Geometry.h

// Copyright (C) 2006-2022 Anders Logg and Garth N. Wells
//
// This file is part of DOLFINx (https://www.fenicsproject.org)
//
// SPDX-License-Identifier:    LGPL-3.0-or-later
 
#pragma once
 
#include "Topology.h"
#include <algorithm>
#include <basix/mdspan.hpp>
#include <cassert>
#include <concepts>
#include <cstdint>
#include <dolfinx/common/IndexMap.h>
#include <dolfinx/common/MPI.h>
#include <dolfinx/fem/CoordinateElement.h>
#include <dolfinx/fem/ElementDofLayout.h>
#include <dolfinx/fem/dofmapbuilder.h>
#include <dolfinx/graph/AdjacencyList.h>
#include <dolfinx/graph/partition.h>
#include <functional>
#include <iterator>
#include <memory>
#include <numeric>
#include <span>
#include <spdlog/spdlog.h>
#include <stdexcept>
#include <type_traits>
#include <utility>
#include <vector>
 
namespace dolfinx::mesh
{

template <std::floating_point T>
class Geometry
{
public:
  using value_type = T;

  template <typename U, typename V, typename W>
    requires std::is_convertible_v<std::remove_cvref_t<U>,
                                   std::vector<std::vector<std::int32_t>>>
                 and std::is_convertible_v<std::remove_cvref_t<V>,
                                           std::vector<T>>
                 and std::is_convertible_v<std::remove_cvref_t<W>,
                                           std::vector<std::int64_t>>
  Geometry(
      std::shared_ptr<const common::IndexMap> index_map, U&& dofmaps,
      const std::vector<fem::CoordinateElement<
          typename std::remove_reference_t<typename V::value_type>>>& elements,
      V&& x, int dim, W&& input_global_indices)
      : _dim(dim), _dofmaps(std::forward<U>(dofmaps)),
        _index_map(std::move(index_map)), _cmaps(elements),
        _x(std::forward<V>(x)),
        _input_global_indices(std::forward<W>(input_global_indices))
  {
    if (_x.size() % 3 != 0)
      throw std::invalid_argument("x size must be a multiple of 3.");
    if (_x.size() / 3 != _input_global_indices.size())
      throw std::invalid_argument("Geometry size mismatch.");
 
    if (_dofmaps.size() != _cmaps.size())
    {
      throw std::invalid_argument("Geometry number of dofmaps not equal to the "
                                  "number of coordinate elements.");
    }
 
    // TODO: check that elements dim == number of dofmap columns
  }

  Geometry(const Geometry&) = default;

  Geometry(Geometry&&) = default;

  ~Geometry() = default;
 
  // Copy assignment (deleted)
  Geometry& operator=(const Geometry&) = delete;

  Geometry& operator=(Geometry&&) = default;

  int dim() const { return _dim; }

  [[deprecated("Use dofmaps().front() instead.")]]
  md::mdspan<const std::int32_t, md::dextents<std::size_t, 2>> dofmap() const
  {
    if (_dofmaps.size() != 1)
      throw std::runtime_error("Multiple dofmaps");
    std::size_t ndofs = _cmaps.front().dim();
    return md::mdspan<const std::int32_t, md::dextents<std::size_t, 2>>(
        _dofmaps.front().data(), _dofmaps.front().size() / ndofs, ndofs);
  }

  std::vector<md::mdspan<const std::int32_t, md::dextents<std::size_t, 2>>>
  dofmaps() const
  {
    std::vector<md::mdspan<const std::int32_t, md::dextents<std::size_t, 2>>>
        dms(_dofmaps.size());
    for (std::size_t i = 0; i < _dofmaps.size(); ++i)
    {
      std::size_t ndofs = _cmaps.at(i).dim();
      dms[i] = md::mdspan<const std::int32_t, md::dextents<std::size_t, 2>>(
          _dofmaps.at(i).data(), _dofmaps.at(i).size() / ndofs, ndofs);
    }
    return dms;
  }

  std::shared_ptr<const common::IndexMap> index_map() const
  {
    return _index_map;
  }

  std::span<const value_type> x() const { return _x; }

  std::span<value_type> x() { return _x; }

  const std::vector<fem::CoordinateElement<value_type>>& cmaps() const
  {
    return _cmaps;
  }

  const std::vector<std::int64_t>& input_global_indices() const
  {
    return _input_global_indices;
  }
 
private:
  // Geometric dimension
  int _dim;
 
  // Map per cell for extracting coordinate data for each cmap
  std::vector<std::vector<std::int32_t>> _dofmaps;
 
  // IndexMap for geometry 'dofmap'
  std::shared_ptr<const common::IndexMap> _index_map;
 
  // The coordinate elements
  std::vector<fem::CoordinateElement<value_type>> _cmaps;
 
  // Coordinates for all points stored as a contiguous array (row-major,
  // column size = 3)
  std::vector<value_type> _x;
 
  // Global indices as provided on Geometry creation
  std::vector<std::int64_t> _input_global_indices;
};

template <typename U, typename V, typename W>
Geometry(std::shared_ptr<const common::IndexMap>, U&&,
         const std::vector<fem::CoordinateElement<
             typename std::remove_reference_t<typename V::value_type>>>&,
         V&&, int, W&&)
    -> Geometry<typename std::remove_cvref_t<typename V::value_type>>;

template <typename U>
Geometry<typename std::remove_reference_t<typename U::value_type>>
create_geometry(const Topology& topology,
                const std::vector<fem::CoordinateElement<
                    std::remove_reference_t<typename U::value_type>>>& elements,
                std::span<const std::int64_t> nodes,
                std::span<const std::int64_t> xdofs, const U& x, int dim,
                const std::function<std::vector<int>(
                    const graph::AdjacencyList<std::int32_t>&)>& reorder_fn
                = nullptr)
{
  spdlog::info("Create Geometry (multiple)");
 
  if (dim < 1 or dim > 3)
    throw std::invalid_argument("dim must be 1, 2 or 3.");
 
  assert(std::ranges::is_sorted(nodes));
  using T = typename std::remove_reference_t<typename U::value_type>;
 
  // Check elements match cell types in topology
  const int tdim = topology.dim();
  const std::size_t num_cell_types = topology.entity_types(tdim).size();
  if (elements.size() != num_cell_types)
    throw std::invalid_argument("Mismatch between topology and geometry.");
 
  std::vector<fem::ElementDofLayout> dof_layouts;
  dof_layouts.reserve(elements.size());
  for (auto& el : elements)
    dof_layouts.push_back(el.create_dof_layout());
 
  //  Build 'geometry' dofmap on the topology
  auto [_dof_index_map, bs, dofmaps]
      = fem::build_dofmap_data(topology.index_maps(topology.dim())[0]->comm(),
                               topology, dof_layouts, reorder_fn);
  auto dof_index_map
      = std::make_shared<common::IndexMap>(std::move(_dof_index_map));
 
  // If the mesh has higher order geometry, permute the dofmap
  if (elements.front().needs_dof_permutations())
  {
    const std::int32_t num_cells
        = topology.connectivity(topology.dim(), 0)->num_nodes();
    const std::vector<std::uint32_t>& cell_info
        = topology.get_cell_permutation_info();
    int d = elements.front().dim();
    for (std::int32_t cell = 0; cell < num_cells; ++cell)
    {
      std::span dofs(dofmaps.front().data() + cell * d, d);
      elements.front().permute_inv(dofs, cell_info[cell]);
    }
  }
 
  // Compute local-to-global map from local indices in dofmap to the
  // corresponding global indices in cells, and pass to function to
  // compute local (dof) to local (position in coords) map from (i)
  // local-to-global for dofs and (ii) local-to-global for entries in
  // coords
 
  std::vector<std::int32_t> all_dofmaps;
  all_dofmaps.reserve(std::accumulate(
      dofmaps.begin(), dofmaps.end(), std::size_t(0),
      [](std::size_t n, const auto& q) { return n + q.size(); }));
  for (const std::vector<std::int32_t>& q : dofmaps)
    all_dofmaps.insert(all_dofmaps.end(), q.begin(), q.end());
 
  const std::vector<std::int32_t> l2l = graph::build::compute_local_to_local(
      graph::build::compute_local_to_global(xdofs, all_dofmaps), nodes);
 
  // Cross-validate the three independently-derived quantities that the
  // rest of this function assumes are equal: the number of coordinate
  // rows in `x`, `nodes.size()`, and the geometry-dof count implied by
  // `xdofs`/`dofmaps` (l2l.size()).
  if (x.size() % dim != 0)
    throw std::invalid_argument("x size must be a multiple of dim.");
  if (x.size() / dim != nodes.size())
    throw std::invalid_argument("x row count must equal nodes.size().");
  if (l2l.size() != nodes.size())
  {
    throw std::invalid_argument(
        "Mismatch between xdofs/dofmaps and nodes: derived geometry dof "
        "count does not equal nodes.size().");
  }
 
  // Allocate space for input global indices and copy data
  std::vector<std::int64_t> igi(nodes.size());
  std::ranges::transform(l2l, igi.begin(),
                         [&nodes](auto index) { return nodes[index]; });
 
  // Build coordinate dof array, copying coordinates to correct position
  const std::size_t shape0 = x.size() / dim;
  const std::size_t shape1 = dim;
  std::vector<T> xg(3 * shape0, 0);
  for (std::size_t i = 0; i < shape0; ++i)
  {
    std::copy_n(std::next(x.begin(), shape1 * l2l[i]), shape1,
                std::next(xg.begin(), 3 * i));
  }
 
  return Geometry(dof_index_map, std::move(dofmaps), elements, std::move(xg),
                  dim, std::move(igi));
}
 
} // namespace dolfinx::mesh