Benchmark constant access vs two ways to support overrides in derived class

const-benchmark.rb

#!/usr/bin/ruby

# Adapted from https://github.com/bbatsov/ruby-style-guide/issues/328#issuecomment-227967489

require 'benchmark'

n = 5000000

$priv_const = ( ARGV[0] == 'priv_const' )

class C1

  # == Constants ==

  BLACK  = 0
  RED    = 1
  GREEN  = 2
  BLUE   = 3
  YELLOW = 4
  VIOLET = 5
  PURPLE = 6
  BROWN  = 7
  PINK   = 8
  WHITE  = 9

  # Note: This won't work with use_via_self
  if $priv_const
    private_constant :BLACK, :RED, :GREEN, :BLUE, :YELLOW,
                     :VIOLET,:PURPLE, :BROWN, :PINK, :WHITE
  end

  # == Wrapper methods (which could be overridden) ==

  def self.black
    BLACK
  end

  def self.red
    RED
  end

  def self.green
    GREEN
  end

  def self.blue
    BLUE
  end

  def self.yellow
    YELLOW
  end

  def self.violet
    VIOLET
  end

  def self.purple
    PURPLE
  end

  def self.brown
    BROWN
  end

  def self.pink
    PINK
  end

  def self.white
    WHITE
  end

  # Use defined constants directly
  def self.use_direct( i )
    case i
    when BLACK
      0
    when RED
      1
    when GREEN
      2
    when BLUE
      3
    when YELLOW
      4
    when VIOLET
      5
    when PURPLE
      6
    when BROWN
      7
    when PINK
      8
    when WHITE
      9
    end
  end

  # Use `self::` for contant lookup, so that these constants may be
  # effectively "overridden" in a derived class.
  def self.use_via_self( i )
    case i
    when self::BLACK
      0
    when self::RED
      1
    when self::GREEN
      2
    when self::BLUE
      3
    when self::YELLOW
      4
    when self::VIOLET
      5
    when self::PURPLE
      6
    when self::BROWN
      7
    when self::PINK
      8
    when self::WHITE
      9
    end
  end

  # Use the wrapper methods for access to the underlying (potentially
  # private) constants.
  def self.use_wrappers( i )
    case i
    when black
      0
    when red
      1
    when green
      2
    when blue
      3
    when yellow
      4
    when violet
      5
    when purple
      6
    when brown
      7
    when pink
      8
    when white
      9
    end
  end
end

# Derived class using constant "override" for C2.use_via_self
class C2 < C1
  BLACK  = 0
  RED    = 1
  GREEN  = 2
  BLUE   = 3
  YELLOW = 4
  VIOLET = 5
  PURPLE = 6
  BROWN  = 7
  PINK   = 8
  WHITE  = 9
end

# Derived class using wrapper override for C3.use_wrappers
class C3 < C1
  BLACK  = 0
  RED    = 1
  GREEN  = 2
  BLUE   = 3
  YELLOW = 4
  VIOLET = 5
  PURPLE = 6
  BROWN  = 7
  PINK   = 8
  WHITE  = 9

  if $priv_const
    private_constant :BLACK, :RED, :GREEN, :BLUE, :YELLOW,
                     :VIOLET,:PURPLE, :BROWN, :PINK, :WHITE
  end

  def self.black
    BLACK
  end

  def self.red
    RED
  end

  def self.green
    GREEN
  end

  def self.blue
    BLUE
  end

  def self.yellow
    YELLOW
  end

  def self.violet
    VIOLET
  end

  def self.purple
    PURPLE
  end

  def self.brown
    BROWN
  end

  def self.pink
    PINK
  end

  def self.white
    WHITE
  end
end

Benchmark.bm(26) do |x|
  x.report('C1.use_direct:')         { 1.upto(n) { |i| C1.use_direct(i%10); } }

  unless $priv_const
    x.report('C1.use_via_self:')     { 1.upto(n) { |i| C1.use_via_self(i%10); } }
  end

  x.report('C1.use_wrappers:')       { 1.upto(n) { |i| C1.use_wrappers(i%10); } }

  unless $priv_const
    x.report('C2.use_via_self:')     { 1.upto(n) { |i| C2.use_via_self(i%10); } }
  end

  x.report('C3.use_wrappers:')       { 1.upto(n) { |i| C3.use_wrappers(i%10); } }
end

results.txt

ruby -v ./const-benchmark.rb
ruby 2.2.5p319 (2016-04-26 revision 54774) [x86_64-linux]
                                 user     system      total        real
C1.use_direct:               1.110000   0.000000   1.110000 (  1.107700)
C1.use_via_self:             1.630000   0.000000   1.630000 (  1.631611)
C1.use_wrappers:             1.690000   0.000000   1.690000 (  1.694374)
C2.use_via_self:             1.580000   0.000000   1.580000 (  1.581633)
C3.use_wrappers:             1.640000   0.000000   1.640000 (  1.640261)

ruby -v ./const-benchmark.rb priv_const
ruby 2.2.5p319 (2016-04-26 revision 54774) [x86_64-linux]
                                 user     system      total        real
C1.use_direct:               1.100000   0.000000   1.100000 (  1.093155)
C1.use_wrappers:             1.590000   0.000000   1.590000 (  1.598704)
C3.use_wrappers:             1.610000   0.000000   1.610000 (  1.601593)