gistfile1.txt

require 'benchmark'
require 'benchmark/ips'
Benchmark.ips do |r|
  r.report('merge!') do
    (1..100).inject({}) do |h, e|
      h.merge!(e => e)
    end
  end
  ref = (1..100).to_a
  r.report('Hash[]') do
    Hash[ref.map{|e|[e, e]}]
  end
  r.report('[]=') do
    (1..100).inject({}) do |h, e|
      h[e] = e
      h
    end
  end
end
# Calculating -------------------------------------
#               merge!      1172 i/100ms
#               Hash[]      2363 i/100ms
#                  []=      2790 i/100ms
# -------------------------------------------------
#               merge!    12282.7 (±6.1%) i/s -      62116 in   5.075818s
#               Hash[]    25815.9 (±3.0%) i/s -     129965 in   5.038789s
#                  []=    29528.6 (±5.6%) i/s -     147870 in   5.021272s