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Introduce Coefficient of variation aggregate (#1220)

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* Introduce Coefficient of variation aggregate

I believe, it is much more useful / use to understand,
because it is already normalized by the mean,
so it is not affected by the duration of the benchmark,
unlike the standard deviation.

Example of real-world output:
```
raw.pixls.us-unique/GoPro/HERO6 Black$ ~/rawspeed/build-old/src/utilities/rsbench/rsbench GOPR9172.GPR --benchmark_repetitions=27 --benchmark_display_aggregates_only=true --benchmark_counters_tabular=true
2021-09-03T18:05:56+03:00
Running /home/lebedevri/rawspeed/build-old/src/utilities/rsbench/rsbench
Run on (32 X 3596.16 MHz CPU s)
CPU Caches:
  L1 Data 32 KiB (x16)
  L1 Instruction 32 KiB (x16)
  L2 Unified 512 KiB (x16)
  L3 Unified 32768 KiB (x2)
Load Average: 7.00, 2.99, 1.85
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Benchmark                                                      Time             CPU   Iterations  CPUTime,s CPUTime/WallTime     Pixels Pixels/CPUTime Pixels/WallTime Raws/CPUTime Raws/WallTime WallTime,s
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
GOPR9172.GPR/threads:32/process_time/real_time_mean         11.1 ms          353 ms           27   0.353122          31.9473        12M       33.9879M        1085.84M      2.83232       90.4864  0.0110535
GOPR9172.GPR/threads:32/process_time/real_time_median       11.0 ms          352 ms           27   0.351696          31.9599        12M       34.1203M        1090.11M      2.84336       90.8425  0.0110081
GOPR9172.GPR/threads:32/process_time/real_time_stddev      0.159 ms         4.60 ms           27   4.59539m        0.0462064          0       426.371k        14.9631M    0.0355309       1.24692   158.944u
GOPR9172.GPR/threads:32/process_time/real_time_cv           1.44 %          1.30 %            27  0.0130136         1.44633m          0      0.0125448       0.0137802    0.0125448     0.0137802  0.0143795
```

Fixes https://github.com/google/benchmark/issues/1146

* Be consistent, it's CV, not 'rel std dev'
This commit is contained in:
Roman Lebedev 2021-09-03 20:44:10 +03:00 committed by GitHub
parent 12dc5eeafc
commit 45b194e4d4
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9 changed files with 95 additions and 20 deletions
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20
docs/user_guide.md
View File

@ -930,7 +930,7 @@ Note that `ClobberMemory()` is only available for GNU or MSVC based compilers.
<a name="reporting-statistics" />
## Statistics: Reporting the Mean, Median and Standard Deviation of Repeated Benchmarks
## Statistics: Reporting the Mean, Median and Standard Deviation / Coefficient of variation of Repeated Benchmarks
By default each benchmark is run once and that single result is reported.
However benchmarks are often noisy and a single result may not be representative
@ -940,16 +940,17 @@ benchmark.
The number of runs of each benchmark is specified globally by the
`--benchmark_repetitions` flag or on a per benchmark basis by calling
`Repetitions` on the registered benchmark object. When a benchmark is run more
than once the mean, median and standard deviation of the runs will be reported.
than once the mean, median, standard deviation and coefficient of variation
of the runs will be reported.
Additionally the `--benchmark_report_aggregates_only={true|false}`,
`--benchmark_display_aggregates_only={true|false}` flags or
`ReportAggregatesOnly(bool)`, `DisplayAggregatesOnly(bool)` functions can be
used to change how repeated tests are reported. By default the result of each
repeated run is reported. When `report aggregates only` option is `true`,
only the aggregates (i.e. mean, median and standard deviation, maybe complexity
measurements if they were requested) of the runs is reported, to both the
reporters - standard output (console), and the file.
only the aggregates (i.e. mean, median, standard deviation and coefficient
of variation, maybe complexity measurements if they were requested) of the runs
is reported, to both the reporters - standard output (console), and the file.
However when only the `display aggregates only` option is `true`,
only the aggregates are displayed in the standard output, while the file
output still contains everything.
@ -961,11 +962,10 @@ benchmark.
## Custom Statistics
While having mean, median and standard deviation is nice, this may not be
enough for everyone. For example you may want to know what the largest
observation is, e.g. because you have some real-time constraints. This is easy.
The following code will specify a custom statistic to be calculated, defined
by a lambda function.
While having these aggregates is nice, this may not be enough for everyone.
For example you may want to know what the largest observation is, e.g. because
you have some real-time constraints. This is easy. The following code will
specify a custom statistic to be calculated, defined by a lambda function.
```c++
void BM_spin_empty(benchmark::State& state) {

1
src/benchmark_register.cc
View File

@ -215,6 +215,7 @@ Benchmark::Benchmark(const char* name)
ComputeStatistics("mean", StatisticsMean);
ComputeStatistics("median", StatisticsMedian);
ComputeStatistics("stddev", StatisticsStdDev);
ComputeStatistics("cv", StatisticsCV, kPercentage);
}
Benchmark::~Benchmark() {}

9
src/statistics.cc
View File

@ -74,6 +74,15 @@ double StatisticsStdDev(const std::vector<double>& v) {
return Sqrt(v.size() / (v.size() - 1.0) * (avg_squares - Sqr(mean)));
}
double StatisticsCV(const std::vector<double>& v) {
if (v.size() < 2) return 0.0;
const auto stddev = StatisticsStdDev(v);
const auto mean = StatisticsMean(v);
return stddev / mean;
}
std::vector<BenchmarkReporter::Run> ComputeStats(
const std::vector<BenchmarkReporter::Run>& reports) {
typedef BenchmarkReporter::Run Run;

1
src/statistics.h
View File

@ -31,6 +31,7 @@ std::vector<BenchmarkReporter::Run> ComputeStats(
double StatisticsMean(const std::vector<double>& v);
double StatisticsMedian(const std::vector<double>& v);
double StatisticsStdDev(const std::vector<double>& v);
double StatisticsCV(const std::vector<double>& v);
} // end namespace benchmark

10
test/display_aggregates_only_test.cc
View File

@ -19,21 +19,23 @@ BENCHMARK(BM_SummaryRepeat)->Repetitions(3)->DisplayAggregatesOnly();
int main(int argc, char* argv[]) {
const std::string output = GetFileReporterOutput(argc, argv);
if (SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3") != 6 ||
if (SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3") != 7 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3\"") != 3 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_mean\"") != 1 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_median\"") !=
1 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_stddev\"") !=
1) {
std::cout << "Precondition mismatch. Expected to only find 6 "
1 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_cv\"") != 1) {
std::cout << "Precondition mismatch. Expected to only find 8 "
"occurrences of \"BM_SummaryRepeat/repeats:3\" substring:\n"
"\"name\": \"BM_SummaryRepeat/repeats:3\", "
"\"name\": \"BM_SummaryRepeat/repeats:3\", "
"\"name\": \"BM_SummaryRepeat/repeats:3\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_mean\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_median\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_stddev\"\nThe entire "
"\"name\": \"BM_SummaryRepeat/repeats:3_stddev\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_cv\"\nThe entire "
"output:\n";
std::cout << output;
return 1;

1
test/output_test_helper.cc
View File

@ -49,6 +49,7 @@ SubMap& GetSubstitutions() {
{" %s ", "[ ]+"},
{"%time", "[ ]*" + time_re + "[ ]+ns"},
{"%console_report", "[ ]*" + time_re + "[ ]+ns [ ]*" + time_re + "[ ]+ns [ ]*[0-9]+"},
{"%console_percentage_report", "[ ]*" + time_re + "[ ]+% [ ]*" + time_re + "[ ]+% [ ]*[0-9]+"},
{"%console_us_report", "[ ]*" + time_re + "[ ]+us [ ]*" + time_re + "[ ]+us [ ]*[0-9]+"},
{"%console_ms_report", "[ ]*" + time_re + "[ ]+ms [ ]*" + time_re + "[ ]+ms [ ]*[0-9]+"},
{"%console_s_report", "[ ]*" + time_re + "[ ]+s [ ]*" + time_re + "[ ]+s [ ]*[0-9]+"},

10
test/report_aggregates_only_test.cc
View File

@ -19,17 +19,19 @@ BENCHMARK(BM_SummaryRepeat)->Repetitions(3)->ReportAggregatesOnly();
int main(int argc, char* argv[]) {
const std::string output = GetFileReporterOutput(argc, argv);
if (SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3") != 3 ||
if (SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3") != 4 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_mean\"") != 1 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_median\"") !=
1 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_stddev\"") !=
1) {
std::cout << "Precondition mismatch. Expected to only find three "
1 ||
SubstrCnt(output, "\"name\": \"BM_SummaryRepeat/repeats:3_cv\"") != 1) {
std::cout << "Precondition mismatch. Expected to only find four "
"occurrences of \"BM_SummaryRepeat/repeats:3\" substring:\n"
"\"name\": \"BM_SummaryRepeat/repeats:3_mean\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_median\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_stddev\"\nThe entire "
"\"name\": \"BM_SummaryRepeat/repeats:3_stddev\", "
"\"name\": \"BM_SummaryRepeat/repeats:3_cv\"\nThe entire "
"output:\n";
std::cout << output;
return 1;

7
test/statistics_gtest.cc
View File

@ -25,4 +25,11 @@ TEST(StatisticsTest, StdDev) {
1.151086443322134);
}
TEST(StatisticsTest, CV) {
EXPECT_DOUBLE_EQ(benchmark::StatisticsCV({101, 101, 101, 101}), 0.0);
EXPECT_DOUBLE_EQ(benchmark::StatisticsCV({1, 2, 3}), 1. / 2.);
EXPECT_DOUBLE_EQ(benchmark::StatisticsCV({2.5, 2.4, 3.3, 4.2, 5.1}),
0.32888184094918121);
}
} // end namespace

56
test/user_counters_tabular_test.cc
View File

@ -18,12 +18,14 @@ ADD_CASES(TC_ConsoleOut,
{"^BM_Counters_Tabular/repeats:2/threads:1 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:1_mean %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:1_median %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:1_stddev %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:1_stddev %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:1_cv %console_percentage_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2 %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2_mean %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2_median %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2_stddev %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2_stddev %console_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_Counters_Tabular/repeats:2/threads:2_cv %console_percentage_report [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat [ ]*%hrfloat$", MR_Next},
{"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
{"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
{"^BM_CounterRates_Tabular/threads:%int %console_report [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s [ ]*%hrfloat/s$", MR_Next},
@ -181,6 +183,28 @@ ADD_CASES(TC_JSONOut,
{"\"Frob\": %float,$", MR_Next},
{"\"Lob\": %float$", MR_Next},
{"}", MR_Next}});
ADD_CASES(TC_JSONOut,
{{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:1_cv\",$"},
{"\"family_index\": 0,$", MR_Next},
{"\"per_family_instance_index\": 0,$", MR_Next},
{"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:1\",$",
MR_Next},
{"\"run_type\": \"aggregate\",$", MR_Next},
{"\"repetitions\": 2,$", MR_Next},
{"\"threads\": 1,$", MR_Next},
{"\"aggregate_name\": \"cv\",$", MR_Next},
{"\"aggregate_unit\": \"percentage\",$", MR_Next},
{"\"iterations\": %int,$", MR_Next},
{"\"real_time\": %float,$", MR_Next},
{"\"cpu_time\": %float,$", MR_Next},
{"\"time_unit\": \"ns\",$", MR_Next},
{"\"Bar\": %float,$", MR_Next},
{"\"Bat\": %float,$", MR_Next},
{"\"Baz\": %float,$", MR_Next},
{"\"Foo\": %float,$", MR_Next},
{"\"Frob\": %float,$", MR_Next},
{"\"Lob\": %float$", MR_Next},
{"}", MR_Next}});
ADD_CASES(TC_JSONOut,
{{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$"},
@ -268,6 +292,28 @@ ADD_CASES(TC_JSONOut,
{"\"Frob\": %float,$", MR_Next},
{"\"Lob\": %float$", MR_Next},
{"}", MR_Next}});
ADD_CASES(TC_JSONOut,
{{"\"name\": \"BM_Counters_Tabular/repeats:2/threads:2_cv\",$"},
{"\"family_index\": 0,$", MR_Next},
{"\"per_family_instance_index\": 1,$", MR_Next},
{"\"run_name\": \"BM_Counters_Tabular/repeats:2/threads:2\",$",
MR_Next},
{"\"run_type\": \"aggregate\",$", MR_Next},
{"\"repetitions\": 2,$", MR_Next},
{"\"threads\": 2,$", MR_Next},
{"\"aggregate_name\": \"cv\",$", MR_Next},
{"\"aggregate_unit\": \"percentage\",$", MR_Next},
{"\"iterations\": %int,$", MR_Next},
{"\"real_time\": %float,$", MR_Next},
{"\"cpu_time\": %float,$", MR_Next},
{"\"time_unit\": \"ns\",$", MR_Next},
{"\"Bar\": %float,$", MR_Next},
{"\"Bat\": %float,$", MR_Next},
{"\"Baz\": %float,$", MR_Next},
{"\"Foo\": %float,$", MR_Next},
{"\"Frob\": %float,$", MR_Next},
{"\"Lob\": %float$", MR_Next},
{"}", MR_Next}});
ADD_CASES(TC_CSVOut,
{{"^\"BM_Counters_Tabular/repeats:2/threads:1\",%csv_report,"
"%float,%float,%float,%float,%float,%float$"}});
@ -283,6 +329,9 @@ ADD_CASES(TC_CSVOut,
ADD_CASES(TC_CSVOut,
{{"^\"BM_Counters_Tabular/repeats:2/threads:1_stddev\",%csv_report,"
"%float,%float,%float,%float,%float,%float$"}});
ADD_CASES(TC_CSVOut,
{{"^\"BM_Counters_Tabular/repeats:2/threads:1_cv\",%csv_report,"
"%float,%float,%float,%float,%float,%float$"}});
ADD_CASES(TC_CSVOut,
{{"^\"BM_Counters_Tabular/repeats:2/threads:2\",%csv_report,"
"%float,%float,%float,%float,%float,%float$"}});
@ -298,6 +347,9 @@ ADD_CASES(TC_CSVOut,
ADD_CASES(TC_CSVOut,
{{"^\"BM_Counters_Tabular/repeats:2/threads:2_stddev\",%csv_report,"
"%float,%float,%float,%float,%float,%float$"}});
ADD_CASES(TC_CSVOut,
{{"^\"BM_Counters_Tabular/repeats:2/threads:2_cv\",%csv_report,"
"%float,%float,%float,%float,%float,%float$"}});
// VS2013 does not allow this function to be passed as a lambda argument
// to CHECK_BENCHMARK_RESULTS()
void CheckTabular(Results const& e) {