gistfile1.rb

# Adaptive benchmarking code I copied from the blog of Mauricio Fernandez

module Adaptive
   class Benchmark

      # The version of the adaptive-benchmark library
      VERSION = '0.1.0'

      # Default options
      REPORT_OPT = {:precision => 0.1, :confidence => 0.95}

      def initialize(field_length, minimum_iterations)
         @field_length = field_length
         @minimum_iterations = minimum_iterations
      end
     
      def self.bm(field_length = 10, minimum_iterations = 10)
         puts "#{" " * field_length}\t\t\tstddev\t\truns\tinterval\tconfidence"
         yield new(field_length, minimum_iterations)
      end
     
      def report(name, options = {})
         old_sync, $stdout.sync = $stdout.sync, true
         opt = REPORT_OPT.clone.update(options)
         sample_avg = sample_variance = 0

         tms_to_total = lambda{ |tms| tms.utime + tms.stime }
    
         take_sample = lambda do |i|
            GC.start

            t0 = tms_to_total[Process.times]

            yield

            exec_time = tms_to_total[Process.times] - t0
            new_sample_avg = sample_avg + (exec_time - sample_avg) / i

            if i == 1
              sample_avg = new_sample_avg
              next
            end

            sample_variance = (1 - 1.0/i) * sample_variance + (i+1) * (new_sample_avg - sample_avg) ** 2
            sample_avg = new_sample_avg
         end
    
         (1..@minimum_iterations).each{ |i| take_sample[i] }

         population_variance = 1.0 * @minimum_iterations / (@min_runs - 1) * sample_variance
         a = opt[:precision] * sample_avg
         num_runs = (sample_variance / (a ** 2 * (1 - opt[:confidence]))).ceil
         total_runs = @minimum_iterations + num_runs
         (@minimum_iterations + 1..total_runs + 1).each{ |i| take_sample[i] }

         population_variance = 1.0 * total_runs / (total_runs - 1) * sample_variance
         puts "%-#{@field_length}s %8.6f\t%8.6f\t%-6d\t%8.6f\t%3d%%" % 
            [name, sample_avg, Math.sqrt(population_variance), total_runs, a, opt[:confidence] * 100]
      ensure
         $stdout.sync = old_sync
      end
  end
end