Parallel Fibonacci

fibonacci.exs

defmodule Fibonacci do
  def fib(0), do: 0
  def fib(1), do: 1
  def fib(n), do: fib(n-1) + fib(n-2)
end

defmodule Fibonacci.Parallel do
  def fib(n, processes) do
    (1..processes) |> Enum.map(fn id ->
      srv = self()
      pid = spawn(fn -> send(srv, {:fib, {n, Fibonacci.fib(n), self(), id}}) end)
      {id, pid}
    end)
    |> loop_until
  end

  defp loop_until([]), do: nil
  defp loop_until(workers) do
    receive do
      {:fib, {nfib, res, from, id}} ->
        IO.puts "Calculated fibonacci(#{nfib}) -> #{res}, (#{inspect from} - #{id})"
        workers = Enum.filter workers, fn {i,p} -> !(i == id && p == from) end
      _ ->
        IO.puts "Unknown"
    end

    loop_until(workers)
  end
end