array_flatten_1.9.2.rb

require 'benchmark'

class Foo
  def method_missing(method_name, *args)
    if method_name.match(/foo_bar/)
      # code
    else
      super(method_name, *args)
    end
  end
end

GC.disable # Don't let GarbageCollector change outcome

Benchmark.bm(40) do |b|
  n = 100_000
  normal_objects = n.times.map{Object.new}
  foo_objects = n.times.map{Foo.new}

  b.report("flatten Object objects") { normal_objects.flatten }
  b.report("flatten Foo objects") { foo_objects.flatten }
end

GC.enable

# Results
#                            user     system      total        real
# flatten Object objects  0.000000   0.000000   0.000000 (  0.013034)
# flatten Foo objects     3.740000   1.560000   5.300000 ( 11.905745)