const-get-bench.rb

# frozen_string_literal: true

CONSTS = {}
module Mod
  1000.times do |i|
    CONSTS["CONST_#{i}"] = i
    const_set("CONST_#{i}", i)
  end
end

require 'benchmark/ips'

module Inflector
  class << self
    def constantize(camel_cased_word)
      Object.const_get(camel_cased_word)
    end

    def safe_constantize(camel_cased_word)
      constantize(camel_cased_word)
    rescue NameError => e
      raise if e.name && !(camel_cased_word.to_s.split("::").include?(e.name.to_s) ||
        e.name.to_s == camel_cased_word.to_s)
    rescue LoadError => e
      message = e.respond_to?(:original_message) ? e.original_message : e.message
      raise unless /Unable to autoload constant #{const_regexp(camel_cased_word)}/.match?(message)
    end
  end
end

class String
  def safe_constantize
    Inflector.safe_constantize(self)
  end
end

Benchmark.ips do |x|
  x.report("Hash#[]") { CONSTS["CONST_999"] }
  x.report("const_get 1 sym") { Mod.const_get(:CONST_999) }
  x.report("const_get 1 str") { Mod.const_get("CONST_999") }
  x.report("const_get 2 str") { Object.const_get("Mod::CONST_999") }
  x.report("safe_constantize") { "Mod::CONST_999".safe_constantize }
  x.compare!(order: :baseline)
end

results.txt

Warming up --------------------------------------
             Hash#[]     1.479M i/100ms
     const_get 1 sym     1.503M i/100ms
     const_get 1 str   920.881k i/100ms
     const_get 2 str   647.367k i/100ms
    safe_constantize   485.857k i/100ms
Calculating -------------------------------------
             Hash#[]     14.834M (± 2.5%) i/s -     75.417M in   5.087217s
     const_get 1 sym     15.016M (± 4.8%) i/s -     76.653M in   5.119995s
     const_get 1 str      9.126M (± 2.7%) i/s -     46.044M in   5.049378s
     const_get 2 str      6.389M (± 7.1%) i/s -     31.721M in   5.002337s
    safe_constantize      4.863M (± 1.1%) i/s -     24.779M in   5.095572s

Comparison:
             Hash#[]: 14834315.0 i/s
     const_get 1 sym: 15016010.6 i/s - same-ish: difference falls within error
     const_get 1 str:  9126454.1 i/s - 1.63x  slower
     const_get 2 str:  6389107.4 i/s - 2.32x  slower
    safe_constantize:  4863389.2 i/s - 3.05x  slower