86 lines
1.4 KiB
Markdown
86 lines
1.4 KiB
Markdown
# [testing](https://golang.org/pkg/testing/)
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## Benchmark
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Any benchmark should be careful to prevent **compiler optimization**.
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Example `calc.go` in package `calc`:
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```go
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package calc
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import (
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"time"
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)
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var input float64
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func init() {
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if time.Now().Year() > 1900 {
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input = 426942694269
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}
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}
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func calc() int {
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x := input
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x /= 6.9
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x /= 4.2
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x /= 6.9
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x /= 4.2
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return int(x)
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}
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```
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Example `calc_test.go` in package `calc`:
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```go
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package calc
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import (
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"runtime"
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"testing"
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)
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func BenchmarkX(b *testing.B) {
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for i := 0; i < b.N; i++ {
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calc()
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}
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}
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var sink int
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func BenchmarkCalcSink(b *testing.B) {
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var result int
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for i := 0; i < b.N; i++ {
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result = calc()
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}
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// prevent compiler optimization
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sink = result
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}
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func BenchmarkCalcKeepAlive(b *testing.B) {
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for i := 0; i < b.N; i++ {
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result := calc()
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// prevent compiler optimization
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runtime.KeepAlive(result)
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}
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}
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```
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Benchmark result when run with `go test -bench=.`
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```txt
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goos: linux
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goarch: amd64
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BenchmarkCalc-4 1000000000 0.343 ns/op
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BenchmarkCalcSink-4 229652618 5.30 ns/op
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BenchmarkCalcKeepAlive-4 225297381 5.27 ns/op
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```
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`BenchmarkCalc` is fast because it has compiler optimization.
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There are 2 methods for preventing compiler optimization:
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sink (`BenchmarkCalcSink`) or keep alive (`BenchmarkCalcKeepAlive`).
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