xoroshiro128p

Documentation

Overview

Package xoroshiro128p implements xoroshiro128+ 1.0, our best and fastest small-state generator for floating-point numbers. We suggest to use its upper bits for floating-point generation, as it is slightly faster than xoroshiro128++/xoroshiro128**. It passes all tests we are aware of except for the four lower bits, which might fail linearity tests (and just those), so if low linear complexity is not considered an issue (as it is usually the case) it can be used to generate 64-bit outputs, too; moreover, this generator has a very mild Hamming-weight dependency making our test (http://prng.di.unimi.it/hwd.php) fail after 5 TB of output; we believe this slight bias cannot affect any application. If you are concerned, use xoroshiro128++, xoroshiro128** or xoshiro256+.

We suggest to use a sign test to extract a random Boolean value, and right shifts to extract subsets of bits.

The state must be seeded so that it is not everywhere zero. If you have a 64-bit seed, we suggest to seed a splitmix64 generator and use its output to fill s.

NOTE: the parameters (a=24, b=16, b=37) of this version give slightly better results in our test than the 2016 version (a=55, b=14, c=36).

Index

• type Source
  • func New(state [2]uint64) *Source
  • func (s *Source) Int63() int64
  • func (s *Source) Seed(seed int64)
  • func (s *Source) Uint64() uint64

Examples

• Source

Types

type Source

type Source struct {
	// contains filtered or unexported fields
}

Source is a random source using xoroshiro128+ algorithm.

Go port of http://prng.di.unimi.it/xoroshiro128plus.c

Example

package main

import (
	"fmt"
	"math/rand"

	"github.com/shogo82148/randsrc/xoroshiro128p"
)

func main() {
	src := xoroshiro128p.New([2]uint64{1})
	r := rand.New(src)
	for i := 0; i < 10; i++ {
		fmt.Println(r.Int63())
	}
}

Output:

0
68727898112
1162069580936380928
36099245263065744
1306769709744035040
2568221860186161298
3046776487690310554
8213190904191315488
3214698032120034443
292334754365524544

func New

func New(state [2]uint64) *Source

New create a new source.

func (*Source) Int63

func (s *Source) Int63() int64

Int63 implements math/rand.Source.

func (*Source) Seed

func (s *Source) Seed(seed int64)

Seed implements math/rand.Source.

func (*Source) Uint64

func (s *Source) Uint64() uint64

Uint64 implements math/rand.Source64