each_with_index.rb

require 'benchmark'

arr = (1..100).to_a


Benchmark.bm(20) do |x|
  x.report("each.with_index") do
    100_000.times do
      arr.each_with_index do |v, i|
      end
    end
  end

  x.report("each.with_index b&") do
    100_000.times do
      bv = arr.each.with_index
      arr.length.times do |i|
        bv.next
      end
    end
  end

end

Seems a Fiber adds about 1 ms per call. Wonder what this would look like if you compared Fibers against Threads.