performace.rb

def random_bytes
  100_000 + rand(128849018880)
end

require 'benchmark/ips'

file_sizes = 350_000.times.map { random_bytes }
MEGA_BYTE = 1048576.0

Benchmark.ips do |x|
  x.time = 5
  x.warmup = 2

  x.report("devide first") {
    file_sizes.map{|a| a / MEGA_BYTE }.inject(&:+)
  }

  x.report("devide last") {
    file_sizes.inject(&:+) / MEGA_BYTE
  }

  x.compare!
end


HASH = Hash[500.times.map { [random_bytes, random_bytes] } ]

Benchmark.ips do |x|
  x.time = 5
  x.warmup = 2

  x.report("inject assign") {
    HASH.inject({}) do |memo, (k, v)|
      memo[k] = v
      memo
    end
  }

  x.report("inject merge") {
    HASH.inject({}) do |memo, (k, v)|
      memo.merge({k => v})
    end
  }

  x.report("inject merge!") {
    HASH.inject({}) do |memo, (k, v)|
      memo.merge!({k => v})
    end
  }

  x.report("with_object assign") {
    HASH.each_with_object({}) do |(k, v), memo|
      memo[k] = v
    end
  }

  x.report("with_object merge") {
    HASH.each_with_object({}) do |(k, v), memo|
      memo.merge(k => v)
    end
  }

  x.report("with_object merge!") {
    HASH.each_with_object({}) do |(k, v), memo|
      memo.merge!(k => v)
    end
  }

  x.compare!
end