More statistics

lib/benchee.ex

@@ -1,6 +1,8 @@
 defmodule Benchee do
  @default_config %{time: 5}
 
+ alias Benchee.{Statistics, Time}
+
  @doc """
  Returns the initial benchmark suite data structure for Benshee.
  Given an optional map of configuration options, converts seconds in there
@@ -20,7 +22,7 @@ defmodule Benchee do
  @seconds_to_microseconds 1_000_000
  defp convert_time_to_micro_s(config) do
  {_, config} = Map.get_and_update! config, :time, fn(seconds) ->
- {seconds, seconds * @seconds_to_microseconds}
+ {seconds, Time.seconds_to_microseconds(seconds)}
  end
  config
  end
@@ -58,14 +60,12 @@ defmodule Benchee do
  Creates a report of the benchmark suite run.
  """
  def report(%{jobs: jobs}) do
+
  Enum.map jobs, fn(%{name: name, run_times: times}) ->
- "#{name} #{Enum.count(times)} #{average(times)}"
+ %{average: average, ips: ips, std_dev: std_dev} = Statistics.statistics(times)
+ "#{name} #{ips} #{average}μs #{std_dev}"
  end
  end
 
- defp average(series) do
- total = Enum.sum(series)
- iterations = Enum.count(series)
- total / iterations
- end
+
 end

lib/benchee/statistics.ex

@@ -0,0 +1,35 @@
+defmodule Benchee.Statistics do
+ alias Benchee.Time
+
+ @doc """
+ Calculates statistical data based on a series of run times in microseconds.
+
+ iex> Benchee.Statistics.statistics([200, 400, 400, 400, 500, 500, 700, 900])
+ %{average: 500.0, std_dev: 200.0, ips: 2000.0}
+ """
+ def statistics(run_times) do
+ total_time = Enum.sum(run_times)
+ iterations = Enum.count(run_times)
+ average_time = total_time / iterations
+ iterations_per_second = iterations_per_second(iterations, total_time)
+ standard_deviation = standard_deviation(run_times, average_time, iterations)
+
+ %{
+ average: average_time,
+ ips:  iterations_per_second,
+ std_dev: standard_deviation
+ }
+ end
+
+ defp iterations_per_second(iterations, time_microseconds) do
+ iterations / (Time.microseconds_to_seconds(time_microseconds))
+ end
+
+ defp standard_deviation(samples, average, iterations) do
+ total_variance = Enum.reduce samples, 0, fn(sample, total) ->
+ total + :math.pow((sample - average), 2)
+ end
+ variance = total_variance / iterations
+ :math.sqrt variance
+ end
+end

lib/benchee/time.ex

@@ -0,0 +1,11 @@
+defmodule Benchee.Time do
+ @seconds_to_microseconds 1_000_000
+
+ def microseconds_to_seconds(microseconds) do
+ microseconds / @seconds_to_microseconds
+ end
+
+ def seconds_to_microseconds(seconds) do
+ seconds * @seconds_to_microseconds
+ end
+end

test/benchee/statistics_test.exs

@@ -0,0 +1,5 @@
+defmodule Benchee.StatistcsTest do
+ use ExUnit.Case
+ doctest Benchee.Statistics
+
+end