Generator of a random cumulative sum of which a chunk is kept in memory. More...

#include <prrng.h>

Public Member Functions
template<class R , typename T = uint64_t, typename S = uint64_t>
	pcg32_cumsum (const R &shape, T initstate=0x853c49e6748fea9bULL, S initseq=0xda3e39cb94b95bdbULL, enum distribution distribution=distribution::custom, const std::vector< double > &parameters=std::vector< double >{}, const alignment &align=alignment())

void	set_functions (std::function< Data(size_t)> get_chunk, std::function< double(size_t)> get_cumsum, bool uses_generator=true)
	Use external functions to draw the random numbers.

	pcg32_cumsum (const pcg32_cumsum &other)
	Copy constructor.

void	operator= (const pcg32_cumsum &other)
	Copy constructor.

bool	is_extendible () const
	`true` if the chunk is extendible.

const pcg32_index &	generator () const
	Pointer to the generator.

const auto &	shape () const
	Shape of the chunk.

auto	size () const
	Size of the chunk.

template<class T >
pcg32_cumsum &	operator+= (const T &value)
	Add value(s) to the chunk.

template<class T >
pcg32_cumsum &	operator-= (const T &value)
	Subtract value(s) from the chunk.

const Data &	data () const
	The current chunk of the cumsum of random numbers.

void	set_data (const Data &data)
	Overwrite the current chunk of the cumsum of random numbers.

ptrdiff_t	start () const
	Global index of the first element in the chunk.

void	set_start (ptrdiff_t index)
	Set global index of the first element in the chunk.

ptrdiff_t	index_at_align () const
	Global index of `target` (the last time prrng::pcg32_cumsum::align() was called).

ptrdiff_t	chunk_index_at_align () const
	Index of `target` relative to the beginning of the chunk (the last time prrng::pcg32_cumsum::align() was called).

double	left_of_align () const
	Return the value of the cumsum left of the `target` (the last time prrng::pcg32_cumsum::align() was called).

double	right_of_align () const
	Return the value of the cumsum right of the `target` (the last time prrng::pcg32_cumsum::align() was called).

uint64_t	state_at (ptrdiff_t index)
	The current "state" of the generator.

void	restore (uint64_t state, double value, ptrdiff_t index)
	Restore a specific state in the cumulative sum.

bool	contains (double target) const
	Check if the chunk contains a target.

void	prev (size_t margin=0)
	Shift chunk left.

void	next (size_t margin=0)
	Shift chunk right.

void	align (double target)
	Align the chunk to encompass a target value.

Detailed Description

template<class Data>
class prrng::pcg32_cumsum< Data >

Generator of a random cumulative sum of which a chunk is kept in memory.

The random number generated by the pcg32 algorithm.

Suppose that cumsum is the unlimited cumulative of random numbers starting from a seed, then a chunk gen.data() == cumsum[gen.start() : gen.start() + gen.size()] is kept in memory by this class. The chunk that is kept in memory can be changed by calling:

prrng::pcg32_cumsum::prev() to get the previous chunk.
prrng::pcg32_cumsum::next() to get the next chunk.
prrng::pcg32_cumsum::align() to align the chunk with a target value.

Note that if the current chunk is far away from the seed a quick way to restore it without drawing all random numbers from the seed is to call prrng::pcg32_cumsum::restore(). Note that you need to know one value and its index.

Template Parameters

Storage of the data.

Definition at line 3504 of file prrng.h.

Constructor & Destructor Documentation

◆ pcg32_cumsum() [1/2]

template<class Data >

template<class R , typename T = uint64_t, typename S = uint64_t>

prrng::pcg32_cumsum< Data >::pcg32_cumsum	(	const R &	shape,
		T	initstate = `0x853c49e6748fea9bULL`,
		S	initseq = `0xda3e39cb94b95bdbULL`,
		enum distribution	distribution = `distribution::custom`,
		const std::vector< double > &	parameters = `std::vector<double>{}`,
		const alignment &	align = `alignment()`
	)

inline

Parameters

shape	Shape of the chunk.
initstate	State initiator.
initseq	Sequence initiator.
distribution	Distribution type, see prrng::distribution().
parameters	Parameters for the distribution. The following is default (and the expected order):

prrng::distribution::random: {scale = 1, offset = 0}
prrng::distribution::delta: {scale = 1, offset = 0}
prrng::distribution::exponential: {scale = 1, offset = 0}
prrng::distribution::power: {k = 1, offset = 0}
prrng::distribution::gamma: {k = 1, scale = 1, offset = 0}
prrng::distribution::pareto: {k = 1, scale = 1, offset = 0}
prrng::distribution::weibull: {k = 1, scale = 1, offset = 0}
prrng::distribution::normal: {mu = 1, sigma = , offset = 0}
prrng::distribution::custom: {}

Warning: if you want to use a custom distribution, you have to call prrng::pcg32_cumsum::set_functions().

Parameters

align Alignment parameters, see prrng::alignment().

Definition at line 3648 of file prrng.h.

◆ pcg32_cumsum() [2/2]

template<class Data >

prrng::pcg32_cumsum< Data >::pcg32_cumsum ( const pcg32_cumsum< Data > & other )

inline

Copy constructor.

This function resets all internal pointers.

Parameters

other Object to copy.

Definition at line 3702 of file prrng.h.

Member Function Documentation

◆ align()

template<class Data >

void prrng::pcg32_cumsum< Data >::align ( double target )

inline

Align the chunk to encompass a target value.

After this call:

prrng::pcg32_cumsum::index_at_align(): global index of target in the cumulative sum.
prrng::pcg32_cumsum::chunk_index_at_align(): local index of target in the currently held chunk, whereby:
- gen.left_of_align() == gen.data()[gen.chunk_index_at_align()] <= target.
- gen.right_of_align() == gen.data()[gen.chunk_index_at_align() + 1] > target.

Parameters

target Target value.

Definition at line 3945 of file prrng.h.

◆ chunk_index_at_align()

template<class Data >

ptrdiff_t prrng::pcg32_cumsum< Data >::chunk_index_at_align ( ) const

inline

Index of target relative to the beginning of the chunk (the last time prrng::pcg32_cumsum::align() was called).

The currently held chunk of the cumsum of random numbers is is gen.data(). As such,

gen.left_of_align() == gen.data()[gen.chunk_index_at_align()] <= target.
gen.right_of_align() == gen.data()[gen.chunk_index_at_align() + 1] > target.

Returns: Local index.

Definition at line 3842 of file prrng.h.

◆ contains()

template<class Data >

bool prrng::pcg32_cumsum< Data >::contains ( double target ) const

inline

Check if the chunk contains a target.

Parameters

target The target.

Returns: true if the chunk contains the target.

Definition at line 3904 of file prrng.h.

◆ data()

template<class Data >

const Data & prrng::pcg32_cumsum< Data >::data ( ) const

inline

The current chunk of the cumsum of random numbers.

Returns: Reference to the chunk.

Definition at line 3777 of file prrng.h.

◆ generator()

template<class Data >

const pcg32_index & prrng::pcg32_cumsum< Data >::generator ( ) const

inline

Pointer to the generator.

Returns: const pcg32&

Definition at line 3728 of file prrng.h.

◆ index_at_align()

template<class Data >

ptrdiff_t prrng::pcg32_cumsum< Data >::index_at_align ( ) const

inline

Global index of target (the last time prrng::pcg32_cumsum::align() was called).

Suppose that cumsum is the unlimited cumsum of random numbers starting from a seed, then:

gen.left_of_align() == cumsum[gen.index_at_align()] <= target.
gen.right_of_align() == cumsum[gen.index_at_align() + 1] > target.

Note thought that cumsum is not constructed by this class, that instead only holds a chunk gen.data() == cumsum[gen.start():gen.start() + gen.size()].

Returns: Global index.

Definition at line 3826 of file prrng.h.

◆ is_extendible()

template<class Data >

bool prrng::pcg32_cumsum< Data >::is_extendible ( ) const

inline

true if the chunk is extendible.

Returns: bool

Definition at line 3719 of file prrng.h.

◆ left_of_align()

template<class Data >

double prrng::pcg32_cumsum< Data >::left_of_align ( ) const

inline

Return the value of the cumsum left of the target (the last time prrng::pcg32_cumsum::align() was called).

gen.left_of_align() == gen.data()[gen.chunk_index_at_align()] <= target.

Returns: double

Definition at line 3854 of file prrng.h.

◆ next()

template<class Data >

void prrng::pcg32_cumsum< Data >::next ( size_t margin = 0 )

inline

Shift chunk right.

Parameters

margin Overlap to keep with the current chunk.

Definition at line 3924 of file prrng.h.

◆ operator+=()

template<class Data >

template<class T >

pcg32_cumsum & prrng::pcg32_cumsum< Data >::operator+= ( const T & value )

inline

Add value(s) to the chunk.

Parameters

value Value(s) to add.

Definition at line 3756 of file prrng.h.

◆ operator-=()

template<class Data >

template<class T >

pcg32_cumsum & prrng::pcg32_cumsum< Data >::operator-= ( const T & value )

inline

Subtract value(s) from the chunk.

Parameters

value Value(s) to subtract.

Definition at line 3767 of file prrng.h.

◆ operator=()

template<class Data >

void prrng::pcg32_cumsum< Data >::operator= ( const pcg32_cumsum< Data > & other )

inline

Copy constructor.

This function resets all internal pointers.

Parameters

other Object to copy.

Definition at line 3710 of file prrng.h.

◆ prev()

template<class Data >

void prrng::pcg32_cumsum< Data >::prev ( size_t margin = 0 )

inline

Shift chunk left.

Parameters

margin Overlap to keep with the current chunk.

Definition at line 3913 of file prrng.h.

◆ restore()

template<class Data >

void prrng::pcg32_cumsum< Data >::restore	(	uint64_t	state,
		double	value,
		ptrdiff_t	index
	)

inline

Restore a specific state in the cumulative sum.

Parameters

state	The state at the beginning of the new chunk.
value	The value of the first entry of the new chunk.
index	The index of the first entry of the new chunk.

Definition at line 3886 of file prrng.h.

◆ right_of_align()

template<class Data >

double prrng::pcg32_cumsum< Data >::right_of_align ( ) const

inline

Return the value of the cumsum right of the target (the last time prrng::pcg32_cumsum::align() was called).

gen.right_of_align() == gen.data()[gen.chunk_index_at_align() + 1] > target.

Returns: double

Definition at line 3866 of file prrng.h.

◆ set_data()

template<class Data >

void prrng::pcg32_cumsum< Data >::set_data ( const Data & data )

inline

Overwrite the current chunk of the cumsum of random numbers.

Please check if set_state() or set_start() should be called too.

Parameters

data	The chunk.

Definition at line 3788 of file prrng.h.

◆ set_functions()

template<class Data >

void prrng::pcg32_cumsum< Data >::set_functions	(	std::function< Data(size_t)>	get_chunk,
		std::function< double(size_t)>	get_cumsum,
		bool	uses_generator = `true`
	)

inline

Use external functions to draw the random numbers.

Parameters

get_chunk	Function to draw the random numbers, called as `get_chunk(n)`.
get_cumsum	Function to get the cumsum of random numbers, called: `get_cumsum(n)`.
uses_generator	Set `true` is the random generator is used by the functions.

Definition at line 3682 of file prrng.h.

◆ set_start()

template<class Data >

void prrng::pcg32_cumsum< Data >::set_start ( ptrdiff_t index )

inline

Set global index of the first element in the chunk.

Parameters

index Global index.

Definition at line 3807 of file prrng.h.

◆ shape()

template<class Data >

const auto & prrng::pcg32_cumsum< Data >::shape ( ) const

inline

Shape of the chunk.

Returns: const auto&

Definition at line 3737 of file prrng.h.

◆ size()

template<class Data >

auto prrng::pcg32_cumsum< Data >::size ( ) const

inline

Size of the chunk.

Returns: auto

Definition at line 3746 of file prrng.h.

◆ start()

template<class Data >

ptrdiff_t prrng::pcg32_cumsum< Data >::start ( ) const

inline

Global index of the first element in the chunk.

Returns: Global index.

Definition at line 3798 of file prrng.h.

◆ state_at()

template<class Data >

uint64_t prrng::pcg32_cumsum< Data >::state_at ( ptrdiff_t index )

inline

The current "state" of the generator.

If the same initseq() is used, this exact point in the sequence can be restored with restore().

Returns: State of the generator.

Template Parameters

R	use a different return-type. There are some internal checks if the type is able to store the internal state of type `uint64_t`.

Definition at line 3874 of file prrng.h.

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

prrng.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ pcg32_cumsum() [1/2]

◆ pcg32_cumsum() [2/2]

Member Function Documentation

◆ align()

◆ chunk_index_at_align()

◆ contains()

◆ data()

◆ generator()

◆ index_at_align()

◆ is_extendible()

◆ left_of_align()

◆ next()

◆ operator+=()

◆ operator-=()

◆ operator=()

◆ prev()

◆ restore()

◆ right_of_align()

◆ set_data()

◆ set_functions()

◆ set_start()

◆ shape()

◆ size()

◆ start()

◆ state_at()