gistfile1.txt

#!/usr/bin/env ruby

require 'benchmark/ips'
require 'securerandom'

class MyClass
  FOO = -> { SecureRandom.hex }

  def bar
    -> { SecureRandom.hex }
  end

  def baz
    @baz ||= -> { SecureRandom.hex }
  end

  def benchmark
    Benchmark.ips do |benchmark|
      benchmark.config(time: 10, warmup: 10)
      benchmark.report('foo') { FOO.call }
      benchmark.report('bar') { bar.call }
      benchmark.report('baz') { baz.call }
      benchmark.compare!
    end
  end
end

MyClass.new.benchmark

# Warming up --------------------------------------
#                  foo    74.303k i/100ms
#                  bar    51.173k i/100ms
#                  baz    67.876k i/100ms
# Calculating -------------------------------------
#                  foo    928.900k (± 2.2%) i/s -      9.288M in  10.003990s
#                  bar    606.895k (± 1.6%) i/s -      6.090M in  10.036827s
#                  baz    879.370k (± 3.4%) i/s -      8.824M in  10.049572s

# Comparison:
#                  foo:   928899.6 i/s
#                  baz:   879370.1 i/s - same-ish: difference falls within error
#                  bar:   606895.3 i/s - 1.53x  slower
#