StateRow.hpp

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// Copyright (c) 2019 Maikel Nadolski
//
// 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 copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#ifndef FUB_STATE_ROW_HPP
#define FUB_STATE_ROW_HPP
 
#include "fub/State.hpp"
#include "fub/core/tuple.hpp"
 
namespace fub {
 
template <typename T, typename Depth> struct DepthToRowType {
  using type = mdspan<T, 2, layout_stride>;
};
 
template <typename T> struct DepthToRowType<T, ScalarDepth> {
  using type = span<T>;
};
 
template <typename State> struct RowBaseImpl {
  template <typename Depth>
  using fn = typename DepthToRowType<double, Depth>::type;
  using type = boost::mp11::mp_transform<fn, meta::Depths<State>>;
};
 
template <typename State> struct RowBaseImpl<const State> {
  template <typename Depth>
  using fn = typename DepthToRowType<const double, Depth>::type;
  using type = boost::mp11::mp_transform<fn, meta::Depths<State>>;
};
 
template <typename State> using RowBase = typename RowBaseImpl<State>::type;
 
template <typename State> struct Row : RowBase<State> {
  static constexpr int Rank = 1;
  using Traits = StateTraits<RowBase<State>>;
  using ElementType =
      std::conditional_t<std::is_const_v<State>, const double, double>;
 
  Row() = default;
 
  Row(const ViewPointer<State>& pointer, std::ptrdiff_t extent) {
    ForEachVariable(
        overloaded{[extent](span<ElementType>& s, auto p) {
                     s = span<ElementType>(p, extent);
                   },
                   [extent](mdspan<ElementType, 2, layout_stride>& mds,
                            const auto& p) {
                     layout_stride::mapping<dynamic_extents<2>> mapping{
                         dynamic_extents<2>{extent, 2}, {1, p.second}};
                     mds = mdspan<ElementType, 2, layout_stride>(p.first,
                                                                 mapping);
                   }},
        *this, pointer);
  }
};
 
template <typename State>
struct StateTraits<Row<State>> : StateTraits<RowBase<State>> {};
 
template <typename State> ViewPointer<State> Begin(const Row<State>& row) {
  ViewPointer<State> pointer;
  ForEachVariable(
      overloaded{
          [&](double*& p, span<double> s) { p = s.begin(); },
          [&](const double*& p, span<const double> s) { p = s.begin(); },
          [&](auto& p, const mdspan<double, 2, layout_stride>& mds) {
            p = std::pair{mds.get_span().begin(), mds.stride(1)};
          },
          [&](auto& p, const mdspan<const double, 2, layout_stride>& mds) {
            p = std::pair{mds.get_span().begin(), mds.stride(1)};
          }},
      pointer, row);
  return pointer;
}
 
template <typename State> ViewPointer<State> End(const Row<State>& row) {
  ViewPointer<State> pointer;
  ForEachVariable(
      overloaded{
          [&](double*& p, span<double> s) { p = s.end(); },
          [&](const double*& p, span<const double> s) { p = s.end(); },
          [&](auto& p, const mdspan<double, 2, layout_stride>& mds) {
            p = std::pair{mds.get_span().end(), mds.stride(1)};
          },
          [&](auto& p, const mdspan<const double, 2, layout_stride>& mds) {
            p = std::pair{mds.get_span().end(), mds.stride(1)};
          }},
      pointer, row);
  return pointer;
}
 
template <Direction Dir> struct ToStride {
  template <typename T, int R, typename L>
  std::ptrdiff_t operator()(const PatchDataView<T, R, L>& pdv) const {
    if constexpr (R == 1) {
      return pdv.Extent(0);
    } else {
      return pdv.Stride(static_cast<int>(Dir));
    }
  }
 
  template <typename T, typename L, int R>
  std::ptrdiff_t operator()(const BasicView<T, L, R>& view) const {
    return get<0>(view).Stride(static_cast<int>(Dir));
  }
};
 
template <Direction Dir, typename T, int R, typename L>
std::ptrdiff_t Extent(const PatchDataView<T, R, L>& pdv) {
  return pdv.Extent(static_cast<std::size_t>(Dir));
}
 
template <Direction Dir, typename T, typename L, int R>
std::ptrdiff_t Extent(const BasicView<T, L, R>& view) {
  return Extent<Dir>(get<0>(view));
}
 
struct ToRow {
  std::ptrdiff_t extent;
 
  template <typename T> span<T> operator()(T* pointer) {
    return {pointer, extent};
  }
 
  template <typename T> Row<T> operator()(const ViewPointer<T>& pointer) {
    return {pointer, extent};
  }
};
 
template <typename T> void Advance(T*& pointer, std::ptrdiff_t n) {
  pointer += n;
}
 
template <typename T, int R, typename L>
T* Begin(const PatchDataView<T, R, L>& pdv) {
  return pdv.Span().begin();
}
 
template <typename T, int R, typename L>
T* End(const PatchDataView<T, R, L>& pdv) {
  return pdv.Span().end();
}
 
template <int N, typename T> constexpr T* GetOrForward(T* pointer) noexcept {
  return pointer;
}
 
template <int N, typename T>
constexpr decltype(auto) GetOrForward(const ViewPointer<T>& pointer) noexcept {
  return get<N>(pointer);
}
 
template <typename Tuple, typename Function>
void ForEachRow(const Tuple& views, Function f) {
  std::tuple firsts = Transform(views, [](const auto& v) { return Begin(v); });
  const std::ptrdiff_t row_extent = Extent<Direction::X>(std::get<0>(views));
  if constexpr (std::tuple_element_t<0, Tuple>::rank() == 1) {
    std::tuple rows = Transform(firsts, ToRow{row_extent});
    std::apply(f, rows);
  } else if constexpr (std::tuple_element_t<0, Tuple>::rank() == 2) {
    std::tuple lasts = Transform(views, [](const auto& v) { return End(v); });
    std::tuple strides = Transform(views, ToStride<Direction::Y>());
    const auto& first = std::get<0>(firsts);
    const auto& last = std::get<0>(lasts);
    std::ptrdiff_t n = GetOrForward<0>(last) - GetOrForward<0>(first);
    while (n >= std::get<0>(strides)) {
      std::tuple rows = Transform(firsts, ToRow{row_extent});
      std::apply(f, rows);
      std::tuple firsts_and_strides = Zip(firsts, strides);
      std::apply(
          [](auto&... ps) { (Advance(std::get<0>(ps), std::get<1>(ps)), ...); },
          firsts_and_strides);
      firsts = std::apply(
          [](auto&&... fs) { return std::tuple{std::get<0>(fs)...}; },
          firsts_and_strides);
      n = GetOrForward<0>(last) - GetOrForward<0>(first);
    }
  } else {
    const std::ptrdiff_t ny = Extent<Direction::Y>(std::get<0>(views));
    const std::ptrdiff_t nz = Extent<Direction::Z>(std::get<0>(views));
    std::tuple strides_y = Transform(views, ToStride<Direction::Y>());
    std::tuple strides_z = Transform(views, ToStride<Direction::Z>());
    for (std::ptrdiff_t j = 0; j < nz; ++j) {
      std::tuple pointers = firsts;
      for (std::ptrdiff_t i = 0; i < ny; ++i) {
        std::tuple rows = Transform(pointers, ToRow{row_extent});
        std::apply(f, rows);
        pointers = std::apply(
            [](auto... ps) {
              (Advance(std::get<0>(ps), std::get<1>(ps)), ...);
              return std::tuple{std::get<0>(ps)...};
            },
            Zip(pointers, strides_y));
      }
      firsts = std::apply(
          [](auto... ps) {
            (Advance(std::get<0>(ps), std::get<1>(ps)), ...);
            return std::tuple{std::get<0>(ps)...};
          },
          Zip(firsts, strides_z));
    }
  }
}
 
} // namespace fub
 
#endif