Const check performance

results.md

# frozen_string_literal: true

# require 'pry-byebug'

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


puts '```ruby'
puts File.read(__FILE__).gsub("\t", '  ')
puts '```'
puts
puts '### Output'
puts
puts '```'


module MyRbConfig
  CONFIG = { 'ruby_install_name' => 'jruby' }
end

class PlatformA
  def jruby?
    MyRbConfig::CONFIG['ruby_install_name'] == 'jruby'
  end
end

class PlatformB
  case MyRbConfig::CONFIG['ruby_install_name']
  when 'jruby'
    def jruby?; true; end
  else
    def jruby?; false; end
  end
end

class PlatformC
  def jruby?
    return @jruby if defined? @jruby
    @jruby = MyRbConfig::CONFIG['ruby_install_name'] == 'jruby'
  end
end

class PlatformD
  IS_JRUBY = MyRbConfig::CONFIG['ruby_install_name'] == 'jruby'

  private_constant :IS_JRUBY

  def jruby?
    IS_JRUBY
  end
end


def via_simple_method
  PlatformA.new.jruby?
end

def via_inline_method
  PlatformB.new.jruby?
end

def via_memoization
  PlatformC.new.jruby?
end

def via_constant
  PlatformD.new.jruby?
end


def test
  exit if p(pp([
    via_simple_method,
    via_inline_method,
    via_memoization,
    via_constant
  ]).uniq.size) > 1
end

test

Benchmark.ips do |x|
  x.report('via_simple_method') { via_simple_method }
  x.report('via_inline_method') { via_inline_method }
  x.report('via_memoization') { via_memoization }
  x.report('via_constant') { via_constant }

  x.compare!
end

Benchmark.memory do |x|
  x.report('via_simple_method') { 100.times { via_simple_method } }
  x.report('via_inline_method') { 100.times { via_inline_method } }
  x.report('via_memoization') { 100.times { via_memoization } }
  x.report('via_constant') { 100.times { via_constant } }

  x.compare!
end


puts '```'

Output

[true, true, true, true]
1
Warming up --------------------------------------
   via_simple_method   307.877k i/100ms
   via_inline_method   359.601k i/100ms
     via_memoization   263.984k i/100ms
        via_constant   353.513k i/100ms
Calculating -------------------------------------
   via_simple_method      5.094M (± 0.7%) i/s -     25.554M in   5.016296s
   via_inline_method      6.216M (± 1.7%) i/s -     31.285M in   5.034356s
     via_memoization      4.155M (± 1.4%) i/s -     20.855M in   5.019941s
        via_constant      6.450M (± 1.0%) i/s -     32.523M in   5.042713s

Comparison:
        via_constant:  6450142.1 i/s
   via_inline_method:  6216235.8 i/s - 1.04x  slower
   via_simple_method:  5094405.0 i/s - 1.27x  slower
     via_memoization:  4155210.7 i/s - 1.55x  slower

Calculating -------------------------------------
   via_simple_method     4.000k memsize (     0.000  retained)
                       100.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)
   via_inline_method     4.000k memsize (     0.000  retained)
                       100.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)
     via_memoization     4.000k memsize (     0.000  retained)
                       100.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)
        via_constant     4.000k memsize (     0.000  retained)
                       100.000  objects (     0.000  retained)
                         0.000  strings (     0.000  retained)

Comparison:
   via_simple_method:       4000 allocated
   via_inline_method:       4000 allocated - same
     via_memoization:       4000 allocated - same
        via_constant:       4000 allocated - same