string_concat.rb

require 'stringio'
require 'benchmark/ips'

list = 1...10_000

Benchmark.ips do |x|
  x.config(:time => 10, :warmup => 2)

  x.report('String#<<') do
    s = ''
    list.each { |x| s << "#{x}\n" }
  end

  x.report('String#+') do
    s = ''
    list.each { |x| s += "#{x}\n" }
  end

  x.report('StringIO.open') do
    StringIO.open do |s|
      list.each { |x| s.puts(x) }
      s.string
    end
  end

end

# Calculating -------------------------------------
#            String#<<    24.000  i/100ms
#             String#+     1.000  i/100ms
#        StringIO.open    14.000  i/100ms
# -------------------------------------------------
#            String#<<    236.078  (± 5.1%) i/s -      2.376k
#             String#+     15.901  (± 6.3%) i/s -    159.000
#        StringIO.open    134.767  (± 6.7%) i/s -      1.344k