Guesstimator

guesstimator.rb

require 'benchmark'

class Guesstimator

  @@instances={}

  attr_accessor :total_operations
  attr_accessor :remaining_operations
  attr_reader :exp_moving_average

  SMOOTHING_FACTOR = 0.005

  def estimated_time_arrival
    Time.now + estimated_time_remaining
  end

  def estimated_time_remaining
    remaining_operations * @exp_moving_average
  end

  def ops_per_sec
    1.0 / @exp_moving_average
  end

  def run_operation
    runtime_ms = Benchmark.realtime do
      yield()
    end

    @remaining_operations -= 1
    @exp_moving_average  ||= runtime_ms
    @exp_moving_average = SMOOTHING_FACTOR * runtime_ms + (1-SMOOTHING_FACTOR) * @exp_moving_average;

    runtime_ms
  end

  def self.format_estimated_time(secs)
    hours = (secs/3600).to_i
    minutes = (secs/60.0 - hours * 60.0).to_i
    seconds = (secs- (minutes * 60 + hours * 3600.0))
    sprintf("%02d:%02d:%02d", hours, minutes, seconds)
  end

  def self.estimate_by_total_operations(total_operation_count, operation_id, &block)
    guesstimator = get_or_create_instance(operation_id, total_operation_count)
    runtime_ms = guesstimator.run_operation(&block)
    print_progress(guesstimator, operation_id, runtime_ms)
  end

  def self.print_progress(guesstimator, operation_id, runtime_ms)
    puts "#{operation_id}: last=#{runtime_ms}s, avg=#{guesstimator.exp_moving_average}s, avg_ops/s=#{guesstimator.ops_per_sec} ops_remaining=#{guesstimator.remaining_operations}, time_remaining=#{self.format_estimated_time(guesstimator.estimated_time_remaining)}, eta=#{guesstimator.estimated_time_arrival}"
  end

  def self.get_or_create_instance(operation_id, total_operation_count)
    if obj = @@instances[operation_id]
      return obj
    end

    instance = self.new
    instance.total_operations = total_operation_count
    instance.remaining_operations = total_operation_count
    @@instances[operation_id] = instance
  end
end