celeritas::Selector< F, T > Class Template Reference

On-the-fly selection of a weighted discrete distribution. More...

#include <Selector.hh>

Public Types
Type aliases
using	arg_type = T
using	real_type = typename std::invoke_result< F, arg_type >::type

Public Member Functions
CELER_FUNCTION	Selector (F &&eval, arg_type size, real_type total, SelectorNormalization)
	Construct with function, size, and accumulated value.
template<class Engine >
CELER_FUNCTION T	operator() (Engine &rng) const
	Sample from the distribution.

Detailed Description

template<class F, class T>
class celeritas::Selector< F, T >

On-the-fly selection of a weighted discrete distribution.

This algorithm encapsulates the loop for sampling from distributions of a function f(index) -> real (usually with the function prototype real_type(*)(size_type) ). The index can be an integer, an enumeration, or an OpaqueId . The Selector is constructed with the size of the distribution (but using the indexing type).

Edge cases are thoroughly tested (it will never iterate off the end if normalized, even for incorrect values of the "total" probability/xs), and it uses one fewer register than the typical accumulation algorithm. When building with debug checking and normalization, the constructor asserts that the provided "total" value is consistent.

The given function must return a consistent value for the same given argument.

auto select_el = make_selector(
    [](ElementId i) { return xs[i.get()]; },
    ElementId{num_elements()},
    tot_xs);
ElementId el = select_el(rng);

or

auto select_val = make_selector([](size_type i) { return pdf[i]; },
                                pdf.size());
size_type idx = select_val(rng);

Create a normalized selector from a function and total accumulated value.

See also

celeritas::make_selector , celeritas::make_unnormalized_selector

Template Parameters

F	function type to sample from
T	index type passed to the function

Constructor & Destructor Documentation

Selector()

template<class F , class T >

CELER_FUNCTION celeritas::Selector< F, T >::Selector ( F &&  eval, arg_type  size, real_type  total, SelectorNormalization  norm  )

inline

Construct with function, size, and accumulated value.

The SelectorNormalization argument determines whether to allow an "off the end" value. If unnormalized, the sum of all evaluated arguments can be nontrivially less than the given total.

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

• Selector.hh