创建一个rand结构

Question

I found the following in this codebase, someone commented on this method with a TODO like so

    // TODO avoid using rand.Float64 method. it uses a singleton lock and may cause
    // performance issues. Instead, instantiate a rand struct and use that to call
    // Float64()

    func standardStrategy(l *ledger) bool {
        return rand.Float64() <= probabilitySend(l.Accounting.Value())
    }

func probabilitySend(ratio float64) float64 {
    x := 1 + math.Exp(6-3*ratio)
    y := 1 / x
    return 1 - y
}

What does this mean?

Answer 1

I think what it means is this: the rand package has something called a Rand struct, which has random generating functions, that probably don't lock a global lock, so probably the writer of the comment meant using this struct. i.e.:

r := rand.New(rand.NewSource(1234))

fmt.Println(r.Float64())

The function used in this code is global to the package and uses a globally initialized Rand struct, called internally globalRand, which has an internal mutex. So avoiding using it saves this locking.