Partitioning.h

#pragma once
 
#include <Eigen/Core>
 
#include <memory>
 
namespace wmtk {
 
using metis_index_t = int32_t;
 
template <typename DerivedF>
std::pair<std::unique_ptr<metis_index_t[]>, std::unique_ptr<metis_index_t[]>> convert_index_buffer(
    const Eigen::MatrixBase<DerivedF>& facets)
{
    const auto num_elems = static_cast<metis_index_t>(facets.rows());
    const auto elem_size = static_cast<metis_index_t>(facets.cols());
 
    auto e_ptr = std::unique_ptr<metis_index_t[]>(new metis_index_t[num_elems + 1]);
    auto e_ind = std::unique_ptr<metis_index_t[]>(new metis_index_t[num_elems * elem_size]);
    for (metis_index_t f = 0; f < num_elems; ++f) {
        e_ptr[f] = f * elem_size;
        for (metis_index_t lv = 0; lv < elem_size; ++lv) {
            e_ind[f * elem_size + lv] = facets(f, lv);
        }
    }
    e_ptr[num_elems] = num_elems * elem_size;
    return std::make_pair(std::move(e_ptr), std::move(e_ind));
}
 
Eigen::Matrix<metis_index_t, Eigen::Dynamic, 1> partition_mesh_vertices_raw(
    metis_index_t num_elems,
    metis_index_t num_nodes,
    metis_index_t* e_ptr,
    metis_index_t* e_ind,
    metis_index_t num_partitions);
 
template <typename DerivedF>
Eigen::Matrix<metis_index_t, Eigen::Dynamic, 1> partition_mesh_vertices(
    const Eigen::MatrixBase<DerivedF>& facets,
    metis_index_t num_partitions)
{
    const auto num_elems = static_cast<metis_index_t>(facets.rows());
    const auto num_nodes = static_cast<metis_index_t>(facets.maxCoeff() + 1);
    auto res = convert_index_buffer(facets);
    return partition_mesh_vertices_raw(
        num_elems,
        num_nodes,
        res.first.get(),
        res.second.get(),
        num_partitions);
}
 
} // namespace wmtk