Benchmark of various solutions to a question on #ruby IRC

benchmark.rb

# frozen_string_literal: true

require 'benchmark/ips'

Benchmark.ips do |ips|
  words = [*'a'..'all'].freeze
  separator = '-'

  ips.report('map & join') { words.map { |word| separator + word }.join }
  ips.report('join & prepend') { words.join(separator).prepend(separator) }
  ips.report('prepend & join') { words.dup.prepend(separator).join(separator) }
  ips.report('reduce') { words.reduce('') { |acc, word| "#{acc}#{separator}#{word}" } }
  ips.report('each_with_object') { words.each_with_object(+'') { |word, acc| acc << separator << word } }

  ips.compare!
end

jruby-9.2.9.0

Warming up --------------------------------------
          map & join   910.000  i/100ms
      join & prepend     2.882k i/100ms
      prepend & join     2.819k i/100ms
              reduce   213.000  i/100ms
    each_with_object     1.349k i/100ms
Calculating -------------------------------------
          map & join     11.818k (± 6.5%) i/s -     59.150k in   5.029508s
      join & prepend     26.100k (± 6.8%) i/s -    132.572k in   5.104441s
      prepend & join     26.037k (± 6.2%) i/s -    129.674k in   5.000904s
              reduce      2.492k (±13.7%) i/s -     12.354k in   5.057033s
    each_with_object     12.878k (± 4.8%) i/s -     64.752k in   5.039571s

Comparison:
      join & prepend:    26099.7 i/s
      prepend & join:    26036.6 i/s - same-ish: difference falls within error
    each_with_object:    12878.4 i/s - 2.03x  slower
          map & join:    11818.4 i/s - 2.21x  slower
              reduce:     2492.4 i/s - 10.47x  slower

ruby-2.7.0

Warming up --------------------------------------
          map & join   691.000  i/100ms
      join & prepend     1.490k i/100ms
      prepend & join     1.486k i/100ms
              reduce   190.000  i/100ms
    each_with_object   747.000  i/100ms
Calculating -------------------------------------
          map & join      7.080k (± 2.2%) i/s -     35.932k in   5.077814s
      join & prepend     15.571k (± 2.8%) i/s -     78.970k in   5.075875s
      prepend & join     15.153k (± 2.3%) i/s -     75.786k in   5.004352s
              reduce      1.917k (± 2.5%) i/s -      9.690k in   5.057762s
    each_with_object      7.519k (± 2.0%) i/s -     38.097k in   5.068544s

Comparison:
      join & prepend:    15570.7 i/s
      prepend & join:    15152.8 i/s - same-ish: difference falls within error
    each_with_object:     7519.5 i/s - 2.07x  slower
          map & join:     7079.8 i/s - 2.20x  slower
              reduce:     1917.1 i/s - 8.12x  slower

truffleruby-19.3.1

Warming up --------------------------------------
          map & join   425.000  i/100ms
      join & prepend   196.000  i/100ms
      prepend & join   289.000  i/100ms
              reduce   276.000  i/100ms
    each_with_object   306.000  i/100ms
Calculating -------------------------------------
          map & join      5.988k (±44.2%) i/s -     22.100k in   5.020160s
      join & prepend      4.799k (±38.0%) i/s -     17.444k in   4.999857s
      prepend & join      4.688k (±35.4%) i/s -     19.652k in   5.061994s
              reduce      3.824k (±36.1%) i/s -     16.008k in   5.074519s
    each_with_object      4.727k (±36.3%) i/s -     19.278k in   5.019630s

Comparison:
          map & join:     5988.3 i/s
      join & prepend:     4798.9 i/s - same-ish: difference falls within error
    each_with_object:     4727.3 i/s - same-ish: difference falls within error
      prepend & join:     4688.4 i/s - same-ish: difference falls within error
              reduce:     3824.0 i/s - same-ish: difference falls within error