Xfce Foundation Classes

Xfc::G::Rand Class Reference

A GRand C++ wrapper interface. More...

#include <xfc/glib/rand.hh>

Inheritance diagram for Xfc::G::Rand:

List of all members.

Public Member Functions

Constructors

Rand ()
Constructs a new random number generator initialized with a seed taken either from /dev/urandom (if existing) or from the current time (as a fallback).
Rand (unsigned int seed)
Constructs a new random number generator initialized with seed.
Rand (const std::vector< unsigned int > &seed)
Constructs a new random number generator initialized with seed.
Rand (const Rand &src)
Copy constructor.
~Rand ()
Destructor.
Rand & operator= (const Rand &src)
Assignment operator.

Accessors

GRand * g_rand () const
Get a pointer to the GRand object.
operator GRand * () const
Conversion operator; Safely converts a G::Rand object into a GRand pointer.
bool get_bool () const
Gets a random boolean value (this corresponds to a unbiased coin toss).
unsigned int get_int () const
Gets the next random unsigned integer from the rand equally distributed over the range [0..2^32-1].
int get_int_range (int begin, int end) const
Gets the next random integer from the rand equally distributed over the range [begin..end-1].
double get_double () const
Gets the next random double from the rand equally distributed over the range [0..1).
double get_double_range (double begin, double end) const
Gets the next random double from the rand equally distributed over the range [begin..end).

Methods

void set_seed (unsigned int seed)
Sets the seed for the random number generator to seed.
void set_seed (const std::vector< unsigned int > &seed)
Initializes the random number generator with a vector of unsigned int.

Detailed Description

A GRand C++ wrapper interface.

Rand is a portable, fast and good pseudo-random number generator (PRNG). It uses the Mersenne Twister PRNG, which was originally developed by Makoto Matsumoto and Takuji Nishimura. Further information can be found at http://www.math.keio.ac.jp/~matumoto/emt.html.

If you just need a random number, you can simply call the G::random* methods, which will create a globally used Rand object and use its methods internally. Whenever you need a stream of reproducible random numbers, you should create a Rand object yourself and call its methods directly, which will also be slightly faster. Initializing a Rand with a certain seed will produce exactly the same series of random numbers on all platforms. This can thus be used as a seed for games.

The Rand range methods will return high quality equally distributed random numbers, whereas for example the (G::Random::get_int()%max) approach often doesn't yield equally distributed numbers.

GLib changed the seeding algorithm for the pseudo-random number generator Mersenne Twister, as used by GRand and GRandom. This was necessary, because some seeds would yield very bad pseudo-random streams. Also the pseudo-random integers generated by Rand range methods will have a slightly better equal distribution with the new version of GLib.

The original seeding and generation algorithms, as found in GLib 2.0.x, can be used instead of the new ones by setting the environment variable G_RANDOM_VERSION to the value of '2.0'. Use the GLib-2.0 algorithms only if you have sequences of numbers generated with Glib-2.0 that you need to reproduce exactly.

Constructor & Destructor Documentation

Xfc::G::Rand::Rand ( unsigned int seed )

Constructs a new random number generator initialized with seed.

Parameters:

seed A value to initialize the random number generator.

Xfc::G::Rand::Rand ( const std::vector< unsigned int > & seed )

Constructs a new random number generator initialized with seed.

Parameters:

seed A vector of seeds to initialize the random number generator.

Xfc::G::Rand::Rand ( const Rand & src )

Copy constructor.

Parameters:

src The source random number generator.

Member Function Documentation

bool Xfc::G::Rand::get_bool ( ) const

Gets a random boolean value (this corresponds to a unbiased coin toss).

Returns:
A random bool value.

double Xfc::G::Rand::get_double ( ) const

Gets the next random double from the rand equally distributed over the range [0..1).

Returns:
A random number.

double Xfc::G::Rand::get_double_range ( double begin,

double end

) const

Gets the next random double from the rand equally distributed over the range [begin..end).

Parameters:

begin The lower closed bound of the interval.

end The upper open bound of the interval.

Returns:
A random number.

unsigned int Xfc::G::Rand::get_int ( ) const

Gets the next random unsigned integer from the rand equally distributed over the range [0..2^32-1].

Returns:
A random number.

int Xfc::G::Rand::get_int_range ( int begin,

int end

) const

Gets the next random integer from the rand equally distributed over the range [begin..end-1].

Parameters:

begin The lower closed bound of the interval.

end The upper open bound of the interval.

Returns:
A random number.

Rand& Xfc::G::Rand::operator= ( const Rand & src )

Assignment operator.

Parameters:

src The source random number generator.

void Xfc::G::Rand::set_seed ( const std::vector< unsigned int > & seed )

Initializes the random number generator with a vector of unsigned int.

Parameters:

seed The vector to initialize random number generator with.

The vector can be of arbitrary size, though only the first 624 values are taken. This function is useful if you have many low entropy seeds, or if you require more then 32bits of actual entropy for your application.

void Xfc::G::Rand::set_seed ( unsigned int seed )

Sets the seed for the random number generator to seed.

Parameters:

seed A value to reinitialize the random number generator.

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

rand.hh

Xfce Foundation Classes

XFC 4.3