.allocate vs .new

allocate_vs_new.rb

puts RUBY_DESCRIPTION

require 'benchmark'

count = (ARGV[0] || 1_000_000).to_i

class Thing
  def foo
    :bar
  end
end

Thing.new
Thing.allocate

Benchmark.bm(7) do |bm|
  bm.report :new do
    count.times do
      Thing.new.foo
    end
  end

  bm.report :allocate do
    count.times do
      Thing.allocate.foo
    end
  end
end

output.log

$ for ruby in 1.9 2.0 2.1; do chruby $ruby; ruby allocate_vs_new.rb; done

ruby 1.9.3p545 (2014-02-24 revision 45159) [x86_64-darwin13.0.0]
              user     system      total        real
new       0.270000   0.000000   0.270000 (  0.277544)
allocate  0.210000   0.000000   0.210000 (  0.203312)

ruby 2.0.0p451 (2014-02-24 revision 45167) [x86_64-darwin13.0.0]
              user     system      total        real
new       0.240000   0.010000   0.250000 (  0.249500)
allocate  0.220000   0.000000   0.220000 (  0.215938)

ruby 2.1.1p76 (2014-02-24 revision 45161) [x86_64-darwin13.0]
              user     system      total        real
new       0.180000   0.000000   0.180000 (  0.188794)
allocate  0.150000   0.010000   0.160000 (  0.143627)