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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Benchstat computes and compares statistics about benchmarks.
//
// Usage:
//
// benchstat [-delta-test name] [-geomean] [-html] old.txt [new.txt] [more.txt ...]
//
// Each input file should contain the concatenated output of a number
// of runs of ``go test -bench.'' For each different benchmark listed in an input file,
// benchstat computes the mean, minimum, and maximum run time,
// after removing outliers using the interquartile range rule.
//
// If invoked on a single input file, benchstat prints the per-benchmark statistics
// for that file.
//
// If invoked on a pair of input files, benchstat adds to the output a column
// showing the statistics from the second file and a column showing the
// percent change in mean from the first to the second file.
// Next to the percent change, benchstat shows the p-value and sample
// sizes from a test of the two distributions of benchmark times.
// Small p-values indicate that the two distributions are significantly different.
// If the test indicates that there was no significant change between the two
// benchmarks (defined as p > 0.05), benchstat displays a single ~ instead of
// the percent change.
//
// The -delta-test option controls which significance test is applied:
// utest (Mann-Whitney U-test), ttest (two-sample Welch t-test), or none.
// The default is the U-test, sometimes also referred to as the Wilcoxon rank
// sum test.
//
// If invoked on more than two input files, benchstat prints the per-benchmark
// statistics for all the files, showing one column of statistics for each file,
// with no column for percent change or statistical significance.
//
// The -html option causes benchstat to print the results as an HTML table.
//
// Example
//
// Suppose we collect benchmark results from running ``go test -bench=Encode''
// five times before and after a particular change.
//
// The file old.txt contains:
//
// BenchmarkGobEncode 100 13552735 ns/op 56.63 MB/s
// BenchmarkJSONEncode 50 32395067 ns/op 59.90 MB/s
// BenchmarkGobEncode 100 13553943 ns/op 56.63 MB/s
// BenchmarkJSONEncode 50 32334214 ns/op 60.01 MB/s
// BenchmarkGobEncode 100 13606356 ns/op 56.41 MB/s
// BenchmarkJSONEncode 50 31992891 ns/op 60.65 MB/s
// BenchmarkGobEncode 100 13683198 ns/op 56.09 MB/s
// BenchmarkJSONEncode 50 31735022 ns/op 61.15 MB/s
//
// The file new.txt contains:
//
// BenchmarkGobEncode 100 11773189 ns/op 65.19 MB/s
// BenchmarkJSONEncode 50 32036529 ns/op 60.57 MB/s
// BenchmarkGobEncode 100 11942588 ns/op 64.27 MB/s
// BenchmarkJSONEncode 50 32156552 ns/op 60.34 MB/s
// BenchmarkGobEncode 100 11786159 ns/op 65.12 MB/s
// BenchmarkJSONEncode 50 31288355 ns/op 62.02 MB/s
// BenchmarkGobEncode 100 11628583 ns/op 66.00 MB/s
// BenchmarkJSONEncode 50 31559706 ns/op 61.49 MB/s
// BenchmarkGobEncode 100 11815924 ns/op 64.96 MB/s
// BenchmarkJSONEncode 50 31765634 ns/op 61.09 MB/s
//
// The order of the lines in the file does not matter, except that the
// output lists benchmarks in order of appearance.
//
// If run with just one input file, benchstat summarizes that file:
//
// $ benchstat old.txt
// name time/op
// GobEncode 13.6ms ± 1%
// JSONEncode 32.1ms ± 1%
// $
//
// If run with two input files, benchstat summarizes and compares:
//
// $ benchstat old.txt new.txt
// name old time/op new time/op delta
// GobEncode 13.6ms ± 1% 11.8ms ± 1% -13.31% (p=0.016 n=4+5)
// JSONEncode 32.1ms ± 1% 31.8ms ± 1% ~ (p=0.286 n=4+5)
// $
//
// Note that the JSONEncode result is reported as
// statistically insignificant instead of a -0.93% delta.
//
package main
import (
"bytes"
"flag"
"fmt"
"io/ioutil"
"log"
"os"
"strings"
"golang.org/x/perf/benchstat"
)
func usage() {
fmt.Fprintf(os.Stderr, "usage: benchstat [options] old.txt [new.txt] [more.txt ...]\n")
fmt.Fprintf(os.Stderr, "options:\n")
flag.PrintDefaults()
os.Exit(2)
}
var (
flagDeltaTest = flag.String("delta-test", "utest", "significance `test` to apply to delta: utest, ttest, or none")
flagAlpha = flag.Float64("alpha", 0.05, "consider change significant if p < `α`")
flagGeomean = flag.Bool("geomean", false, "print the geometric mean of each file")
flagHTML = flag.Bool("html", false, "print results as an HTML table")
flagSplit = flag.String("split", "pkg,goos,goarch", "split benchmarks by `labels`")
)
var deltaTestNames = map[string]benchstat.DeltaTest{
"none": benchstat.NoDeltaTest,
"u": benchstat.UTest,
"u-test": benchstat.UTest,
"utest": benchstat.UTest,
"t": benchstat.TTest,
"t-test": benchstat.TTest,
"ttest": benchstat.TTest,
}
func main() {
log.SetPrefix("benchstat: ")
log.SetFlags(0)
flag.Usage = usage
flag.Parse()
deltaTest := deltaTestNames[strings.ToLower(*flagDeltaTest)]
if flag.NArg() < 1 || deltaTest == nil {
flag.Usage()
}
c := &benchstat.Collection{
Alpha: *flagAlpha,
AddGeoMean: *flagGeomean,
DeltaTest: deltaTest,
}
if *flagSplit != "" {
c.SplitBy = strings.Split(*flagSplit, ",")
}
for _, file := range flag.Args() {
data, err := ioutil.ReadFile(file)
if err != nil {
log.Fatal(err)
}
c.AddConfig(file, data)
}
tables := c.Tables()
var buf bytes.Buffer
if *flagHTML {
buf.WriteString(htmlHeader)
benchstat.FormatHTML(&buf, tables)
buf.WriteString(htmlFooter)
} else {
benchstat.FormatText(&buf, tables)
}
os.Stdout.Write(buf.Bytes())
}
var htmlHeader = `<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Performance Result Comparison</title>
<style>
.benchstat { border-collapse: collapse; }
.benchstat th:nth-child(1) { text-align: left; }
.benchstat tbody td:nth-child(1n+2):not(.note) { text-align: right; padding: 0em 1em; }
.benchstat tr:not(.configs) th { border-top: 1px solid #666; border-bottom: 1px solid #ccc; }
.benchstat .nodelta { text-align: center !important; }
.benchstat .better td.delta { font-weight: bold; }
.benchstat .worse td.delta { font-weight: bold; color: #c00; }
</style>
</head>
<body>
`
var htmlFooter = `</body>
</html>
`