Return time taken in milliseconds to process a block of code, along with its result.

benchmark.rb

module Benchmark

  # Similar to Benchmark.realtime, but returns the result of the block along with time taken in milliseconds.
  #   Ex: Benchmark.perform{ sleep(3); "hello" } => [3003.2030000002123, "hello"]
  # 
  # Benchmark.realtime    | https://ruby-doc.org/stdlib-2.5.0/libdoc/benchmark/rdoc/Benchmark.html#method-c-realtime
  # Process.clock_gettime | http://ruby-doc.org/core-2.5.0/Process.html#method-c-clock_gettime
  
  def self.perform
    t0 = Process.clock_gettime(Process::CLOCK_MONOTONIC)
    result = yield
    [(Process.clock_gettime(Process::CLOCK_MONOTONIC) - t0) * 1000, result]
  end

end