random.h File Reference

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Namespaces
namespace	vita
	The main namespace for the project.

Typedefs
using	vita::random::engine_t = vigna::xoshiro256ss
	xoshiro256** (XOR/shift/rotate) is an all-purpose, rock-solid generator (not a cryptographically secure generator). More...

Enumerations
enum class	distribution { uniform , normal }

Functions
template<class T >
std::enable_if_t< std::is_floating_point_v< T >, T >	vita::random::between (T min, T sup)
	A specialization for floating point values of the random::between(T, T) template function. More...
template<class T >
std::enable_if_t< std::is_integral_v< T >, T >	vita::random::between (T min, T sup)
	Picks up a random integer value uniformly distributed in the set of integers {min, min+1, ..., sup-1}. More...
template<class T >
std::enable_if_t< std::is_enum_v< T >, T >	vita::random::between (T min, T sup)
bool	vita::random::boolean (double=0.5)
template<class C >
C::value_type &	vita::random::element (C &c)
template<class C >
const C::value_type &	vita::random::element (const C &c)
template<class T >
T	vita::random::ephemeral (distribution d, T p1, T p2)
	Used for ephemeral random constant generation. More...
template<class T >
T	vita::random::in (range_t< T > r)
	Uniformly extracts a random value in a range. More...
void	vita::random::randomize ()
	Sets the shared engine to an unpredictable state. More...
unsigned	vita::random::ring (unsigned base, unsigned width, unsigned n)
	Returns a random number in a modular arithmetic system. More...
void	vita::random::seed (unsigned s)
	Initalizes the random number generator. More...
template<class T >
T	vita::random::sup (T)

Detailed Description

Remarks

This file is part of VITA.

Copyright

Copyright (C) 2011-2024 EOS di Manlio Morini.

License\n

This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/

Definition in file random.h.

Typedef Documentation

engine_t

using vita::random::engine_t = typedef vigna::xoshiro256ss

xoshiro256** (XOR/shift/rotate) is an all-purpose, rock-solid generator (not a cryptographically secure generator).

It has excellent (sub-ns) speed, a state space (256 bits) that is large enough for any parallel application, and it passes all tests we are aware of.

Definition at line 34 of file random.h.

Enumeration Type Documentation

distribution

enum class vita::random::distribution

strong

Definition at line 26 of file random.h.

Function Documentation

between() [1/3]

template<class T >

std::enable_if_t< std::is_floating_point_v< T >, T > vita::random::between	(	T	min,
		T	sup
	)

A specialization for floating point values of the random::between(T, T) template function.

Parameters

[in]	min	minimum random number
[in]	sup	upper bound

Returns

a random double in the [min;sup[ range

See also

For further details:

• https://stackoverflow.com/q/24566574/3235496
• https://stackoverflow.com/q/25222167/3235496

Definition at line 85 of file random.h.

between() [2/3]

template<class T >

std::enable_if_t< std::is_integral_v< T >, T > vita::random::between	(	T	min,
		T	sup
	)

Picks up a random integer value uniformly distributed in the set of integers {min, min+1, ..., sup-1}.

Parameters

[in]	min	minimum random number
[in]	sup	upper bound

Returns

a random number in the [min;sup[ range

Note

Contrary to boost usage this function does not take a closed range. Instead it takes a half-open range (C++ usage and same behaviour of the real number distribution).

Definition at line 108 of file random.h.

between() [3/3]

template<class T >

std::enable_if_t< std::is_enum_v< T >, T > vita::random::between	(	T	min,
		T	sup
	)

Definition at line 118 of file random.h.

boolean()

bool vita::random::boolean ( double  p )

inline

Parameters

[in]

p

a probability ([0;1] range)

Returns

true p% times

Note

bool values are produced according to the Bernoulli distribution.

Definition at line 183 of file random.h.

element() [1/2]

template<class C >

C::value_type & vita::random::element

(

C &

c

)

Parameters

[in]

c

a STL container

Returns

a random element of container c

Definition at line 168 of file random.h.

element() [2/2]

template<class C >

const C::value_type & vita::random::element

(

const C &

c

)

Parameters

[in]

c

a STL container

Returns

a random element of container c

Examples

example4.cc, and titanic04.cc.

Definition at line 154 of file random.h.

ephemeral()

template<class T >

T vita::random::ephemeral	(	distribution	d,
		T	p1,
		T	p2
	)

Used for ephemeral random constant generation.

Parameters

[in]	d	type of distribution
[in]	p1	minimum for uniform distribution; mean for normal distribution
[in]	p2	maximum for uniform distribution, standard deviation for normal distribution

Returns

a random number distributed according to distribution d

Definition at line 58 of file random.h.

in()

template<class T >

T vita::random::in

(

range_t< T >

r

)

Uniformly extracts a random value in a range.

Parameters

[in]

r

a half-open range

Returns

a random value in range r

Definition at line 132 of file random.h.

randomize()

void vita::random::randomize

(

)

Sets the shared engine to an unpredictable state.

Definition at line 50 of file random.cc.

ring()

unsigned vita::random::ring	(	unsigned	base,
		unsigned	width,
		unsigned	n
	)

Returns a random number in a modular arithmetic system.

Parameters

[in]	base	a base number
[in]	width	maximum distance from the base number
[in]	n	modulus

Returns

a random number in the [base - width/2, base + width/2] mod n interval

Definition at line 65 of file random.cc.

seed()

void vita::random::seed

(

unsigned

s

)

Initalizes the random number generator.

Parameters

[in]

s

the seed for the random number generator

The seed is used to initalize the random number generator. With the same seed the numbers produced will be the same every time the program is run.

Note

A common method to seed a PRNG is using the current time (std::time(0)). It works... but the preferred way in Vita is the randomize method (which is based on std::random_device).

Definition at line 42 of file random.cc.

sup()

template<class T >

T vita::random::sup

(

T

sup

)

Parameters

[in]

sup

upper bound

Returns

a random number in the [0;sup[ range

Note

This is a shortcut for: between<T>(0, sup)

Definition at line 144 of file random.h.