FEAT::Random Class Reference

Pseudo-Random Number Generator. More...

#include <random.hpp>

Public Types
typedef std::uint64_t	SeedType
	seed type More...

Public Member Functions
	Random ()
	Default constructor that seeds the RNG with the current high-resolution clock time. More...
	Random (SeedType seed)
	Constructor. More...
SeedType	get_seed () const
uint64_t	next ()
	Returns the next number in the stream. More...
template<typename T_ >
T_	operator() (T_ a, T_ b)
	Ranged evaluation operator. More...
template<typename T_ >
Random &	operator>> (T_ &x)
	Extraction operator. More...

Static Public Attributes
static constexpr SeedType	xor_mult = SeedType(2685821657736338717ull)
	internal multiplier More...

Private Attributes
std::uint64_t	_seed
	the rng's original seed More...
std::uint64_t	_x
	the rng's working values More...

Detailed Description

Pseudo-Random Number Generator.

This class implements a 64-bit XOR-Shift* pseudo-random number generator with a 64-bit cycle.

The intention of this class is to provide a pseudo-random number generator which generates (warning: paradox ahead) a reproducible random number stream independent of the platform and the compiler in use.

Warning

This class is (intentionally) not thread-safe – in a multi-threaded application each thread should use its own random number generator.

See also

S. Vigna: An experimental exploration of Marsaglia's xorshift generators, scrambled; Cornell University Library, arXiv:1402.6246
http://arxiv.org/abs/1402.6246

G. Marsaglia: Xorshift RNGs; Journal of Statistical Software, Vol. 8 (Issue 14), 2003
http://www.jstatsoft.org/v08/i14

http://en.wikipedia.org/wiki/Xorshift

Note

The implementation in this class corresponds to the xorshift64* example in Figure 10 of the first article by Vigna mentioned above.

Author

Peter Zajac

Definition at line 53 of file random.hpp.

Member Typedef Documentation

SeedType

typedef std::uint64_t FEAT::Random::SeedType

seed type

Definition at line 57 of file random.hpp.

Constructor & Destructor Documentation

Random() [1/2]

FEAT::Random::Random ( )

inlineexplicit

Default constructor that seeds the RNG with the current high-resolution clock time.

Definition at line 72 of file random.hpp.

References _seed, and _x.

Random() [2/2]

FEAT::Random::Random ( SeedType  seed )

inlineexplicit

Constructor.

Parameters

[in]

seed

The seed for the random number generator; must not be 0.

Definition at line 87 of file random.hpp.

References XASSERTM.

Member Function Documentation

get_seed()

SeedType FEAT::Random::get_seed ( ) const

inline

Returns

The original seed that was used to create this RNG object.

Definition at line 95 of file random.hpp.

References _seed.

next()

uint64_t FEAT::Random::next ( )

inline

Returns the next number in the stream.

This function returns the next unsigned 32-bit integer in the random number stream and advances the stream.

Definition at line 106 of file random.hpp.

References _x, and xor_mult.

operator()()

template<typename T_ >

T_ FEAT::Random::operator() ( T_  a, T_  b  )

inline

Ranged evaluation operator.

This operator returns a random number in the range passed to this operator.

Template Parameters

T_	The type of the value to be extracted. Is determined automatically by a and b.

Parameters

[in]

a,b

The minimum and maximum values for the range of the random number to be generated.

Note

If b < a, then a and b are swapped.

If a = b, then the returned value will be equal to a, however, the generator will still advance its position within the random number stream.

Returns

A random value in the range [a, b].

Definition at line 157 of file random.hpp.

operator>>()

template<typename T_ >

Random & FEAT::Random::operator>> ( T_ &  x )

inline

Extraction operator.

This function extracts the next random number in the stream.

• If the type of the value to be extracted is integral, then the value will be within the full range, i.e.
  • for a signed n-bit integer, it will hold -2^(n-1) <= x < 2^(n-1)
  • for an unsigned n-bit integer, it will hold that 0 <= x < 2^n
• If the type of the value to be extracted is a floating point type, then the value will be within the closed interval [0,1].

Template Parameters

T_	The type of the value to be extracted. Must be either of integral or floating point type.

Parameters

[out]

x

The transient reference to an object receiving the extracted value.

Returns

*this

Definition at line 133 of file random.hpp.

Member Data Documentation

_seed

std::uint64_t FEAT::Random::_seed

private

the rng's original seed

Definition at line 64 of file random.hpp.

Referenced by Random(), and get_seed().

_x

std::uint64_t FEAT::Random::_x

private

the rng's working values

Definition at line 66 of file random.hpp.

Referenced by Random(), and next().

xor_mult

constexpr SeedType FEAT::Random::xor_mult = SeedType(2685821657736338717ull)

staticconstexpr

internal multiplier

Definition at line 60 of file random.hpp.

Referenced by next().

---

The documentation for this class was generated from the following file:

• kernel/util/random.hpp