fibonacci_tail.rb

require 'benchmark'
require 'json'

class Fib
  def self.main
    RubyVM::InstructionSequence.compile_option = {
      tailcall_optimization: true,
      trace_instruction: false
    }
    puts 'What number do you want to give Fib?'
    new(gets.chomp.to_i).report
  end

  attr_reader :x
  def initialize(x)
    @x = x
  end

  def slow
    return if x <= 0
    [0, 1][x - 1] || Fib.new(x - 2).slow + Fib.new(x - 1).slow
  end

  def tail(y = x, a = 0, b = 1)
    return if y == 0
    [a, b][y - 1] || tail(y - 1, b, a + b)
  end

  def report(count = 100)
    result = %i[tail slow].reduce({}) do |acc, el|
      acc.merge(el => { average: average(el, count), result: send(el) })
    end
    puts JSON.pretty_generate(result)
  end

  private

  def bm(&block)
    Benchmark.realtime(&block)
  end

  def average(method, count)
    (Array.new(count).map { bm { send(method) } }.reduce(:+) / count).round(5)
  end
end

Fib.main if $PROGRAM_NAME == __FILE__