Also compute relative standard deviation in perf_stats.py

performance/perf_stats.py

@@ -20,13 +20,17 @@ def main():
                 perf_per_test[test_name].append(measurement)
 
             for test_name, measurement_list in perf_per_test.items():
+                avg = utils.mean(measurement_list)
                 utils.write_perf_entry_to_stream(
-                    test_name, opt_level, quantity,
-                    utils.mean(measurement_list), sys.stdout)
+                    test_name, opt_level, quantity, avg, sys.stdout)
                 if len(measurement_list) > 1:
+                    standard_dev = utils.standard_deviation(measurement_list)
                     utils.write_perf_entry_to_stream(
                         test_name, opt_level, quantity + '-standard-deviation',
-                        utils.standard_deviation(measurement_list), sys.stdout)
+                        standard_dev, sys.stdout)
+                    utils.write_perf_entry_to_stream(
+                        test_name, opt_level, quantity + '-relative-standard-deviation',
+                        standard_dev / avg if avg != 0.0 else 0.0, sys.stdout)
 
                 utils.write_perf_entry_to_stream(
                     test_name, opt_level, quantity + '-sample-size',