Benchmark of WeakRef Cache

result

$ ruby weakref_cache.rb
                    user   system        total        real
no_cache        0.000000   0.000000   0.000000 (  0.000611)
weakref_cache   0.000000   0.000000   0.000000 (  0.000349)
cache           0.000000   0.000000   0.000000 (  0.000208)

weakref_cache.rb

require 'digest/sha1'
require "weakref"

class WeakCache
  def initialize
    @caches = {}
  end

  def [](key)
    @caches[key]
  end

  def []=(key, value)
    ref = WeakRef.new(value)
    ObjectSpace.define_finalizer(value, WeakCache.ensure_cleanup(@caches, key, ref))
    @caches[key] = ref
  end

  def self.ensure_cleanup(caches, key, ref)
    proc{
      caches.delete(key) if caches[key] == ref
    }
  end
end

class Dog
  Info = Struct.new :name, :age, :sex, :strength
  @@cache_basic_calc = {}

  def initialize(name, breed="mix")
    sex = calc_sex(name)
    strength = calc_strength(breed) + calc_strength(name)
    @info = Info.new name, 0, sex, strength
  end

  private

  def basic_calc(str)
    key = str.to_s.downcase
    @@cache_basic_calc[key] ||=
      Digest::SHA1.hexdigest(key).split(/[^0-9]/).inject(0){|sum, num| sum + num.to_i}
  end

  #  @return [Symbol] 犬の性別 (:male or :female)
  def calc_sex(str)
    sex = basic_calc(str) % 2
    sex.zero? ? :male : :female
  end

  #  @return [Integer] 犬の強さ (0-255)
  def calc_strength(str)
    basic_calc(str) % 256
  end
end

class DogTeam1
  @@cache_dog = ::WeakCache.new

  def initialize(breed, dog1, dog2, dog3, dog4, dog5)
    @team = [
      dog(dog1, breed),
      dog(dog2, breed),
      dog(dog3, breed),
      dog(dog4, breed),
      dog(dog5, breed),
    ]
  end

  private

  def dog(name, breed)
    Dog.new(name, breed)
  end
end

class DogTeam2
  @@cache_dog = ::WeakCache.new

  def initialize(breed, dog1, dog2, dog3, dog4, dog5)
    @team = [
      dog(dog1, breed),
      dog(dog2, breed),
      dog(dog3, breed),
      dog(dog4, breed),
      dog(dog5, breed),
    ]
  end

  private

  def dog(name, breed)
    @@cache_dog[[name, breed]] ||= Dog.new(name, breed)
  end
end

class DogTeam3
  @@cache_dog = {}

  def initialize(breed, dog1, dog2, dog3, dog4, dog5)
    @team = [
      dog(dog1, breed),
      dog(dog2, breed),
      dog(dog3, breed),
      dog(dog4, breed),
      dog(dog5, breed),
    ]
  end

  private

  def dog(name, breed)
    @@cache_dog[[name, breed]] ||= Dog.new(name, breed)
  end
end


###################################
# Benchmark Test
###################################
require "benchmark"

Benchmark.bm(500) do |b|
  b.report(:no_cache){
    10.times{|n| DogTeam1.new("team", "won", "one", "nyao", "wan#{n}", "nyao#{n}") }
  }
  b.report(:weakref_cache){
    10.times{|n| DogTeam2.new("team", "won", "one", "nyao", "wan#{n}", "nyao#{n}") }
  }
  b.report(:cache){
    10.times{|n| DogTeam3.new("team", "won", "one", "nyao", "wan#{n}", "nyao#{n}") }
  }
end