tpl_ca_lattice.H

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
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  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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*/
 
#ifndef TPL_CA_LATTICE_H
#define TPL_CA_LATTICE_H
 
#include <cstddef>
#include <limits>
#include <type_traits>
#include <utility>
 
#include <ah-errors.H>
 
#include <ca-traits.H>
#include <tpl_ca_concepts.H>
 
namespace Aleph {
namespace CA {
 
namespace ca_lattice_detail {
 
inline ca_size_t magnitude(const ca_index_t c) noexcept
{
  if (c >= 0)
    return static_cast<ca_size_t>(c);
  return static_cast<ca_size_t>(-(c + 1)) + 1;
}
 
inline ca_size_t wrap_into_range(ca_index_t c, const ca_size_t n) noexcept
{
  if (n == 0)
    return 0;
 
  const ca_size_t mag = magnitude(c);
  if (c >= 0)
    return mag % n;
 
  const ca_size_t r = mag % n;
  return r == 0 ? 0 : n - r;
}
 
inline ca_size_t reflect_into_range(const ca_index_t c, const ca_size_t n) noexcept
{
  if (n <= 1)
    return 0;
 
  const ca_size_t mag = magnitude(c);
  if (n > (std::numeric_limits<ca_size_t>::max() >> 1))
    return c >= 0 ? mag : mag - 1;
 
  const ca_size_t period = 2 * n;
  ca_size_t r = 0;
  if (c >= 0)
    r = mag % period;
  else
    {
      const ca_size_t mod = mag % period;
      r = mod == 0 ? 0 : period - mod;
    }
 
  if (r >= n)
    r = period - 1 - r;
  return r;
}
 
template <typename B>
struct is_constant_boundary : std::false_type
{
};
 
template <typename T, T V>
struct is_constant_boundary<ConstantBoundary<T, V>> : std::true_type
{
};
 
template <typename B>
inline constexpr bool is_constant_boundary_v = is_constant_boundary<B>::value;
}  // namespace ca_lattice_detail
 
template <typename Storage, typename Boundary = OpenBoundary>
class Lattice
{
public:
  using storage_type = Storage;
  using boundary_type = Boundary;
  using state_type = typename Storage::state_type;
  using coord_type = typename Storage::coord_type;
  using extents_type = typename Storage::extents_type;
 
  static constexpr std::size_t rank = Storage::rank;
 
private:
  Storage store_;
 
  [[nodiscard]] state_type out_of_range_value() const
  {
    if constexpr (ca_lattice_detail::is_constant_boundary_v<Boundary>)
      return static_cast<state_type>(Boundary::value);
    else
      return state_type{};
  }
 
  [[nodiscard]] bool fold_coord(coord_type &c) const
  {
    using namespace ca_lattice_detail;
    for (std::size_t d = 0; d < rank; ++d)
      {
        const ca_size_t n = store_.size(d);
        if (n == 0)
          return false;
 
        if constexpr (std::is_same_v<Boundary, ToroidalBoundary>)
          {
            c[d] = static_cast<ca_index_t>(wrap_into_range(c[d], n));
          }
        else if constexpr (std::is_same_v<Boundary, ReflectiveBoundary>)
          {
            c[d] = static_cast<ca_index_t>(reflect_into_range(c[d], n));
          }
        else if constexpr (std::is_same_v<Boundary, NeumannBoundary>)
          {
            // Zero-gradient: clamp to the nearest in-range coordinate.
            if (c[d] < 0)
              c[d] = 0;
            else if (static_cast<ca_size_t>(c[d]) >= n)
              c[d] = static_cast<ca_index_t>(n - 1);
          }
        else
          {
            // OpenBoundary or ConstantBoundary<...>
            if (c[d] < 0 or static_cast<ca_size_t>(c[d]) >= n)
              return false;
          }
      }
    return true;
  }
 
public:
  Lattice() = default;
 
  explicit Lattice(const extents_type &extents, const state_type &init = state_type{})
    : store_(extents, init)
  {}
 
  explicit Lattice(Storage &&s) noexcept(std::is_nothrow_move_constructible_v<Storage>)
    : store_(std::move(s))
  {}
 
  [[nodiscard]] static constexpr std::size_t dimension() noexcept
  {
    return rank;
  }
 
  [[nodiscard]] ca_size_t size() const noexcept
  {
    return store_.size();
  }
  [[nodiscard]] ca_size_t size(std::size_t d) const
  {
    return store_.size(d);
  }
 
  [[nodiscard]] const extents_type &extents() const noexcept
  {
    return store_.extents();
  }
 
  [[nodiscard]] state_type at(const coord_type &c) const
  {
    return store_.at(c);
  }
 
  void set(const coord_type &c, const state_type &v)
  {
    store_.set(c, v);
  }
 
  [[nodiscard]] state_type at_safe(coord_type c) const
  {
    if (fold_coord(c))
      return store_.at(c);
    return out_of_range_value();
  }
 
  [[nodiscard]] const Storage &storage() const noexcept
  {
    return store_;
  }
 
  [[nodiscard]] Storage &storage() noexcept
  {
    return store_;
  }
 
  void fill(const state_type &value)
  {
    store_.fill(value);
  }
 
  void swap(Lattice &other) noexcept(noexcept(store_.swap(other.store_)))
  {
    store_.swap(other.store_);
  }
};
 
template <typename Storage, typename Boundary>
inline void swap(Lattice<Storage, Boundary> &a,
                 Lattice<Storage, Boundary> &b) noexcept(noexcept(a.swap(b)))
{
  a.swap(b);
}
 
}  // namespace CA
}  // namespace Aleph
 
#endif  // TPL_CA_LATTICE_H