chromium / chromium / src / 8cd93e585ae7f85b41a54b9328657ac0ab48eedb / . / tools / auto_bisect / bisect_results.py

# Copyright 2014 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 math | |

import os | |

import bisect_utils | |

import math_utils | |

import source_control | |

import ttest | |

from bisect_state import RevisionState | |

class BisectResults(object): | |

"""Contains results of the completed bisect. | |

Properties: | |

error: Error message if the bisect failed. | |

If the error is None, the following properties are present: | |

warnings: List of warnings from the bisect run. | |

state: BisectState object from which these results were generated. | |

first_working_revision: First good revision. | |

last_broken_revision: Last bad revision. | |

If both of above revisions are not None, the follow properties are present: | |

culprit_revisions: A list of revisions, which contain the bad change | |

introducing the failure. | |

regression_size: For performance bisects, this is a relative change of | |

the mean metric value. For other bisects this field always contains | |

'zero-to-nonzero'. | |

regression_std_err: For performance bisects, it is a pooled standard error | |

for groups of good and bad runs. Not used for other bisects. | |

confidence: For performance bisects, it is a confidence that the good and | |

bad runs are distinct groups. Not used for non-performance bisects. | |

""" | |

def __init__(self, bisect_state=None, depot_registry=None, opts=None, | |

runtime_warnings=None, error=None, abort_reason=None): | |

"""Computes final bisect results after a bisect run is complete. | |

This constructor should be called in one of the following ways: | |

BisectResults(state, depot_registry, opts, runtime_warnings) | |

BisectResults(error=error) | |

First option creates an object representing successful bisect results, while | |

second option creates an error result. | |

Args: | |

bisect_state: BisectState object representing latest bisect state. | |

depot_registry: DepotDirectoryRegistry object with information on each | |

repository in the bisect_state. | |

opts: Options passed to the bisect run. | |

runtime_warnings: A list of warnings from the bisect run. | |

error: Error message. When error is not None, other arguments are ignored. | |

""" | |

self.error = error | |

self.abort_reason = abort_reason | |

if error is not None or abort_reason is not None: | |

return | |

assert (bisect_state is not None and depot_registry is not None and | |

opts is not None and runtime_warnings is not None), ( | |

'Incorrect use of the BisectResults constructor. ' | |

'When error is None, all other arguments are required.') | |

self.state = bisect_state | |

rev_states = bisect_state.GetRevisionStates() | |

first_working_rev, last_broken_rev = self.FindBreakingRevRange(rev_states) | |

self.first_working_revision = first_working_rev | |

self.last_broken_revision = last_broken_rev | |

self.warnings = runtime_warnings | |

self.retest_results_tot = None | |

self.retest_results_reverted = None | |

if first_working_rev is not None and last_broken_rev is not None: | |

statistics = self._ComputeRegressionStatistics( | |

rev_states, first_working_rev, last_broken_rev) | |

self.regression_size = statistics['regression_size'] | |

self.regression_std_err = statistics['regression_std_err'] | |

self.confidence = statistics['confidence'] | |

self.culprit_revisions = self._FindCulpritRevisions( | |

rev_states, depot_registry, first_working_rev, last_broken_rev) | |

self.warnings += self._GetResultBasedWarnings( | |

self.culprit_revisions, opts, self.confidence) | |

elif first_working_rev is not None: | |

# Setting these attributes so that bisect printer does not break when the | |

# regression cannot be reproduced (no broken revision was found) | |

self.regression_size = 0 | |

self.regression_std_err = 0 | |

self.confidence = 0 | |

self.culprit_revisions = [] | |

def AddRetestResults(self, results_tot, results_reverted): | |

if not results_tot or not results_reverted: | |

self.warnings.append( | |

'Failed to re-test reverted culprit CL against ToT.') | |

return | |

confidence = BisectResults.ConfidenceScore( | |

results_reverted[0]['values'], | |

results_tot[0]['values']) | |

self.retest_results_tot = RevisionState('ToT', 'n/a', 0) | |

self.retest_results_tot.value = results_tot[0] | |

self.retest_results_reverted = RevisionState('Reverted', 'n/a', 0) | |

self.retest_results_reverted.value = results_reverted[0] | |

if confidence <= bisect_utils.HIGH_CONFIDENCE: | |

self.warnings.append( | |

'Confidence of re-test with reverted CL is not high.' | |

' Check that the regression hasn\'t already recovered. ' | |

' There\'s still a chance this is a regression, as performance of' | |

' local builds may not match official builds.') | |

@staticmethod | |

def _GetResultBasedWarnings(culprit_revisions, opts, confidence): | |

warnings = [] | |

if len(culprit_revisions) > 1: | |

warnings.append('Due to build errors, regression range could ' | |

'not be narrowed down to a single commit.') | |

if opts.repeat_test_count == 1: | |

warnings.append('Tests were only set to run once. This may ' | |

'be insufficient to get meaningful results.') | |

if 0 < confidence < bisect_utils.HIGH_CONFIDENCE: | |

warnings.append('Confidence is not high. Try bisecting again ' | |

'with increased repeat_count, larger range, or ' | |

'on another metric.') | |

if not confidence: | |

warnings.append('Confidence score is 0%. Try bisecting again on ' | |

'another platform or another metric.') | |

return warnings | |

@staticmethod | |

def ConfidenceScore(sample1, sample2, accept_single_bad_or_good=False): | |

"""Calculates a confidence score. | |

This score is based on a statistical hypothesis test. The null | |

hypothesis is that the two groups of results have no difference, | |

i.e. there is no performance regression. The alternative hypothesis | |

is that there is some difference between the groups that's unlikely | |

to occur by chance. | |

The score returned by this function represents our confidence in the | |

alternative hypothesis. | |

Note that if there's only one item in either sample, this means only | |

one revision was classified good or bad, so there's not much evidence | |

to make a decision. | |

Args: | |

sample1: A flat list of "good" result numbers. | |

sample2: A flat list of "bad" result numbers. | |

accept_single_bad_or_good: If True, compute a value even if | |

there is only one bad or good revision. | |

Returns: | |

A float between 0 and 100; 0 if the samples aren't large enough. | |

""" | |

if ((len(sample1) <= 1 or len(sample2) <= 1) and | |

not accept_single_bad_or_good): | |

return 0.0 | |

if not sample1 or not sample2: | |

return 0.0 | |

_, _, p_value = ttest.WelchsTTest(sample1, sample2) | |

return 100.0 * (1.0 - p_value) | |

@staticmethod | |

def FindBreakingRevRange(revision_states): | |

"""Finds the last known good and first known bad revisions. | |

Note that since revision_states is expected to be in reverse chronological | |

order, the last known good revision is the first revision in the list that | |

has the passed property set to 1, therefore the name | |

`first_working_revision`. The inverse applies to `last_broken_revision`. | |

Args: | |

revision_states: A list of RevisionState instances. | |

Returns: | |

A tuple containing the two revision states at the border. (Last | |

known good and first known bad.) | |

""" | |

first_working_revision = None | |

last_broken_revision = None | |

for revision_state in revision_states: | |

if revision_state.passed == 1 and not first_working_revision: | |

first_working_revision = revision_state | |

if not revision_state.passed: | |

last_broken_revision = revision_state | |

return first_working_revision, last_broken_revision | |

@staticmethod | |

def _FindCulpritRevisions(revision_states, depot_registry, first_working_rev, | |

last_broken_rev): | |

cwd = os.getcwd() | |

culprit_revisions = [] | |

for i in xrange(last_broken_rev.index, first_working_rev.index): | |

depot_registry.ChangeToDepotDir(revision_states[i].depot) | |

info = source_control.QueryRevisionInfo(revision_states[i].revision) | |

culprit_revisions.append((revision_states[i].revision, info, | |

revision_states[i].depot)) | |

os.chdir(cwd) | |

return culprit_revisions | |

@classmethod | |

def _ComputeRegressionStatistics(cls, rev_states, first_working_rev, | |

last_broken_rev): | |

# TODO(sergiyb): We assume that value has "values" key, which may not be | |

# the case for failure-bisects, where there is a single value only. | |

broken_means = [state.value['values'] | |

for state in rev_states[:last_broken_rev.index+1] | |

if state.value] | |

working_means = [state.value['values'] | |

for state in rev_states[first_working_rev.index:] | |

if state.value] | |

# Flatten the lists to calculate mean of all values. | |

working_mean = sum(working_means, []) | |

broken_mean = sum(broken_means, []) | |

# Calculate the approximate size of the regression | |

mean_of_bad_runs = math_utils.Mean(broken_mean) | |

mean_of_good_runs = math_utils.Mean(working_mean) | |

regression_size = 100 * math_utils.RelativeChange(mean_of_good_runs, | |

mean_of_bad_runs) | |

if math.isnan(regression_size): | |

regression_size = 'zero-to-nonzero' | |

regression_std_err = math.fabs(math_utils.PooledStandardError( | |

[working_mean, broken_mean]) / | |

max(0.0001, min(mean_of_good_runs, mean_of_bad_runs))) * 100.0 | |

# Give a "confidence" in the bisect culprit by seeing whether the results | |

# of the culprit revision and the revision before that appear to be | |

# statistically significantly different. | |

confidence = cls.ConfidenceScore( | |

sum([first_working_rev.value['values']], []), | |

sum([last_broken_rev.value['values']], [])) | |

bad_greater_than_good = mean_of_bad_runs > mean_of_good_runs | |

return {'regression_size': regression_size, | |

'regression_std_err': regression_std_err, | |

'confidence': confidence, | |

'bad_greater_than_good': bad_greater_than_good} |