fibonacci-algorithms-in-elixir

fibonacci-algorithms-in-elixir.exs

defmodule Benchmark do
  def measure(function) do
    function
    |> :timer.tc
    |> elem(0)
    |> Kernel./(1_000_000)
  end
end

defmodule Fibonacci1 do
  def fibonacci(number) do
   Enum.reverse(fibonacci_do(number))
  end

  def fibonacci_do(1), do: [0]
  def fibonacci_do(2), do: [1|fibonacci_do(1)]
  def fibonacci_do(number) when number > 2 do
    [x, y|_] = all = fibonacci_do(number-1)
    [x + y|all]
  end
end

Benchmark.measure(fn -> Fibonacci1.fibonacci(10000) end)
0.009856

defmodule Fibonacci2 do
    def fib(0), do: 0
    def fib(1), do: 1
    def fib(n), do: fib(0, 1, n-2)

    def fib(_, prv, -1), do: prv
    def fib(prvprv, prv, n) do
        next = prv + prvprv
        fib(prv, next, n-1)
    end
end

Benchmark.measure(fn -> IO.inspect Enum.map(0..10000, fn i-> Fibonacci2.fib(i) end) end)
5.50795

defmodule Fibonacci3 do
    def fib(0), do: 0
    def fib(1), do: 1
    def fib(n), do: fib(n-1) + fib(n-2)
end

Benchmark.measure(fn -> Enum.map(0..40, fn i-> Fibonacci3.fib(i) end) end)
7.477463

http://stratus3d.com/blog/2018/08/18/fibonacci-algorithms-in-elixir/

http://stratus3d.com/blog/2018/12/24/fibonacci-algorithms-in-elixir-part-2/