Concept definition

template<typename T>
concept stencil::concepts::TransitionFunction = 
    std::semiregular<typename T::Cell> && std::copyable<typename T::TimeDependentValue> &&
 
    std::same_as<decltype(T::stencil_radius), const uindex_t> && (T::stencil_radius >= 1) &&
    std::same_as<decltype(T::n_subiterations), const uindex_t> && (T::n_subiterations >= 1) &&
 
    requires(T const &trans_func,
             Stencil<typename T::Cell, T::stencil_radius, typename T::TimeDependentValue> const
                 &stencil) {
        { trans_func(stencil) } -> std::same_as<typename T::Cell>;
    } &&
    requires(T const &trans_func, uindex_t i_iteration) {
        {
            trans_func.get_time_dependent_value(i_iteration)
        } -> std::same_as<typename T::TimeDependentValue>;
    }

Detailed Description

A technical definition of a stencil transition function.

This concept lists all required type definitions, constants, and methods that a StencilUpdate needs from a transition function. This includes multiple definitions for advanced features. Most users are adviced to extend the stencil::BaseTransitionFunction class. It provides default definitions that disable those features.

The required type definitions are:

Cell: The cell type the transition function operates on. It must be semiregular, i.e. copyable bit by bit.
TimeDependentValue: The type of the time-dependent value computed by the get_time_dependent_value method. It must also be semiregular.

The required constants are:

uindex_t stencil_radius: The radius of the stencil. It must be greater than or equal to 1.
uindex_t n_subiterations: The number of sub-iterations of the transition function. It must be greater than or equal to 1.

The required methods are:

Cell operator()(Stencil<Cell, stencil_radius> const&stencil) const: Compute the next iteration of the stencil's central cell. This method must be pure, i.e. it must not modify either the stencil's or the transition function's state.
TimeDependentValue get_time_dependent_value(uindex_t i_iteration) const: Compute the time-dependent value for the given iteration. This method must be pure, i.e. it must not modify the transition function's state.