Iterate v. reduce over array of hashes

gistfile.rb

module Test
  def self.iterate(array)
    Hash.new(0).tap do |result|
      array.each do |hash|
        hash.each do |key, val|
          result[key] = result[key] + val
        end
      end
    end
  end

  def self.reduce(array)
    array.reduce do |memo, hash|
      memo.merge(hash) do |_key, old_val, new_val|
        old_val + new_val
      end
    end
  end

  def self.random_array_of_hashes(array_size)
    Array.new(array_size) { { a: rand(1000), b: rand(1000) } }
  end

  def self.bench(ntimes = 1000, array_size = 1000)
    arr = random_array_of_hashes(array_size)

    Benchmark.bmbm do |results|
      results.report('reduce:  ') do
        ntimes.times { reduce(arr) }
      end

      results.report('iterate: ') do
        ntimes.times { iterate(arr) }
      end
    end
  end
end

Test.bench