Benchmarks Comparing First Hash Key in CRuby, JRuby, TruffleRuby and Rubinius

benchmarks.sh

~ chruby ruby-2.5.1
~ ruby -v
ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-darwin17]
~ ruby first_key_bench.rb
Warming up --------------------------------------
                keys   238.442k i/100ms
            each_key   114.229k i/100ms
               first   153.335k i/100ms
             flatten   229.021k i/100ms
Calculating -------------------------------------
                keys      7.163M (± 4.2%) i/s -     35.766M in   5.002627s
            each_key      1.813M (± 2.8%) i/s -      9.138M in   5.043558s
               first      2.525M (± 3.0%) i/s -     12.727M in   5.044937s
             flatten      5.920M (± 3.0%) i/s -     29.773M in   5.033696s

Comparison:
                keys:  7162938.3 i/s
             flatten:  5920454.4 i/s - 1.21x  slower
               first:  2525033.6 i/s - 2.84x  slower
            each_key:  1813436.5 i/s - 3.95x  slower

~
~ chruby jruby
~ ruby -v
jruby 9.2.0.0 (2.5.0) 2018-05-24 81156a8 GraalVM 1.0.0-rc1 25.71-b01-internal-jvmci-0.42 on 1.8.0_161-b12 +jit [darwin-x86_64]
~ ruby -Xcompile.invokedynamic first_key_bench.rb
Warming up --------------------------------------
                keys   190.567k i/100ms
            each_key    55.809k i/100ms
               first   246.750k i/100ms
             flatten   136.328k i/100ms
Calculating -------------------------------------
                keys     39.866M (± 9.4%) i/s -    196.665M in   4.992307s
            each_key      1.494M (±40.9%) i/s -      4.744M in   5.026491s
               first     21.614M (±10.2%) i/s -    106.349M in   4.998362s
             flatten      3.382M (± 5.3%) i/s -     16.905M in   5.013187s

Comparison:
                keys: 39865568.1 i/s
               first: 21613530.8 i/s - 1.84x  slower
             flatten:  3381734.0 i/s - 11.79x  slower
            each_key:  1494299.7 i/s - 26.68x  slower

~
~ chruby truffleruby
~ ruby -v
truffleruby 1.0.0-rc1, like ruby 2.3.7 <native build with Graal> [x86_64-darwin]
~ ruby first_key_bench.rb
Warming up --------------------------------------
                keys     1.412M i/100ms
            each_key     1.961M i/100ms
               first     1.782M i/100ms
             flatten   306.020k i/100ms
Calculating -------------------------------------
                keys     42.110M (±38.5%) i/s -    169.434M in   5.000957s
            each_key    611.510M (± 7.3%) i/s -      2.665B in   4.992264s
               first     23.136M (±26.5%) i/s -    103.335M in   5.024682s
             flatten      4.840M (±25.1%) i/s -     22.033M in   5.041441s

Comparison:
            each_key: 611510252.3 i/s
                keys: 42109687.3 i/s - 14.52x  slower
               first: 23135572.4 i/s - 26.43x  slower
             flatten:  4840388.0 i/s - 126.33x  slower

~
~ chruby rbx
~ ruby -v
rubinius 3.104 (2.3.1 eced203d 2018-05-15 4.0.1) [x86_64-darwin17.5.0]
~ ruby first_key_bench.rb
Warming up --------------------------------------
                keys    36.392k i/100ms
            each_key    14.339k i/100ms
               first    45.738k i/100ms
             flatten    16.239k i/100ms
Calculating -------------------------------------
                keys    626.855k (± 6.3%) i/s -      3.130M
            each_key    192.763k (±11.0%) i/s -    960.713k
               first    827.696k (± 8.3%) i/s -      4.116M
             flatten    204.028k (± 5.5%) i/s -      1.023M

Comparison:
               first:   827696.4 i/s
                keys:   626854.8 i/s - 1.32x  slower
             flatten:   204027.9 i/s - 4.06x  slower
            each_key:   192763.2 i/s - 4.29x  slower

first_key_bench.rb

require 'benchmark/ips'

Benchmark.ips do |x|
  H = {key: :value}.freeze

  x.report('keys') { H.keys.first }
  x.report('each_key') { H.each_key.first }
  x.report('first') { H.first.first }
  x.report('flatten') { H.flatten.first }

  x.compare!
end