dasmig::core::discrete Class Reference

Index chosen with probability proportional to a weight. More...

#include <distributions.hpp>

Public Member Functions
	discrete (std::span< const double > weights)
	Build from weights.
	discrete (std::initializer_list< double > weights)
	Build from a list of weights.
std::size_t	operator() (rng &r) const
	Draw an index.
std::size_t	size () const noexcept
	Number of weights.
double	total () const noexcept
	Sum of the weights.
double	probability (std::size_t i) const
	Probability of an index.

Detailed Description

Index chosen with probability proportional to a weight.

Keeps the cumulative sums of the weights (added left to right). A draw is the first index whose cumulative sum exceeds uniform01(r) * total, so a zero weight is never chosen. Consumes one value.

dasmig::core::discrete eye_colour{{0.7, 0.2, 0.1}};
std::size_t i = eye_colour(r);

Definition at line 256 of file distributions.hpp.

Constructor & Destructor Documentation

discrete() [1/2]

dasmig::core::discrete::discrete ( std::span< const double >  weights )

inlineexplicit

Build from weights.

Parameters

weights

Non-negative, finite weights, at least one positive.

Exceptions

std::invalid_argument

If the weights are empty, a weight is negative or not finite, or they sum to 0 or overflow.

Definition at line 263 of file distributions.hpp.

discrete() [2/2]

dasmig::core::discrete::discrete ( std::initializer_list< double >  weights )

inline

Build from a list of weights.

Parameters

weights

Non-negative, finite weights, at least one positive.

Exceptions

std::invalid_argument

As the span constructor.

Definition at line 293 of file distributions.hpp.

Member Function Documentation

operator()()

std::size_t dasmig::core::discrete::operator() ( rng &  r ) const

inline

Draw an index.

Parameters

r

Engine.

Returns

An index in [0, size()) with a positive weight.

Definition at line 301 of file distributions.hpp.

probability()

double dasmig::core::discrete::probability ( std::size_t  i ) const

inline

Probability of an index.

Parameters

i

Index.

Returns

weight(i) / total().

Exceptions

std::out_of_range

If i >= size().

Definition at line 318 of file distributions.hpp.

size()

std::size_t dasmig::core::discrete::size ( ) const

inlinenoexcept

Number of weights.

Returns

The number of indices.

Definition at line 308 of file distributions.hpp.

total()

double dasmig::core::discrete::total ( ) const

inlinenoexcept

Sum of the weights.

Returns

The total weight.

Definition at line 312 of file distributions.hpp.

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

• dasmig/core/distributions.hpp