benchmark: split a string every n characters in Ruby

0_output.txt

                                               user     system      total        real
String#scan                                1.774321   0.007220   1.781541 (  1.799350)
String.unpack                              0.665138   0.003861   0.668999 (  0.678201)
String#chars.each_slice.map(join)         10.444911   0.023717  10.468628 ( 10.521092)
String#[] slice with times iteration       2.244066   0.006614   2.250680 (  2.264310)
String#slice with times iteration          2.271120   0.005431   2.276551 (  2.290473)

bm.rb

require 'benchmark'

Benchmark.bm 40 do |r|
  n = 100_000
  str = ('a'..'z').to_a.join * 10

  r.report "String#scan" do
    n.times do
      v = str.scan(/.{4}/)
    end
  end

  r.report "String#unpack" do
    n.times do
      str.unpack("a4" * (str.size / 4))
    end
  end

  r.report "String#chars.each_slice.map(join)" do
    n.times do
      v = str.chars.each_slice(4).map {|c| c.join "" }
    end
  end

  r.report "String#[] slice with times iteration" do
    n.times do
      v = []
      (str.length / 4).times do |i|
        offset = i * 4
        v << str[0+offset...4+offset]
      end
    end
  end

  r.report "String#slice with times iteration" do
    n.times do
      v = []
      (str.length / 4).times do |i|
        offset = i * 4
        v << str.slice(0+offset...4+offset)
      end
    end
  end
end