test-enumerator.rb

require 'benchmark'

big_number = 1_000_000
a = 1.upto big_number
b = big_number.upto big_number * 2
a_array = a.to_a
b_array = b.to_a

class MultipleEnumerator
  include Enumerable
  def initialize(*args)
    @data = *args
  end

  def each(&block)
    @data.each do |data|
        data.each(&block)
    end
  end
end

Benchmark.bm do |x|
  x.report 'MultipleEnumerator' do
    e = MultipleEnumerator.new(a, b)
    puts e.reduce :+
  end
  x.report 'to_a.flatten' do
    puts [a, b].map(&:to_a).flatten.reduce :+
  end
  x.report 'flatten' do
    puts [a_array, b_array].flatten.reduce :+
  end
end