stats.rb

# Run the given block +num+ times and then print out the mean, median, min,
# max, and stddev of the run. For example:
#
# irb> stats(10) { sleep(rand / 100) }
# mean:   5.99ms
# median: 6.76ms
# min:    1.49ms
# max:    9.28ms
# stddev: 2.54ms
def stats(num)
  records = []
  num.times do
    t0 = Time.now
    yield
    records << (Time.now - t0)
  end
  srecords = records.sort

  mean = records.inject(0) { |acc, x| acc + x } / num.to_f
  stddev = Math.sqrt(records.inject(0) { |sum, e| sum + (e - mean) ** 2 } / num.to_f )

  puts "mean:   %1.2fms" % (mean * 1000)
  puts "median: %1.2fms" % (srecords[num / 2] * 1000)
  puts "min:    %1.2fms" % (srecords.first * 1000)
  puts "max:    %1.2fms" % (srecords.last * 1000)
  puts "stddev: %1.2fms" % (stddev * 1000)
end