tpl_ca_neighborhood.H File Reference

Neighborhoods catalogue for Aleph::CA. More...

#include <array>
#include <cstddef>
#include <span>
#include <utility>
#include <ah-errors.H>
#include <ca-traits.H>
#include <tpl_ca_concepts.H>

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Classes
class	Aleph::CA::Moore< N, R >
	Moore (Chebyshev) neighborhood of radius R in N dimensions. More...
class	Aleph::CA::Von_Neumann< N, R >
	Von Neumann (L1) neighborhood of radius R in N dimensions. More...
class	Aleph::CA::Hex_Neighborhood
	Six-neighbour hex pattern in axial coordinates over a 2D lattice. More...
class	Aleph::CA::Triangular_Neighborhood
	Three edge-neighbours over a 2D lattice with parity coupling. More...
class	Aleph::CA::Custom_Neighborhood< N, K, Radius >
	User-supplied list of offsets for arbitrary connectivity. More...

Namespaces
namespace	Aleph
	Main namespace for Aleph-w library functions.
namespace	Aleph::CA
namespace	Aleph::CA::ca_neighborhood_detail

Functions
constexpr std::size_t	Aleph::CA::ca_neighborhood_detail::static_pow (std::size_t base, std::size_t exp) noexcept
	Compile-time integer power.
template<std::size_t N, std::size_t R>
constexpr std::size_t	Aleph::CA::ca_neighborhood_detail::von_neumann_count () noexcept
	Number of integer points in the L1 ball of radius R in N dimensions, excluding the origin.
template<std::size_t N, std::size_t R>
constexpr auto	Aleph::CA::ca_neighborhood_detail::compute_moore_offsets () noexcept
	Generate the canonical-ordered list of Moore offsets for N/R.
template<std::size_t N, std::size_t R>
constexpr auto	Aleph::CA::ca_neighborhood_detail::compute_von_neumann_offsets () noexcept
	Generate the canonical-ordered list of Von Neumann offsets for N/R (L1 radius).
template<typename Nbh , typename L , typename T >
void	Aleph::CA::gather_neighbors (const Nbh &nh, const L &lat, const typename L::coord_type &center, std::span< T > out)
	Populate out[0..nh.size()) with neighbour values of center.

Detailed Description

Neighborhoods catalogue for Aleph::CA.

Provides:

• Moore<N, R> — Chebyshev-radius neighborhood ((2R+1)^N - 1).
• Von_Neumann<N, R> — L1-radius neighborhood.
• Hex_Neighborhood — 6 axial-coord neighbours over a 2D lattice.
• Triangular_Neighborhood— 3 edge neighbours, parity-dependent.
• Custom_Neighborhood<N, K, Radius> — explicit list of offsets supplied at runtime.

Every neighborhood satisfies the NeighborhoodLike concept and publishes a uniform compile-time API:

static constexpr std::size_t rank_v;     // lattice dim
static constexpr std::size_t size_v;     // neighbour count
static constexpr std::size_t radius_v;   // Chebyshev radius
std::size_t radius() const;
std::size_t size()   const;
template <typename F>
void for_each_offset(const Coord_Vec<rank_v> & center, F && f) const;

Plus a free function template:

template <class Nbh, class L, class T>
void gather_neighbors(const Nbh & nh, const L & lat,
                      const typename L::coord_type & center,
                      std::span<T> out);

which fills the caller-supplied stack buffer with the values returned by lat.at_safe(center + offset) in canonical order. No heap.

Author

Leandro Rabindranath Leon

Definition in file tpl_ca_neighborhood.H.