containerdescriptors.hh

// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
 
// SPDX-FileCopyrightText: Copyright © DUNE Project contributors, see file AUTHORS.md
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception OR LGPL-3.0-or-later
 
#ifndef DUNE_FUNCTIONS_FUNCTIONSPACEBASES_CONTAINERDESCRIPTORS_HH
#define DUNE_FUNCTIONS_FUNCTIONSPACEBASES_CONTAINERDESCRIPTORS_HH
 
#include <array>
#include <cassert>
#include <functional>
#include <type_traits>
#include <vector>
 
#include <dune/common/filledarray.hh>
#include <dune/common/tuplevector.hh>
#include <dune/common/typeutilities.hh>
#include <dune/common/hybridutilities.hh>
#include <dune/common/rangeutilities.hh>
 
#include <dune/functions/common/type_traits.hh>
#include <dune/functions/functionspacebases/basistags.hh>
 
namespace Dune::Functions {
namespace ContainerDescriptors {
 
struct Unknown {};
 
} // end namespace ContainerDescriptors
 
template<class PreBasis>
auto containerDescriptor(const PreBasis& preBasis)
{
  if constexpr (requires{ preBasis.containerDescriptor(); })
    return preBasis.containerDescriptor();
  else
    return ContainerDescriptors::Unknown{};
}
 
 
namespace ContainerDescriptors {
 
struct Value
{
  template<class Index>
  Value operator[] (const Index&) const { return {}; }
 
  static constexpr std::size_t size () { return 0; }
};
 
template<class... Children>
using Tuple = Dune::TupleVector<Children...>;
 
template<class Child0, class... Children,
  std::enable_if_t<(sizeof...(Children) > 0), int> = 0,
  std::enable_if_t<(...|| (not std::is_same_v<Child0, Children>)), int> = 0>
auto makeDescriptor (Child0 child0, Children... children)
{
  using Descriptor = Tuple<Child0,Children...>;
  return Descriptor{std::move(child0),std::move(children)...};
}
 
 
template<class Child, std::size_t n>
using Array = std::array<Child, n>;
 
template<class Child0, class... Children,
  std::enable_if_t<(std::is_same_v<Child0, Children> &&...), int> = 0>
auto makeDescriptor (Child0 child, Children... children)
{
  using Descriptor = Array<Child0,1+sizeof...(Children)>;
  return Descriptor{std::move(child),std::move(children)...};
}
 
 
template<class Child>
using Vector = std::vector<Child>;
 
template<class Child, std::size_t n>
struct UniformArray
{
  template<class C = Child,
    std::enable_if_t<std::is_default_constructible_v<C>, int> = 0>
  UniformArray ()
    : child_{}
  {}
 
  explicit UniformArray (Child child)
    : child_{std::move(child)}
  {}
 
  template<class Index>
  const Child& operator[] (const Index& /*i*/) const { return child_; }
 
  static constexpr std::size_t size () { return n; }
 
private:
  Child child_;
};
 
template<std::size_t n>
using FlatArray = UniformArray<Value,n>;
 
template<class Child, std::size_t n>
auto makeUniformDescriptor (std::integral_constant<std::size_t,n>, Child child)
{
  return UniformArray<Child,n>{std::move(child)};
}
 
 
template<class Child>
struct UniformVector
{
  template<class C = Child,
    std::enable_if_t<std::is_default_constructible_v<C>, int> = 0>
  explicit UniformVector (std::size_t size)
    : size_{size}
    , child_{}
  {}
 
  UniformVector (std::size_t size, Child child)
    : size_{size}
    , child_{std::move(child)}
  {}
 
  template<class Index>
  const Child& operator[] (const Index& /*i*/) const { return child_; }
 
  std::size_t size () const { return size_; }
 
private:
  std::size_t size_;
  Child child_;
};
 
using FlatVector = UniformVector<Value>;
 
template<class Child>
auto makeUniformDescriptor (std::size_t n, Child child)
{
  return UniformVector<Child>{n,std::move(child)};
}
 
namespace Impl {
 
template<class InnerFunc, class LeafFunc>
struct TreeTransform
{
  TreeTransform (const InnerFunc& innerFunc, const LeafFunc& leafFunc)
    : innerFunc_(innerFunc)
    , leafFunc_(leafFunc)
  {}
 
  Unknown operator() (const Unknown& tree) const
  {
    return tree;
  }
 
  auto operator() (const Value& tree) const
  {
    return leafFunc_(tree);
  }
 
  template<class... V>
  auto operator() (const Tuple<V...>& tree) const
  {
    return unpackIntegerSequence([&](auto... ii) {
      return makeDescriptor(innerFunc_(tree[ii])...);
    }, std::make_index_sequence<sizeof...(V)>());
  }
 
  template<class V, std::size_t n>
  auto operator() (const Array<V,n>& tree) const
  {
    return unpackIntegerSequence([&](auto... ii) {
      return makeDescriptor(innerFunc_(tree[ii])...);
    }, std::make_index_sequence<n>());
  }
 
  template<class V>
  auto operator() (const Vector<V>& tree) const
  {
    using W = decltype(innerFunc_(tree[0]));
    Vector<W> result;
    result.reserve(tree.size());
    for (std::size_t i = 0; i < tree.size(); ++i)
      result.emplace_back(innerFunc_(tree[i]));
    return result;
  }
 
  template<class V, std::size_t n>
  auto operator() (const UniformArray<V,n>& tree) const
  {
    return makeUniformDescriptor(Dune::index_constant<n>{}, innerFunc_(tree[0]));
  }
 
  template<class V>
  auto operator() (const UniformVector<V>& tree) const
  {
    return makeUniformDescriptor(tree.size(), innerFunc_(tree[0]));
  }
 
private:
  InnerFunc innerFunc_;
  LeafFunc leafFunc_;
};
 
 
template<class Size, class T>
auto appendToTree (Size s, const T& tree)
{
  auto transform = TreeTransform(
    [s](auto&& node) { return appendToTree(s, node); },
    [s](auto&& node) { return makeUniformDescriptor(s, node); });
  return transform(tree);
}
 
template<class... Child>
auto flatLexicographic (Child... child)
{
  if constexpr ((std::is_same_v<Child, FlatVector> && ...))
    return FlatVector((child.size() + ...));
  else
    return Unknown{};
}
 
template<class N, class Child>
auto flatLexicographicN (N n, Child child)
{
  return Unknown{};
}
 
template<class N, class GrandChild>
auto flatLexicographicN (N n, UniformVector<GrandChild> child)
{
  return UniformVector<GrandChild>{child.size()*n, child[0]};
}
 
template<class N, class GrandChild, std::size_t m>
auto flatLexicographicN (N n, UniformArray<GrandChild, m> child)
{
  if constexpr (std::is_same_v<N, std::size_t>)
    return UniformVector<GrandChild>{n*m, child[0]};
  else
    return UniformArray<GrandChild, N::value*m>{child[0]};
}
 
template<class N, class GrandChild>
auto flatLexicographicN (N n, Vector<GrandChild> child)
{
  auto result = Vector<GrandChild>{};
  result.reserve(child.size()*n);
  for (auto j : Dune::range(n))
    for (auto i : Dune::range(child.size()))
      result.emplace_back(child[i]);
  return result;
}
 
template<class N, class GrandChild, std::size_t m>
auto flatLexicographicN (N n, Array<GrandChild, m> child)
{
  if constexpr (std::is_same_v<N, std::size_t>)
  {
    auto result = Vector<GrandChild>{};
    result.reserve(child.size()*n);
    for (auto j : Dune::range(n))
      for (auto i : Dune::range(child.size()))
        result.emplace_back(child[i]);
    return result;
  }
  else
  {
    auto result = Array<GrandChild, N::value*m>{};
    for (auto j : Dune::range(n))
      for (auto i : Dune::range(child.size()))
        result.emplace_back(child[i]);
    return result;
  }
}
 
template<class N, class... GrandChild>
auto flatLexicographicN (N n, Tuple<GrandChild...> child)
{
  constexpr std::size_t m = sizeof...(GrandChild);
  return Dune::unpackIntegerSequence([&](auto... i) {
    return makeDescriptor(std::get<i%m>(child)...);
  }, std::make_index_sequence<n*m>{});
}
 
template<class N, class Child>
auto flatInterleavedN (N n, Child child)
{
  return Unknown{};
}
 
template<class N, class GrandChild>
auto flatInterleavedN (N n, UniformVector<GrandChild> child)
{
  return UniformVector<GrandChild>{child.size()*n, child[0]};
}
 
template<class N, class GrandChild, std::size_t m>
auto flatInterleavedN (N n, UniformArray<GrandChild, m> child)
{
  if constexpr (std::is_integral_v<N>)
    return UniformVector<GrandChild>{n*m, child[0]};
  else
    return UniformArray<GrandChild, N::value*m>{child[0]};
}
 
template<class N, class GrandChild>
auto flatInterleavedN (N n, Vector<GrandChild> child)
{
  auto result = Vector<GrandChild>{};
  result.reserve(child.size()*n);
  for (auto i : Dune::range(child.size()))
    for (auto j : Dune::range(n))
      result.emplace_back(child[i]);
  return result;
}
 
template<class N, class GrandChild, std::size_t m>
auto flatInterleavedN (N n, Array<GrandChild, m> child)
{
  if constexpr (std::is_integral_v<N>)
  {
    auto result = Vector<GrandChild>{};
    result.reserve(child.size()*n);
    for (auto i : Dune::range(child.size()))
      for (auto j : Dune::range(n))
        result.emplace_back(child[i]);
    return result;
  }
  else
  {
    auto result = Array<GrandChild, N::value*m>{};
    for (auto i : Dune::range(child.size()))
      for (auto j : Dune::range(n))
        result.emplace_back(child[i]);
    return result;
  }
}
 
template<class N, class... GrandChild>
auto flatInterleavedN (N n, Tuple<GrandChild...> child)
{
  constexpr std::size_t m = sizeof...(GrandChild);
  return Dune::unpackIntegerSequence([&](auto... i) {
    return makeDescriptor(std::get<i/n>(child)...);
  }, std::make_index_sequence<n*m>{});
}
 
} // end namespace Impl
} // end namespace ContainerDescriptors
} // end namespace Dune::Functions
 
#endif // DUNE_FUNCTIONS_FUNCTIONSPACEBASES_CONTAINERDESCRIPTORS_HH