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author | Ian Lance Taylor <ian@gcc.gnu.org> | 2011-12-07 01:11:29 +0000 |
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committer | Ian Lance Taylor <ian@gcc.gnu.org> | 2011-12-07 01:11:29 +0000 |
commit | 9c63abc9a1d127f95162756467284cf76b47aff8 (patch) | |
tree | 84f27a6ab44d932e4b0455f18390b070b4de626e /libgo/go/math/rand/rand.go | |
parent | 374280238f934fa851273e2ee16ba53be890c6b8 (diff) | |
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libgo: Update to weekly 2011-11-09.
From-SVN: r182073
Diffstat (limited to 'libgo/go/math/rand/rand.go')
-rw-r--r-- | libgo/go/math/rand/rand.go | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/libgo/go/math/rand/rand.go b/libgo/go/math/rand/rand.go new file mode 100644 index 0000000..459aed1 --- /dev/null +++ b/libgo/go/math/rand/rand.go @@ -0,0 +1,179 @@ +// 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()) } + +// 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() } + +// 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() +} |