perf_tests_results_helper.py 文件源码

def GeomMeanAndStdDevFromHistogram(histogram_json):
  histogram = json.loads(histogram_json)
  # Handle empty histograms gracefully.
  if not 'buckets' in histogram:
    return 0.0, 0.0
  count = 0
  sum_of_logs = 0
  for bucket in histogram['buckets']:
    if 'high' in bucket:
      bucket['mean'] = (bucket['low'] + bucket['high']) / 2.0
    else:
      bucket['mean'] = bucket['low']
    if bucket['mean'] > 0:
      sum_of_logs += math.log(bucket['mean']) * bucket['count']
      count += bucket['count']

  if count == 0:
    return 0.0, 0.0

  sum_of_squares = 0
  geom_mean = math.exp(sum_of_logs / count)
  for bucket in histogram['buckets']:
    if bucket['mean'] > 0:
      sum_of_squares += (bucket['mean'] - geom_mean) ** 2 * bucket['count']
  return geom_mean, math.sqrt(sum_of_squares / count)