Adjusts the bench expectations calculation to consider average value.

bench/gen_bench_expectations.py

 #!/usr/bin/env python
 # Copyright (c) 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.
 
 """ Generate bench_expectations file from a given set of bench data files. """
 
 import argparse
 import bench_util
 import os
 import re
 import sys
 
 # Parameters for calculating bench ranges.
 RANGE_RATIO = 1.0  # Ratio of range for upper and lower bounds.
-ABS_ERR = 1.0  # Additional allowed error in milliseconds.
+ERR_RATIO = 0.05  # Further widens the range by the ratio of average value.
 
 # List of bench configs to monitor. Ignore all other configs.
 CONFIGS_TO_INCLUDE = ['simple_viewport_1000x1000',
                       'simple_viewport_1000x1000_gpu',
                       'simple_viewport_1000x1000_scalar_1.100000',
                       'simple_viewport_1000x1000_scalar_1.100000_gpu',
                      ]
 
 
 def compute_ranges(benches):
   """Given a list of bench numbers, calculate the alert range.
 
   Args:
     benches: a list of float bench values.
 
   Returns:
     a list of float [lower_bound, upper_bound].
   """
   minimum = min(benches)
   maximum = max(benches)
   diff = maximum - minimum
+  avg = sum(benches) / len(benches)
 
-  return [minimum - diff * RANGE_RATIO - ABS_ERR,
-          maximum + diff * RANGE_RATIO + ABS_ERR]
+  return [minimum - diff * RANGE_RATIO - avg * ERR_RATIO,
+          maximum + diff * RANGE_RATIO + avg * ERR_RATIO]
 
 
 def create_expectations_dict(revision_data_points):
   """Convert list of bench data points into a dictionary of expectations data.
 
   Args:
     revision_data_points: a list of BenchDataPoint objects.
 
   Returns:
     a dictionary of this form:
@@ skipping 55 matching lines @@
               'expected': expected,
               'lower_bound': lower_bound,
               'upper_bound': upper_bound})
 
     with open(args.output_file, 'w') as file_handle:
       file_handle.write('\n'.join(out_lines))
 
 
 if __name__ == "__main__":
     main()