Class: Perfer::IterationJob

Inherits:
Job
  • Object
show all
Defined in:
lib/perfer/job/iteration_job.rb

Constant Summary collapse

CHANGE_ITERATIONS_MARGIN =

This factor ensure some margin, to avoid endlessly changing the number of iterations

0.1
MAX_GROW_FACTOR = 
10
UNIQUE_NAME = 
"a"

Instance Attribute Summary

Attributes inherited from Job

#metadata, #session, #title

Instance Method Summary collapse

Methods inherited from Job

#load_metadata, #minimal_time, #number_of_measurements, #results, #verbose

Constructor Details

#initialize(session, title, code = nil, data = nil, &block) ⇒ IterationJob

Returns a new instance of IterationJob.



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# File 'lib/perfer/job/iteration_job.rb', line 13

def initialize(session, title, code = nil, data = nil, &block)
  super(session, title, &block)
  load_metadata
  compile_method(code, data) if code and !block
end

Instance Method Details

#compile_method(code, data) ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 19

def compile_method(code, data)
  @data = data || {}
  if obj = @data.delete(:self)
    klass = obj.singleton_class
    meth = generate_method_name
  else
    klass = singleton_class
    meth = :measure_call_times_code
  end

  if klass.method_defined?(meth)
    raise Error, "method #{meth} already defined on #{klass} (#{obj})!"
  end

  begin
    klass.class_eval <<-EOR
    def #{meth}(__n#{@data.keys.map { |k| ", #{k}" }.join})
      ::Perfer.measure do
        __i = 0
        while __i < __n
          #{"#{code}; " * repeat_eval}
          __i += 1
        end
      end
    end
    EOR
  rescue SyntaxError => e
    raise Error, "There was an error while eval'ing the code: #{code.inspect}\n#{e}"
  end

  if obj
    singleton_class.send(:define_method, :measure_call_times_code) do |*args|
      obj.send(meth, *args)
    end
  end
end

#compute_new_iterations(iterations, time) ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 84

def compute_new_iterations(iterations, time)
  (minimal_time * iterations / time).ceil
end

#find_number_of_iterations_required(last_iterations = 1, last_time = 0) ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 88

def find_number_of_iterations_required(last_iterations = 1, last_time = 0)
  iterations = last_iterations
  if last_time > 0
    iterations = compute_new_iterations(last_iterations, last_time)
  end
  iterations = round_for_eval(iterations)
  puts "Start search for iterations: start=#{iterations}" if verbose
  loop do
    puts "iterations: #{iterations}" if verbose
    time = measure_call_times(iterations)[:real]
    break if time > minimal_time

    if time <= 0
      iterations *= 2
      next
    end

    new_iterations = compute_new_iterations(iterations, time)
    # ensure the number of iterations increases
    if new_iterations <= iterations
      puts "new_iterations <= iterations: #{new_iterations} <= #{iterations}" if verbose
      new_iterations = (iterations*1.5).ceil
    end
    if new_iterations > MAX_GROW_FACTOR * iterations
      new_iterations = MAX_GROW_FACTOR * iterations
    end
    iterations = round_for_eval(new_iterations)
  end
  puts "End search for iterations: iterations=#{iterations}" if verbose
  iterations
end

#generate_method_name ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 56

def generate_method_name
  :"perfer_eval_#{UNIQUE_NAME.succ!}"
end

#mad(measurements) ⇒ Object

median absolute deviation / median



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# File 'lib/perfer/job/iteration_job.rb', line 121

def mad(measurements)
  stats = Statistics.new(measurements.map { |m| m[:real] })
  mad = stats.median_absolute_deviation
  mad /= stats.median
  puts "mad: #{mad}" if verbose
  mad
end

#measure_call_times(n) ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 60

def measure_call_times(n)
  GC.start
  if !@block
    if n % repeat_eval != 0
      raise Error, "Implementation error: #{n} not multiple of #{repeat_eval}"
    end
    n /= repeat_eval
    measure_call_times_code(n, *@data.values)
  elsif @block.arity == 1
    # give n, the block must iterate n times
    Perfer.measure { @block.call(n) }
  else
    Perfer.measure { n.times(&@block) }
  end.tap { |m| p m if verbose }
end

#repeat_eval ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 9

def repeat_eval
  100
end

#round_for_eval(iterations) ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 76

def round_for_eval(iterations)
  if @block
    iterations
  else
    ((iterations + repeat_eval - 1) / repeat_eval) * repeat_eval
  end
end

#run ⇒ Object 



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# File 'lib/perfer/job/iteration_job.rb', line 129

def run
  super
  measurements = []

  # Run one iteration, so system-level buffers and other OS warm-up can take place
  # This is usually a very inaccurate measurement, so just discard it
  measure_call_times(round_for_eval(1))

  iterations = find_number_of_iterations_required

  measurements_taken = 0
  until measurements.size == number_of_measurements and
        mad(measurements) < 0.01 * measurements_taken / number_of_measurements
    time = measure_call_times(iterations)
    measurements_taken += 1
    if time[:real] < (1.0 - CHANGE_ITERATIONS_MARGIN) * minimal_time
      # restart and find a more appropriate number of iterations
      puts "Restarting, #{time[:real]} < #{minimal_time}" if verbose
      measurements.clear
      measurements_taken = 0
      iterations = find_number_of_iterations_required(iterations, time[:real])
    else
      # circular buffer needed!
      measurements.shift if measurements.size == number_of_measurements
      measurements << time
    end
  end

  result = Result.new(@metadata)
  result[:iterations] = iterations
  result.data = measurements
  @session.add_result(result)
end