benchmark.ex

iex> So.Exclude.exclude1
Name                        ips        average  deviation         median
substract                9.18 M       0.109 μs   ±358.78%       0.100 μs
mapset_difference        4.00 M        0.25 μs ±17781.86%         0.0 μs
enum_filter              3.70 M        0.27 μs  ±1712.25%        0.20 μs
ordsets                  2.63 M        0.38 μs  ±1348.35%        0.30 μs

Comparison:
substract                9.18 M
mapset_difference        4.00 M - 2.30x slower
enum_filter              3.70 M - 2.48x slower
ordsets                  2.63 M - 3.49x slower

iex> So.Exclude.exclude2(100)
Name                        ips        average  deviation         median
enum_filter             69.86 K       14.31 μs    ±68.81%       14.00 μs
ordsets                 46.50 K       21.51 μs    ±73.18%       20.00 μs
mapset_difference       35.97 K       27.80 μs    ±16.81%       27.00 μs
substract               31.04 K       32.22 μs    ±32.36%       31.00 μs

Comparison:
enum_filter             69.86 K
ordsets                 46.50 K - 1.50x slower
mapset_difference       35.97 K - 1.94x slower
substract               31.04 K - 2.25x slower

iex> So.Exclude.exclude2(1000)
Name                        ips        average  deviation         median
ordsets                  2.88 K        0.35 ms     ±6.36%        0.34 ms
mapset_difference        2.06 K        0.49 ms    ±15.54%        0.45 ms
enum_filter              0.94 K        1.07 ms    ±20.62%        0.93 ms
substract                0.31 K        3.24 ms    ±14.54%        3.04 ms

Comparison:
ordsets                  2.88 K
mapset_difference        2.06 K - 1.40x slower
enum_filter              0.94 K - 3.08x slower
substract                0.31 K - 9.34x slower

iex> So.Exclude.exclude2(100000)
Name                        ips        average  deviation         median
ordsets                   13.46       0.0743 s     ±9.42%       0.0724 s
mapset_difference         12.81       0.0781 s     ±6.77%       0.0763 s
enum_filter              0.0581        17.21 s     ±0.00%        17.21 s
substract                0.0220        45.41 s     ±0.00%        45.41 s

Comparison:
ordsets                   13.46
mapset_difference         12.81 - 1.05x slower
enum_filter              0.0581 - 231.67x slower
substract                0.0220 - 611.30x slower

exclude.ex

defmodule So.Exclude do
  def exclude1() do
    a = [1,2,3,4]
    b = [3,4,5,6]

    run_benchmarks(a, b)
  end

  def exclude2(size, max_value \\ nil) do
    max_value = max_value || size

    a = random_list(size, max_value)
    b = random_list(size, max_value)

    run_benchmarks(a, b)
  end

  defp run_benchmarks(a, b) do
    Benchee.run(%{
      "enum_filter" => fn ->
        Enum.filter(a, fn el -> !Enum.member?(b, el) end)
      end,
      "substract" => fn ->
        a -- b
      end,
      "mapset_difference" => fn ->
        MapSet.difference(MapSet.new(a), MapSet.new(b)) |> MapSet.to_list
      end,
      "ordsets" => fn ->
        :ordsets.subtract(:ordsets.from_list(a), :ordsets.from_list(b)) |> :ordsets.to_list
      end
    }, time: 10)
  end

  defp random_list(size, max_value) do
    Enum.map(1..size, fn(_size) -> Enum.random(1..max_value) end)
  end
end