the_dup_cost.rb

require 'benchmark'


class Tester
  attr_accessor :hash

  HASH = Hash[*(1..100).to_a]

  def init_with_dup
    @hash = HASH.dup
  end

  def init_with_hash
    @hash = Hash[HASH]
  end

  def init_with_copy
    @hash = HASH
  end

  def look_all_up
    50.times{|i| @hash[i]}
  end

  def look_all_up_with_fallback
    @bla = nil
    50.times{|i| @bla[i] if @bla; @hash[i]}
  end
end


@iterations = 100_000

@tester = Tester.new

Benchmark.bmbm do |x|
  x.report("init with dup") do
    @iterations.times{@tester.init_with_dup}
  end

  x.report("init with hash") do
    @iterations.times{@tester.init_with_hash}
  end

  x.report("init with copy") do
    @iterations.times{@tester.init_with_copy}
  end

  x.report("init with dup with lookup") do
    @iterations.times{@tester.init_with_dup; @tester.look_all_up}
  end

  x.report("init with hash with lookup") do
    @iterations.times{@tester.init_with_hash; @tester.look_all_up}
  end

  x.report("init with copy with lookup") do
    @iterations.times{@tester.init_with_copy; @tester.look_all_up}
  end

  x.report("init with copy with fallback lookup") do
    @iterations.times{@tester.init_with_copy; @tester.look_all_up_with_fallback}
  end
end