go benchmark 源码
golang benchmark 代码
文件路径：/src/go/doc/testdata/benchmark.go
// Copyright 2009 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.
package testing
import (
"flag"
"fmt"
"os"
"runtime"
"time"
)
var matchBenchmarks = flag.String("test.bench", "", "regular expression to select benchmarks to run")
var benchTime = flag.Duration("test.benchtime", 1*time.Second, "approximate run time for each benchmark")
// An internal type but exported because it is cross-package; part of the implementation
// of go test.
type InternalBenchmark struct {
Name string
F func(b *B)
}
// B is a type passed to Benchmark functions to manage benchmark
// timing and to specify the number of iterations to run.
type B struct {
common
N int
benchmark InternalBenchmark
bytes int64
timerOn bool
result BenchmarkResult
}
// StartTimer starts timing a test. This function is called automatically
// before a benchmark starts, but it can also used to resume timing after
// a call to StopTimer.
func (b *B) StartTimer() {
if !b.timerOn {
b.start = time.Now()
b.timerOn = true
}
}
// StopTimer stops timing a test. This can be used to pause the timer
// while performing complex initialization that you don't
// want to measure.
func (b *B) StopTimer() {
if b.timerOn {
b.duration += time.Now().Sub(b.start)
b.timerOn = false
}
}
// ResetTimer sets the elapsed benchmark time to zero.
// It does not affect whether the timer is running.
func (b *B) ResetTimer() {
if b.timerOn {
b.start = time.Now()
}
b.duration = 0
}
// SetBytes records the number of bytes processed in a single operation.
// If this is called, the benchmark will report ns/op and MB/s.
func (b *B) SetBytes(n int64) { b.bytes = n }
func (b *B) nsPerOp() int64 {
if b.N <= 0 {
return 0
}
return b.duration.Nanoseconds() / int64(b.N)
}
// runN runs a single benchmark for the specified number of iterations.
func (b *B) runN(n int) {
// Try to get a comparable environment for each run
// by clearing garbage from previous runs.
runtime.GC()
b.N = n
b.ResetTimer()
b.StartTimer()
b.benchmark.F(b)
b.StopTimer()
}
func min(x, y int) int {
if x > y {
return y
}
return x
}
func max(x, y int) int {
if x < y {
return y
}
return x
}
// roundDown10 rounds a number down to the nearest power of 10.
func roundDown10(n int) int {
var tens = 0
// tens = floor(log_10(n))
for n > 10 {
n = n / 10
tens++
}
// result = 10^tens
result := 1
for i := 0; i < tens; i++ {
result *= 10
}
return result
}
// roundUp rounds x up to a number of the form [1eX, 2eX, 5eX].
func roundUp(n int) int {
base := roundDown10(n)
if n < (2 * base) {
return 2 * base
}
if n < (5 * base) {
return 5 * base
}
return 10 * base
}
// run times the benchmark function in a separate goroutine.
func (b *B) run() BenchmarkResult {
go b.launch()
<-b.signal
return b.result
}
// launch launches the benchmark function. It gradually increases the number
// of benchmark iterations until the benchmark runs for a second in order
// to get a reasonable measurement. It prints timing information in this form
// testing.BenchmarkHello 100000 19 ns/op
// launch is run by the fun function as a separate goroutine.
func (b *B) launch() {
// Run the benchmark for a single iteration in case it's expensive.
n := 1
// Signal that we're done whether we return normally
// or by FailNow's runtime.Goexit.
defer func() {
b.signal <- b
}()
b.runN(n)
// Run the benchmark for at least the specified amount of time.
d := *benchTime
for !b.failed && b.duration < d && n < 1e9 {
last := n
// Predict iterations/sec.
if b.nsPerOp() == 0 {
n = 1e9
} else {
n = int(d.Nanoseconds() / b.nsPerOp())
}
// Run more iterations than we think we'll need for a second (1.5x).
// Don't grow too fast in case we had timing errors previously.
// Be sure to run at least one more than last time.
n = max(min(n+n/2, 100*last), last+1)
// Round up to something easy to read.
n = roundUp(n)
b.runN(n)
}
b.result = BenchmarkResult{b.N, b.duration, b.bytes}
}
// The results of a benchmark run.
type BenchmarkResult struct {
N int // The number of iterations.
T time.Duration // The total time taken.
Bytes int64 // Bytes processed in one iteration.
}
func (r BenchmarkResult) NsPerOp() int64 {
if r.N <= 0 {
return 0
}
return r.T.Nanoseconds() / int64(r.N)
}
func (r BenchmarkResult) mbPerSec() float64 {
if r.Bytes <= 0 || r.T <= 0 || r.N <= 0 {
return 0
}
return (float64(r.Bytes) * float64(r.N) / 1e6) / r.T.Seconds()
}
func (r BenchmarkResult) String() string {
mbs := r.mbPerSec()
mb := ""
if mbs != 0 {
mb = fmt.Sprintf("\t%7.2f MB/s", mbs)
}
nsop := r.NsPerOp()
ns := fmt.Sprintf("%10d ns/op", nsop)
if r.N > 0 && nsop < 100 {
// The format specifiers here make sure that
// the ones digits line up for all three possible formats.
if nsop < 10 {
ns = fmt.Sprintf("%13.2f ns/op", float64(r.T.Nanoseconds())/float64(r.N))
} else {
ns = fmt.Sprintf("%12.1f ns/op", float64(r.T.Nanoseconds())/float64(r.N))
}
}
return fmt.Sprintf("%8d\t%s%s", r.N, ns, mb)
}
// An internal function but exported because it is cross-package; part of the implementation
// of go test.
func RunBenchmarks(matchString func(pat, str string) (bool, error), benchmarks []InternalBenchmark) {
// If no flag was specified, don't run benchmarks.
if len(*matchBenchmarks) == 0 {
return
}
for _, Benchmark := range benchmarks {
matched, err := matchString(*matchBenchmarks, Benchmark.Name)
if err != nil {
fmt.Fprintf(os.Stderr, "testing: invalid regexp for -test.bench: %s\n", err)
os.Exit(1)
}
if !matched {
continue
}
for _, procs := range cpuList {
runtime.GOMAXPROCS(procs)
b := &B{
common: common{
signal: make(chan any),
},
benchmark: Benchmark,
}
benchName := Benchmark.Name
if procs != 1 {
benchName = fmt.Sprintf("%s-%d", Benchmark.Name, procs)
}
fmt.Printf("%s\t", benchName)
r := b.run()
if b.failed {
// The output could be very long here, but probably isn't.
// We print it all, regardless, because we don't want to trim the reason
// the benchmark failed.
fmt.Printf("--- FAIL: %s\n%s", benchName, b.output)
continue
}
fmt.Printf("%v\n", r)
// Unlike with tests, we ignore the -chatty flag and always print output for
// benchmarks since the output generation time will skew the results.
if len(b.output) > 0 {
b.trimOutput()
fmt.Printf("--- BENCH: %s\n%s", benchName, b.output)
}
if p := runtime.GOMAXPROCS(-1); p != procs {
fmt.Fprintf(os.Stderr, "testing: %s left GOMAXPROCS set to %d\n", benchName, p)
}
}
}
}
// trimOutput shortens the output from a benchmark, which can be very long.
func (b *B) trimOutput() {
// The output is likely to appear multiple times because the benchmark
// is run multiple times, but at least it will be seen. This is not a big deal
// because benchmarks rarely print, but just in case, we trim it if it's too long.
const maxNewlines = 10
for nlCount, j := 0, 0; j < len(b.output); j++ {
if b.output[j] == '\n' {
nlCount++
if nlCount >= maxNewlines {
b.output = append(b.output[:j], "\n\t... [output truncated]\n"...)
break
}
}
}
}
// Benchmark benchmarks a single function. Useful for creating
// custom benchmarks that do not use go test.
func Benchmark(f func(b *B)) BenchmarkResult {
b := &B{
common: common{
signal: make(chan any),
},
benchmark: InternalBenchmark{"", f},
}
return b.run()
}
相关信息
相关文章
0
赞
热门推荐
-
2、 - 优质文章
-
3、 gate.io
-
6、 golang
-
7、 openharmony