String #<< benchmark

bm.rb

require 'rubygems'
require 'benchmark'
require 'benchmark/ips'

FOO = 'foo'

Benchmark.ips do |x|
  x.report('=') { |times|
    i = 0
    while i < times
      s = 'bar'
      s = "#{s}--#{FOO}"
      i += 1
    end
  }

  x.report('<<') { |times|
    i = 0
    while i < times
      s = 'bar'
      s << "--#{FOO}"
      i += 1
    end
  }
end

results.txt

== 1.9.3-p0
$ ruby bm.rb 
                   =  2117084.4 (±1.4%) i/s -   10633565 in   5.023815s (cycle=53435)
                  <<  2716465.9 (±2.4%) i/s -   13593125 in   5.006961s (cycle=56875)

== 1.9.2-p290
$ ruby bm.rb 
                   =  1870793.2 (±1.3%) i/s -    9384385 in   5.017105s (cycle=54245)
                  <<  2382036.8 (±1.1%) i/s -   11934816 in   5.010962s (cycle=58504)

== 1.8.7-p352
$ ruby bm.rb 
                   =  1076985.5 (±5.6%) i/s -    5376000 in   5.007787s (cycle=19200)
                  <<   965328.5 (±5.9%) i/s -    4812474 in   5.003429s (cycle=18653)

== rbx-1.2.4
$ ruby bm.rb
                   =  6234133.6 (±0.2%) i/s -   31097085 in   4.988210s (cycle=51915)
                  <<  1922727.0 (±0.3%) i/s -    9604609 in   4.995348s (cycle=31909)

== jruby-1.6.5
$ jruby bm.rb 
                   =  3736923.4 (±2.0%) i/s -   18594728 in   4.977991s (cycle=44168)
                  <<  3157849.3 (±1.8%) i/s -   15793324 in   5.003011s (cycle=56204)

== rbx-head
$ ruby bm.rb 
                   =  5145416.8 (±0.8%) i/s -   25690995 in   4.993268s (cycle=39831)
                  <<  1736795.3 (±1.2%) i/s -    8678054 in   4.997312s (cycle=33506)