180 lines
5.2 KiB
Go
180 lines
5.2 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package rand implements pseudo-random number generators.
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package rand
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import "sync"
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// A Source represents a source of uniformly-distributed
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// pseudo-random int64 values in the range [0, 1<<63).
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type Source interface {
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Int63() int64
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Seed(seed int64)
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}
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// NewSource returns a new pseudo-random Source seeded with the given value.
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func NewSource(seed int64) Source {
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var rng rngSource
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rng.Seed(seed)
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return &rng
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}
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// A Rand is a source of random numbers.
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type Rand struct {
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src Source
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}
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// New returns a new Rand that uses random values from src
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// to generate other random values.
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func New(src Source) *Rand { return &Rand{src} }
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// Seed uses the provided seed value to initialize the generator to a deterministic state.
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func (r *Rand) Seed(seed int64) { r.src.Seed(seed) }
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// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
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func (r *Rand) Int63() int64 { return r.src.Int63() }
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// Uint32 returns a pseudo-random 32-bit value as a uint32.
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func (r *Rand) Uint32() uint32 { return uint32(r.Int63() >> 31) }
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// Int31 returns a non-negative pseudo-random 31-bit integer as an int32.
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func (r *Rand) Int31() int32 { return int32(r.Int63() >> 32) }
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// Int returns a non-negative pseudo-random int.
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func (r *Rand) Int() int {
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u := uint(r.Int63())
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return int(u << 1 >> 1) // clear sign bit if int == int32
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}
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// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n).
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func (r *Rand) Int63n(n int64) int64 {
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if n <= 0 {
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return 0
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}
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max := int64((1 << 63) - 1 - (1<<63)%uint64(n))
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v := r.Int63()
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for v > max {
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v = r.Int63()
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}
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return v % n
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}
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// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n).
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func (r *Rand) Int31n(n int32) int32 {
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if n <= 0 {
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return 0
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}
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max := int32((1 << 31) - 1 - (1<<31)%uint32(n))
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v := r.Int31()
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for v > max {
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v = r.Int31()
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}
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return v % n
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}
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// Intn returns, as an int, a non-negative pseudo-random number in [0,n).
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func (r *Rand) Intn(n int) int {
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if n <= 1<<31-1 {
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return int(r.Int31n(int32(n)))
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}
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return int(r.Int63n(int64(n)))
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}
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// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0).
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func (r *Rand) Float64() float64 { return float64(r.Int63()) / (1 << 63) }
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// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0).
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func (r *Rand) Float32() float32 { return float32(r.Float64()) }
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// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n).
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func (r *Rand) Perm(n int) []int {
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m := make([]int, n)
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for i := 0; i < n; i++ {
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m[i] = i
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}
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for i := 0; i < n; i++ {
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j := r.Intn(i + 1)
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m[i], m[j] = m[j], m[i]
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}
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return m
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}
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/*
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* Top-level convenience functions
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*/
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var globalRand = New(&lockedSource{src: NewSource(1)})
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// Seed uses the provided seed value to initialize the generator to a deterministic state.
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func Seed(seed int64) { globalRand.Seed(seed) }
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// Int63 returns a non-negative pseudo-random 63-bit integer as an int64.
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func Int63() int64 { return globalRand.Int63() }
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// Uint32 returns a pseudo-random 32-bit value as a uint32.
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func Uint32() uint32 { return globalRand.Uint32() }
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// Int31 returns a non-negative pseudo-random 31-bit integer as an int32.
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func Int31() int32 { return globalRand.Int31() }
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// Int returns a non-negative pseudo-random int.
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func Int() int { return globalRand.Int() }
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// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n).
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func Int63n(n int64) int64 { return globalRand.Int63n(n) }
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// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n).
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func Int31n(n int32) int32 { return globalRand.Int31n(n) }
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// Intn returns, as an int, a non-negative pseudo-random number in [0,n).
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func Intn(n int) int { return globalRand.Intn(n) }
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// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0).
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func Float64() float64 { return globalRand.Float64() }
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// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0).
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func Float32() float32 { return globalRand.Float32() }
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// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n).
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func Perm(n int) []int { return globalRand.Perm(n) }
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// NormFloat64 returns a normally distributed float64 in the range
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// [-math.MaxFloat64, +math.MaxFloat64] with
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// standard normal distribution (mean = 0, stddev = 1).
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// To produce a different normal distribution, callers can
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// adjust the output using:
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//
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// sample = NormFloat64() * desiredStdDev + desiredMean
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//
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func NormFloat64() float64 { return globalRand.NormFloat64() }
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// ExpFloat64 returns an exponentially distributed float64 in the range
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// (0, +math.MaxFloat64] with an exponential distribution whose rate parameter
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// (lambda) is 1 and whose mean is 1/lambda (1).
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// To produce a distribution with a different rate parameter,
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// callers can adjust the output using:
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//
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// sample = ExpFloat64() / desiredRateParameter
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//
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func ExpFloat64() float64 { return globalRand.ExpFloat64() }
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type lockedSource struct {
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lk sync.Mutex
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src Source
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}
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func (r *lockedSource) Int63() (n int64) {
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r.lk.Lock()
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n = r.src.Int63()
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r.lk.Unlock()
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return
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}
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func (r *lockedSource) Seed(seed int64) {
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r.lk.Lock()
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r.src.Seed(seed)
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r.lk.Unlock()
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}
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