random.h File Reference

Random number generator. More...

#include "host.h"

Data Structures
struct	VlRand
	Random numbber generator state. More...
Functions
Setting and reading the state
void	vl_rand_init (VlRand *self)
	Initialise random number generator.
void	vl_rand_seed (VlRand *self, vl_uint32 s)
	Seed the state of the random number generator.
void	vl_rand_seed_by_array (VlRand *self, vl_uint32 const key[], vl_size keySize)
	Seed the state of the random number generator by an array.
Generate random numbers
vl_uint64	vl_rand_uint64 (VlRand *self)
	Generate a random UINT64.
vl_int64	vl_rand_int63 (VlRand *self)
	Generate a random INT63.
vl_uint32	vl_rand_uint32 (VlRand *self)
	Generate a random UINT32.
vl_int32	vl_rand_int31 (VlRand *self)
	Generate a random INT31.
double	vl_rand_real1 (VlRand *self)
	Generate a random number in [0,1].
double	vl_rand_real2 (VlRand *self)
	Generate a random number in [0,1)
double	vl_rand_real3 (VlRand *self)
	Generate a random number in (0,1)
double	vl_rand_res53 (VlRand *self)
	Generate a random number in [0,1) with 53-bit resolution.
vl_uindex	vl_rand_uindex (VlRand *self, vl_uindex range)
	Generate a random index in a given range.

---

Detailed Description

This module implements the popular Mersenne Twister algorithm (MATLAB random generator from version 7.4).

Overview

A random number generator can be initalized by

 VlRand rand ;
 vl_rand_init (&rand) ;

VlRand is a simple structure holding the state of the random number generator. The generator can be seeded by vl_rand_seed and vl_rand_seed_by_array. For intsance:

 vl_rand_seed (&rand, clock()) ;

The generator can be used to obtain random quantities of various types:

• vl_rand_int31, vl_rand_uint32 for 32-bit random integers;
• vl_rand_real1 for a double in [0,1];
• vl_rand_real2 for a double in [0,1);
• vl_rand_real3 for a double in (0,1);
• vl_rand_res53 for a double in [0,1) with high resolution.

There is no need to explicitly destroy a VlRand instance.

[1] http://en.wikipedia.org/wiki/Mersenne_twister

Author:

Andrea Vedaldi

---

Function Documentation

void vl_rand_init

(

VlRand *

self

)

Parameters:

self	number generator.

vl_int32 vl_rand_int31

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number in [0, 0x7fffffff].

vl_int64 vl_rand_int63

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number in [0, 0x7fffffffffffffff].

double vl_rand_real1

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number.

double vl_rand_real2

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number.

double vl_rand_real3

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number.

double vl_rand_res53

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number.

void vl_rand_seed	(	VlRand *	self,
		vl_uint32	s
	)

Parameters:

self	random number generator.
s	seed.

void vl_rand_seed_by_array	(	VlRand *	self,
		vl_uint32 const	key[],
		vl_size	keySize
	)

Parameters:

self	random number generator.
key	array of numbers.
keySize	length of the array.

vl_uindex vl_rand_uindex	(	VlRand *	self,
		vl_uindex	range
	)		[inline]

Parameters:

self	random number generator.
range	range.

Returns:

an index sampled uniformly at random in the interval [0, range - 1]

Remarks:

Currently, this function uses a simple algorithm that may yield slightly biased samples if range is not a power of two.

vl_uint32 vl_rand_uint32

(

VlRand *

self

)

Parameters:

self	random number generator.

Returns:

a random number in [0, 0xffffffff].

vl_uint64 vl_rand_uint64

(

VlRand *

self

)

[inline]

Parameters:

self	random number generator.

Returns:

a random number in [0, 0xffffffffffffffff].