x/perf/benchstat: no group headers shown if only one group #33169
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Change https://golang.org/cl/309969 mentions this issue: |
zchee
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Nov 28, 2021
This is a complete rewrite of benchstat. Basic usage remains the same, as does the core idea of showing statistical benchmark summaries and A/B comparisons in a table, but there are several major improvements. The statistics is now more robust. Previously, benchstat used IQR-based outlier rejection, showed the mean of the reduced sample, its range, and did a non-parametric difference-of-distribution test on reduced samples. Any form of outlier rejection must start with distributional assumptions, in this case assuming normality, which is generally not sound for benchmark data. Hence, now benchstat does not do any outlier rejection. As a result, it must use robust summary statistics as well, so benchstat now uses the median and confidence interval of the median as summary statistics. Benchstat continues to use the same Mann-Whitney U-test for the delta, but now does it on the full samples since the U-test is already non-parametric, hence increasing the power of this test. As part of these statistical improvements, benchstat now detects and warns about several common mistakes, such as having too few samples for meaningful statistical results, or having incompar 8000 able geomeans. The output format is more consistent. Previously, benchstat transformed units like "ns/op" into a metric like "time/op", which it used as a column header; and a numerator like "sec", which it used to label each measurement. This was easy enough for the standard units used by the testing framework, but was basically impossible to generalize to custom units. Now, benchstat does unit scaling, but otherwise leaves units alone. The full (scaled) unit is used as a column header and each measurement is simply a scaled value shown with an SI prefix. This also means that the text and CSV formats can be much more similar while still allowing the CSV format to be usefully machine-readable. Benchstat will also now do A/B comparisons even if there are more than two inputs. It shows a comparison to the base in the second and all subsequent columns. This approach is consistent for any number of inputs. Benchstat now supports the full Go benchmark format, including sophisticated control over exactly how it structures the results into rows, columns, and tables. This makes it easy to do meaningful comparisons across benchmark data that isn't simply structured into two input files, and gives significantly more control over how results are sorted. The default behavior is still to turn each input file into a column and each benchmark into a row. Fixes golang/go#19565 by showing all results, even if the benchmark sets don't match across columns, and warning when geomean sets are incompatible. Fixes golang/go#19634 by no longer doing outlier rejection and clearly reporting when there are not enough samples to do a meaningful difference test. Updates golang/go#23471 by providing more through command documentation. I'm not sure it quite fixes this issue, but it's much better than it was. Fixes golang/go#30368 because benchstat now supports filter expressions, which can also filter down units. Fixes golang/go#33169 because benchstat now always shows file configuration labels. Updates golang/go#43744 by integrating unit metadata to control statistical assumptions into the main tool that implements those assumptions. Fixes golang/go#48380 by introducing a way to override labels from the command line rather than always using file names. Change-Id: Ie2c5a12024e84b4918e483df2223eb1f10413a4f
skyzyx
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Apr 12, 2024
This is a complete rewrite of benchstat. Basic usage remains the same, as does the core idea of showing statistical benchmark summaries and A/B comparisons in a table, but there are several major improvements. The statistics is now more robust. Previously, benchstat used IQR-based outlier rejection, showed the mean of the reduced sample, its range, and did a non-parametric difference-of-distribution test on reduced samples. Any form of outlier rejection must start with distributional assumptions, in this case assuming normality, which is generally not sound for benchmark data. Hence, now benchstat does not do any outlier rejection. As a result, it must use robust summary statistics as well, so benchstat now uses the median and confidence interval of the median as summary statistics. Benchstat continues to use the same Mann-Whitney U-test for the delta, but now does it on the full samples since the U-test is already non-parametric, hence increasing the power of this test. As part of these statistical improvements, benchstat now detects and warns about several common mistakes, such as having too few samples for meaningful statistical results, or having incomparable geomeans. The output format is more consistent. Previously, benchstat transformed units like "ns/op" into a metric like "time/op", which it used as a column header; and a numerator like "sec", which it used to label each measurement. This was easy enough for the standard units used by the testing framework, but was basically impossible to generalize to custom units. Now, benchstat does unit scaling, but otherwise leaves units alone. The full (scaled) unit is used as a column header and each measurement is simply a scaled value shown with an SI prefix. This also means that the text and CSV formats can be much more similar while still allowing the CSV format to be usefully machine-readable. Benchstat will also now do A/B comparisons even if there are more than two inputs. It shows a comparison to the base in the second and all subsequent columns. This approach is consistent for any number of inputs. Benchstat now supports the full Go benchmark format, including sophisticated control over exactly how it structures the results into rows, columns, and tables. This makes it easy to do meaningful comparisons across benchmark data that isn't simply structured into two input files, and gives significantly more control over how results are sorted. The default behavior is still to turn each input file into a column and each benchmark into a row. Fixes golang/go#19565 by showing all results, even if the benchmark sets don't match across columns, and warning when geomean sets are incompatible. Fixes golang/go#19634 by no longer doing outlier rejection and clearly reporting when there are not enough samples to do a meaningful difference test. Updates golang/go#23471 by providing more through command documentation. I'm not sure it quite fixes this issue, but it's much better than it was. Fixes golang/go#30368 because benchstat now supports filter expressions, which can also filter down units. Fixes golang/go#33169 because benchstat now always shows file configuration labels. Updates golang/go#43744 by integrating unit metadata to control statistical assumptions into the main tool that implements those assumptions. Fixes golang/go#48380 by introducing a way to override labels from the command line rather than always using file names. Change-Id: Ie2c5a12024e84b4918e483df2223eb1f10413a4f Reviewed-on: https://go-review.googlesource.com/c/perf/+/309969 Run-TryBot: Austin Clements <austin@google.com> Reviewed-by: Michael Pratt <mpratt@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
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What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
Yes.
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
#install benchstat
go get -d golang.org/x/perf/cmd/benchstat
go install golang.org/x/perf/cmd/benchstat
#run benchmark of a SINGLE package under /src
go test -count 5 -timeout 20m -run=^$ -bench=. crypto/sha256 | tee bench.log
#run benchstat to do analysis, using default options
benchstat bench.log
#output of the benchstat doesn't have group header (pkg, goos, goarch)
name time/op
Hash8Bytes-40 294ns ± 3%
Hash1K-40 3.50µs ± 5%
Hash8K-40 26.2µs ± 4%
name speed
Hash8Bytes-40 27.2MB/s ± 3%
Hash1K-40 293MB/s ± 4%
Hash8K-40 313MB/s ± 4%
What did you expect to see?
Expect benchstat to output group header even the benchmarking data only contains one group.
Since there are a few Go benchmarks from different packages sharing the same name, for example, both crypto/sha256 and crypto/sha512 have benchmarks "BenchmarkHash8Bytes", "BenchmarkHash1K", etc., having a package name, which is part of the group header by default, would facilitate recording their performance data in a database.
We can fulfill the above requirement via multiple ways, just wondering if having benchstat support it is a better option.
The restriction was introduced in commit add18dd,
Any comment is highly appreciated.
Attaching two benchmark log files for your reference.
bench_one_pkg.log: benchmark log of package crypto/sha256, benchstat's output has no group
bench_two_pkgs.log: benchmark log of packages crypto/sha256 and crypto/sha512, benchstat's output has groups.
bench_one_pkg.log
bench_two_pkgs.log
What did you see instead?
The text was updated successfully, but these errors were encountered: