gorandomgranularity

Random number within range and a given granularity in Golang


I've written the following code to create a random number between 0.0 and 10.0.

const minRand = 0
const maxRand = 10
v := minRand + rand.Float64()*(maxRand-minRand)

However, I would like to set the granularity to 0.05, so having all the digits as the least significant decimal should not be allowed, only 0 and 5 should be allowed, e.g.:

How can I produce such numbers in Go?


Solution

  • You can divide with the granularity, get a pseudo random integer and then multiply with the granularity to scale the result down.

    const minRand = 8
    const maxRand = 10
    v := float64(rand.Intn((maxRand-minRand)/0.05))*0.05 + minRand
    fmt.Printf("%.2f\n", v)
    

    This will print:

    8.05
    8.35
    8.35
    8.95
    8.05
    9.90
    ....
    

    If you don't want to get the same sequence every time rand.Seed(time.Now().UTC().UnixNano()).

    From the docs

    Seed uses the provided seed value to initialize the default Source to a deterministic state. If Seed is not called, the generator behaves as if seeded by Seed(1). Seed values that have the same remainder when divided by 2^31-1 generate the same pseudo-random sequence. Seed, unlike the Rand.Seed method, is safe for concurrent use.