex_popcount: true

You also need to add Rustler to your dependencies:

def deps do
  [
    {:ex_popcount, "~> 0.1.0"},
    {:rustler, ">= 0.0.0", optional: true}
  ]
end

Usage

To calculate a popcount for an arbitrary value, use ExPopcount.popcount/1 function:

  4 = ExPopcount.popcount(0b1111)
  4 = ExPopcount.popcount(<<0b1111>>)
  4 = ExPopcount.popcount(<<0::32, 0b1111::4>>)

popcount/1 returns ArgumentError if the provided data is not an integer or bitstring, or if the provided data is a negative integer.

Contributing

1. Fork it!
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request

License

ExPopcount is released under the MIT License.