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[Tools] Drop compare_bench.py, compare.py is to be used, add U-test docs. (#645) 

As discussed in IRC, time to deduplicate.
This commit is contained in:
Roman Lebedev 2018-08-13 17:42:35 +03:00 committed by Dominic Hamon
parent f85304e4e3
commit 94c4d6d5c6
3 changed files with 26 additions and 143 deletions
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4
README.md
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@ -910,6 +910,10 @@ by `--benchmark_out=<filename>`. The format of the output can be specified
using `--benchmark_out_format={json|console|csv}`. Specifying
`--benchmark_out` does not suppress the console output.
## Result comparison
It is possible to compare the benchmarking results. See [Additional Tooling Documentation](docs/tools.md)
## Debug vs Release
By default, benchmark builds as a debug library. You will see a warning in the
output when this is the case. To build it as a release library instead, use:

98
docs/tools.md
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@ -1,86 +1,16 @@
# Benchmark Tools
## compare_bench.py
The `compare_bench.py` utility which can be used to compare the result of benchmarks.
The program is invoked like:
``` bash
$ compare_bench.py <old-benchmark> <new-benchmark> [benchmark options]...
```
Note, it relies on the scipy package which can be installed using [these instructions](https://www.scipy.org/install.html).
Where `<old-benchmark>` and `<new-benchmark>` either specify a benchmark executable file, or a JSON output file. The type of the input file is automatically detected. If a benchmark executable is specified then the benchmark is run to obtain the results. Otherwise the results are simply loaded from the output file.
`[benchmark options]` will be passed to the benchmarks invocations. They can be anything that binary accepts, be it either normal `--benchmark_*` parameters, or some custom parameters your binary takes.
The sample output using the JSON test files under `Inputs/` gives:
``` bash
$ ./compare_bench.py ./gbench/Inputs/test1_run1.json ./gbench/Inputs/test1_run2.json
Comparing ./gbench/Inputs/test1_run1.json to ./gbench/Inputs/test1_run2.json
Benchmark Time CPU Time Old Time New CPU Old CPU New
-------------------------------------------------------------------------------------------------------------
BM_SameTimes +0.0000 +0.0000 10 10 10 10
BM_2xFaster -0.5000 -0.5000 50 25 50 25
BM_2xSlower +1.0000 +1.0000 50 100 50 100
BM_1PercentFaster -0.0100 -0.0100 100 99 100 99
BM_1PercentSlower +0.0100 +0.0100 100 101 100 101
BM_10PercentFaster -0.1000 -0.1000 100 90 100 90
BM_10PercentSlower +0.1000 +0.1000 100 110 100 110
BM_100xSlower +99.0000 +99.0000 100 10000 100 10000
BM_100xFaster -0.9900 -0.9900 10000 100 10000 100
BM_10PercentCPUToTime +0.1000 -0.1000 100 110 100 90
BM_ThirdFaster -0.3333 -0.3334 100 67 100 67
BM_BadTimeUnit -0.9000 +0.2000 0 0 0 1
```
As you can note, the values in `Time` and `CPU` columns are calculated as `(new - old) / |old|`.
When a benchmark executable is run, the raw output from the benchmark is printed in real time to stdout. The sample output using `benchmark/basic_test` for both arguments looks like:
```
./compare_bench.py test/basic_test test/basic_test --benchmark_filter=BM_empty.*
RUNNING: test/basic_test --benchmark_filter=BM_empty.* --benchmark_out=/tmp/tmpN7LF3a
Run on (8 X 4000 MHz CPU s)
2017-11-07 23:28:36
---------------------------------------------------------------------
Benchmark Time CPU Iterations
---------------------------------------------------------------------
BM_empty 4 ns 4 ns 170178757
BM_empty/threads:8 1 ns 7 ns 103868920
BM_empty_stop_start 0 ns 0 ns 1000000000
BM_empty_stop_start/threads:8 0 ns 0 ns 1403031720
RUNNING: /test/basic_test --benchmark_filter=BM_empty.* --benchmark_out=/tmp/tmplvrIp8
Run on (8 X 4000 MHz CPU s)
2017-11-07 23:28:38
---------------------------------------------------------------------
Benchmark Time CPU Iterations
---------------------------------------------------------------------
BM_empty 4 ns 4 ns 169534855
BM_empty/threads:8 1 ns 7 ns 104188776
BM_empty_stop_start 0 ns 0 ns 1000000000
BM_empty_stop_start/threads:8 0 ns 0 ns 1404159424
Comparing ../build/test/basic_test to ../build/test/basic_test
Benchmark Time CPU Time Old Time New CPU Old CPU New
---------------------------------------------------------------------------------------------------------------------
BM_empty -0.0048 -0.0049 4 4 4 4
BM_empty/threads:8 -0.0123 -0.0054 1 1 7 7
BM_empty_stop_start -0.0000 -0.0000 0 0 0 0
BM_empty_stop_start/threads:8 -0.0029 +0.0001 0 0 0 0
```
As you can note, the values in `Time` and `CPU` columns are calculated as `(new - old) / |old|`.
Obviously this example doesn't give any useful output, but it's intended to show the output format when 'compare_bench.py' needs to run benchmarks.
## compare.py
The `compare.py` can be used to compare the result of benchmarks.
**NOTE**: the utility relies on the scipy package which can be installed using [these instructions](https://www.scipy.org/install.html).
### Modes of operation
There are three modes of operation:
1. Just compare two benchmarks, what `compare_bench.py` did.
1. Just compare two benchmarks
The program is invoked like:
``` bash
@ -242,3 +172,19 @@ Benchmark Time CPU Time Old
```
This is a mix of the previous two modes, two (potentially different) benchmark binaries are run, and a different filter is applied to each one.
As you can note, the values in `Time` and `CPU` columns are calculated as `(new - old) / |old|`.
### U test
If there is a sufficient repetition count of the benchmarks, the tool can do
a [U Test](https://en.wikipedia.org/wiki/Mann%E2%80%93Whitney_U_test), of the
null hypothesis that it is equally likely that a randomly selected value from
one sample will be less than or greater than a randomly selected value from a
second sample.
If the calculated p-value is below this value is lower than the significance
level alpha, then the result is said to be statistically significant and the
null hypothesis is rejected. Which in other words means that the two benchmarks
aren't identical.
**WARNING**: requires **LARGE** (no less than 9) number of repetitions to be
meaningful!

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tools/compare_bench.py
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@ -1,67 +0,0 @@
#!/usr/bin/env python
"""
compare_bench.py - Compare two benchmarks or their results and report the
difference.
"""
import argparse
from argparse import ArgumentParser
import sys
import gbench
from gbench import util, report
from gbench.util import *
def check_inputs(in1, in2, flags):
"""
Perform checking on the user provided inputs and diagnose any abnormalities
"""
in1_kind, in1_err = classify_input_file(in1)
in2_kind, in2_err = classify_input_file(in2)
output_file = find_benchmark_flag('--benchmark_out=', flags)
output_type = find_benchmark_flag('--benchmark_out_format=', flags)
if in1_kind == IT_Executable and in2_kind == IT_Executable and output_file:
print(("WARNING: '--benchmark_out=%s' will be passed to both "
"benchmarks causing it to be overwritten") % output_file)
if in1_kind == IT_JSON and in2_kind == IT_JSON and len(flags) > 0:
print("WARNING: passing --benchmark flags has no effect since both "
"inputs are JSON")
if output_type is not None and output_type != 'json':
print(("ERROR: passing '--benchmark_out_format=%s' to 'compare_bench.py`"
" is not supported.") % output_type)
sys.exit(1)
def main():
parser = ArgumentParser(
description='compare the results of two benchmarks')
parser.add_argument(
'test1', metavar='test1', type=str, nargs=1,
help='A benchmark executable or JSON output file')
parser.add_argument(
'test2', metavar='test2', type=str, nargs=1,
help='A benchmark executable or JSON output file')
parser.add_argument(
'benchmark_options', metavar='benchmark_options', nargs=argparse.REMAINDER,
help='Arguments to pass when running benchmark executables'
)
args, unknown_args = parser.parse_known_args()
# Parse the command line flags
test1 = args.test1[0]
test2 = args.test2[0]
if unknown_args:
# should never happen
print("Unrecognized positional argument arguments: '%s'"
% unknown_args)
exit(1)
benchmark_options = args.benchmark_options
check_inputs(test1, test2, benchmark_options)
# Run the benchmarks and report the results
json1 = gbench.util.run_or_load_benchmark(test1, benchmark_options)
json2 = gbench.util.run_or_load_benchmark(test2, benchmark_options)
output_lines = gbench.report.generate_difference_report(json1, json2)
print('Comparing %s to %s' % (test1, test2))
for ln in output_lines:
print(ln)
if __name__ == '__main__':
main()