配列からハッシュを作る際のパフィーマンスを測定するコードです

generata_hash_from_list.rb

require 'benchmark'

list = (1..10000).to_a
Benchmark.bm(20) do |x|
  x.report('for:') do
    hash = {}
    for n in list do
      hash[n.to_s] = n * 2
    end
  end

  x.report('each:') do
    hash = {}
    list.each do |n|
      hash[n.to_s] = n * 2
    end
  end

  x.report('each_with_object:') do
    list.each_with_object({}) do |n, hash|
      hash[n.to_s] = n * 2
    end
  end

  x.report('reduce:') do
    list.reduce({}) do |hash, n|
      hash[n.to_s] = n * 2
      hash
    end
  end
end