Re: Enumerable#mins_by

http://ujihisa.nowa.jp/entry/67a15ef440

Experiment

require 'benchmark'

module Enumerable
  def my_mins_by(&block)
    min = min_by(&block)
    select {|e| e == min }
  end

  def uj_mins_by(&b)
    memo = []
    memo_value = 1/0.0
    each do |e|
      value = yield e
      if value < memo_value
        memo = [e]
        memo_value = value
      elsif value == memo_value
        memo << e
      end
    end
    memo
  end
end

target = 1000.times.map { rand 10 } - [0]

Benchmark.bmbm do |x|
  x.report('my') { target.my_mins_by {|e| e ** 2 } }
  x.report('uj') { target.uj_mins_by {|e| e ** 2 } }
end

Result

Rehearsal --------------------------------------
my   0.000000   0.000000   0.000000 (  0.000808)
uj   0.000000   0.000000   0.000000 (  0.001566)
----------------------------- total: 0.000000sec

         user     system      total        real
my   0.010000   0.000000   0.010000 (  0.000773)
uj   0.000000   0.000000   0.000000 (  0.000940)

Consider

直感的には僕の方が遅くなりそうなのに。