Pathname.join (Rails.root.join) vs String Interpolation benchmark

path-join.rb

# frozen_string_literal: true

require "benchmark/ips"
require "pathname"

Benchmark.ips do |x|
  x.config(:time => 5, :warmup => 2)

  root = Pathname.new("/home/foo/bar/app")

  x.report("pathname join") do |times|
    i = 0

    while i < times
      var = root.join("tmp", "path", "file").to_s
      i += 1
    end
  end

  x.report("string iterp.") do |times|
    i = 0

    while i < times
      var = "#{root}/tmp/path/file"

      i += 1
    end
  end

  x.compare!
end

Pathname Join Benchmark

Warming up --------------------------------------
       pathname join     5.643k i/100ms
       string iterp.   252.100k i/100ms
Calculating -------------------------------------
       pathname join     57.791k (± 4.4%) i/s -    293.436k in   5.086740s
       string iterp.      3.994M (± 2.1%) i/s -     20.168M in   5.051901s

Comparison:
       string iterp.:  3993877.9 i/s
       pathname join:    57791.3 i/s - 69.11x  slower