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// Copyright ©2020 The Gonum 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 testrand
import (
"math"
"golang.org/x/exp/rand"
)
// extreme is a pseudo-random number generator that has high probability of returning extreme values.
type extreme struct {
probability float64
nanProbability float64
rnd Rand
}
// newExtreme creates a new extreme pseudo-random generator.
// p is the probability of returning an extreme value.
// nan is the probability of returning a NaN.
func newExtreme(p, nan float64, rnd Rand) *extreme {
return &extreme{p, nan, rnd}
}
// Perm returns a permutation of integers [0, n).
func (e *extreme) Perm(n int) []int { return e.rnd.Perm(n) }
// Read generates len(p) pseudo-random bytes.
func (e *extreme) Read(p []byte) (n int, err error) { return e.rnd.Read(p) }
// Seed reseeds the pseudo-random generator.
func (e *extreme) Seed(seed uint64) { e.rnd.Seed(seed) }
// Shuffle shuffles n items using the swap callback.
func (e *extreme) Shuffle(n int, swap func(i, j int)) { e.rnd.Shuffle(n, swap) }
// p returns true when the generator should output an extreme value.
func (e *extreme) p() bool {
if e.probability <= 0 {
return false
}
return e.rnd.Float64() < e.probability
}
// nan returns true when the generator should output nan.
func (e *extreme) nan() bool {
if e.nanProbability <= 0 {
return false
}
return e.rnd.Float64() < e.nanProbability
}
// ExpFloat64 returns an exponentialy distributed pseudo-random float64 in range (0, math.MaxFloat64].
func (e *extreme) ExpFloat64() float64 {
switch {
case e.p():
return extremeFloat64Exp[e.rnd.Intn(len(extremeFloat64Exp))]
case e.nan():
return math.NaN()
}
return e.rnd.ExpFloat64()
}
// Float32 returns a pseudo-random float32 in range [0.0, 1.0).
func (e *extreme) Float32() float32 {
switch {
case e.p():
return extremeFloat32Unit[e.rnd.Intn(len(extremeFloat32Unit))]
case e.nan():
return float32(math.NaN())
}
return e.rnd.Float32()
}
// Float64 returns a pseudo-random float64 in range [0.0, 1.0).
func (e *extreme) Float64() float64 {
switch {
case e.p():
return extremeFloat64Unit[e.rnd.Intn(len(extremeFloat64Unit))]
case e.nan():
return math.NaN()
}
return e.rnd.Float64()
}
// Int returns a non-negative pseudo-random int.
func (e *extreme) Int() int {
if e.p() {
return extremeInt[e.rnd.Intn(len(extremeInt))]
}
return e.rnd.Int()
}
// Int31 returns a non-negative pseudo-random int32.
func (e *extreme) Int31() int32 {
if e.p() {
return extremeInt31[e.rnd.Intn(len(extremeInt31))]
}
return e.rnd.Int31()
}
// Int31n returns a non-negative pseudo-random int32 from range [0, n).
func (e *extreme) Int31n(n int32) int32 {
if e.p() {
switch rand.Intn(4) {
case 0:
return 0
case 1:
return 1
case 2:
return n / 2
case 3:
return n - 1
}
}
return e.rnd.Int31n(n)
}
// Int63 returns a non-negative pseudo-random int64.
func (e *extreme) Int63() int64 {
if e.p() {
return extremeInt63[e.rnd.Intn(len(extremeInt63))]
}
return e.rnd.Int63()
}
// Int63n returns a non-negative pseudo-random int from range [0, n).
func (e *extreme) Int63n(n int64) int64 {
if e.p() {
switch rand.Intn(4) {
case 0:
return 0
case 1:
return 1
case 2:
return n / 2
case 3:
return n - 1
}
}
return e.rnd.Int63n(n)
}
// Int returns a non-negative pseudo-random int from range [0, n).
func (e *extreme) Intn(n int) int {
if e.p() {
switch rand.Intn(4) {
case 0:
return 0
case 1:
return 1
case 2:
return n / 2
case 3:
return n - 1
}
}
return e.rnd.Intn(n)
}
// NormFloat64 returns a normally distributed pseudo-random float64 in range [-math.MaxFloat64, math.MaxFloat64].
func (e *extreme) NormFloat64() float64 {
switch {
case e.p():
return extremeFloat64Norm[e.rnd.Intn(len(extremeFloat64Norm))]
case e.nan():
return math.NaN()
}
return e.rnd.NormFloat64()
}
// Uint32 returns a pseudo-random uint32.
func (e *extreme) Uint32() uint32 {
if e.p() {
return extremeUint32[e.rnd.Intn(len(extremeUint32))]
}
return e.rnd.Uint32()
}
// Uint64 returns a pseudo-random uint64.
func (e *extreme) Uint64() uint64 {
if e.p() {
return extremeUint64[e.rnd.Intn(len(extremeUint64))]
}
return e.rnd.Uint64()
}
// Uint64n returns a pseudo-random uint64 from range [0, n).
func (e *extreme) Uint64n(n uint64) uint64 {
if e.p() {
switch rand.Intn(4) {
case 0:
return 0
case 1:
return 1
case 2:
return n / 2
case 3:
return n - 1
}
}
return e.rnd.Uint64n(n)
}
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