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