performance - 在结构 "functions"中使用指针与复制

Question

我是 Go 的新手，在编写结构“函数”时我真的无法决定何时使用指针还是副本(这是正确的术语吗？)

type Blah struct {
    c complex128
    s string
    f float64
}

func (b * Blah) doPtr() {
    fmt.Println(b.c, b.s, b.f);
}

func (b Blah) doCopy() {
    fmt.Println(b.c, b.s, b.f);
}

现在，我的 C++ 背景告诉我 doPtr 在速度和内存方面都更高效，但是很多示例使用 doCopy 除非你正在修改对象，所以我错过了什么吗？

Answer 1

[Go] Frequently Asked Questions (FAQ)

Should I define methods on values or pointers?

For types such as basic types, slices, and small structs, a value receiver is very cheap so unless the semantics of the method requires a pointer, a value receiver is efficient and clear.

对于性能问题，请勿猜测。运行基准测试。例如，

文件:bench_test.go

package main

import (
    "testing"
)

type Blah struct {
    c complex128
    s string
    f float64
}

func (b *Blah) doPtr() {
}

func (b Blah) doCopy() {
}

func BenchmarkDoPtr(b *testing.B) {
    blah := Blah{}
    for i := 0; i < b.N; i++ {
        (&blah).doPtr()
    }
}

func BenchmarkDoCopy(b *testing.B) {
    blah := Blah{}
    for i := 0; i < b.N; i++ {
        blah.doCopy()
    }
}

输出:

$ go test -bench=.
testing: warning: no tests to run
PASS
BenchmarkDoPtr  2000000000           1.26 ns/op
BenchmarkDoCopy 50000000            32.6 ns/op
ok      so/test 4.317s
$