random.h File Reference

(892c46283a5ea4179500d951c9d4866c0051f27b)

MT19937 backended pseudo random number generator. More...

#include "ruby/internal/dllexport.h"
#include "ruby/internal/value.h"

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Functions
unsigned int	rb_genrand_int32 (void)
	Generates a 32 bit random number. More...
double	rb_genrand_real (void)
	Generates a double random number. More...
void	rb_reset_random_seed (void)
	Resets the RNG behind rb_genrand_int32()/rb_genrand_real(). More...
VALUE	rb_random_bytes (VALUE rnd, long n)
	Generates a String of random bytes. More...
unsigned int	rb_random_int32 (VALUE rnd)
	Identical to rb_genrand_int32(), except it generates using the passed RNG. More...
double	rb_random_real (VALUE rnd)
	Identical to rb_genrand_real(), except it generates using the passed RNG. More...
unsigned long	rb_random_ulong_limited (VALUE rnd, unsigned long limit)
	Identical to rb_genrand_ulong_limited(), except it generates using the passed RNG. More...
unsigned long	rb_genrand_ulong_limited (unsigned long i)
	Generates a random number whose upper limit is i. More...

Detailed Description

MT19937 backended pseudo random number generator.

Author

Ruby developers ruby-.nosp@m.core.nosp@m.@ruby.nosp@m.-lan.nosp@m.g.org

Copyright

This file is a part of the programming language Ruby. Permission is hereby granted, to either redistribute and/or modify this file, provided that the conditions mentioned in the file COPYING are met. Consult the file for details.

Warning

Symbols prefixed with either RBIMPL or rbimpl are implementation details. Don't take them as canon. They could rapidly appear then vanish. The name (path) of this header file is also an implementation detail. Do not expect it to persist at the place it is now. Developers are free to move it anywhere anytime at will.

Note

To ruby-core: remember that this header can be possibly recursively included from extension libraries written in C++. Do not expect for instance __VA_ARGS__ is always available. We assume C99 for ruby itself but we don't assume languages of extension libraries. They could be written in C++98.

See also

Matsumoto, M., Nishimura, T., "Mersenne Twister: A 623- dimensionally equidistributed uniform pseudorandom number generator", ACM Trans. on Modeling and Computer Simulation, 8 (1): pp 3-30, 1998. https://doi.org/10.1145/272991.272995

Definition in file random.h.

Function Documentation

rb_genrand_int32()

unsigned int rb_genrand_int32

(

void

)

Generates a 32 bit random number.

Returns

A random number.

Note

Now that we have ractors, the RNG behind this function is per-ractor.

Definition at line 199 of file random.c.

rb_genrand_real()

double rb_genrand_real

(

void

)

Generates a double random number.

Returns

A random number.

Note

This function shares the RNG with rb_genrand_int32().

Definition at line 206 of file random.c.

rb_genrand_ulong_limited()

unsigned long rb_genrand_ulong_limited

(

unsigned long

i

)

Generates a random number whose upper limit is i.

Parameters

[in]

i

Max possible return value.

Returns

A random number, uniformly distributed in [0, limit] interval.

Note

Note it can return i.

Definition at line 1076 of file random.c.

rb_random_bytes()

VALUE rb_random_bytes	(	VALUE	rnd,
		long	n
	)

Generates a String of random bytes.

Parameters

[in,out]	rnd	An instance of rb_cRandom.
[in]	n	Requested number of bytes.

Returns

An instance of rb_cString, of binary, of n bytes length, whose contents are random bits.

Definition at line 1306 of file random.c.

rb_random_int32()

unsigned int rb_random_int32

(

VALUE

rnd

)

Identical to rb_genrand_int32(), except it generates using the passed RNG.

Parameters

[in,out]

rnd

An instance of rb_cRandom.

Returns

A random number.

Definition at line 1105 of file random.c.

rb_random_real()

double rb_random_real

(

VALUE

rnd

)

Identical to rb_genrand_real(), except it generates using the passed RNG.

Parameters

[in,out]

rnd

An instance of rb_cRandom.

Returns

A random number.

Definition at line 1148 of file random.c.

rb_random_ulong_limited()

unsigned long rb_random_ulong_limited	(	VALUE	rnd,
		unsigned long	limit
	)

Identical to rb_genrand_ulong_limited(), except it generates using the passed RNG.

Parameters

[in,out]	rnd	An instance of rb_cRandom.
[in]	limit	Max possible return value.

Returns

A random number, distributed in [0, limit] interval.

Note

Note it can return limit.

Whether the return value distributes uniformly in the interval or not depends on how the argument RNG behaves; at least in case of MT19937 it does.

Definition at line 1208 of file random.c.

rb_reset_random_seed()

void rb_reset_random_seed

(

void

)

Resets the RNG behind rb_genrand_int32()/rb_genrand_real().

Postcondition

The (now per-ractor) default RNG's internal state is cleared.

Definition at line 1787 of file random.c.