A simple helper for timing sequences of code.

lap_timer.rb

# Easy to use:
#
#   timer = LapTimer.new
#   # some task that might take awhile
#   timer.mark :step2
#   # another task that needs timing
#   timer.mark :step3
#   # and another task to time
#   timer.report
#
# Emits the elapsed (wallclock) time between each of the marked sections,
# including the total elapsed time for the entire block.

class LapTimer
  def initialize(name=:start)
    @times = []
    mark(name)
  end

  def mark(name)
    @times << [name, Time.now]
  end

  def report
    mark :end
    total_elapsed = @times.last[1] - @times.first[1]

    (@times.length-1).times do |n|
      from_name, from_time = @times[n]
      to_name, to_time = @times[n+1]
      elapsed = to_time - from_time

      puts "%5.2fs (%5.1f%%) :: %s" % [elapsed, (elapsed / total_elapsed) * 100, from_name]
    end

    puts "%5.2fs elapsed time" % total_elapsed
  end
end