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Diffstat (limited to 'src/pkg/math/rand/rand.go')
-rw-r--r-- | src/pkg/math/rand/rand.go | 246 |
1 files changed, 0 insertions, 246 deletions
diff --git a/src/pkg/math/rand/rand.go b/src/pkg/math/rand/rand.go deleted file mode 100644 index 3ffb5c4e5..000000000 --- a/src/pkg/math/rand/rand.go +++ /dev/null @@ -1,246 +0,0 @@ -// 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. -// -// Random numbers are generated by a Source. Top-level functions, such as -// Float64 and Int, use a default shared Source that produces a deterministic -// sequence of values each time a program is run. Use the Seed function to -// initialize the default Source if different behavior is required for each run. -// The default Source is safe for concurrent use by multiple goroutines. -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). -// It panics if n <= 0. -func (r *Rand) Int63n(n int64) int64 { - if n <= 0 { - panic("invalid argument to Int63n") - } - if n&(n-1) == 0 { // n is power of two, can mask - return r.Int63() & (n - 1) - } - 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). -// It panics if n <= 0. -func (r *Rand) Int31n(n int32) int32 { - if n <= 0 { - panic("invalid argument to Int31n") - } - if n&(n-1) == 0 { // n is power of two, can mask - return r.Int31() & (n - 1) - } - 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). -// It panics if n <= 0. -func (r *Rand) Intn(n int) int { - if n <= 0 { - panic("invalid argument to Intn") - } - 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 { - // A clearer, simpler implementation would be: - // return float64(r.Int63n(1<<53)) / (1<<53) - // However, Go 1 shipped with - // return float64(r.Int63()) / (1 << 63) - // and we want to preserve that value stream. - // - // There is one bug in the value stream: r.Int63() may be so close - // to 1<<63 that the division rounds up to 1.0, and we've guaranteed - // that the result is always less than 1.0. To fix that, we treat the - // range as cyclic and map 1 back to 0. This is justified by observing - // that while some of the values rounded down to 0, nothing was - // rounding up to 0, so 0 was underrepresented in the results. - // Mapping 1 back to zero restores some balance. - // (The balance is not perfect because the implementation - // returns denormalized numbers for very small r.Int63(), - // and those steal from what would normally be 0 results.) - // The remapping only happens 1/2⁵³ of the time, so most clients - // will not observe it anyway. - f := float64(r.Int63()) / (1 << 63) - if f == 1 { - f = 0 - } - return f -} - -// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0). -func (r *Rand) Float32() float32 { - // Same rationale as in Float64: we want to preserve the Go 1 value - // stream except we want to fix it not to return 1.0 - // There is a double rounding going on here, but the argument for - // mapping 1 to 0 still applies: 0 was underrepresented before, - // so mapping 1 to 0 doesn't cause too many 0s. - // This only happens 1/2²⁴ of the time (plus the 1/2⁵³ of the time in Float64). - f := float32(r.Float64()) - if f == 1 { - f = 0 - } - return f -} - -// 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++ { - j := r.Intn(i + 1) - m[i] = m[j] - m[j] = i - } - return m -} - -/* - * Top-level convenience functions - */ - -var globalRand = New(&lockedSource{src: NewSource(1)}) - -// 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). -func Seed(seed int64) { globalRand.Seed(seed) } - -// Int63 returns a non-negative pseudo-random 63-bit integer as an int64 -// from the default Source. -func Int63() int64 { return globalRand.Int63() } - -// Uint32 returns a pseudo-random 32-bit value as a uint32 -// from the default Source. -func Uint32() uint32 { return globalRand.Uint32() } - -// Int31 returns a non-negative pseudo-random 31-bit integer as an int32 -// from the default Source. -func Int31() int32 { return globalRand.Int31() } - -// Int returns a non-negative pseudo-random int from the default Source. -func Int() int { return globalRand.Int() } - -// Int63n returns, as an int64, a non-negative pseudo-random number in [0,n) -// from the default Source. -// It panics if n <= 0. -func Int63n(n int64) int64 { return globalRand.Int63n(n) } - -// Int31n returns, as an int32, a non-negative pseudo-random number in [0,n) -// from the default Source. -// It panics if n <= 0. -func Int31n(n int32) int32 { return globalRand.Int31n(n) } - -// Intn returns, as an int, a non-negative pseudo-random number in [0,n) -// from the default Source. -// It panics if n <= 0. -func Intn(n int) int { return globalRand.Intn(n) } - -// Float64 returns, as a float64, a pseudo-random number in [0.0,1.0) -// from the default Source. -func Float64() float64 { return globalRand.Float64() } - -// Float32 returns, as a float32, a pseudo-random number in [0.0,1.0) -// from the default Source. -func Float32() float32 { return globalRand.Float32() } - -// Perm returns, as a slice of n ints, a pseudo-random permutation of the integers [0,n) -// from the default Source. -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) -// from the default Source. -// 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) from the default Source. -// 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() -} |