cdt::Random Class Reference

A run-owned PCG engine with a recorded seed and stream identifier. More...

#include <Random.hpp>

Collaboration diagram for cdt::Random:

Public Types
using	result_type = pcg64::result_type
	Unsigned result type required by std::uniform_random_bit_generator.

Public Member Functions
	Random ()
	Construct a root stream from operating-system entropy.
	Random (RandomSeed const seed, RandomStream const stream=RandomStream{})
	Construct a reproducible PCG stream without consulting entropy.
	Random (std::uint64_t const seed)
	Construct a root stream from a raw seed value.
auto	operator() () -> result_type
auto	seed () const noexcept -> RandomSeed
auto	serialized_state () const -> std::string
	Serialize the complete mutable PCG state for exact continuation.
auto	split (RandomStream const stream) const -> Random
	Create a fresh reproducible stream from the same root seed.
auto	stream () const noexcept -> RandomStream

Static Public Member Functions
static auto	from_serialized_state (RandomSeed const seed, RandomStream const stream, std::string_view const state) -> Random
	Restore an exact PCG continuation point.
static constexpr auto	max () noexcept -> result_type
static constexpr auto	min () noexcept -> result_type

Detailed Description

A run-owned PCG engine with a recorded seed and stream identifier.

Construct one root engine per simulation. Pass engines by reference to distributions and stochastic algorithms instead of drawing fresh entropy for each sample. split() creates a reproducible, independently parameterized PCG stream for a subsystem or worker.

Random is intentionally not internally synchronized. A mutable instance belongs to one run or one thread. Parallel code must give each worker a distinct stream before drawing from it.

See also

PCG random-number generators

Definition at line 136 of file Random.hpp.

Member Typedef Documentation

result_type

using cdt::Random::result_type = pcg64::result_type

Unsigned result type required by std::uniform_random_bit_generator.

Definition at line 140 of file Random.hpp.

Constructor & Destructor Documentation

Random() [1/3]

cdt::Random::Random ( )

inline

Construct a root stream from operating-system entropy.

Definition at line 158 of file Random.hpp.

References Random().

Referenced by Random(), Random(), from_serialized_state(), and split().

Random() [2/3]

cdt::Random::Random ( std::uint64_t const seed )

inlineexplicit

Construct a root stream from a raw seed value.

Parameters

seed	Root seed recorded for the run.

Definition at line 162 of file Random.hpp.

References Random(), and seed().

Random() [3/3]

cdt::Random::Random ( RandomSeed const seed, RandomStream const stream = RandomStream{} )

inlineexplicit

Construct a reproducible PCG stream without consulting entropy.

Parameters

seed	Root seed recorded for the run.
stream	PCG stream selector; distinct values select distinct sequences for the same root seed.

Definition at line 168 of file Random.hpp.

References seed(), and stream().

Member Function Documentation

from_serialized_state()

auto cdt::Random::from_serialized_state ( RandomSeed const seed, RandomStream const stream, std::string_view const state ) -> Random

inlinestaticnodiscard

Restore an exact PCG continuation point.

Parameters

seed	Recorded root seed.
stream	Recorded stream selector.
state	Complete state produced by serialized_state().

Returns

A generator whose next draw is the saved generator's next draw.

Exceptions

std::invalid_argument

if the state is malformed, contains trailing data, or selects a different PCG stream.

Definition at line 218 of file Random.hpp.

References Random(), seed(), and stream().

Referenced by main().

max()

constexpr auto cdt::Random::max ( ) -> result_type

inlinestaticnodiscardconstexprnoexcept

Returns

The maximum value the engine can generate.

Definition at line 178 of file Random.hpp.

min()

constexpr auto cdt::Random::min ( ) -> result_type

inlinestaticnodiscardconstexprnoexcept

Returns

The minimum value the engine can generate.

Definition at line 174 of file Random.hpp.

operator()()

auto cdt::Random::operator() ( ) -> result_type

inlinenodiscard

Returns

The next value from this engine, advancing its state.

Definition at line 182 of file Random.hpp.

seed()

auto cdt::Random::seed ( ) const -> RandomSeed

inlinenodiscardnoexcept

Returns

The effective root seed for replaying this run.

Definition at line 185 of file Random.hpp.

Referenced by Random(), Random(), and from_serialized_state().

serialized_state()

auto cdt::Random::serialized_state ( ) const -> std::string

inlinenodiscard

Serialize the complete mutable PCG state for exact continuation.

Returns

Locale-independent PCG engine state.

Definition at line 199 of file Random.hpp.

split()

auto cdt::Random::split ( RandomStream const stream ) const -> Random

inlinenodiscard

Create a fresh reproducible stream from the same root seed.

Parameters

stream

PCG sequence selector for the new engine.

Returns

A new engine at the beginning of the selected sequence.

Definition at line 194 of file Random.hpp.

References Random(), and stream().

stream()

auto cdt::Random::stream ( ) const -> RandomStream

inlinenodiscardnoexcept

Returns

The PCG stream selector used by this engine.

Definition at line 188 of file Random.hpp.

Referenced by Random(), from_serialized_state(), and split().

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

• include/Random.hpp