Ruby Hash merge benchmark

ruby_hash_merge_benchmark.rb

require 'benchmark/ips'
h = { a: 1 }
=> {:a=>1}

Benchmark.ips do |x|
  x.report('merge')  { {b: 12}.merge(h) }
  x.report('merge!') { {b: 12}.merge!(h) }
  x.report('merge ** ') { {b: 12, **h} }
  x.compare!
end

Warming up --------------------------------------
               merge   293.453k i/100ms
              merge!   424.041k i/100ms
           merge **    382.969k i/100ms
Calculating -------------------------------------
               merge      3.169M (±14.5%) i/s -     15.553M in   5.016664s
              merge!      4.351M (± 9.9%) i/s -     21.626M in   5.021534s
           merge **       3.748M (± 9.1%) i/s -     18.765M in   5.051223s

Comparison:
              merge!:  4350698.3 i/s
           merge ** :  3748037.4 i/s - same-ish: difference falls within error
               merge:  3168824.0 i/s - 1.37x  (± 0.00) slower