Compare performance `Hash#merge` and `Hash#merge!` for Ruby 2.6

merge_vs_mergex.rb

require 'benchmark/ips'
require 'benchmark/memory'

class Hoge
  class << self
    DEFAULT_TIME = 5
    DEFAULT_WARMUP = 2

    def ips(title:,
            time: DEFAULT_TIME,
            warmup: DEFAULT_WARMUP,
            suite: nil,
            &block)
      Benchmark.ips do |x|
        x.time = time
        x.warmup = warmup

        x.config(suite: suite) unless suite.nil?

        x.report(title) { block.call }
      end
    end

    def memory(title:, &block)
      Benchmark.memory do |x|
        x.report(title) { block.call }
      end
    end

    def ips_compare(procs:,
                    time: DEFAULT_TIME,
                    warmup: DEFAULT_WARMUP,
                    suite: nil,
                    result_holder: nil,
                    result_saver: nil)
      Benchmark.ips do |x|
        x.time = time
        x.warmup = warmup

        x.config(suite: suite) unless suite.nil?

        procs.each do |p|
          x.report(p[:title]) { p[:proc].call }
        end

        x.hold!(result_holder) unless result_holder.nil?
        x.save!(result_saver) unless result_saver.nil?

        x.compare!
      end
    end

    def memory_compare(procs:, result_holder: nil)
      Benchmark.memory do |x|
        procs.each do |p|
          x.report(p[:title]) { p[:proc].call }
        end

        x.hold!(result_holder) unless result_holder.nil?

        x.compare!
      end
    end
  end
end

PROCS = [
  {
    title: 'merge',
    proc: Proc.new do
      h = { hoge: 'hogehoge' }
      h.merge({ huga: 'hugahugahuga' })
    end
  },
  {
    title: 'merge!',
    proc: Proc.new do
      h = { hoge: 'hogehoge' }
      h.merge!({ huga: 'hugahugahuga' })
    end
  },
]

Hoge.ips_compare(procs: PROCS)
Hoge.memory_compare(procs: PROCS)

 % ruby -v
ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin19]

% ruby merge_vs_mergex.rb
Warming up --------------------------------------
               merge   307.079k i/100ms
              merge!   355.438k i/100ms
Calculating -------------------------------------
               merge      3.054M (± 1.3%) i/s -     15.354M in   5.029121s
              merge!      3.605M (± 1.2%) i/s -     18.127M in   5.028477s

Comparison:
              merge!:  3605480.7 i/s
               merge:  3053507.7 i/s - 1.18x  (± 0.00) slower

Calculating -------------------------------------
               merge   776.000  memsize (     0.000  retained)
                         5.000  objects (     0.000  retained)
                         2.000  strings (     0.000  retained)
              merge!   544.000  memsize (     0.000  retained)
                         4.000  objects (     0.000  retained)
                         2.000  strings (     0.000  retained)

Comparison:
              merge!:        544 allocated
               merge:        776 allocated - 1.43x more