Hanami::Action::Params#error_messages: each_with_object vs flat_map benchmark

bench.rb

#!/usr/bin/env ruby
require 'bundler/setup'
require 'benchmark/ips'
require 'hanami/controller'

class Hanami::Action::Params
  def flat_map_error_messages(error_set = errors)
    error_set.flat_map do |key, messages|
      k = Hanami::Utils::String.new(key).titleize

      if messages.is_a?(Hash)
        flat_map_error_messages(messages)
      else
        messages.map! { |message| "#{k} #{message}" }
      end
    end
  end
end

class TestParams < Hanami::Action::Params
  params do
    required(:email).filled(format?: /\A.+@.+\z/)
    required(:name).filled
    required(:tos).filled(:bool?)
    required(:age).filled(:int?)
    required(:address).schema do
      required(:line_one).filled
      required(:deep).schema do
        required(:deep_attr).filled(:str?)
      end
    end
  end
end

params = TestParams.new({})

Benchmark.ips do |x|
  x.report('each_with_object') { params.error_messages }
  x.report('flat_map')         { params.flat_map_error_messages }
  x.compare!
end

__END__

Result:

  Warming up --------------------------------------
      each_with_object   465.000  i/100ms
              flat_map   450.000  i/100ms
  Calculating -------------------------------------
      each_with_object      4.598k (± 6.2%) i/s -     23.250k in   5.079603s
              flat_map      4.602k (± 4.1%) i/s -     23.400k in   5.093111s

  Comparison:
              flat_map:     4602.1 i/s
      each_with_object:     4597.7 i/s - same-ish: difference falls within error

Ruby:

    ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin15]

Hardware:

    Hardware Overview:

      Model Name: MacBook Pro
      Model Identifier: MacBookPro12,1
      Processor Name: Intel Core i7
      Processor Speed: 3.1 GHz
      Number of Processors: 1
      Total Number of Cores: 2
      L2 Cache (per Core): 256 KB
      L3 Cache: 4 MB
      Memory: 16 GB
      Boot ROM Version: MBP121.0167.B16
      SMC Version (system): 2.28f7

Software:

    System Software Overview:

      System Version: OS X 10.11.5 (15F34)
      Kernel Version: Darwin 15.5.0
      Time since boot: 2 days 1:00