Ruby Benchmark: ivar vs accessor

ivar_vs_accessor.rb

#!/usr/bin/env ruby
# frozen_string_literal: true

require "benchmark/ips"

class Ivar
  def initialize
    @ivar = 23
  end

  def call
    @ivar * 10
  end
end

class AttrAccessor
  def initialize
    @ivar = 23
  end

  def call
    ivar * 10
  end

  private

  attr_reader :ivar
end

ivar = Ivar.new
attr = AttrAccessor.new

Benchmark.ips do |x|
  x.report("ivar") { ivar.call }
  x.report("attr") { attr.call }
  x.compare!
end

__END__
Result:
  Warming up --------------------------------------
                  ivar     1.646M i/100ms
                  attr     1.457M i/100ms
  Calculating -------------------------------------
                  ivar     16.896M (± 2.9%) i/s -     85.613M in   5.071429s
                  attr     14.560M (± 2.5%) i/s -     72.854M in   5.006994s

  Comparison:
                  ivar: 16895535.5 i/s
                  attr: 14559729.1 i/s - 1.16x  (± 0.00) slower

Ruby:

    ruby 3.1.0p0 (2021-12-25 revision fb4df44d16) [x86_64-darwin21]

Hardware:

    Hardware Overview:

      Model Name: MacBook Pro
      Model Identifier: MacBookPro16,2
      Processor Name: Quad-Core Intel Core i7
      Processor Speed: 2,3 GHz
      Number of Processors: 1
      Total Number of Cores: 4
      L2 Cache (per Core): 512 KB
      L3 Cache: 8 MB
      Hyper-Threading Technology: Enabled
      Memory: 32 GB
      System Firmware Version: 1731.120.10.0.0 (iBridge: 19.16.15071.0.0,0)
      OS Loader Version: 540.120.3~6

Software:

    System Software Overview:

      System Version: macOS 12.4 (21F79)
      Kernel Version: Darwin 21.5.0
      Time since boot: 4 days 18:52