gistfile1.txt

[] ~/projects/jruby $ cat blah.rb
require 'benchmark/ips'

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

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

  x.compare!
end

[] ~/projects/jruby $ JAVA_OPTS=$GRAAL jruby -v -Xcompile.invokedynamic -Xfixnum.cache=false blah.rb
jruby 9.2.0.0 (2.5.0) 2018-05-30 d386338 GraalVM 1.0.0-rc1 25.71-b01-internal-jvmci-0.42 on 1.8.0_161-b12 +indy +jit [darwin-x86_64]
Warming up --------------------------------------
                keys   184.574k i/100ms
            each_key    15.901k i/100ms
               first    55.859k i/100ms
             flatten    42.019k i/100ms
Calculating -------------------------------------
                keys     33.138M (± 5.0%) i/s -    164.824M in   4.991467s
            each_key    286.528k (±24.0%) i/s -    763.248k in   5.030546s
               first    946.603k (±10.2%) i/s -      4.469M in   5.055190s
             flatten    656.361k (± 6.1%) i/s -      3.277M in   5.016448s

Comparison:
                keys: 33137700.9 i/s
               first:   946602.8 i/s - 35.01x  slower
             flatten:   656361.3 i/s - 50.49x  slower
            each_key:   286527.5 i/s - 115.65x  slower


[] ~/projects/jruby $ /Library/Java/JavaVirtualMachines/graalvm/Contents/Home/bin/ruby -v blah.rb
truffleruby 1.0.0-rc1, like ruby 2.3.7 <native build with Graal> [x86_64-darwin]
Warming up --------------------------------------
                keys   961.330k i/100ms
            each_key    23.504k i/100ms
               first   800.983k i/100ms
             flatten    55.507k i/100ms
Calculating -------------------------------------
                keys      8.535M (±40.1%) i/s -     36.531M in   5.028190s
            each_key    333.279k (±31.5%) i/s -      1.434M in   5.108025s
               first     58.686M (± 9.3%) i/s -    248.305M in   5.002389s
             flatten      1.027M (±33.4%) i/s -      4.219M in   5.034057s

Comparison:
               first: 58685913.4 i/s
                keys:  8534539.3 i/s - 6.88x  slower
             flatten:  1027289.6 i/s - 57.13x  slower
            each_key:   333279.2 i/s - 176.09x  slower