Ruby - Benchmark Instance Variable vs Private Getters Access

benchmark-instance-variables-vs-private-getters.rb

require 'benchmark'
require 'benchmark/ips'

class TestClass
  def initialize
    @value = "test value"
  end

  def direct_access
    @value
  end


  def reader_access
    value
  end

  private

  attr_reader :value
end


test_obj = TestClass.new


puts "Simple time benchmark (lower is better):"
Benchmark.bm(15) do |x|
  x.report("Instance variable access:") { 1_000_000.times { test_obj.direct_access } }
  x.report("Getter access:") { 1_000_000.times { test_obj.reader_access } }
end

puts "Iterations per second (higher is better):"
Benchmark.ips do |x|
  x.report("Instance variable access:") { test_obj.direct_access }
  x.report("Getter access:") { test_obj.reader_access }
  x.compare!
end

Result:

Simple time benchmark (lower is better):
                               user     system      total        real
Instance variable access:  0.024115   0.000012   0.024127 (  0.024128)
Getter access:             0.027965   0.000010   0.027975 (  0.027979)

Iterations per second (higher is better):
ruby 3.4.1 (2024-12-25 revision 48d4efcb85) +PRISM [arm64-darwin23]
Warming up --------------------------------------
Instance variable access:
                         3.571M i/100ms
      Getter access:     3.215M i/100ms
Calculating -------------------------------------
Instance variable access:
                         35.951M (± 1.0%) i/s   (27.82 ns/i) -    182.110M in   5.065990s
      Getter access:     31.687M (± 1.1%) i/s   (31.56 ns/i) -    160.749M in   5.073622s

Comparison:
Instance variable access:: 35951125.5 i/s
      Getter access:: 31687428.0 i/s - 1.13x  slower