rnd

README

Package rnd provides a pre-seeded PRNG. See the package docs for details.

Documentation

Overview

Package rnd provides a pre-seeded PRNG.

It is meant for cases where a library wants to guarantee non-deterministic behavior. In that case, the API of math/rand provides several challenges:

1. *rand.Rand is not concurrency safe, so you need to wrap it into a mutex or use a sync.Pool. Locking is less efficient, as it holds the mutex for longer than required. sync.Pool means random number generation might allocate.
2. The default source (used by the top-level function) is concurrency safe, but not seeded. A library can not assume its user remembered to properly seed it. It can also not be sure a different library did not seed it with a bad seed (e.g. many people use the current time).

This package works around that by using a concurrency safe and properly seeded shared source and not allowing to seed it manually.

Index

• func ExpFloat64() float64
• func Float32() float32
• func Float64() float64
• func Int() int
• func Int31() int32
• func Int31n(n int32) int32
• func Int63() int64
• func Int63n(n int64) int64
• func Intn(n int) int
• func NormFloat64() float64
• func Perm(n int) []int
• func Read(p []byte) (n int, err error)
• func Shuffle[T any](s []T)
• func Uint32() uint32
• func Uint64() uint64

Functions

func ExpFloat64

func ExpFloat64() float64

ExpFloat64 returns an exponentially distributed float64 in the range (0, +math.MaxFloat64] with an exponential distribution whose rate parameter (lambda) is 1 and whose mean is 1/lambda (1). To produce a distribution with a different rate parameter, callers can adjust the output using:

sample = ExpFloat64() / desiredRateParameter

func Float32

func Float32() float32

Float32 returns, as a float32, a pseudo-random number in [0.0,1.0).

func Float64

func Float64() float64

Float64 returns, as a float64, a pseudo-random number in [0.0,1.0).

func Int

func Int() int

Int returns a non-negative pseudo-random int.

func Int31

func Int31() int32

Int31 returns a non-negative pseudo-random 31-bit integer as an int32.

func Int31n

func Int31n(n int32) int32

Int31n returns, as an int32, a non-negative pseudo-random number in [0,n). It panics if n <= 0.

func Int63

func Int63() int64

Int63 returns a non-negative pseudo-random 63-bit integer as an int64.

func Int63n

func Int63n(n int64) int64

Int63n returns, as an int64, a non-negative pseudo-random number in [0,n). It panics if n <= 0.

func Intn

func Intn(n int) int

Intn returns, as an int, a non-negative pseudo-random number in [0,n). It panics if n <= 0.

func NormFloat64

func NormFloat64() float64

NormFloat64 returns a normally distributed float64 in the range [-math.MaxFloat64, +math.MaxFloat64] with standard normal distribution (mean = 0, stddev = 1). To produce a different normal distribution, callers can adjust the output using:

sample = NormFloat64() * desiredStdDev + desiredMean

func Perm

func Perm(n int) []int

Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n).

func Read

func Read(p []byte) (n int, err error)

Read generates len(p) random bytes and writes them into p. It always returns len(p) and a nil error.

func Shuffle

func Shuffle[T any](s []T)

Shuffle pseudo-randomizes the order of elements of s.

func Uint32

func Uint32() uint32

Uint32 returns a pseudo-random 32-bit value as a uint32.

func Uint64

func Uint64() uint64

Uint64 returns a pseudo-random 64-bit value as a uint64.