tools/telemetry/telemetry/value/histogram.py

# Copyright 2013 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
import json

from telemetry import value as value_module
from telemetry import perf_tests_helper

class HistogramValueBucket(object):
  def __init__(self, low, high, count=0):
    self.low = low
    self.high = high
    self.count = count

  def AsDict(self):
    return {
      'low': self.low,
      'high': self.high,
      'count': self.count
    }

  def ToJSONString(self):
    return '{%s}' % ', '.join([
      '"low": %i' % self.low,
      '"high": %i' % self.high,
      '"count": %i' % self.count])

class HistogramValue(value_module.Value):
  def __init__(self, page, name, units,
               raw_value=None, raw_value_json=None, important=True):
    super(HistogramValue, self).__init__(page, name, units, important)
    if raw_value_json:
      assert raw_value == None, 'Dont specify both raw_value and raw_value_json'
      raw_value = json.loads(raw_value_json)
    if raw_value:
      assert 'buckets' in raw_value
      assert isinstance(raw_value['buckets'], list)
      self.buckets = []
      for bucket in raw_value['buckets']:
        self.buckets.append(HistogramValueBucket(
          low=bucket['low'],
          high=bucket['high'],
          count=bucket['count']))
    else:
      self.buckets = []

  def __repr__(self):
    if self.page:
      page_name = self.page.url
    else:
      page_name = None
    return 'HistogramValue(%s, %s, %s, raw_json_string="%s", important=%s)' % (
      page_name,
      self.name, self.units,
      self.ToJSONString(),
      self.important)

  def GetBuildbotDataType(self, output_context):
    if self._IsImportantGivenOutputIntent(output_context):
      return 'histogram'
    return 'unimportant-histogram'

  def GetBuildbotValue(self):
    # More buildbot insanity: perf_tests_results_helper requires the histogram
    # to be an array of size one.
    return [self.ToJSONString()]

  def ToJSONString(self):
    # This has to hand-JSONify the histogram to ensure the order of keys
    # produced is stable across different systems.
    #
    # This is done because the buildbot unittests are string equality
    # assertions. Thus, tests that contain histograms require stable
    # stringification of the histogram.
    #
    # Sigh, buildbot, Y U gotta be that way.
    return '{"buckets": [%s]}' % (
      ', '.join([b.ToJSONString() for b in self.buckets]))

  def GetRepresentativeNumber(self):
    (mean, _) = perf_tests_helper.GeomMeanAndStdDevFromHistogram(
        self.ToJSONString())
    return mean

  def GetRepresentativeString(self):
    return self.GetBuildbotValue()

  def GetJSONTypeName(self):
    return 'histogram'

  def AsDict(self):
    d = super(HistogramValue, self).AsDict()
    d['buckets'] = [b.AsDict() for b in self.buckets]
    return d

  @classmethod
  def MergeLikeValuesFromSamePage(cls, values):
    assert len(values) > 0
    v0 = values[0]
    return HistogramValue(
        v0.page, v0.name, v0.units,
        raw_value_json=v0.ToJSONString(),
        important=v0.important)

  @classmethod
  def MergeLikeValuesFromDifferentPages(cls, values,
                                        group_by_name_suffix=False):
    # Histograms cannot be merged across pages, at least for now. It should be
    # theoretically possible, just requires more work. Instead, return None.
    # This signals to the merging code that the data is unmergable and it will
    # cope accordingly.
    return None