Benchmark to compare accessing sequential items in an array. Firstly, array is accessed via an incrementing index. Secondly, array is accessed after conversion into an enumerator.

bm: array[index] vs. enum.next

#!/usr/bin/env ruby

require 'benchmark'
max = 1_000_000
a = (1..max).to_a

Benchmark.bmbm do |bm|
  bm.report('array[index]') do # Over 20 times faster than using enum.next.
    i = 0
    while i < max
      a[i]
      i += 1
    end
  end
  bm.report('enum.next') do
    e = a.to_enum
    i = 0
    while i < max
      e.next
      i += 1
    end
  end
  bm.report('enum.next with rescue') do # In reality, we need to rescue enum.next.
    e = a.to_enum
    i = 0
    while i < max
      begin
        e.next
      rescue StopIteration
        nil
      end
      i += 1
    end
  end
  bm.report('enum.next with times') do # Using times is even slower.
    e = a.to_enum
    max.times do
      e.next
    end
  end
end

                            user     system      total        real
array[index]            0.030000   0.000000   0.030000 (  0.032193)
enum.next               0.550000   0.110000   0.660000 (  0.656447)
enum.next with rescue   0.570000   0.090000   0.660000 (  0.662478)
enum.next with times    0.570000   0.110000   0.680000 (  0.675471)